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There are some risks involved with this procedure. While it is possible to experience an allergic reaction to the dye, new contrast agents have lowered the risk of a severe reaction to less than one in 80,000 exams. Blood vessels may be damaged at the puncture site, anywhere along the vessel during passage of the catheter, or at the dye injection site.

Techniques have been modified recently to allow for treatment in addition to diagnosis; in balloon angioplasty, small balloons can be inflated at the tip of a catheter to expand a narrowed or blocked segment of artery. other material can be injected to reduce or shunt blood supply away from a tumor, and medication to control bleeding or treat tumors can be infused directly into the local blood supply targeted at individual organs.

aniracetam One of a class of nootropic drugs that some studies suggest may be capable of improving cognitive performance on a number of intelligence and memory tests. Its chemical structure is similar to piracetam, a drug being investigated in the treatment of Alzheimer's disease.

Studies suggest it stimulates the function of certain brain receptors. Both long- and short-term memory improvement has been shown in research. It appears to be a general enhancer of transmitter release for a number of transmitter systems.

Aniracetam is not approved for distribution in any country. other names for aniracetam include Draganon, RO 13-5057, and Sarpul.

anomia A type of aphasia involving the inability to verbalize the names of people, objects, and places. It appears to relate to speech output, since patients usually have no problem understanding when the object is named for them.

anoxia The complete disruption of oxygen supply to a given cell. This loss of oxygen causes a disruption of cell metabolism and can be fatal to the cell unless it is corrected within a few minutes. Anoxia refers to oxygen deprivation, as opposed to ischemia, which produces a loss of oxygen and other blood constituents. (See also hypoxia.)

anterior commissure A collection of nerve cells that connects the brain's two hemispheres. It is smaller and appeared earlier in evolution than the corpus callosum. Recent research has suggested that in men, this part of the brain is smaller than in women, even though men's brains are generally larger than women's brains. The larger commissure in women may help explain, at least in part, why the two hemispheres of the female brain seem to work together on activities ranging from language to emotional responses.

See also cerebral commissure.

anterior communicating artery A short artery located in the forebrain that connects the two arteries in the front of each hemisphere. Aneurysms often occur along this artery, which can cause a type of amnesia when the aneurysm bursts, damaging the forebrain.

See also aneurysm, brain; anterior communicating ARTERY.

anticholinergics Agents that disrupt acetylcholine transmission by blocking cholinergic receptors, preventing acetylcholine release or completely depleting neurons that use acetylcholine.

anticoagulant drugs and the brain This group of drugs prevents abnormal blood clotting and is used to prevent and treat stroke or transient ischemic attacks. If the drugs are given by injection, they begin to work within a few hours; those given by mouth work within a day. They increase the effect of an enzyme that blocks the activity of coagulation factors that are needed for blood to clot.

By interfering with the blood-clotting mechanism, these drugs can prevent an abnormal blood clot from forming; if a clot already exists, the drugs can stop it from growing larger and reduce the risk of a piece of it breaking off (embolus) and blocking another blood vessel. Unlike thrombolytic drugs, these drugs do not dissolve clots that already exist.

anticonvulsant drugs and the brain This group of drugs is used to prevent seizures or to interrupt a seizure taking place by inhibiting the excess elec trical activity in the brain and blocking its spread. Anticonvulsants include carbamazepine, clon-azepam, diazepam, ethosuximide, phenobarbital, phenytoin, primidone, and valproic acid.

The choice of drug is determined by the type of seizure; in long-term seizure prevention, more than one type of drug may be needed.

Adverse effects include reduced concentration, memory problems, poor coordination, and fatigue.

See also epilepsy.

antidepressant drugs and the brain Drugs that appear to correct a chemical imbalance or dysfunction in the brains of depressed people by boosting the level of neurotransmitters. Each of the major classes of antidepressants, which include

MONOAMINE OXIDASE (MAO) INHIBITORS, CYCLICS and serotonin inhibitors—affect different neurotransmitter systems in different ways.

