Pain Assessment
Content
Pain assessment
A. Core questions to be answered as part of a pain assessment:
• • • • • •
What is the type or category of pain? Is there a primary cause of the pain? What additional factors are contributing to the pain? Are treatments available for the primary cause of the pain? Are treatments available for the additional factors which contribute to the pain? Are there other medical or psychosocial conditions which should influence the choice of treatment?
B. The methodology of the pain assessment:
• • • • • • •
History Past medical history Current medications Physical examination Special tests Psychological evaluation Differential diagnosis
II. INTRODUCTION The basics of the assessment of pain are the same as the assessment of other medical complaints. Yet pain is the most common complaint that presents to the primary care practitioner; therefore, it is valuable to give some focused attention to the specifics of the methodology for assessing this problem. III. CORE QUESTIONS TO BE ANSWERED AS PART OF A PAIN ASSESSMENT A. What is the type or category of pain? 8 1. Nociceptive Pain -This is the typical pain that we have all experienced. It is the signal of tissue irritation, impending injury, or actual injury. Nociceptors in the affected area are activated and then transmit signals via the peripheral nerves and the spinal cord to the brain. Complex spinal reflexes (withdrawal) may be activated, followed by perception, cognitive and affective responses, and possibly voluntary action. The pain is typically perceived as related to the specific stimulus (hot, sharp, etc.) or with an aching or throbbing quality. Visceral pain is a subtype of nociceptive pain. It tends to be paroxysmal and poorly localized, as opposed to somatic pain which is more constant and well localized. Nociceptive pain is usually
time limited--arthritis is a notable exception--and tends to respond well to treatment with opioids. 2. Neuropathic Pain -Neuropathic pain is the result of a malfunction somewhere in the nervous system. The site of the nervous system injury or malfunction can be either in the peripheral or in the central nervous system. The pain is often triggered by an injury, but this injury may not clearly involve the nervous system, and the pain may persist for months or years beyond the apparent healing of any damaged tissues. In this setting, pain signals no longer represent ongoing or impending injury. The pain frequently has burning, lancinating, or electric shock qualities. Persistent allodynia--pain resulting from a nonpainful stimulus, such as light touch--is also a common characteristic of neuropathic pain. Neuropathic pain is frequently chronic, and tends to have a less robust response to treatment with opioids.
3. Psychogenic Pain-The use of this category should be reserved for those rare situations where it is clear that no somatic disorder is present. It is universal that psychological factors play a role in the perception and complaint of pain. These psychological factors may lead to an exaggerated or histrionic presentation of the pain problem, but even in these circumstances, it is rare that the psychological factors represent the exclusive etiology of the patient's pain. 4. Mixed Category Pain-In some conditions the pain appears to be caused by a complex mixture of nociceptive and neuropathic factors. An initial nervous system dysfunction or injury may trigger the neural release of inflammatory mediators and subsequent neurogenic inflammation. For example, migraine headaches probably represent a mixture of neuropathic and nociceptive pain. Myofascial pain is probably secondary to nociceptive input from the muscles, but the abnormal muscle activity may be the result of neuropathic conditions.
Chronic pain, including chronic myofascial pain, may cause the development of ongoing representations of pain within the central nervous system which are independent of signals from the periphery. This is called the centralization or encephalization of pain. B. Is there a primary cause of the pain? After determining if the pain is most likely nociceptive or neuropathic, the next step is to determine, as precisely as possible, the cause or specific source of the pain. Frequently, reversible causes can be identified. Nociceptive pain indicates ongoing or impending injury; therefore, identification and removal or treatment of the problem is critical. Is there an underlying sprain, tear, fracture, infection, obstruction, or foreign body? Is there inflammation caused by an underlying arthritic or autoimmune disorder? Myofascial pain may indicate abnormal acute or chronic muscle stresses. Neuropathic pain may also be caused by injury, but the injury in that case is actually to the nervous system. Nerves can be infiltrated or compressed by tumors, strangulated by scar tissue, or inflamed by infection. Some of these, and other neuropathic etiologies, may also be reversible. Usually, neuropathic problems are not fully reversible, but partial improvement is often possible with proper treatment. For example, neuromas may respond to excision or ablation; phantom pain may respond to transcutaneous nerve stimulation (TENS); and peripheral neuropathy may respond to tricyclic antidepressants. C. What additional factors are contributing to the pain? For most of the last 300 years, our understanding of pain has been dominated by the Cartesian model. Viewed from this perspective, the human body is a complex machine which is separate and distinct from the mind and the process of perception. Therefore, physical pain is a function of the mechanics of the body. In the last 30 years, we have come to appreciate that pain is an experience rather than a bodily function. Experience is a function of the mind; therefore, the experience of pain cannot be separated from the patient's mental state, including their social-cultural background. We now know that environmental and mental factors can be so critical that they can actually trigger or abolish the experience of pain, independent of what is occurring in the body.38 We now understand some of the mechanisms of how the brain can influence the spinal processing of pain via descending inhibitory and facilitory neural pathways. Furthermore, suffering should not be considered synonymous with pain. The emotional impact and distress caused by pain differs from person to person. Different patients may report very different intensities of pain for similar injuries, but even when they report similar degrees of pain, they may have vastly different amounts of suffering. When assessing a complaint of pain, it is critical to remember that pain is an experience, rather than a bodily function. Therefore it is valuable to investigate the appropriate mental and environmental factors: 1. Mood disorder--
Depressive disorders are found in approximately 50% of chronic pain patients. 33 The patient may say, "Cure the pain, and I won't be depressed;" however, it would be a mistake to ignore the depression. Depression can significantly intensify the experience of pain and the associated suffering. In some cases, depression manifests primarily with somatic symptoms and complaints. Therefore, on occasion, depression may even be the primary etiology of the pain. 2. Anxiety disorder-Again, more than 50% of chronic pain patients suffer with anxiety disorders which may alter the experience of pain and suffering. 14 3. Somatization and hypochondriasis34-Stress affects the bodily functions and sensations in all people. Emotional distress is often felt and expressed as physical distress. These processes, when predominant, lead to excessive somatic attention and communication in the forms of somatization and hypochondriasis. These can sometimes be primary psychiatric disorders or tendencies, but often they are part of depressive or anxiety disorders. These patients are prone to misinterpreting normal bodily sensations and to exaggerating the symptoms of illness. They are therefore more likely to believe that they are suffering from a catastrophic illness or complication. 4. Secondary gain15-Patients with chronic pain undergo many losses--financial, vocational, recreational, and impaired relationships. They also incur benefits which may be financial or involve emotional support from friends and family. If the secondary gains outweigh the secondary losses, then there may be motivational factors impeding the recovery. These factors are frequently unconscious, and they are not usually the "cause" of the pain. Malingering occurs in those rare situations where the patient is consciously lying about their condition for reasons of gain. Also rarely, the patient may be consciously lying about symptoms, but without conscious benefit or gain--this represents a factitious disorder. 5. Other physical factors Other physical factors may also contribute to the experience of pain, including:
• • • •
sleep disturbance inactivity and poor muscle conditioning weight gain other injuries or illnesses
D. Are treatments available for the primary cause of the pain? 28,36 The physician will find it valuable to have some familiarity with the treatments available for various pain syndromes. Subsequent chapters in this handbook will help to find information regarding available therapies. Nociceptive pain is usually quite responsive to treatment with classical analgesics such as narcotics, nonsteroidal antiinflammatory drugs, or acetaminophen. Frequently, synergistic effects can be achieved by combining these medications. For acute, nociceptive pain, regional or nerve block techniques may also be effective. Clearly, while analgesia is being provided, the clinician must be diligently searching for underlying sources of tissue injury, irritation, or inflammation. TENS (transcutaneous electrical nerve stimulation) units and relaxation training may also benefit the patient suffering with nociceptive pain. Neuropathic pain also typically responds to treatment with narcotics, but less robustly than does nociceptive pain. Anticonvulsants and tricyclic antidepressants may be particularly beneficial. The allodynia (pain in response to a non-noxious stimulus) and hyperalgesia present in some neuropathic conditions may, in part, be the result of the production of increased numbers of adrenergic receptors on sensory nerve terminals and on surrounding inflammatory and mast cells. Therefore, sympatholytics such as clonidine, prazosin, and terazosin may be helpful in decreasing allodynia and hyperalgesia. Antiarrhythmics, most notably mexiletine, may alter neuronal sodium channel conduction, and thereby decrease ectopic or abnormal firing with in damaged, malfunctioning, pain producing parts of the nervous system. Referral to a Pain Clinic may be helpful in guiding further treatment or complex pharmacotherapy for the patient with chronic neuropathic pain. Other treatments might include nerve blocks, TENS units, biofeedback, psychological and physical therapies.
