Table 4-4 lists diseases characterized mainly by chorea or localized lesions that may at times cause chorea. Of the degenerative conditions, chorea is a major feature of Huntington disease, in which the movements tend more typically to be a merging of choreiform and the below-described athetotic (choreoathetotic) motions. Not infrequently, chorea has its onset in late life without the other identifying features of Huntington disease. It is then referred to as senile chorea, a term that is hardly helpful in understanding the process. Its relation to Huntington chorea in any individual case is settled by genetic testing. A number of less common degenerative conditions are associated with chorea, among them dentatorubropallidoluysian atrophy (DRPLA) and a form of chorea associated with acanthocytosis of red blood cells. Also, there is an inherited form of chorea of childhood onset without dementia that has been referred to as benign hereditary chorea. There may be subtle additional ataxia of gait, as noted by Breedveld and colleagues. These are discussed in Chap. 38.
Typical choreic movements are the dominant feature of several immune-related conditions, perhaps the best characterized being Sydenham chorea that is strongly linked to streptococcal infection, mainly in women. Striatal abnormalities, usually transient and rarely persistent, have been demonstrated by MRI (Emery and Vieco). It is perhaps not surprising that antibodies directed against cells of the basal ganglia have been detected in both acute and late Sydenham chorea (Church et al). Following from the connection to streptococcal infection and the detection of these antibodies, it has been suggested in recent years that the spectrum of poststreptococcal disorders can be extended to tic and obsessive-compulsive behavior in children (PANDAS syndrome discussed in a later section). In these cases the neurologic problems are said to arise suddenly, subside, and return with future streptococcal infections, as discussed further on. This seems unlikely to explain chorea in adults. There also exists a variety of chorea associated with pregnancy (chorea gravidarum), which in the past had a close linkage to prior episodes of Sydenham chorea. Alternatively, pregnancy may expose lupus-related chorea or be concordant with the onset of Huntington chorea. However, the elicitation of chorea by oral contraceptives in the modern era, as noted below, suggests a hormonal rather than immune causation in many cases. There have been instances of paraneoplastic chorea associated in a very few cases with lung cancer and anti-CRMP or anti-Hu antibodies of the type described as reported by O’Toole and colleagues and by Vernino et al. The paraneoplastic variety may combine several aspects of chorea with athetosis, ballismus, or dystonia; inflammatory lesions are found in the striatum (see Chap. 30).
The use of oral contraceptives sometimes elicits chorea in an otherwise healthy young woman, but many such patients have underlying systemic lupus erythematosus and antiphospholipid antibodies. Whether the chorea (usually unilateral) is the result of a small infarction (as suggested by a mild hemiparesis on the affected side) or is an immunologic condition is not settled. The reemergence of chorea in these circumstances as steroids are withdrawn or birth control pills are introduced suggests a more complex process than simply a small, deep infarction—perhaps something akin to Sydenham chorea as discussed above. A connection between hemichorea and the antiphospholipid syndrome alone, without lupus, is more tenuous.