Most of these drugs usually take at least 10 days before they begin to work and up to two months before they are fully effective; they all carry some type of side effects of varying intensity.

The complex array of various brain chemicals and processes that influence depression tend to differ from one patient to the next; because there is no foolproof way to identify which neurotransmit-ters may be causing depression, prescribing antide-pressants may be a trial-and-error process until the right one is found.

For many people, the first antidepressant is often not the right antidepressant. In fact, only a little more than half of all patients who are given antidepressants find relief with their first prescription. No one is quite sure how or why antidepres-sants work, and no one can predict who will respond to which drug. The best a physician can do is to look at a person's symptoms and try to match those symptoms with an antidepressant.

There is no one miracle antidepressant that works better than any other, all the time, for everybody. Because depression itself is a complex disease with many causes, doctors must choose among a wide range of antidepressants that work on different brain systems and affect different processes.

Cyclic antidepressants are a class of traditional drugs that treat depression by boosting the level of several different neurotransmitters (norepinephrine, epinephrine, serotonin, and dopamine) by blocking their reabsorption. MAo inhibitors destroy enzymes responsible for breaking down monoamine neurotransmitters, boosting the neu-rotransmitter levels. in general, MAois are used to treat those who do not respond to tricyclics. Some of the newest antidepressants (called selective serotonin reuptake inhibitors, including prozac) interfere with the reuptake of one specific neuro-transmitter (serotonin).

Antidepressants include the tricyclics amitripty-line, amoxapine, clomipramine, desipramine, dox-epin, imipramine, nortriptyline, and protriptyline; the tetracyclic maprotiline (Ludiomil); monoamine oxidase inhibitors (MAOIs) isocarboxazid (Mar-plan), phenelzine (Nardil) and tranylcypromine; the selective serotonin reuptake inhibitors (SSRis) fluoxetine, paroxetine, citalopram, fluvoxamine and sertraline; and the structurally unrelated compounds bupropion, nefazodone, mirtazapine, ven-lafaxine and trazodone. lithium is another antidepressant used to treat bipolar disorder (manic depression).

Adverse Effects

Side effects from antidepressants generally fall into three categories: Sedation; dry mouth, blurry vision, constipation, urinary problems, increased heart rate, and memory problems; and dizziness on standing up (orthostatic hypotension). Many anti-depressants can produce rapid heartbeat, tremor, and sexual problems (loss of interest or inability to reach orgasm). Those that interfere with dopamine (such as Wellbutrin and Asendin) may produce movement disorders and endocrine system changes. Blocking serotonin may create stomach problems, insomnia, and anxiety.

Those that work on the other side of the synapse, blocking receptors that pick up neuro-transmitters, have other side effects, depending on which receptors are affected. Blocking histamine H1 receptors produces weight gain and sedation; muscarinic receptor blockade causes dry mouth, constipation, blurry vision, and memory problems.

This is why a tricyclic such as amitriptyline (Elavil) causes so many side effects—it blocks the absorption of both norepinephrine and serotonin, plus four different receptors (Alpha1, Dopamine D2, Histamine H1 and muscarinic).

Each drug has a profile of its own particular side effects. Tricyclics often cause dry mouth, constipation, sedation, nervousness, weight gain, and diminished sex drive. MAois interact with certain foods and other medications to produce potentially fatal high blood pressure. Such antidepressants as the SSRIs (including Prozac, Paxil, and Zoloft) produce fewer side effects than MAOIs or tricyclics because they affect fewer brain pathways, but nausea, headache, and sexual problems may occur.

Still, even though a drug is characterized by certain side effects, it does not mean a patient will experience any of them. in addition, many antide-pressants can be taken before bed so that the side effects will occur during sleep. if a bedtime dose makes a patient too sleepy the next morning, a dose at dinner may be a better idea. A physician can work with a person's schedule to find the dosage timetable that works best.