E. Are treatments available for the additional factors which contribute to the pain? For pain treatments to be fully effective it is critical that all factors be treated simultaneously. If depression or anxiety are contributing, these are highly treatable conditions. Appropriate therapy with antidepressants or anxiolytics, together with psychotherapy, should be instituted early in the treatment process. Somatization and hypochondriasis are more chronic and relatively more refractory conditions. However, here too, psychotherapeutic and possibly psychopharmacologic interventions may be critically helpful components of the treatment for the chronic pain patient. An understanding of these factors will also help to guide all aspects of the patients treatment. For example, the patient who is prone to high levels of somatization, is a relatively poor candidate for invasive treatments, since such interventions are likely to exacerbate the patients somatic concerns and preoccupation. 31 Secondary gain is not an illness, nor is it treated, but we must pay attention to this factor. The physician must be careful not to alter the balance of secondary losses versus secondary gains in such a manner that tips the scales in the direction of greater illness and disability. Psychotherapy may also help the patient to recognize that disability is associated with greater losses and fewer gains than the patient might consciously or unconsciously realize. Factitious disorders, when identified, indicate that treatment must focus on intensive psychotherapy (although it is difficult to get the patient to be compliant with such treatment). Malingering is a moral and legal problem rather than a medical problem, but recognition of malingering can help to avoid unnecessary, costly, and potentially dangerous treatments. 15, 31 Other health factors, such as sleep, weight, and overall conditioning can also contribute to the problem. Like most of the above associated factors, pain can cause these problems and then, in a vicious cycle, be exacerbated by these same problems. Appropriate medical management focused on these problems can be most beneficial. F. Are there other medical or psychosocial conditions which should influence the choice of treatment? 31
The previous questions have focused on understanding the nature of the patient's pain and the additional factors contributing to the problem. When treating the patient it is important to consider what other conditions or factors (which are not directly contributory to the pain) might influence the choice of treatment. Other medical conditions, such cardiac or pulmonary disease, may be relative contraindications for some medications or for various blocks. Examples include arrhythmias (especially bundle branch blocks) as a relative contraindication for tricyclic antidepressants or for right stellate ganglion blocks, bullous emphysema as a contraindication for intercostal nerve blocks, and pulmonary disease in general as a cautionary note regarding the use of narcotics (especially intravenous narcotics). Psychiatric conditions may also influence the choice of treatment. A history of mania or bipolar disorder is a relative contraindication for the use of antidepressants, a history of recent drug abuse indicates a need to avoid narcotics or benzodiazepines where possible, and high levels of somatization or anxiety argue against the use of invasive techniques or therapies. Some of the newer and more invasive pain therapies, such as spinal dorsal column stimulators and intrathecal morphine pumps, require that the patient have a good understanding of the medical condition and be highly compliant with complex treatments. IV. THE METHODOLOGY OF THE PAIN ASSESSMENT The previous section reviewed the overall questions that the care provider should keep in mind when assessing a complaint of pain. The next section provides some of the specifics of the data gathering process. A. History6, 12
1. How the pain developed? Was there an injury, illness, or major stress associated with the start of the pain?
This may give clues regarding any underlying pathology. Did the pain start immediately after the injury or was there a delay of weeks or months? Neuropathic pains such as entrapment neuropathy or complex regional pain syndromes (RSD) frequently development weeks to months after the injury. Is the pain associated with any treatment or medication? Headaches may occur as a rebound phenomena, associated with the use of analgesics.Occasionally, physically manipulative therapies may exacerbate a painful condition. Has the condition been stable or deteriorating? Ongoing deterioration mandates a more aggressive search for underlying pathology and possible interventions. Worsening low back pain, especially with deteriorating neurologic signs, may require surgical intervention; as opposed to stable, chronic low back pain, where more conservative measures are usually more appropriate. 2. Description of the pain. What are the adjectives used to describe the pain? The patient's description of the pain can help determine the type of pain.See the previous section on categories of pain. The patient's choice of adjectives may also provide clues regarding the emotional impact of the pain. Are there associated symptoms, such as nausea or sweating, flushing, or sensations of hot or cold in the affected area? These symptoms may indicate a autonomic or sympathetic component of the pain. How intense is the pain? There is tremendous individual variation in the perception of the intensity of pain. Yet obtaining this information is very important to help gauge the impact of the pain, and for the monitoring of change or progress. Standardizing the pain description. The Visual (or Verbal) Analog Scale (VAS) is the most common method for assessing pain intensity, and its change over time.
No pain
Worst possible pain
The patient is presented with a 10 cm line, labeled as above, and asked to mark an `X' on the line indicating the intensity of their pain. The result is then measured with a metric ruler and scored between 0 - 10. The same scale can be given verbally by asking the patient, "On a scale of 0 to 10, with 0 meaning no pain, and 10 meaning the worst pain you can imagine, how much pain are you having now?" These scales can also be used to assess the range of the patient's pain by asking them to indicate their level of pain at its worst, its best, and its average. Similar scales are available for children. The FACES scale shows cartoon-like pictures of faces in various degrees of distress. The child is asked to choose the one that shows how much pain she is having. Standardized, multiple choice lists of pain adjectives are also useful, especially in a pain clinic setting. The McGill Pain Inventory is the most commonly used of these. It may also be useful to ask the patient to keep a diary of their pain problem. The downside to this approach is that it asks to the patient to maintain a focus on their pain; this may be counterproductive to their treatment. 3. The location of the pain and any spread. Pain drawings. Ask the patient to draw the distribution of their pain on an outline of the human body. Is the pain limited to the distribution of a root or peripheral nerve? Such distributions help to isolate the site and possibly the source of the pathology. Pain which does not have a limited distribution, but instead occurs in multiple sites or has a diffuse distribution, implies a systemic etiology. Is the pain in a stocking or glove distribution? A stocking or glove distribution does NOT indicate a psychogenic etiology.Such a distribution is entirely consistent with a Complex Regional Pain Syndrome (RSD or causalgia), or if bilateral with a peripheral neuropathy. Could the pain be referred from another site? Possibly because of the convergent structure of the nervous system, it is common for pain to be referred from a separate, possibly quite distant site. This is most commonly seen if the site of painful stimulation or irritation is visceral or muscular. 7
4. How does the pain fluctuate over time. Is there any daily, monthly, or seasonal pattern associated with the pain? The physician is looking for clues as to the etiology of the pain. Arthritic conditions may be worse in the mornings and during cold seasons. Migraine headaches may have occur in patterns associated with a variety of factors such as stress or menstrual cycling. Are there aggravating or alleviating factors which lead to exacerbation or reduction of the pain? Understanding aggravating and alleviating activities can help to pinpoint the diagnosis or refine the treatment. Low back pain which is worse walking uphill suggests a discogenic etiology. If the pain is worse when walking downhill, this points more to facet disease or foraminal stenosis. Some headache syndromes are triggered by specific dietary elements such as alcohol or monosodium glutamate (MSG). Identifying and avoiding these triggers can be most helpful. 5. What is the overall level of patient function? Are there changes in the patients weight and sleep pattern? Such changes suggest the need to investigate further regarding possible depression or cancer. What is the patient's employment status? Issues of lost productivity and income or workers compensation may affect the patient's emotional and motivational state. It is usually a priority to enable the patient to return to work as soon as possible--vocational rehabilitation may be a crucial part of the treatment. What are the patient's daily activities?
