Degenerative Disease

---Degenerative disease affecting the brain range from the swiftly fatal to some that may produce only slight disability after many years. New understanding of brain chemistry now relieves symptoms in thousands of patients.

---Multiple sclerosis (literally, "multiple scars") alias disseminated sclerosis, is a disease that destroys in seemingly random fashion the myelin sheaths that help axons conduct signals from one neuron to another. The brain’s white matter, optic nerves and spinal cord can all be affected. Victims may first notice loss of vision in one eye, or partial paralysis. The symptoms may go, but others appear later, perhaps with eventual incapacity and other interference with brain function. Young adults are those most often hit. However, many patients remain active for years - some for decades. ACTH or steroids relieve acute inflammatory attacks, but life expectancy is shortened in most cases.

---Between he ages of 0 and 45, some 6 people per 100,000 develop Huntington’s chores ("dance"). Degeneration of cerebrum and basal ganglia cause involuntary movements of face, body, hands and feet, and victims of this rare hereditary affliction usually die in mental hospitals.

---Over 50’s are likeliest to contract motor-neuron disease, an especially unpleasant condition that attacks neurons which operate muscles. Speech or swallowing may become difficult, and there may be wasting and weakness in muscles of the tongue, hands, and later other parts of the body. Twice as many men as women contract motor-neuron disease, for which there is as yet no satisfactory treatment.

---Parkinson’s disease attacks mainly people aged 50 to 75, causing shaking limbs, shuffling steps, and poor balance. The face becomes blank, with staring eyes. Handwriting gets small and cramped, and fastening buttons may become difficult. The disease is progressive but affects some patients only slightly for many years.

---The immediate cause is degeneration of dark cells in the substantia nigra ("black substance") in the brainstem. These are major producers of the neurotransmitter dopamine, whose absence produces rigidity and tremor. Luckily, symptoms can now be relieved and life prolonged by giving anticholinergics and L-dopa, a substance that is taken up by the brain and there converted to dopamine.

---The quest for a true cure at last offers a glimmering of hope. Researchers grafting brain tissue from normal rate foetuses into brains of rats with Parkinson-like symptoms found that some grafts successfully took and improved the patients’ conditions. This suggests that one day, there might be a role for human grafts too. In 1981, other workers suggested stimulating the body to make dopamine by giving doses of synthetically made pterins - natural chemical agents that help to persuade amino acids to form neurotransmitters. In old age (sometimes earlier) brain atrophy due to impaired blood supply may impair mental faculties, producing Alzheimer’s dementia, in which patients become unable to think or remember, and selfish emotions override judgement. As senile dementia progresses, the brain’s highest, most recently evolved, centres stop working first. Last to go is the brainstem - the most primitive part of the brain.

Multiple Sclerosis

---This is a disease caused by an unknown agent, possibly by a virus, that attacks myelinated nerves. Nerves of the spinal cord, brainstem, cerebral hemispheres and the optic nerve may all be affected. In a diseased nerve, the myelin sheath surrounding the axon begins to erode. Hard (sclerotic) patches form, resulting in the interruption of nerve impulses, particularly in pathways concerned with vision, sensation and the use of limbs. Early symptoms include temporary loss of vision or double vision, unsteadiness in walking, and dizziness. Eventually, the disease results in permanent paralysis.

Huntington’s Chorea

---This rare, invariably fatal, hereditary disease resembles accelerate again. It is associated with degeneration of nerve tissue in the basal ganglia - particularly the caudate nucleus and putamen and occasionally the globus pallidus.

---Sufferers develop spasmodic movements, speech difficulties, and psychological disorders leading eventually to dementia. Huntington’s chorea is transmitted by an abnormal dominant gene. Only one parent need to possess this gene for 1 in 2 children to be at risk. By the time the disease develops - sometimes only in a person’s 50s or 60s - an affected person may have grandchildren with a 50:50 chance of developing this disease.

Parkinson’s Disease

---Parkinsonism (paralysis agitans) is another disease of the basal ganglia, especially the substantia nigra. The disease , which affects voluntary motor nerves, results in slowness and loss of movement (akinesia), muscular rigidity, and tremor which may at first be localised but spreads to many muscles as the disease progresses. Speech difficulties (dysarthria) and inability to perform everyday activities like washing and dressing may be experienced. The sufferer develops a characteristics stance with the knees and elbows slightly bent, the shoulders stooping and the chin sunk onto the chest. Rigidity of the facial muscles causes the face to take on a fixed, mask-like expression.

Senile Dementia

---Nerve cells do not divide, unlike most other cells in the body, so brain cells that die are never replaced. In old age, a poor supply of blood often leads to cells dying off very rapidly. This results in a general lowering of intelligence and the cessation of higher functions like memory and the ability to reason. However, only a minority of old people develop Alzheimer’s Dementia. Poor sight and hearing are more often due to deterioration of the ears and eyes than death of brain cells. Old age is not necessarily a time of decreasing intelligence and mental activity: vocabulary and the ability to use words often carry on improving, even into extreme old age.

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