Diagnosis.—In typical cases no great difficulties in diagnosis are presented, the characteristic muscular movements being, in themselves, sufficient to make the nature of the case plain. In atypical forms some doubt /nay arise, and there are a few other states which may be con founded with acute chorea. Thus, in hysteria choreiform movements suggest ing chorea may take place ("hysterical chorea"). The anmsthesia and accom panying symptoms discoverable upon examination, together with the fact that in hysteria the movements are more rhythmical than in chorea, should make a diagnosis easy.
The muscular weakness may be so ex treme as to suggest acute anterior poli omyelitis. The presence of the choreic movements are, however, enough to ex clude poliomyelitis. Some forms of scle rosis and degenerative changes in the cerebral cortex are attended by chorei form movements, and may, when occur ring in young persons, lead to thought of acnte chorea. The presence of mental disorder, exaggerated reflexes, muscular rigidity, and other spastic symptoms should prevent mistake. Friedreich's ataxia was formerly and is still some times mistaken for chorea by those un familiar with the symptomatology of nervous diseases. The scanning speech, nystagmus, and the irregular, slow, and peculiar inco-ordina.te movements of Friedreich's ataxia are sufficiently dif ferent from the clinical picture of chorea to prevent confusion if a proper examina tion is made.
Involuntary movement, muscular weakness, and muscular rigidity are three symptoms belonging to the group that depends on impaired functional in tegrity of the upper segment of the motor path. They are found in two diseases which are due, not to structural, but to functional or, perhaps, rattier nu tritional changes in the cortex, viz.: pa ralysis agitans and chorea, which have a certain kinship to oue another, the former bein,g commonly hemiplegic in its mode of commencement and extension, while the other is frequently hemiplegic in its distribution throughout its entire course. In the case of chorea the ab normal movements are so obtrusive in comparison with the others that there is danger of the latter being overlooked, although weakness, at any rate, is now generally known as a frequent symptom. In exceptional instances weakness may be practically the only symptom, and the diagnosis may then be somewhat dif ficult. The age of the patient, the limita
tion of the weakness to one arm, and the occasional manifestation of slight choreic movements in the affected limb or iu other parts may furnish the neces sary clue. Monroe (Glasgow Med. Jour., Feb., '07).
Peculiarities of the knee-jerk. If, the patient being in the recumbent position, one raises the knee, *allowing the heel to rest on the couch, making sure that all the muscles of the limbs are relaxed for the time being, and if one then tests the knee-jerk in the usual way, the foot is found to rise more or less smartly, but, instead of falling back im mediately, it remains suspended for a variable time—hung up, as it were— and then slowly sinks back to its initial position. W. Gordon (Brit. Med. Jour., Mar. 30, 1901).
Etiology and Pathology.—In general terms, choreic movements of all kinds are primarily due to inherent neuronic weakness or instability, especially in motor sphere, with abnormally-devel oped motor association-tracts, or to fective insulation in lines of motor dis charge.
An unstable condition of the higher nerve-eentres predisposes to the condi tion, and a poison affecting these centres might produce in one person epilepsy, in another general neurasthenia, and in a third chorea. Bishop (Can. Pract., NOV.. '97).
Chorea considered a condition of ex hausted nerve-control. Upon this theory the association of chorea, and rheumatism seems to be readily explained. As a re sult of the rheumatic poison there oc curs a failure in the nutrition of the nerve-cells regulating and balancing mus cular movements, and thus in certain individuals of neurotic tendency rheuma tism becomes the causative factor of chorea. G. M. Swift (Archives of Pedi atrics, Sept., '99).
The immediate exciting cause is irri tation of cortical motor neurones from toxic substances in the blood due to in fectious diseases, autointoxications, etc., nerve-cell fatigue, and in some cases tem porarily induced abnormal "neuronic contacts" in sensorimotor sphere from sudden shock or emotion.
In the form of acute chorea under consideration the neurotic constitution with the anatomical and physiological stigma of degeneration can usually be traced. Anmmia with general bodily en feeblement is common.