Understanding the day-to-day activities of the patient and what activities are limited by the pain will help the clinician to focus the physical and psychological rehabilitation process. If the patient has acquired a totally disabled lifestyle, then it may be important to help the patient understand that he is capable of some productive functioning. Is the patient engaging in any exercise and physical activity? Physical activity is critical for preventing further physical deterioration. Exercise is often a crucial part of the treatment process; however, it is important that the patient's physical activities be reviewed, since some activities may exacerbate the problem. What is the quality of the family and personal relationships? Chronic pain may lead to irritability and personality changes. Such changes may in turn lead to the deterioration of personal relationships. Such problems should be identified so that interventions can be initiated. Families typically need some education regarding adaptive responses to chronic pain. Overly solicitous responses may reinforce the patient's pain behaviors and undermine the relationship. 6. What treatments have been attempted? Identifying prior treatment failures will not only prevent unnecessary repetition, but can also help guide the diagnosis. For example, if a variety of sympathetic blocks have not, even briefly, alleviated the pain, then perhaps the pain is not sympathetically mediated. B. Past Medical History In the assessment of the patient with pain, the past medical history should include the following information: 1. Do other medical problems relate to the patient's complaint of pain? For example, a history of diabetes or alcoholism point towards diagnoses of neuropathy. For headaches or abdominal pain, have there been any recent medication changes associated with the onset of the problem. 2. Do other medical problems potentially affect the choice of pain treatments? As noted above, the patient's medical condition may present relative contraindications to various medications or procedures. 3. Does the patient have any prior or current substance abuse history? Treating chronic pain with narcotics requires special caution with the addiction prone patient. In some patients it may not be possible to use narcotics except in the most dire circumstances.
C. Current Medications 1. Dosage and pattern of use Obtain a complete list of the patient's medications and usage. Include over-the-counter medications. 2. Effectiveness Note the effectiveness of medications. Analgesics (even if only partially effective) should lead to some increase of function in at least one sphere of the patient's life. 3. Drug tolerance The chronic use of some drugs is associated with tolerance (the gradual need to increase the dose to maintain the same effect). Tolerance does not imply addiction, but the development of physiologic tolerance can be hard to distinguish from inappropriate drug seeking behavior.
4. Potential for drug interactions and toxicity Acetaminophen 13 The analgesic ceiling for a single oral dose is reached at 1000 mg. There is the potential for hepatic toxicity; therefore, the daily use should not exceed 4 grams, and extra caution is warranted if the patient is malnourished or abuses alcohol. Nonsteroidal Antiinflammatory Drugs (NSAIDs) 22, 25 Prostaglandins are important factors in the maintenance of renal perfusion in those patients with hypovolemia or reduced renal blood flow. These patients and the elderly are at increased risk for renal damage from NSAIDs. Prostaglandins help maintain gastric mucosal integrity; therefore, NSAIDs may also produce gastroduodenal damage. All
NSAIDs may provoke asthmatic reactions in patients with underlying asthma or sensitivity to aspirin or other NSAIDs. These drugs inhibit platelet function and are associated with increased bruising; they should be discontinued before surgery or other invasive procedures. NSAIDs are relatively contraindicated in patients treated with anticoagulants. There is increased risk of gastrointestinal bleeding and coumadin levels may be altered secondary to displacement from protein binding sites. Tricyclic Antidepressants 9, 16 The side effects and toxicity of tricyclics can be exacerbated secondary to drug interactions. Tricyclic levels are increased by the selective serotonin reuptake inhibitors, especially fluoxetine and paroxetine. Neuroleptics, cimetidine, methylphenidate, and estrogens may also increase tricyclic levels. Additive side effects may occur with alcohol, sedatives, or other anticholinergic medications. Potentially fatal interactions may occur if tricyclics are given to patients on monoamine oxidase inhibitors (MAOIs). Hypertension and hyperpyrexia may occur secondary to administration with sympathomimetics.
Anticonvulsants 1, 16 Carbamazepine has a similar structure to tricyclic antidepressants, it may weakly potentiate tricyclic side effects and have there is a risk of interactions with MAOIs. Disulfiram and isoniazid may increase phenytoin levels. Phenytoin may displace coumarin from protein binding sites, and may alter digoxin levels. Propoxyphene may increase carbamazepine levels. Check for altered levels of other antidepressants.
Opioids 31, 32 Opioid side effects can vary from one narcotic drug to another in an unpredictable manner for each individual. Meperidine, at doses greater than 1 gram per day, is associated with the additional risk of seizures. Meperidine combined with monoamine oxidase inhibitors (MAOIs) can trigger a fatal hyperpyrexic reaction. Opioid side effects may be enhanced by alcohol or sedatives. Propoxyphene may also cause seizures, overdose may also cause fatal heart block; furthermore, propoxyphene may increase carbamazepine levels. Sudden discontinuation of opioids is associated with influenza-like symptoms of withdrawal:
• • • • • • • • • •
restlessness & insomnia nausea & vomiting diarrhea backache leg pain yawning lacrimation rhinorrhea mydriasis muscle cramps
If it is necessary to withdraw a patient from an opioid medication, it is best to decrease the dose by approximately 10% every 24 to 72 hours--further individual tailoring may be necessary.
D. Physical Examination 6, 12 Introduction In pain assessments, there are rarely tests available that will "make the diagnosis." Instead the clinician must rely upon the presenting signs and symptoms. The history will often generate a differential diagnosis; the physical exam will often lead to the selection of the primary diagnosis, and occasionally a test will help to confirm this diagnosis. For example, an MRI scan which reveals an L5-S1 disc herniation is only helpful as far as it confirms or contradicts the findings of the history and physical examination. When preparing to do a physical examination it is important to warn the patient as you approach potentially painful areas. It is also good policy to use chaperones whenever examining patients of the opposite sex. 1. Mental status exam cognitive functions--impairment implies the presence of delirium or dementia mood and affect--provide clues regarding the emotional state of the patient and the presence of anxiety or depression thought process & content--check if the patient is having suicidal ideation, or if there are signs of thought disorder and possible psychosis judgment and insight--many treatments, such as the prescribing of narcotics or the use of relaxation training, require intact judgment and insight 2. Vital signs Vital signs are often elevated in acute pain.
3. Inspection posture, guarding, splinting--if chronic, these behaviors may compound and exacerbate the pain problem, as the patient places abnormal stresses on the body. color and pigmentary changes--these skin changes may indicate sympathetic dysfunction, inflammation, or a prior herpes zoster eruption. sweating--abnormal or asymmetric sweating indicates sympathetic dysfunction. piloerection, gooseflesh (cutis anserina)--areas involved in neuropathic pain may briefly demonstrate this after disrobing. hair, nail changes--evidence of neuropathic injury or sympathetic dysfunction. swelling, edema--indications inflammation or sympathetic dysfunction. atrophy--may indicate guarding and lack of use, or denervation. poor healing--indicates poor perfusion possibly associated with ischemic injuries, diabetic neuropathy, or sympathetic dysfunction. 4. alpation & Musculoskeletal exam temperature changes--indicates inflammation or altered perfusion associated with sympathetic dysfunction. edema--subtle, subcutaneous edema can be appreciated by wrinkling the skin over affected and unaffected areas. Affected areas will not wrinkle into fine lines, but will look more dimpled, like orange peels. This indicates neural injury with denervation or sympathetic dysfunction. muscle tenderness--examination of muscles may reveal tender areas or actual trigger points. The extent of the tenderness and the amount of pressure required to elicit pain should be observed. Reproduction of the patient's characteristic pain is particularly noteworthy. joints--can be examined for effusions, ROM, and pain with compression or distraction 5. Neurologic Cranial nerve assessment--is especially crucial in the evaluation of head and neck pain. Physical examination for radiculopathy 20, 30 UPPER EXTREMITIES
C5
Motor Reflex Sensory Pain Motor Reflex Sensory Pain Motor Reflex Sensory Pain
C6
C7
C8
Motor Reflex Sensory Pain Motor Reflex Sensory Pain
raised elbows (axillary n.) biceps (musculocutaneous n.) upper, lateral arm, near/over deltoid (axillary n.) upper, lateral arm, never below elbow elbow supination (radial n.) / pronation (median n.) brachioradialis (radial n.) lateral forearm (musculocutaneous n.) lower lateral arm, possibly into thumb elbow extension (radial n.) triceps (radial n.) over triceps, mid-forearm, and middle finger deep pain in triceps, front and back of forearm & into middle finger thumb index pinch (ant. interosseus n. off median n. at the elbow) medial forearm (antebrachial cutaneous n.) medial forearm, into the 2 medial fingers finger abduction (ulnar n.) medial arm (brachial cutaneous n.) deep pain in axilla & shoulder w/ some radiation down inside of arm
T1
Cervical spondylosis or disc protrusion can produce cord compression (upper motor neuron signs) or root compression (lower motor neuron signs). C5-6 disc protrusions are the most common cervical disc problems; they can compress the C6 root and also produce C7 upper motor signs.
LOWER EXTREMITIES: L2 Motor Reflex Sensory hip flexion (femoral n.)