Many antidepressants lower sex drive; they might cause impotence or interfere in orgasm. These side effects can be eliminated by adding another drug or changing the antidepressant.

antiemetic drugs A group of drugs used to treat nausea and vomiting; many work by reducing nerve activity at the base of the brain, suppressing the vomiting reflex. Antihistamine drugs and anti-cholinergic drugs also reduce the vomiting associated with vertigo by suppressing nerve activity in the balance center in the inner ear. Some antiemet-ics cause drowsiness, and some should not be taken during pregnancy because they may cause birth defects.

antioxidant A substance that chemically neutralizes free radicals (potentially harmful, highly-charged atoms on molecules). The most common free radical is a species of oxygen. in the brain, it can chemically interact with lipids (the main component of a cell wall), harming the neuron. New research suggests that antioxidants can neutralize free radicals before they begin to damage the brain's cells.

While a certain amount of free radicals are necessary to maintain proper body function, high levels are toxic to brain (and body) cells. Each day, the body generates thousands upon thousands of these free radicals in response to ultraviolet (UV) light, smoke, or pollution. Once activated, they destroy the cells in the brain and elsewhere in the body.

Some of the most common of the antioxidants include vitamins C (found in citrus fruits) and E (found in eggs, butter, and vegetable oil).

antipsychotic drugs A group of drugs used to treat psychoses (mental disorders involving loss of contact with reality) that block the action of certain neurotransmitters in the brain. These drugs are especially helpful in the treatment of schizophrenia and manic-depressive illness and are also used to calm or sedate patients with other mental disorders (such as dementia). The antipsychotic drugs include the phenothiazines (such as chlorpro-mazine, fluphenazine, perphenazine, thioridazine, and trifluoperazine) and various other medications including haloperidol, thiothixene, or lithium, which is used specifically to treat the symptoms of mania.

Most antipsychotics block the action of dopamine, a neurotransmitter found in the brain. Excess dopamine activity has been associated with many forms of psychoses. Lithium may control symptoms of mania by reducing activity in certain nerve impulse transmitters (serotonin and norepinephrine) that influence emotional status and behavior.

Adverse Effects

While these drugs have been helpful in controlling irrational thinking, aggressive behavior, and hyperactivity, serious side effects have appeared with increasing prominence. Especially troublesome is tardive dyskinesia, which began to appear in large numbers of people during the 1970s. This movement disorder is caused by high doses of neurolep-tic drugs for more than six months and appears primarily in adults and the elderly, although children can also be affected. Certain areas of the body are especially affected, including lips, eyes, jaw, arms, legs, and trunk; movements are usually involuntary and irregular and may be confused with parkinsonism (a disorder with symptoms similar to those of Parkinson's disease). Protruding tongue, lip and facial contortions with eye blinks and unplanned opening of the jaw are common. Slow, writhing movements and rapid, jerky expressions are also found, together with a rocking movement of the trunk. In some adults, the condition is irreversible.

Most of the antipsychotics also can cause drowsiness or lethargy; other possible side effects include dry mouth, blurry vision, and urinary problems.

anxiety An unpleasant emotional state ranging from mild discomfort to intense fear that some scientists believe may be the result of an elevated level of arousal in the central nervous system. This excess arousal would lead a person to react more excitedly and adapt more slowly to events surrounding him or her.

While a certain amount of anxiety is normal, it can become a symptom when the anxious feelings interfere with normal daily activities.

Symptoms

The most common symptoms of anxiety center around the chest, including palpitations (more forceful, irregular heartbeat), throbbing or stabbing pains, air hunger (inability to take in enough air), feelings of tightness in the chest, and a tendency to hyperventilate (sigh or overbreathe).

Other symptoms include headaches, neck spasms, back pain, and an inability to relax, together with restlessness, tremors, and sense of tiredness. The symptoms of anxiety may include a feeling of impending doom in the absence of any particular threat.

Stomach symptoms include dry mouth, feelings of distention, diarrhea, nausea, appetite changes, swallowing problems, and constant belching.

