In old age the brain tissue tends to degenerate. Inevitably this results in loss of mental abilities. In most individuals this change is minimal, and they retain their mental faculties till a very advanced age. In some however the disorder is clearly noticeable, and is called senile dementia. Dementia is a degenerative disorder, and patients with dementia have shrinking of the brain, with loss of nerve cells. Glial tissue, which provides support to the nerve cells, increases in amount. The cause of dementia of old age is unknown, but is is suspected that prolonged exposure to oxidants may be a factor.
Patients present with decreased memory and judgement, and alterations in personality. Emotional disturbances are common. The speech and ambulation may be affected. The diagnosis is not difficult, but several diseases should be excluded. These include head injury, hypothyroidism, intoxication, psychiatric diseases.
The treatment is symptomatic, and no specific therapy is available.
Alzheimer's disease is also a disease of the elderly. Clinically it resembles a severe form of senile dementia. The symptoms occur earlier, and are caused by a more widespread loss of nerve tissue.
Apart from senility and Alzheimer's disease, there are several causes of dementia.
brain tumours, atherosclerosis of the brain, other diseases of the brain
hormonal diseases such as hypothyroidism, Cushing's syndrome
Multiple sclerosis (Disseminated sclerosis)
Multiple sclerosis is a chronic illness associated with changes in the nerve tissue in the brain. The changes take the form of demyelination, or loss of the myelin covering of nerve fibers. Myelin is a whitish substance, that is present in some cells in nerve tissue (but not in the nerve cells themselves). It forms a covering around nerve fibers. The process occurs in a patchy form in the brain and spinal cord, and damages the nerve cells resulting in progressive neurological changes.
Multiple sclerosis is commoner in temperate areas, and rare in the tropics. A family history increases the likelihood of developing the disease. Most patients belong to the higher socioeconomic group. It is suspected that a virus or an autoimmune disease may be responsible.
Multiple sclerosis can occur at any age, and tends to be commoner in women than in men. The symptoms include disturbances of vision, speech, balance and movement, bladder control and general weakness. Some patients may have mild psychiatric changes. Most patients live over 20 years after diagnosis, and can carry out their normal activities for many years. The course is, however, progressive, and ultimately fatal. Prior to death most patients are bedridden, incontinent, and have episodes of fever and muscle spasms.
Treatment is difficult, and not uniformly successful. The most effective drug is adrenocorticotrophic hormone, ACTH, given in low doses over very long periods of time.