L3
L4
L5
S1
often no loss, anterior midthigh (femoral n, & lat. femoral cut br.) Pain across thigh knee extension (femoral n.), thigh adduction (obturator Motor n Reflex hip adductors (obturator n.) Sensory often no loss, anterior thigh just above the knee cap Pain across thigh Motor inversion of the foot (tibial & peroneal n.) Reflex knee jerk (femoral n.) Sensory medial lower leg Pain across knee & down to medial malleolus Motor dorsiflex great toe (deep peroneal n.) Reflex Sensory especially dorsum of the foot (peroneal n.) back of thigh to lateral lower leg, dorsum & sole of foot, Pain esp. big toe Motor eversion of the foot (peroneal n.) Reflex ankle jerk (tibial n.) Sensory behind the lateral malleolus Pain back of thigh and calf to lateral foot
It is important to note that lumbar disc lesions can only cause root (lower motor neuron) syndromes. Hyperreflexia is a sign of disease or injury at a higher level, in the spinal cord or brain. 95% of lumbar disc lesions involve L5 or S1.
Gait Observation of gait can help identify weakness or pain (antalgic gait). Distortion of the patient's gait may also lead to improper muscle use and strain, leading to further pain. Sensory dysfunction Neuropathic pain is associated with nerve injury or dysfunction. Frequently, it is possible to demonstrate sensory impairment in one or more modalities including temperature, light touch, sharp/dull discrimination, position, and vibration. The examiner should test the involved areas for at least one function of large fibers, such as vibration or light touch, and one small fiber function, such as temperature (using and ice cube or alcohol swab) or sharp/dull discrimination. The examination should also make note of the presence and distribution of abnormal pain responses. Table of Terms 26 Pain Allodynia Analgesia Anesthesia An unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain due to a stimulus which does not normally provoke pain. Absence of pain in response to stimulation which would normally be painful. Pain in an area or region which is anesthetic.
dolorosa An unpleasant abnormal sensation, whether spontaneous or evoked. An increased response to a stimulus which is Hyperalgesia normally painful. Increased sensitivity to stimulation, excluding the Hyperesthesia special senses. A painful syndrome characterized by an abnormally Hyperpathia painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold. Diminished pain in response to a normally painful Hypoalgesia stimulus. Hypesthesia = Decreased sensitivity to stimulation, excluding the Hypoesthesia special senses. Noxious stimulus A stimulus which is damaging to normal tissues. An abnormal sensation, whether spontaneous or Paresthesia evoked. Dysesthesia Peripheral Nerve & Dermatome Map From DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p.809-10. Motor dysfunction--Assessment of motor strength can help identify neural injury and the roots or peripheral nerves involved. Grading of Muscle Strength Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 0% 10% 25% 50% 75% Zero Trace Poor Fair Good No evidence of contractility Slight contractility but no joint motion Complete motion but with gravity eliminated Barely complete motion against gravity Complete motion against gravity and some resistance Complete motion against gravity and full resistance
100% Normal
DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p. 768.
Abnormal Reflexes 39 Hyporeflexia --focal: indicates lower motor neuron pathology at the level of the peripheral nerve or root --generalized: peripheral neuropathies--diabetic, alcoholic, inflammatory (GuillainBarre). Myopathy may also cause hyporeflexia. Hyperreflexia --focal: indicative of upper motor neuron pathology; frequently associated with upgoing toes on testing of the Babinski's sign--this cannot be secondary to lumbar spine disease since there are no UMNs in the lumbar spine --generalized: suggestive of increased arousal, hyperthyroidism, drug toxicity Grading Deep Reflexes Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 0 + ++ +++ ++++ +++++ Absent Diminished but present Normal Normal Hyperactive Hyperactive with clonus
From DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p.791. E. Diagnostic Testing 37
1. Radiographic
No matter which radiographic technique is used, the results must always be correlated with clinical findings. As the above table2, 4, 11, 17, 18, 19, 21, 23, 24, 27, 35, 40 of diagnostic tests for low back pain demonstrates, radiographic tests are far from perfect and serve best to confirm a clinically suspected diagnosis. Plain films--value is limited to demonstrating bony pathology, some soft tissue tumors can be seen Myelograms--involve the injection of contrast into the intrathecal space. For most of the common spinal diagnostic problems, CT or MRI are superior and free of the risk of postdural puncture headaches. omputerized Tomography (CT)--more bony detail and superior to MRI for bone or joint disease of the spine, including foraminal bony stenosis Magnetic Resonance Imaging (MRI)--superior soft tissue contrast and superior to CT or myelography for diagnosis of spinal disc disease or neural compression secondary to spinal stenosis. Also best for evaluating spinal alignment, infection, or tumor. Bone scans--radionuclide bone imaging identifies osteoblastic activity and can help with the diagnosis of bone tumor or metastatic disease, osteomyelitis, fractures, joint disease, avascular necrosis, and Paget's disease. 2. Diagnostic blocks 3 Nerve blocks with local anesthetics can help to distinguish focal from referred pain, somatic from sympathetically mediated pain, central from peripheral pain, and can help identify which peripheral nerves may be involved. This can help to guide treatment with further blocks or with other medical and surgical interventions. 3. Electromyography & Nerve Conduction Studies (EMG / NCS) These studies can assist in identifying and localizing functional lesions of peripheral nerves, motor units and muscle lesions. Such tests of function can be followed over time and complement the anatomic radiology studies. NCS generally reflect conduction in the larger, faster, myelinated nerves. 4. Somatosensory evoked potential testing (SSEP) SSEPs are better than EMG / NCS tests for assessing upper motor neuron diseases such as MS, syringomyelia, or spinal cord ischemia. SSEP testing involves the senses of touch, position, and vibration, rather than pain or temperature. 5. Other Quantitative Sensory Testing (QST)
Pain syndromes may represent dysfunction more specific to the small A-delta and C fibers. Testing of small fiber function is possible with devices which test thermal or electrical thresholds to perception and pain. Such testing is less invasive and may also be useful to monitor hyperesthetic responses. Fiber Type Innervation/Function 5, 8, 29 (Group) A-alpha (II) A-beta (II) Primary motor & propioception Mean Myelin Diameter (_m) +++ ++ ++ ++ + 15 8 6 3 3 1 Mean Conduction Velocity (m/sec) 100 50 30 20 7 1
Cutaneous touch & pressure (& motor fibers) A-gamma Muscle tone (spindle efferents) A-delta Mechanoreceptors, nociceptors, (III) and thermoreceptors B Sympathetic preganglionics Nociceptors, mechanoreceptors, C (IV thermoreceptors, sympathetic postganglionic .F. Psychological Evaluation
As discussed earlier, the clinician should always assess the patient's psychological state, and the emotions surrounding the pain problem. It is particularly valuable to inquire regarding:
• • • • • • • • • • • • •
Neurovegetative symptoms sleep disturbance appetite disturbance loss of energy loss of libido anhedonia impaired concentration suicidal ideation Impact of the pain on the patient's day-to-day activities work & finances personal relationships recreational pursuits
Factors suggesting the need for more formal psychological evaluation include:
• •
Evidence of mood or anxiety disorders Evidence of substance abuse
• • • • • • • • •
Evidence of psychotic disorder Evidence of cognitive impairment Evidence of overwhelmed coping capacities or suicidal ideation Evidence of prominent secondary gain Problems with hostility, anger, or personality disorder Suspicion of malingering or factitious disorder (e.g. inconsistent findings) Prolonged and extensive course of treatment failures Need for high dose opioids for non-malignant pain Assessment of suitability for aggressive invasive treatments
G. Differential Diagnosis After completing the data gathering process, it is time to consolidate the findings into a differential diagnosis. During this process the clinician should consider:
• • •
• • • •
The meaning of inconsistent findings? Consider psychogenic or malingering diagnoses, but beware that the emotional turmoil which surrounds chronic pain may falsely suggest these diagnoses. Be cautious about reaching a psychogenic diagnosis simply because the pain symptoms cannot be understood physiologically. The clinical and basic sciences of pain are rapidly progressing--what is not understood today may be understood tomorrow. Be wary of obvious diagnoses or therapies that were missed by other clinicians. Check with prior physicians about their findings. Do the signs and symptoms indicate the nature of the pain? nociceptive--suggesting tissue injury or inflammation · neuropathic--indicating central or peripheral dysfunction of the nervous system pain with mixed features --
A. Core questions to be answered as part of a pain assessment:
• • • • • •
What is the type or category of pain? Is there a primary cause of the pain? What additional factors are contributing to the pain? Are treatments available for the primary cause of the pain? Are treatments available for the additional factors which contribute to the pain? Are there other medical or psychosocial conditions which should influence the choice of treatment?
