Other Forms of Chorea

Senile chorea (essential chorea) begins after age 60 and is unaccompanied by any particular neurobehavioral symptoms or a family history of chorea. Whereas some patients have caudate atrophy similar to that seen in HD, others have predominant putaminal degeneration. In occasional cases, genetic detection studies in these patients reveal that the correct diagnosis is actually HD. Treatment of the chorea is similar to that used for HD.

Paroxysmal dyskinesia is a chronic condition that becomes manifest by a sudden onset of transient choreoathetosis, dystonia, or both. The familial paroxysmal dyskinesias are subdivided into kinesigenic and nonkinesigenic disorders depending on whether or not they are induced by sudden voluntary movements. In the familial (autosomal dominant or recessive) kinesigenic paroxysmal choreoathetosis,

the movements are brief, usually lasting less than 3 minutes, and occur many times daily, sometimes up to 100 times a day). y Nonkinesigenic and exertional paroxysmal dyskinesias may also be transmitted as autosomal dominant disorders, and the movements in these forms tend to be more dystonic than choreic in nature. The episodes of dyskinesia are usually more prolonged (lasting 2 minutes to 4 hours) and less frequent (occurring three to five times a day). Attacks are precipitated by alcohol, coffee, fatigue, stress, or excitement. Kinesigenic dyskinesias respond well to anticonvulsant medications such as phenytoin, carbamazepine, or phenobarbital. In contrast, the nonkinesigenic dyskinesias respond poorly to most medical therapy, although some patients improve with clonazepam. y Pathophysiologically, these conditions appear to be an interface between movement disorders and epilepsy, since in some conditions assiduous electrode placement over the frontal and frontocentral regions may reveal epileptic spikes and phase reversals. y Secondary paroxysmal dyskinesias may be associated with structural lesions of the premotor cortex or basal ganglia, and specific causes include multiple sclerosis and hypocalcemia. y

Neuroacanthocytosis (NA) is a rare disorder with autosomal dominant, recessive, or even X-linked inheritance and is manifested by chorea, tics, dystonia, parkinsonism, self-mutilatory behavior, amyotrophy, areflexia, elevated creatine phosphokinase (CK), and other symptoms. y One of the most distinguishing features of NA is an eating dysfunction that is due to orolingual dystonia and is manifested by expulsion of food from the mouth by a protruding tongue. Involuntary vocalizations and parkinsonism also occur. Although the mechanism of acanthocyte formation in NA is unknown, abnormal protein to fatty acid ratios and in some cases abnormal erythrocyte surface antigens have been found. It is possible that, as in the periodic ataxias, some of the paroxysmal dyskinesias represent abnormalities of the calcium channel or other channelopathies. Acanthocytes in most patients can be seen in fresh blood smears, but erythrocytes may require incubation in normal saline for 3 to 5 minutes prior to wet mount preparation. CT or MRI of the head may demonstrate cerebral or caudate atrophy. PET scans reveal 42 and 54 percent reductions in putamenal and caudate fluorodopa uptake, respectively, and a 65 and 53 percent reduction in the D 2 receptor density in these areas.y Treatment may involve the use of dopamine-blocking agents in the form of neuroleptics (haloperidol, fluphenazine) or dopamine-depleting drugs (reserpine, tetrabenazine). As the disease progresses, most care is supportive. Whereas the course of progression varies, death usually occurs within 15 years of diagnosis.

Sydenham's chorea (SC, also known as St. Vitus' dance) develops following exposure to the bacteria Streptococcus pneumoniae and, in the age of antibiotic therapy, is rare.y Most typically, Sydenham's chorea is associated with infection and other sequelae of rheumatic fever. Autopsy studies of patients with Sydenham's chorea reveal edema, chromatolysis, and atrophy that affect primarily the striatum, but the cortex, thalamus, and other basal ganglial nuclei may be variably involved as well.y The clinical picture involves a child with diffuse chorea, motor impersistence, and variable degrees of weakness. Unlike arthritis and carditis, chorea may not develop for weeks or even months after acute infection has occurred. Children are often very distressed in the midst of the chorea, rest poorly, and can develop a number of behavioral abnormalities. In addition to high titers of antistreptolysin, approximately 50 percent of patients have IgG antibodies that react against neurons in the caudate and subthalamic nuclei. The condition is usually self-limited, but during the period of marked chorea, dopamine-blocking or -depleting agents (see earlier discussion) can be used. Because prolonged drug usage is usually not necessary, major concerns about the induction of tardive dyskinesia from neuroleptic drugs do not exist.

In the evaluation of these forms of primary choreic disorders, other secondary choreas must be considered. Chorea gravidarum and endocrine-metabolic choreas, such asbirth control pill chorea, should be considered in appropriate women with hyperkinetic movements. Prior Sydenham's chorea may be a risk factor for these conditions. Estrogens may serve as a facilitator of dopamine pharmacology, either directly at the receptor sites or through second messengers. In pregnancy, DA receptor-blocking drugs (neuroleptics) should be avoided, particularly during the limb-genesis period of the first trimester. Benzodiazepines may be appropriate in the second and third trimesters, but fetal respiratory depression must be avoided. Hyperthyroidism, either primary or pituitary in origin, can be associated with various movement disorders, including chorea.

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