Diseases

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Cerebrovascular disease
Cerebrovascular disease is a group of brain dysfunctions related to disease of the blood vessels supplying the brain. Hypertension is the most important cause; it damages the blood vessel lining, endothelium, exposing the underlying collagen where platelets aggregate to initiate a repairing process which is not always complete and perfect. Sustained hypertension permanently changes the architecture of the blood vessels making them narrow, stiff, deformed, uneven and more vulnerable to fluctuations in blood pressure. A fall in blood pressure during sleep can then lead to a marked reduction in blood flow in the narrowed blood vessels causing ischemic stroke in the morning. Conversely, a sudden rise in blood pressure due to excitation during the daytime can cause tearing of the blood vessels resulting in intracranial hemorrhage. Cerebrovascular disease primarily affects people who are elderly or have a history of diabetes, smoking, or ischemic heart disease. The results of cerebrovascular disease can include a stroke, or occasionally a hemorrhagic stroke. Ischemia or other blood vessel dysfunctions can affect the person during a cerebrovascular accident. Classification A transient ischemic attack (TIA) leaves little to no permanent damage within the brain. The symptoms of this include facial weakness, visual impairment, loss of coordination, or balance and a sudden headache. Severe blockage of the arteries to the brain is known as carotid stenosis. This generally results from high head trauma. Causes Cerebrovascular disease can be divided in to embolism, aneurysms, and low flow states depending on its cause. Major modifiable risk factors include hypertension, smoking, obesity, and diabetes.

Parkinson's disease
Parkinson's disease (also known as Parkinson's, Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills, speech, and other functions. Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and a loss of physical movement (akinesia) in extreme cases. The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain (specifically the substantia nigra). Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive. PD is the most common cause of chronic progressive parkinsonism, a term which refers to the syndrome of tremor, rigidity, bradykinesia and postural instability. PD is also called "primary parkinsonism" or "idiopathic PD" (classically meaning having

no known cause). While many forms of parkinsonism are idiopathic, "secondary" cases may result from toxicity most notably of drugs, head trauma, or other medical disorders. The disease is named after English apothecary James Parkinson, who made a detailed description of the disease in his essay: "An Essay on the Shaking Palsy" (1817). Classification The term Parkinsonism is used for symptoms of tremor, stiffness, and slowing of movement caused by loss of dopamine. "Parkinson's disease" is the synonym of "primary parkinsonism", i.e., isolated parkinsonism due to a neurodegenerative process without any secondary systemic cause. In some cases, it would be inaccurate to say that the cause is "unknown", because a small proportion is caused by genetic mutations. It is possible for a patient to be initially diagnosed with Parkinson's disease but then to develop additional features, requiring revision of the diagnosis. Signs and symptoms Parkinson's disease affects movement, producing motor symptoms. Non-motor symptoms, which include autonomic dysfunction, cognitive and neurobehavioral problems, and sensory and sleep difficulties, are also common but are underappreciated. Causes Most people with Parkinson's disease are described as having idiopathic Parkinson's disease (having no specific known cause). There are far less common causes of Parkinson's disease including genetic, toxins, head trauma, cerebral anoxia, and drug-induced Parkinson's disease.

Huntington's disease
Huntington's disease, chorea, or disorder (HD), is a progressive neurodegenerative genetic disorder, which affects muscle coordination and leads to cognitive decline and dementia. It typically becomes noticeable in middle age. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea and is much more common in people of Western European descent than in those from Asia or Africa. The disease is caused by an autosomal dominant mutation on either of an individual's two copies of a gene called Huntingtin, which means any child of an affected parent has a 50% risk of inheriting the disease. In rare situations where both parents have an affected gene, or either parent has two affected copies, this risk is greatly increased. Physical symptoms of Huntington's disease can begin at any age from infancy to old age, but usually begin between 35 and 44 years of age. If symptoms begin before about 20 years of age, they progress faster and vary slightly, and the disease is classified as juvenile, akinetic-rigid or Westphal variant HD. The Huntingtin gene normally provides the genetic information for a protein that is also called "Huntingtin". The mutation of the Huntingtin gene codes for a different form of the protein, whose presence results in gradual damage to specific areas of the brain. The exact way this happens is not fully understood. Genetic testing can be performed at any stage of development, even before the onset of symptoms.

This raises several ethical debates regarding the age at which an individual is considered mature enough to choose testing, the right of parents to test their children, and confidentiality and disclosure of test results. Genetic counseling has developed to inform and aid individuals considering genetic testing and has become a model for other genetically dominant diseases. The exact way HD affects an individual varies and can differ even between members of the same family, but the symptoms progress predictably for most individuals. The earliest symptoms are a general lack of coordination and an unsteady gait. As the disease advances, uncoordinated, jerky body movements become more apparent, along with a decline in mental abilities and behavioral and psychiatric problems. Physical abilities are gradually impeded until coordinated movement becomes very difficult, and mental abilities generally decline into dementia. Complications such as pneumonia, heart disease, and physical injury from falls reduce life expectancy to around twenty years after symptoms begin. There is no cure for HD, and full-time care is required in the later stages of the disease, but there are emerging treatments to relieve some of its symptoms. Self-help support organizations, first founded in the 1960s and increasing in number, have been working to increase public awareness, to provide support for individuals and their families, and to promote research. The Hereditary Disease Foundation, a research group born out of the first support organization, was instrumental in finding the gene in 1993. Since that time there have been important discoveries every few years and understanding of the disease is improving. Current research directions include determining the exact mechanism of the disease, improving animal models to expedite research, clinical trials of pharmaceuticals to treat symptoms or slow the progression of the disease, and studying procedures such as stem cell therapy with the goal of repairing damage caused by the disease.

Signs and symptoms
Symptoms of Huntington's disease commonly become noticeable between the ages of 35 and 44 years, but they can begin at any age from infancy. In the early stages, there are subtle changes in personality, cognition, or physical skills. The physical symptoms are usually the first to be noticed, as cognitive and psychiatric symptoms are generally not severe enough to be recognized on their own at the earlier stages. Almost everyone with Huntington's disease eventually exhibits similar physical symptoms, but the onset, progression and extent of cognitive and psychiatric symptoms vary significantly between individuals. The most characteristic initial physical symptoms are jerky, random, and uncontrollable movements called chorea. Chorea may be initially exhibited as general restlessness, small unintentionally initiated or uncompleted motions, lack of coordination, or slowed saccadic eye movements. These minor motor abnormalities usually precede more obvious signs of motor dysfunction by at least three years. The clear appearance of symptoms such as rigidity, writhing motions or abnormal posturing appear as the disorder progresses. These are signs that the system in the brain that is responsible for movement is affected. Psychomotor functions become increasingly impaired, such that any action that requires muscle control is affected. Common consequences are physical instability, abnormal facial expression, and

difficulties chewing, swallowing and speaking. Eating difficulties commonly cause weight loss and may lead to malnutrition. Sleep disturbances are also associated symptoms.Juvenile HD differs from these symptoms in that it generally progresses faster and chorea is exhibited briefly, if at all, with rigidity being the dominant symptom. Seizures are also a common symptom of this form of HD.

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