B. The methodology of the pain assessment:
• • • • • • •
History Past medical history Current medications Physical examination Special tests Psychological evaluation Differential diagnosis
II. INTRODUCTION The basics of the assessment of pain are the same as the assessment of other medical complaints. Yet pain is the most common complaint that presents to the primary care practitioner; therefore, it is valuable to give some focused attention to the specifics of the methodology for assessing this problem. III. CORE QUESTIONS TO BE ANSWERED AS PART OF A PAIN ASSESSMENT A. What is the type or category of pain? 8 1. Nociceptive Pain -This is the typical pain that we have all experienced. It is the signal of tissue irritation, impending injury, or actual injury. Nociceptors in the affected area are activated and then transmit signals via the peripheral nerves and the spinal cord to the brain. Complex spinal reflexes (withdrawal) may be activated, followed by perception, cognitive and affective responses, and possibly voluntary action. The pain is typically perceived as related to the specific stimulus (hot, sharp, etc.) or with an aching or throbbing quality. Visceral pain is a subtype of nociceptive pain. It tends to be paroxysmal and poorly localized, as opposed to somatic pain which is more constant and well localized. Nociceptive pain is usually
time limited--arthritis is a notable exception--and tends to respond well to treatment with opioids. 2. Neuropathic Pain -Neuropathic pain is the result of a malfunction somewhere in the nervous system. The site of the nervous system injury or malfunction can be either in the peripheral or in the central nervous system. The pain is often triggered by an injury, but this injury may not clearly involve the nervous system, and the pain may persist for months or years beyond the apparent healing of any damaged tissues. In this setting, pain signals no longer represent ongoing or impending injury. The pain frequently has burning, lancinating, or electric shock qualities. Persistent allodynia--pain resulting from a nonpainful stimulus, such as light touch--is also a common characteristic of neuropathic pain. Neuropathic pain is frequently chronic, and tends to have a less robust response to treatment with opioids.
3. Psychogenic Pain-The use of this category should be reserved for those rare situations where it is clear that no somatic disorder is present. It is universal that psychological factors play a role in the perception and complaint of pain. These psychological factors may lead to an exaggerated or histrionic presentation of the pain problem, but even in these circumstances, it is rare that the psychological factors represent the exclusive etiology of the patient's pain. 4. Mixed Category Pain-In some conditions the pain appears to be caused by a complex mixture of nociceptive and neuropathic factors. An initial nervous system dysfunction or injury may trigger the neural release of inflammatory mediators and subsequent neurogenic inflammation. For example, migraine headaches probably represent a mixture of neuropathic and nociceptive pain. Myofascial pain is probably secondary to nociceptive input from the muscles, but the abnormal muscle activity may be the result of neuropathic conditions.
Chronic pain, including chronic myofascial pain, may cause the development of ongoing representations of pain within the central nervous system which are independent of signals from the periphery. This is called the centralization or encephalization of pain. B. Is there a primary cause of the pain? After determining if the pain is most likely nociceptive or neuropathic, the next step is to determine, as precisely as possible, the cause or specific source of the pain. Frequently, reversible causes can be identified. Nociceptive pain indicates ongoing or impending injury; therefore, identification and removal or treatment of the problem is critical. Is there an underlying sprain, tear, fracture, infection, obstruction, or foreign body? Is there inflammation caused by an underlying arthritic or autoimmune disorder? Myofascial pain may indicate abnormal acute or chronic muscle stresses. Neuropathic pain may also be caused by injury, but the injury in that case is actually to the nervous system. Nerves can be infiltrated or compressed by tumors, strangulated by scar tissue, or inflamed by infection. Some of these, and other neuropathic etiologies, may also be reversible. Usually, neuropathic problems are not fully reversible, but partial improvement is often possible with proper treatment. For example, neuromas may respond to excision or ablation; phantom pain may respond to transcutaneous nerve stimulation (TENS); and peripheral neuropathy may respond to tricyclic antidepressants. C. What additional factors are contributing to the pain? For most of the last 300 years, our understanding of pain has been dominated by the Cartesian model. Viewed from this perspective, the human body is a complex machine which is separate and distinct from the mind and the process of perception. Therefore, physical pain is a function of the mechanics of the body. In the last 30 years, we have come to appreciate that pain is an experience rather than a bodily function. Experience is a function of the mind; therefore, the experience of pain cannot be separated from the patient's mental state, including their social-cultural background. We now know that environmental and mental factors can be so critical that they can actually trigger or abolish the experience of pain, independent of what is occurring in the body.38 We now understand some of the mechanisms of how the brain can influence the spinal processing of pain via descending inhibitory and facilitory neural pathways. Furthermore, suffering should not be considered synonymous with pain. The emotional impact and distress caused by pain differs from person to person. Different patients may report very different intensities of pain for similar injuries, but even when they report similar degrees of pain, they may have vastly different amounts of suffering. When assessing a complaint of pain, it is critical to remember that pain is an experience, rather than a bodily function. Therefore it is valuable to investigate the appropriate mental and environmental factors: 1. Mood disorder--
Depressive disorders are found in approximately 50% of chronic pain patients. 33 The patient may say, "Cure the pain, and I won't be depressed;" however, it would be a mistake to ignore the depression. Depression can significantly intensify the experience of pain and the associated suffering. In some cases, depression manifests primarily with somatic symptoms and complaints. Therefore, on occasion, depression may even be the primary etiology of the pain. 2. Anxiety disorder-Again, more than 50% of chronic pain patients suffer with anxiety disorders which may alter the experience of pain and suffering. 14 3. Somatization and hypochondriasis34-Stress affects the bodily functions and sensations in all people. Emotional distress is often felt and expressed as physical distress. These processes, when predominant, lead to excessive somatic attention and communication in the forms of somatization and hypochondriasis. These can sometimes be primary psychiatric disorders or tendencies, but often they are part of depressive or anxiety disorders. These patients are prone to misinterpreting normal bodily sensations and to exaggerating the symptoms of illness. They are therefore more likely to believe that they are suffering from a catastrophic illness or complication. 4. Secondary gain15-Patients with chronic pain undergo many losses--financial, vocational, recreational, and impaired relationships. They also incur benefits which may be financial or involve emotional support from friends and family. If the secondary gains outweigh the secondary losses, then there may be motivational factors impeding the recovery. These factors are frequently unconscious, and they are not usually the "cause" of the pain. Malingering occurs in those rare situations where the patient is consciously lying about their condition for reasons of gain. Also rarely, the patient may be consciously lying about symptoms, but without conscious benefit or gain--this represents a factitious disorder. 5. Other physical factors Other physical factors may also contribute to the experience of pain, including:
• • • •
sleep disturbance inactivity and poor muscle conditioning weight gain other injuries or illnesses
D. Are treatments available for the primary cause of the pain? 28,36 The physician will find it valuable to have some familiarity with the treatments available for various pain syndromes. Subsequent chapters in this handbook will help to find information regarding available therapies. Nociceptive pain is usually quite responsive to treatment with classical analgesics such as narcotics, nonsteroidal antiinflammatory drugs, or acetaminophen. Frequently, synergistic effects can be achieved by combining these medications. For acute, nociceptive pain, regional or nerve block techniques may also be effective. Clearly, while analgesia is being provided, the clinician must be diligently searching for underlying sources of tissue injury, irritation, or inflammation. TENS (transcutaneous electrical nerve stimulation) units and relaxation training may also benefit the patient suffering with nociceptive pain. Neuropathic pain also typically responds to treatment with narcotics, but less robustly than does nociceptive pain. Anticonvulsants and tricyclic antidepressants may be particularly beneficial. The allodynia (pain in response to a non-noxious stimulus) and hyperalgesia present in some neuropathic conditions may, in part, be the result of the production of increased numbers of adrenergic receptors on sensory nerve terminals and on surrounding inflammatory and mast cells. Therefore, sympatholytics such as clonidine, prazosin, and terazosin may be helpful in decreasing allodynia and hyperalgesia. Antiarrhythmics, most notably mexiletine, may alter neuronal sodium channel conduction, and thereby decrease ectopic or abnormal firing with in damaged, malfunctioning, pain producing parts of the nervous system. Referral to a Pain Clinic may be helpful in guiding further treatment or complex pharmacotherapy for the patient with chronic neuropathic pain. Other treatments might include nerve blocks, TENS units, biofeedback, psychological and physical therapies.