Treatment

Effective treatment may include reassurance, counseling, and therapy, together with antianxiety drugs (such as the benzodiazepines).

aphasia A neurological condition in which language comprehension or expression is disturbed due to brain dysfunction, affecting the ability to speak and write and/or the ability to comprehend and read the written word. Aphasia is a complete absence of these skills, while dysphasia refers to a disturbance in these abilities. A stroke or a head injury are the most common causes of brain damage leading to aphasia.

The speech problems caused by brain damage are different from speech problems caused by dysfunction in other parts of the body. Related disabilities with aphasia include word blindness (alexia) or writing problems (agraphia) .

Language functions within the brain are situated in the dominant cerebral hemisphere, especially in the Broca's and Wernicke's areas, and in the pathways that connect the two. Damage in this area is the most common cause of aphasia. A patient with damage to broca's area will experience problems in expressing language; speech is labored, slow, and dysrhythmic. However, the few words that are uttered are meaningful. A patient with a damaged Wernicke's area will experience problems in comprehending language; speech is fluent, but because of the comprehension problems, the meaning is disturbed. The patient will have problems choosing the right word or the correct grammatical form; writing is affected, and spoken or written commands may not be understood. Irrelevant words intrude.

In global aphasia, the patient has an almost or complete inability to speak, write, or understand spoken or written words, usually with widespread damage to the dominant cerebral hemisphere. This is the most severe type of aphasia. patients with nominal aphasia have problems naming objects or finding words, although the person may be able to choose the correct name from several offered. This condition may be caused by general cerebral dysfunction or damage to a specific language area. In mixed nonfluent aphasia, patients have sparse and effortful speech which resembles that seen in patients with severe Broca's aphasia. However, unlike people with Broca's aphasia, they only have limited comprehension of speech and cannot read or write beyond an elementary level. people with anomic aphasia have a persistent inability to supply the words for the things they want to talk about (especially significant nouns and verbs), referred to as word-finding difficulty. As a result, their speech is grammatically fluent but their speech is full of vague circumlocutions and expressions of frustration. They understand speech well, and in most cases, read adequately. Their problem in finding words is as evident in writing as in speech. In developmental aphasia, the problem is caused by delayed development of the central nervous system.

(For more information about aphasia, contact the National Aphasia Association; see Appendix I for address.)

Treatment

While aphasia may improve after a stroke or head injury, the more severe the aphasia, the less chance for improvement. Speech therapy is the primary treatment. The most effective treatment begins early in the recovery process. How much a patient will improve depends on the cause of the brain damage, the area of the brain that was damaged, the extent of the brain injury, and the age and health of the individual. Additional factors include motivation and handedness. Educational level may also be important.

Treatment strives to improve a person's ability to communicate by helping the person to use remaining abilities, to restore language abilities as much as possible, to compensate for language problems, and to learn other methods of communicating. Treatment may be offered in individual or group settings.

Individual therapy focuses on the specific needs of the person, whereas group therapy offers the chance to use new communication skills in a comfortable setting. Family involvement is often a crucial component of aphasia treatment so that family members can learn the best way to communicate.

apnea A prolonged cessation of breathing that can be caused by a brain stem damage from stroke,

TRANSIENT ISCHEMIC ATTACK, or HEAD INJURY.

Breathing is an automatic process that is controlled by the respiratory center in the brain stem;

these breathing centers send nerve impulses to the muscles of the chest and diaphragm that regulate lung expansion and deflation.

apoplexy An outdated term for stroke. Symptoms include sudden loss of consciousness, paralysis, or loss of sensation. The usual cause of apoplexy is the rupture of a brain artery or blockage by a clot.

appestat outdated term referring to the region of the brain within the hypothalamus that controls food intake. It is believed that appetite suppressants probably decrease the sense of hunger by altering the chemical characteristics in this area. Stimulating the appestat with electrodes provokes overeating in satiated lab animals.

appetite The desire for food that can be a pleasant sensation in anticipation of eating (as compared to hunger, an unpleasant feeling triggered by a physiological need for food). A person's appetite is regulated by two parts of the brain—the hypothalamus and the cerebral cortex—and is a sensation learned by enjoying a variety of food that smells and tastes good. When combined with hunger, it can provide the body with enough foods to maintain health.

