readiness for adjustment back into the community. However, chronic use may cause abnormal muscle movements and tremors in some patients. Safer treatments are being sought. Thus far, most drugs are successful in treating hallucinations and thought disorder. Clozapine, acts somewhat differently from other antipsychotics. It treats the approximately 30 percent of patients who are not helped by conventional medications. However, the drug can induce a potentially fatal blood disorder, agranulocytosis, in about one percent of patients. To prevent this disorder, patients must take regular weekly to biweekly blood tests, a precaution that makes the use of the drug very costly. Several new antipsychotics—risperidone, olanzapine and sertindole—are now available. They do not involve risk of angranulocytosis but may have other side e∑ects.
Neurological AIDS By the end of 2000, some 448,000 deaths and up to 774,000 infections from acquired immune deficiency syndrome (AIDS) had occurred in the U.S. This is dwarfed by the more than 21.8 million deaths and 58 million infections identified worldwide. While the principal target of human immunodeficiency virus (HIV) is the immune system, the nervous system also may be profoundly a∑ected. Some 20 percent to 40 percent of patients with full-blown AIDS also develop clinically significant dementia that includes movement impairment. Those a∑ected have mental problems ranging from mild di≈culty with concentration or coordination to progressive, fatal dementia. Despite advances in treating other aspects of the disease, AIDS dementia remains a mystery. Most current hypotheses center on an indirect e∑ect of HIV infection related to secreted viral products or cell-coded signal molecules called cytokines. Nonetheless, HIV infection appears to be the prime mover in this disorder since antiviral treatment may prevent or reverse this condition in some patients. Experts believe that serious neurologic symptoms are uncommon early in AIDS infection. But later, patients develop di≈culty with concentration and memory and experience general slowing of their mental processes. At the same time, patients may develop leg weakness and a loss of balance. Imaging techniques, such as CT and MRI, show that the brains in these patients have undergone some shrinkage. The examination of brain cells under a microscope suggests that abnormalities are present principally in subcortical areas. Neurons in the cortex also may be altered. Recent studies indicate that highly active combination antiretroviral treatment (‘cocktails’ of three or more drugs active against HIV ) is e∑ective in reducing the incidence of AIDS dementia. Such treatment also can e∑ectively reverse the cognitive abnormalities attributed to brain HIV infection. Despite this remarkable progress, some patients develop these problems and fail to respond to treatment, thus requiring 40
additional approaches to prevention and treatment of these symptoms as well as the common peripheral neuropathy that can aΩict those with AIDS.
Multiple sclerosis The most common central nervous system disease of young adults after epilepsy, multiple sclerosis (MS) is a life-long ailment of unknown origin that a∑ects more than 300,000 Americans. MS is diagnosed in individuals who are mainly between the ages of 20 and 50, with two of three cases occurring in women. MS results in earning losses of about $2 billion annually for families with MS. Although a cause has yet to be found, MS is thought to be an autoimmune disease in which the body’s natural defenses act against the myelin in the central nervous system as though it were foreign tissue. In MS, myelin is destroyed and replaced by scars of hardened “sclerotic” patches of tissue. Such lesions are called “plaques,” and appear in multiple places within the central nervous system. This can be compared to a loss of insulating material around an electrical wire, which interferes with the transmission of signals. Some nerve fibers are actually cut in association with the loss of myelin. Siblings of people with MS are 10 to 15 times more likely than others to be aΩicted by the disorder. In addition, the disease is five times more prevalent in temperate zones, such as the Northern United States and Northern Europe, than it is in the tropics. Thus, genetic and environmental factors are probably involved in the cause. An infection acquired during the first 15 years of life may be responsible for triggering the disease in a genetically susceptible individual. The most common symptoms are blurred vision, awkward gait, numbness and fatigue. These can occur singly or in combination, vary in intensity and last from several weeks to months. In some patients, symptoms include slurred speech, weakness, loss of coordination, uncontrollable tremors, loss of bladder control, memory problems, depression and paralysis. Muscle spasticity can a∑ect balance and coordination, causing pain and involuntary jerking movement—and, if untreated, can create contractures or the “freezing” of a joint that prevents movement. MS cannot be cured at present, but several medications control relapsing forms of MS. A wide range of medications and therapies are available to control symptoms such as spasticity, pain, fatigue, mood swings and bladder, bowel or sexual dysfunctions. Steroids, which have been used in MS for three decades, e∑ectively shorten attacks and speed recovery from MS-related optic nerve inflammation. Promising new agents to control MS or to alleviate its symptoms are in clinical trials.
Down syndrome Down syndrome, the most frequently occurring chromosomal abnormality, appears in one out of every 800 to 1,000 babies