E. Are treatments available for the additional factors which contribute to the pain? For pain treatments to be fully effective it is critical that all factors be treated simultaneously. If depression or anxiety are contributing, these are highly treatable conditions. Appropriate therapy with antidepressants or anxiolytics, together with psychotherapy, should be instituted early in the treatment process. Somatization and hypochondriasis are more chronic and relatively more refractory conditions. However, here too, psychotherapeutic and possibly psychopharmacologic interventions may be critically helpful components of the treatment for the chronic pain patient. An understanding of these factors will also help to guide all aspects of the patients treatment. For example, the patient who is prone to high levels of somatization, is a relatively poor candidate for invasive treatments, since such interventions are likely to exacerbate the patients somatic concerns and preoccupation. 31 Secondary gain is not an illness, nor is it treated, but we must pay attention to this factor. The physician must be careful not to alter the balance of secondary losses versus secondary gains in such a manner that tips the scales in the direction of greater illness and disability. Psychotherapy may also help the patient to recognize that disability is associated with greater losses and fewer gains than the patient might consciously or unconsciously realize. Factitious disorders, when identified, indicate that treatment must focus on intensive psychotherapy (although it is difficult to get the patient to be compliant with such treatment). Malingering is a moral and legal problem rather than a medical problem, but recognition of malingering can help to avoid unnecessary, costly, and potentially dangerous treatments. 15, 31 Other health factors, such as sleep, weight, and overall conditioning can also contribute to the problem. Like most of the above associated factors, pain can cause these problems and then, in a vicious cycle, be exacerbated by these same problems. Appropriate medical management focused on these problems can be most beneficial. F. Are there other medical or psychosocial conditions which should influence the choice of treatment? 31
The previous questions have focused on understanding the nature of the patient's pain and the additional factors contributing to the problem. When treating the patient it is important to consider what other conditions or factors (which are not directly contributory to the pain) might influence the choice of treatment. Other medical conditions, such cardiac or pulmonary disease, may be relative contraindications for some medications or for various blocks. Examples include arrhythmias (especially bundle branch blocks) as a relative contraindication for tricyclic antidepressants or for right stellate ganglion blocks, bullous emphysema as a contraindication for intercostal nerve blocks, and pulmonary disease in general as a cautionary note regarding the use of narcotics (especially intravenous narcotics). Psychiatric conditions may also influence the choice of treatment. A history of mania or bipolar disorder is a relative contraindication for the use of antidepressants, a history of recent drug abuse indicates a need to avoid narcotics or benzodiazepines where possible, and high levels of somatization or anxiety argue against the use of invasive techniques or therapies. Some of the newer and more invasive pain therapies, such as spinal dorsal column stimulators and intrathecal morphine pumps, require that the patient have a good understanding of the medical condition and be highly compliant with complex treatments. IV. THE METHODOLOGY OF THE PAIN ASSESSMENT The previous section reviewed the overall questions that the care provider should keep in mind when assessing a complaint of pain. The next section provides some of the specifics of the data gathering process. A. History6, 12
1. How the pain developed? Was there an injury, illness, or major stress associated with the start of the pain?
This may give clues regarding any underlying pathology. Did the pain start immediately after the injury or was there a delay of weeks or months? Neuropathic pains such as entrapment neuropathy or complex regional pain syndromes (RSD) frequently development weeks to months after the injury. Is the pain associated with any treatment or medication? Headaches may occur as a rebound phenomena, associated with the use of analgesics.Occasionally, physically manipulative therapies may exacerbate a painful condition. Has the condition been stable or deteriorating? Ongoing deterioration mandates a more aggressive search for underlying pathology and possible interventions. Worsening low back pain, especially with deteriorating neurologic signs, may require surgical intervention; as opposed to stable, chronic low back pain, where more conservative measures are usually more appropriate. 2. Description of the pain. What are the adjectives used to describe the pain? The patient's description of the pain can help determine the type of pain.See the previous section on categories of pain. The patient's choice of adjectives may also provide clues regarding the emotional impact of the pain. Are there associated symptoms, such as nausea or sweating, flushing, or sensations of hot or cold in the affected area? These symptoms may indicate a autonomic or sympathetic component of the pain. How intense is the pain? There is tremendous individual variation in the perception of the intensity of pain. Yet obtaining this information is very important to help gauge the impact of the pain, and for the monitoring of change or progress. Standardizing the pain description. The Visual (or Verbal) Analog Scale (VAS) is the most common method for assessing pain intensity, and its change over time.
No pain
Worst possible pain
The patient is presented with a 10 cm line, labeled as above, and asked to mark an `X' on the line indicating the intensity of their pain. The result is then measured with a metric ruler and scored between 0 - 10. The same scale can be given verbally by asking the patient, "On a scale of 0 to 10, with 0 meaning no pain, and 10 meaning the worst pain you can imagine, how much pain are you having now?" These scales can also be used to assess the range of the patient's pain by asking them to indicate their level of pain at its worst, its best, and its average. Similar scales are available for children. The FACES scale shows cartoon-like pictures of faces in various degrees of distress. The child is asked to choose the one that shows how much pain she is having. Standardized, multiple choice lists of pain adjectives are also useful, especially in a pain clinic setting. The McGill Pain Inventory is the most commonly used of these. It may also be useful to ask the patient to keep a diary of their pain problem. The downside to this approach is that it asks to the patient to maintain a focus on their pain; this may be counterproductive to their treatment. 3. The location of the pain and any spread. Pain drawings. Ask the patient to draw the distribution of their pain on an outline of the human body. Is the pain limited to the distribution of a root or peripheral nerve? Such distributions help to isolate the site and possibly the source of the pathology. Pain which does not have a limited distribution, but instead occurs in multiple sites or has a diffuse distribution, implies a systemic etiology. Is the pain in a stocking or glove distribution? A stocking or glove distribution does NOT indicate a psychogenic etiology.Such a distribution is entirely consistent with a Complex Regional Pain Syndrome (RSD or causalgia), or if bilateral with a peripheral neuropathy. Could the pain be referred from another site? Possibly because of the convergent structure of the nervous system, it is common for pain to be referred from a separate, possibly quite distant site. This is most commonly seen if the site of painful stimulation or irritation is visceral or muscular. 7
4. How does the pain fluctuate over time. Is there any daily, monthly, or seasonal pattern associated with the pain? The physician is looking for clues as to the etiology of the pain. Arthritic conditions may be worse in the mornings and during cold seasons. Migraine headaches may have occur in patterns associated with a variety of factors such as stress or menstrual cycling. Are there aggravating or alleviating factors which lead to exacerbation or reduction of the pain? Understanding aggravating and alleviating activities can help to pinpoint the diagnosis or refine the treatment. Low back pain which is worse walking uphill suggests a discogenic etiology. If the pain is worse when walking downhill, this points more to facet disease or foraminal stenosis. Some headache syndromes are triggered by specific dietary elements such as alcohol or monosodium glutamate (MSG). Identifying and avoiding these triggers can be most helpful. 5. What is the overall level of patient function? Are there changes in the patients weight and sleep pattern? Such changes suggest the need to investigate further regarding possible depression or cancer. What is the patient's employment status? Issues of lost productivity and income or workers compensation may affect the patient's emotional and motivational state. It is usually a priority to enable the patient to return to work as soon as possible--vocational rehabilitation may be a crucial part of the treatment. What are the patient's daily activities?