How hungry a person feels at any one time is dependent on the amount of glucose circulating in the blood, which is monitored in the brain. Temporary appetite loss (known medically as anorexia) can be caused by a range of illnesses or minor emotional upsets. A more chronic loss of appetite may be the sign of a more serious illness or mental disorder. Physical causes of loss of appetite could include stroke, brain tumor, or brain injury causing damage to the hypothalamus or cerebral cortex. Other possible physical problems linked to appetite loss include stomach problems, gastric ulcers, or liver disorders (such as hepatitis).

In addition, some youngsters between ages two and four may refuse food; this is usually considered to be a normal phase of child development (if there are no other symptoms).

under normal conditions, healthy people can go hungry for a day or two without causing harm to the brain, as long as plenty of fluids are consumed.

appetite stimulants Although a variety of drugs have been prescribed (including alcohol and iron-containing elixirs), there are no known drugs that safely and effectively stimulate the appetite.

See also appetite suppressants; hunger.

appetite suppressants A group of drugs that suppress the appetite, probably by affecting the hypothalamus, the part of the brain that controls the desire to eat. Common appetite suppressants include diethylpropion, fenfluramine, mazindol, phenmetrazine, phentermine, and phenylpropano-lamine.

Side Effects common side effects include dry mouth, insomnia, dizziness, palpitations, and restlessness. Taking an appetite suppressant for more than six weeks may lead to dependence; however, newer drugs are less addictive than the amphetamines that used to be prescribed for appetite control.

Taking appetite suppressants with alcohol may cause increased sedation; taking them with caffeine may cause excessive stimulation. Taken with food or drinks containing tyramine (such as chianti, robust red wines, vermouth, ale, or beer) can cause an increase in blood pressure.

See also appetite stimulants; hunger.

apraxia The inability to make purposeful movements despite normal muscles and coordination because of nerve tract damage within the cortex (the main mass of the brain). People with apraxia usually know what they want to do, but they seem to be unable to remember the sequence of actions necessary to make the movement. The cortical damage may be caused by head injury, infection, stroke, or brain tumor that results in nerve tract damage within areas of the cortex responsible for translating the idea for a movement into the movement itself.

There are several different types of apraxia, depending on the part of the brain that has been damaged. A person who cannot carry out a spoken command to make a particular movement but who can unconsciously make that movement has ideo-motor apraxia. agraphia (writing problems) and expressive aphasia (severe speaking problems) are both special forms of apraxia.

Treatment

Recovery from head injury or stroke varies widely from one patient to the next; degree of recovery often depends on severity of the initial injury. Even in the best of situations, however, there is usually some deficit that remains, and it may require considerable effort for the patient to relearn the lost skill.

aprosodia A condition caused by damage to certain sections of the right brain hemisphere in which speech can become flat and emotionless or in which the emotional qualities of speech and gestures are not completely comprehended or executed. The speech of a person with this condition lacks cadence, stress, different tones, and emotional gestures.

arachnoid membrane The middle of the three layers (meninges) of connective tissue surrounding and protecting the brain and the spinal cord.

arachnoiditis A fairly rare condition characterized by chronic inflammation and thickening of the arachnoid membrane that may develop several years after meningitis or after bleeding beneath the arachnoid membrane. it may also be caused by a variety of diseases, such as syphilis, from head injury, or errors in diagnostic procedures such as myelography or lumbar puncture. Usually, however, no cause is ever found.

Symptoms

Although symptoms vary with the severity of the disorder, they can include epileptic seizures, headache, blindness, numbness, tingling, stinging leg pain, or spastic paralysis.

Arachnoiditis is a disabling disease causing intractable pain and brain deficits. As the disease progresses, some symptoms may worsen and become permanent. Few people with this disorder are able to continue working. in some cases, progressive paralysis may occur.

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