Parkinson Disease

Parkinson Disease, disorder of the nervous system that affects muscle control. Marked by trembling of the arms and legs, muscular rigidity, and poor balance, Parkinson disease is slowly progressive, worsening over time. Eventually symptoms may cause problems with walking or talking and, in some people, difficulty thinking. Physicians do not know how to cure Parkinson disease, but drug therapy or surgery may alleviate some of the most troubling symptoms. The disease is named for British physician James Parkinson, who first described it in 1817. In a report describing six patients, Parkinson called the disorder paralysis agitans, Latin words that mean “shaking palsy.”

Parkinson disease develops as a part of the brain known as the substantia nigra degenerates. The substantia nigra is located in the midbrain, halfway between the cerebral cortex and the spinal cord. In healthy people, the substantia nigra contains certain nerve cells, called nigral cells, that produce the chemical dopamine. Dopamine travels along nerve cell pathways from the substantia nigra to another region of the brain, called the striatum. In the striatum, dopamine activates nerve cells that coordinate normal muscle activity. In people with Parkinson disease, nigral cells deteriorate and die at an accelerated rate, and the loss of these cells reduces the supply of dopamine to the striatum. Without adequate dopamine, nerve cells of the striatum activate improperly, impairing a person’s ability to control movement.

Parkinson disease most notably affects motor control (muscle activity). The disease progresses differently for each individual—symptoms develop swiftly in some people and slowly in others. Some Parkinson patients may develop problems that affect their intellect or ability to reason, or they may suffer from depression or anxiety.

Doctors look for the presence of four principal symptoms in patients they suspect may have Parkinson disease. Tremor (the involuntary shaking of limbs) is the major symptom for most people who have Parkinson disease, although at least a third of people diagnosed with the disease do not develop this symptom. Tremor typically begins in one hand but may eventually progress to the other hand, as well as to the arms, legs, and jaw.

There is no known cure for Parkinson disease—that is, no treatment that prevents the disease from progressing. But the symptoms of the disease can be controlled by various drugs such as Levodopa, and, in some cases, by surgery.

Anthelmintic Drugs

Anthelmintic Drugs, medicinal drugs used to rid humans or other host animals of infestations by parasitic worms such as tapeworms, roundworms, pinworms, trichinae, flukes, whipworms, schistosomes, and filariae. These drugs are also known as vermifuges. They act by attacking the worms' neuromuscular or respiratory systems, interfering with their metabolism, or making them more susceptible to attack by the host's macrophages. Anthelmintics include mebendazole, pyrantel pamoate, diethylcarbamazine, and niclosamide, among several others. The drugs are generally more effective against gastrointestinal infestations than muscular infestations.

Anesthesia

Anesthesia, absence of physical sensation in part or all of the body. The term more commonly refers to a reversible condition that is induced using anesthetic drugs. These drugs may be injected, inhaled, or applied directly to the surface of the body. It is used for surgery, obstetrics, dentistry, or other medical procedures. Induced anesthesia may be local, involving only part of the body, or general, involving lack of sensation in the entire body as well as a loss of consciousness. Localized anesthesia can also be a result of natural causes, such as nerve injury, leprosy, or diabetes. The lack of sensation caused by these conditions is not easily reversible, and patients’ unawareness of pain and other sensations can put them at risk of serious harm. This article focuses on induced anesthesia used in medical procedures.

Analgesic

Analgesic, class of drugs that relieve pain without causing loss of consciousness. The drugs range from the narcotic opium derivatives morphine and codeine (see Opium) to a wide range of nonnarcotics such as aspirin, acetaminophen (Tylenol), and ibuprofen (Advil), the last entering the nonprescription category in the United States in 1984. External analgesics include such drugs as hydrocortisone. Anesthetics in low doses, or local anesthetics such as benzocaine, are also analgesic in function (see Anesthesia).

Narcotics affect the central nervous system, are addictive, and are used only for severe pain; synthetic opiates such as propoxyphene (Darvon), pentazocine (Talwin), and butorphanol (Stadol) are also quite addictive. The nonnarcotics act by inhibiting the synthesis of prostaglandins in the body. Aspirin is a good anti-inflammatory but can irritate the stomach, whereas acetaminophen is less effective against inflammation. Ibuprofen is also an anti-inflammatory, but it can irritate the stomach, as well as aggravate high blood pressure and damage the kidneys. With the discovery of natural opiate receptors in the brain, and of hormones such as endorphins and enkephalins that link to them, research has been devoted to ways in which these systems could be made to ease pain.

Allergy

Allergy, exaggerated and sometimes harmful reactions to external substances, called allergens. Allergy may result from exposure to such common allergens as plant pollens from grasses, trees, or ragweed; animal danders, which are tiny scales shed from the skin and hair of cats and other furred animals; arachnids and insects, such as house dust mites, bees, and wasps; and drugs, such as penicillin. The most common food allergies are caused by eggs, milk, peanuts, shellfish, wheat, and chocolate.

Diagnosing and treating allergies is usually performed by an allergist, a physician trained to understand the body's immune response. When visiting an allergist for the first time, a patient is usually asked which substances seem to provoke symptoms and whether other family members have allergies. The doctor conducts a brief physical examination, looking in the nose, eyes, ears, and throat, listening to the chest, and examining the skin.

For most patients with allergies, medicines are used to begin therapy. Most forms of hay fever are easily managed with antihistamines, which relieve the symptoms, such as itching and sneezing, produced by histamine. Asthma is usually treated with medications taken orally or inhaled in vapor form using a metered-dose inhaler. Asthma medications include bronchodilators (drugs that expand the air passages) and anti-inflammatory steroids, which suppress the immune response that causes airway inflammation. In cases of anaphylactic shock, emergency treatment with an injection of adrenaline, also known as epinephrine, is required. This injection quickly widens blood vessels and opens up constricted airways.