Understanding the day-to-day activities of the patient and what activities are limited by the pain will help the clinician to focus the physical and psychological rehabilitation process. If the patient has acquired a totally disabled lifestyle, then it may be important to help the patient understand that he is capable of some productive functioning. Is the patient engaging in any exercise and physical activity? Physical activity is critical for preventing further physical deterioration. Exercise is often a crucial part of the treatment process; however, it is important that the patient's physical activities be reviewed, since some activities may exacerbate the problem. What is the quality of the family and personal relationships? Chronic pain may lead to irritability and personality changes. Such changes may in turn lead to the deterioration of personal relationships. Such problems should be identified so that interventions can be initiated. Families typically need some education regarding adaptive responses to chronic pain. Overly solicitous responses may reinforce the patient's pain behaviors and undermine the relationship. 6. What treatments have been attempted? Identifying prior treatment failures will not only prevent unnecessary repetition, but can also help guide the diagnosis. For example, if a variety of sympathetic blocks have not, even briefly, alleviated the pain, then perhaps the pain is not sympathetically mediated. B. Past Medical History In the assessment of the patient with pain, the past medical history should include the following information: 1. Do other medical problems relate to the patient's complaint of pain? For example, a history of diabetes or alcoholism point towards diagnoses of neuropathy. For headaches or abdominal pain, have there been any recent medication changes associated with the onset of the problem. 2. Do other medical problems potentially affect the choice of pain treatments? As noted above, the patient's medical condition may present relative contraindications to various medications or procedures. 3. Does the patient have any prior or current substance abuse history? Treating chronic pain with narcotics requires special caution with the addiction prone patient. In some patients it may not be possible to use narcotics except in the most dire circumstances.
C. Current Medications 1. Dosage and pattern of use Obtain a complete list of the patient's medications and usage. Include over-the-counter medications. 2. Effectiveness Note the effectiveness of medications. Analgesics (even if only partially effective) should lead to some increase of function in at least one sphere of the patient's life. 3. Drug tolerance The chronic use of some drugs is associated with tolerance (the gradual need to increase the dose to maintain the same effect). Tolerance does not imply addiction, but the development of physiologic tolerance can be hard to distinguish from inappropriate drug seeking behavior.
4. Potential for drug interactions and toxicity Acetaminophen 13 The analgesic ceiling for a single oral dose is reached at 1000 mg. There is the potential for hepatic toxicity; therefore, the daily use should not exceed 4 grams, and extra caution is warranted if the patient is malnourished or abuses alcohol. Nonsteroidal Antiinflammatory Drugs (NSAIDs) 22, 25 Prostaglandins are important factors in the maintenance of renal perfusion in those patients with hypovolemia or reduced renal blood flow. These patients and the elderly are at increased risk for renal damage from NSAIDs. Prostaglandins help maintain gastric mucosal integrity; therefore, NSAIDs may also produce gastroduodenal damage. All
NSAIDs may provoke asthmatic reactions in patients with underlying asthma or sensitivity to aspirin or other NSAIDs. These drugs inhibit platelet function and are associated with increased bruising; they should be discontinued before surgery or other invasive procedures. NSAIDs are relatively contraindicated in patients treated with anticoagulants. There is increased risk of gastrointestinal bleeding and coumadin levels may be altered secondary to displacement from protein binding sites. Tricyclic Antidepressants 9, 16 The side effects and toxicity of tricyclics can be exacerbated secondary to drug interactions. Tricyclic levels are increased by the selective serotonin reuptake inhibitors, especially fluoxetine and paroxetine. Neuroleptics, cimetidine, methylphenidate, and estrogens may also increase tricyclic levels. Additive side effects may occur with alcohol, sedatives, or other anticholinergic medications. Potentially fatal interactions may occur if tricyclics are given to patients on monoamine oxidase inhibitors (MAOIs). Hypertension and hyperpyrexia may occur secondary to administration with sympathomimetics.
Anticonvulsants 1, 16 Carbamazepine has a similar structure to tricyclic antidepressants, it may weakly potentiate tricyclic side effects and have there is a risk of interactions with MAOIs. Disulfiram and isoniazid may increase phenytoin levels. Phenytoin may displace coumarin from protein binding sites, and may alter digoxin levels. Propoxyphene may increase carbamazepine levels. Check for altered levels of other antidepressants.
Opioids 31, 32 Opioid side effects can vary from one narcotic drug to another in an unpredictable manner for each individual. Meperidine, at doses greater than 1 gram per day, is associated with the additional risk of seizures. Meperidine combined with monoamine oxidase inhibitors (MAOIs) can trigger a fatal hyperpyrexic reaction. Opioid side effects may be enhanced by alcohol or sedatives. Propoxyphene may also cause seizures, overdose may also cause fatal heart block; furthermore, propoxyphene may increase carbamazepine levels. Sudden discontinuation of opioids is associated with influenza-like symptoms of withdrawal:
• • • • • • • • • •
restlessness & insomnia nausea & vomiting diarrhea backache leg pain yawning lacrimation rhinorrhea mydriasis muscle cramps
If it is necessary to withdraw a patient from an opioid medication, it is best to decrease the dose by approximately 10% every 24 to 72 hours--further individual tailoring may be necessary.
D. Physical Examination 6, 12 Introduction In pain assessments, there are rarely tests available that will "make the diagnosis." Instead the clinician must rely upon the presenting signs and symptoms. The history will often generate a differential diagnosis; the physical exam will often lead to the selection of the primary diagnosis, and occasionally a test will help to confirm this diagnosis. For example, an MRI scan which reveals an L5-S1 disc herniation is only helpful as far as it confirms or contradicts the findings of the history and physical examination. When preparing to do a physical examination it is important to warn the patient as you approach potentially painful areas. It is also good policy to use chaperones whenever examining patients of the opposite sex. 1. Mental status exam cognitive functions--impairment implies the presence of delirium or dementia mood and affect--provide clues regarding the emotional state of the patient and the presence of anxiety or depression thought process & content--check if the patient is having suicidal ideation, or if there are signs of thought disorder and possible psychosis judgment and insight--many treatments, such as the prescribing of narcotics or the use of relaxation training, require intact judgment and insight 2. Vital signs Vital signs are often elevated in acute pain.
3. Inspection posture, guarding, splinting--if chronic, these behaviors may compound and exacerbate the pain problem, as the patient places abnormal stresses on the body. color and pigmentary changes--these skin changes may indicate sympathetic dysfunction, inflammation, or a prior herpes zoster eruption. sweating--abnormal or asymmetric sweating indicates sympathetic dysfunction. piloerection, gooseflesh (cutis anserina)--areas involved in neuropathic pain may briefly demonstrate this after disrobing. hair, nail changes--evidence of neuropathic injury or sympathetic dysfunction. swelling, edema--indications inflammation or sympathetic dysfunction. atrophy--may indicate guarding and lack of use, or denervation. poor healing--indicates poor perfusion possibly associated with ischemic injuries, diabetic neuropathy, or sympathetic dysfunction. 4. alpation & Musculoskeletal exam temperature changes--indicates inflammation or altered perfusion associated with sympathetic dysfunction. edema--subtle, subcutaneous edema can be appreciated by wrinkling the skin over affected and unaffected areas. Affected areas will not wrinkle into fine lines, but will look more dimpled, like orange peels. This indicates neural injury with denervation or sympathetic dysfunction. muscle tenderness--examination of muscles may reveal tender areas or actual trigger points. The extent of the tenderness and the amount of pressure required to elicit pain should be observed. Reproduction of the patient's characteristic pain is particularly noteworthy. joints--can be examined for effusions, ROM, and pain with compression or distraction 5. Neurologic Cranial nerve assessment--is especially crucial in the evaluation of head and neck pain. Physical examination for radiculopathy 20, 30 UPPER EXTREMITIES
C5
Motor Reflex Sensory Pain Motor Reflex Sensory Pain Motor Reflex Sensory Pain
C6
C7
C8
Motor Reflex Sensory Pain Motor Reflex Sensory Pain
raised elbows (axillary n.) biceps (musculocutaneous n.) upper, lateral arm, near/over deltoid (axillary n.) upper, lateral arm, never below elbow elbow supination (radial n.) / pronation (median n.) brachioradialis (radial n.) lateral forearm (musculocutaneous n.) lower lateral arm, possibly into thumb elbow extension (radial n.) triceps (radial n.) over triceps, mid-forearm, and middle finger deep pain in triceps, front and back of forearm & into middle finger thumb index pinch (ant. interosseus n. off median n. at the elbow) medial forearm (antebrachial cutaneous n.) medial forearm, into the 2 medial fingers finger abduction (ulnar n.) medial arm (brachial cutaneous n.) deep pain in axilla & shoulder w/ some radiation down inside of arm
T1
Cervical spondylosis or disc protrusion can produce cord compression (upper motor neuron signs) or root compression (lower motor neuron signs). C5-6 disc protrusions are the most common cervical disc problems; they can compress the C6 root and also produce C7 upper motor signs.
LOWER EXTREMITIES: L2 Motor Reflex Sensory hip flexion (femoral n.)
