Neuritis

Neuritis, inflammation of peripheral nerves, characterized by sensory or motor disturbances that may take the form of pain (often burning), numbness, tingling (or pins-and-needles) sensations, hypersensitivity, or anesthesia, in the area supplied by the involved nerve; weakness or paralysis of the muscles innervated by the involved nerve may also take place. It is generally the result of such localized causes as injuries, pressure from arthritis involving the spine at the area where the nerve root exits, adjacent tumors, or prolonged exposure to extreme cold. Neuritis may also involve several nerves in different parts of the body. This type of neuritis usually affects the extremities. Infectious diseases, such as typhoid fever, malaria, syphilis, or tuberculosis, and diabetes, heavy-metal poisoning, alcoholism, vitamin deficiencies associated with pregnancy, beriberi, and pellagra are among the causes of certain types of neuritis.

Neuralgia

Neuralgia, recurrent pain along the path of a sensory nerve. Neuralgia may be caused by a disorder that affects a nerve, such as tooth decay or carpal tunnel syndrome, or it may accompany such diseases as diabetes mellitus or certain vitamin deficiencies. In some cases the cause of neuralgia cannot be determined. Whatever the cause, the affected nerve does not become inflamed and its tissues are not damaged or destroyed.

Trigeminal neuralgia is one of the most common forms of neuralgia, involving the trigeminal nerve, which carries sensation from the face, eyes, nose, mouth, and jaws to the brain. Trigeminal neuralgia is characterized by overwhelming sensations of stabbing pain that may be momentary or may last for minutes or hours. When it is short-lived, the condition is also known as tic douloureux. Trigeminal neuralgia may be relieved by analgesics such as aspirin, ibuprofen, and acetaminophen. In severe cases, surgery may be performed to reduce pressure on the nerve or to sever it.

In postherpetic neuralgia, pain occurs at a site earlier affected by herpes zoster, or shingles, in which blisters develop on the skin along the path of a nerve. Postherpetic neuralgia may last for weeks or months after the illness, but the pain may be alleviated with analgesics.

Myasthenia Gravis

Myasthenia Gravis, chronic disease marked by progressive weakness and abnormally rapid fatigue of the voluntary muscles. The muscles affected include those used in walking, breathing, chewing, and talking. A characteristic sign of the disease is drooping eyelids. Myasthenia gravis most often affects women between the ages of 20 and 30, but it can strike anyone after adolescence; after 40, it actually afflicts more men than women.

Myasthenia gravis is a noninherited autoimmune disease characterized by the presence of antibodies in the blood that destroy muscle-cell sites for the reception of acetylcholine molecules. Acetylcholine normally transmits signals between nerves and muscles, so when its receptors are destroyed it cannot induce muscle contractions. No cure for the disease yet exists, but it can be treated with drugs called anticholinesterases. These drugs are capable of inhibiting an enzyme, acetylcholinesterase, that breaks down acetylcholine in the body. Myasthenia gravis may also be relieved by surgical removal of the thymus and by a blood-cleansing process called plasmapheresis that eliminates the destructive antibodies.

Muscular Dystrophy

Muscular Dystrophy, crippling disease characterized by gradual wasting of skeletal muscle. As the disease progresses, symptoms include increased weakness and loss of muscle mass and function. Eventually a person with muscular dystrophy needs to use a wheelchair to move around. Four clinical forms of the disease are recognized, based on pattern of inheritance, age when symptoms are first noted, and distribution of the muscles earliest involved. Microscopic abnormalities of skeletal muscle are found in each type.

Muscular dystrophy has its origin in a genetic mutation, but the biochemical steps by which this genetic defect manifests itself in the degenerative process in the muscle are not known. Because specific treatment is not available, general measures, including physical and occupational therapy, are used. Genetic tests for mutations in the different genes causing muscular dystrophy provide rapid and accurate diagnosis for patients.

Malnutrition

Malnutrition, dietary condition caused by a deficiency or excess of one or more essential nutrients in the diet. Malnutrition is characterized by a wide array of health problems, including extreme weight loss, stunted growth, weakened resistance to infection, and impairment of intellect. Severe cases of malnutrition can lead to death. Deficiency diseases are usually associated with lack of vitamins or minerals. The effects of a vitamin or mineral deficiency on the body depend on the function of the particular nutrient lacking. For example, vitamin A is important for good vision, and severe deficiency of this vitamin may cause blindness. Because some vitamins and minerals have many functions, prolonged nutritional deficiencies can therefore have wide-ranging effects on health. Diets that lack a wide variety of foods may result in vitamin deficiency diseases. For example, in countries where people eat maize as the staple food and only few other foods, diets may lack niacin, a B vitamin. Such diets may cause pellagra, a deficiency disease characterized by dermatitis, diarrhea, and dementia.