Pathology.—The pathology of chorea is still a matter of debate. In some fatal cases obstructions have been discovered in the minute arteries ramifying in the corpus striatum and its vicinity, with little points of soft ening and congestion resulting from them. Hence Dr. Kirke's view, since supported by the authority of Dr. Hughlings Jackson, that chorea is a consequence of minute emboli swept out of the heart and arrested in the small arteries of this part of the brain. This theory, if correct, would only explain the cases which have been preceded by rheumatism, and would throw no light on the many cases where the heart is to all appearance healthy.
Dr. Dickinson has proposed another explanation. He believes that the faulty part of the brain is not limited to so small an area. In his opinion the disease depends upon a wide-spread hyperminia of the nervous centres "not due to any mechanical mischance, but produced by causes mainly of two kinds—one being the rheumatic condition, the other comprising vari ous forms of irritation, mental and reflex, belonging especially to the ner vous system." Dr. Dickinson has found, as the result of post-mortem ex aminations of fatal cases, that all the small arteries both of the brain and spinal cord have a general tendency to dilatation. As a consequence, exu dations and sometimes minute hemorrhages occur in the tissues immedi ately surrounding the dilated vessels—shown by the presence of blood crystals and patches of sclerosis. He has noticed these changes to be most advanced in the corpora striate, the vicinity of the trunks of the middle cerebral arteries, and in the posterior and lateral parts of the spinal cord —principally at the upper part ; and states that they are equally distrib uted on the two sides. This theory has the advantage that it explains the wasting of muscles, rigidity of limbs, and occasional permanent paralyses which sometimes follow an attack of chorea.
In opposition to the above theories based upon morbid anatomy, Dr. Sturges has advanced an ingenious explanation of the phenomena attend ant upon chorea, founded upon intimate acquaintance with the peculiarities of childhood. Dr. Sturges regards chorea as a purely functional complaint, arising, in the majority of cases, from some strong nervous impression.
Starting from the fact that in every child placed in an embarrassing posi tion emotional restlessness (or temporary chorea) is produced, he argues that exaggerated limb-movement is the natural expression in young sub jects of emotional states; that disordered movement is increased by the at tention being diverted, as it is by some strong emotional shock ; that the consciousness of this partial loss of control deepens the mental impression and intensifies and extends its consequences ; and, lastly, that want of suc cess in directing movement impairs the child's confidence and entails fur ther failure. The little treatise is well worthy of perusal, for although it
may not offer a full explanation of all the phenomena connected with the disorder, no one can refuse admiration to the ingenuity of its reasoning and the graces of its style.
Dr. Haydon, of Dublin, has started another theory. Like Dr. Sturges he refuses to accept any special organic lesion as the exciting cause of the complaint. He believes that the attack begins with a vaso-motor paresis, the consequence of a profound emotional impression, and that the essen tial symptoms are due to defective polarity or dynamic instability of the motor-nerve tracts, both intracranial and spinal. This hypothesis would explain the post-mortem appearances noted by Dr. Dickinson, and would. account for the phenomena common in the graver cases of the disorder.
phenomena of chorea consist in an inability to and control the muscles, so that while there is excess of motion there is absence of ordered movement. The infirmity begins gradually in most cases. At first the child is noticed to be stupid over her lessons ; she shows less than her usual alacrity at her games, and is emotional, nervous, and altogether strange in manner. Soon she begins to fidget, scraping her feet as she sits on a chair, or restlessly moving one of her hands about her dress. Then she is found to drop articles from her hand, and to. stumble awkwardly as she walks. These symptoms are always at first attributed to carelessness, and the child is admonished and reproved ; but after a time, usually from some eccentricity of movement or facial contor tion, it dawns upon the parents that the child's control over her muscles is impaired, and the matter is referred to the medical attendant.