L3
L4
L5
S1
often no loss, anterior midthigh (femoral n, & lat. femoral cut br.) Pain across thigh knee extension (femoral n.), thigh adduction (obturator Motor n Reflex hip adductors (obturator n.) Sensory often no loss, anterior thigh just above the knee cap Pain across thigh Motor inversion of the foot (tibial & peroneal n.) Reflex knee jerk (femoral n.) Sensory medial lower leg Pain across knee & down to medial malleolus Motor dorsiflex great toe (deep peroneal n.) Reflex Sensory especially dorsum of the foot (peroneal n.) back of thigh to lateral lower leg, dorsum & sole of foot, Pain esp. big toe Motor eversion of the foot (peroneal n.) Reflex ankle jerk (tibial n.) Sensory behind the lateral malleolus Pain back of thigh and calf to lateral foot
It is important to note that lumbar disc lesions can only cause root (lower motor neuron) syndromes. Hyperreflexia is a sign of disease or injury at a higher level, in the spinal cord or brain. 95% of lumbar disc lesions involve L5 or S1.
Gait Observation of gait can help identify weakness or pain (antalgic gait). Distortion of the patient's gait may also lead to improper muscle use and strain, leading to further pain. Sensory dysfunction Neuropathic pain is associated with nerve injury or dysfunction. Frequently, it is possible to demonstrate sensory impairment in one or more modalities including temperature, light touch, sharp/dull discrimination, position, and vibration. The examiner should test the involved areas for at least one function of large fibers, such as vibration or light touch, and one small fiber function, such as temperature (using and ice cube or alcohol swab) or sharp/dull discrimination. The examination should also make note of the presence and distribution of abnormal pain responses. Table of Terms 26 Pain Allodynia Analgesia Anesthesia An unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain due to a stimulus which does not normally provoke pain. Absence of pain in response to stimulation which would normally be painful. Pain in an area or region which is anesthetic.
dolorosa An unpleasant abnormal sensation, whether spontaneous or evoked. An increased response to a stimulus which is Hyperalgesia normally painful. Increased sensitivity to stimulation, excluding the Hyperesthesia special senses. A painful syndrome characterized by an abnormally Hyperpathia painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold. Diminished pain in response to a normally painful Hypoalgesia stimulus. Hypesthesia = Decreased sensitivity to stimulation, excluding the Hypoesthesia special senses. Noxious stimulus A stimulus which is damaging to normal tissues. An abnormal sensation, whether spontaneous or Paresthesia evoked. Dysesthesia Peripheral Nerve & Dermatome Map From DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p.809-10. Motor dysfunction--Assessment of motor strength can help identify neural injury and the roots or peripheral nerves involved. Grading of Muscle Strength Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 0% 10% 25% 50% 75% Zero Trace Poor Fair Good No evidence of contractility Slight contractility but no joint motion Complete motion but with gravity eliminated Barely complete motion against gravity Complete motion against gravity and some resistance Complete motion against gravity and full resistance
100% Normal
DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p. 768.
Abnormal Reflexes 39 Hyporeflexia --focal: indicates lower motor neuron pathology at the level of the peripheral nerve or root --generalized: peripheral neuropathies--diabetic, alcoholic, inflammatory (GuillainBarre). Myopathy may also cause hyporeflexia. Hyperreflexia --focal: indicative of upper motor neuron pathology; frequently associated with upgoing toes on testing of the Babinski's sign--this cannot be secondary to lumbar spine disease since there are no UMNs in the lumbar spine --generalized: suggestive of increased arousal, hyperthyroidism, drug toxicity Grading Deep Reflexes Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Grade 5 0 + ++ +++ ++++ +++++ Absent Diminished but present Normal Normal Hyperactive Hyperactive with clonus
From DeGowin EL, DeGowin RL: Bedside Diagnostic Examination, 3rd edition, Macmillan Publishing, New York, 1976, p.791. E. Diagnostic Testing 37
1. Radiographic
No matter which radiographic technique is used, the results must always be correlated with clinical findings. As the above table2, 4, 11, 17, 18, 19, 21, 23, 24, 27, 35, 40 of diagnostic tests for low back pain demonstrates, radiographic tests are far from perfect and serve best to confirm a clinically suspected diagnosis. Plain films--value is limited to demonstrating bony pathology, some soft tissue tumors can be seen Myelograms--involve the injection of contrast into the intrathecal space. For most of the common spinal diagnostic problems, CT or MRI are superior and free of the risk of postdural puncture headaches. omputerized Tomography (CT)--more bony detail and superior to MRI for bone or joint disease of the spine, including foraminal bony stenosis Magnetic Resonance Imaging (MRI)--superior soft tissue contrast and superior to CT or myelography for diagnosis of spinal disc disease or neural compression secondary to spinal stenosis. Also best for evaluating spinal alignment, infection, or tumor. Bone scans--radionuclide bone imaging identifies osteoblastic activity and can help with the diagnosis of bone tumor or metastatic disease, osteomyelitis, fractures, joint disease, avascular necrosis, and Paget's disease. 2. Diagnostic blocks 3 Nerve blocks with local anesthetics can help to distinguish focal from referred pain, somatic from sympathetically mediated pain, central from peripheral pain, and can help identify which peripheral nerves may be involved. This can help to guide treatment with further blocks or with other medical and surgical interventions. 3. Electromyography & Nerve Conduction Studies (EMG / NCS) These studies can assist in identifying and localizing functional lesions of peripheral nerves, motor units and muscle lesions. Such tests of function can be followed over time and complement the anatomic radiology studies. NCS generally reflect conduction in the larger, faster, myelinated nerves. 4. Somatosensory evoked potential testing (SSEP) SSEPs are better than EMG / NCS tests for assessing upper motor neuron diseases such as MS, syringomyelia, or spinal cord ischemia. SSEP testing involves the senses of touch, position, and vibration, rather than pain or temperature. 5. Other Quantitative Sensory Testing (QST)
Pain syndromes may represent dysfunction more specific to the small A-delta and C fibers. Testing of small fiber function is possible with devices which test thermal or electrical thresholds to perception and pain. Such testing is less invasive and may also be useful to monitor hyperesthetic responses. Fiber Type Innervation/Function 5, 8, 29 (Group) A-alpha (II) A-beta (II) Primary motor & propioception Mean Myelin Diameter (_m) +++ ++ ++ ++ + 15 8 6 3 3 1 Mean Conduction Velocity (m/sec) 100 50 30 20 7 1
Cutaneous touch & pressure (& motor fibers) A-gamma Muscle tone (spindle efferents) A-delta Mechanoreceptors, nociceptors, (III) and thermoreceptors B Sympathetic preganglionics Nociceptors, mechanoreceptors, C (IV thermoreceptors, sympathetic postganglionic .F. Psychological Evaluation
As discussed earlier, the clinician should always assess the patient's psychological state, and the emotions surrounding the pain problem. It is particularly valuable to inquire regarding:
• • • • • • • • • • • • •
Neurovegetative symptoms sleep disturbance appetite disturbance loss of energy loss of libido anhedonia impaired concentration suicidal ideation Impact of the pain on the patient's day-to-day activities work & finances personal relationships recreational pursuits
Factors suggesting the need for more formal psychological evaluation include:
• •
Evidence of mood or anxiety disorders Evidence of substance abuse
• • • • • • • • •
Evidence of psychotic disorder Evidence of cognitive impairment Evidence of overwhelmed coping capacities or suicidal ideation Evidence of prominent secondary gain Problems with hostility, anger, or personality disorder Suspicion of malingering or factitious disorder (e.g. inconsistent findings) Prolonged and extensive course of treatment failures Need for high dose opioids for non-malignant pain Assessment of suitability for aggressive invasive treatments
G. Differential Diagnosis After completing the data gathering process, it is time to consolidate the findings into a differential diagnosis. During this process the clinician should consider:
• • •
• • • •
The meaning of inconsistent findings? Consider psychogenic or malingering diagnoses, but beware that the emotional turmoil which surrounds chronic pain may falsely suggest these diagnoses. Be cautious about reaching a psychogenic diagnosis simply because the pain symptoms cannot be understood physiologically. The clinical and basic sciences of pain are rapidly progressing--what is not understood today may be understood tomorrow. Be wary of obvious diagnoses or therapies that were missed by other clinicians. Check with prior physicians about their findings. Do the signs and symptoms indicate the nature of the pain? nociceptive--suggesting tissue injury or inflammation · neuropathic--indicating central or peripheral dysfunction of the nervous system pain with mixed features --
