No abstract

No abstract

To a considcrablc extent the work of the neurologist is concerned more with the determination of the locality of lesions than with the differentiation of the various grades and types of disturbance of function produced by them. In such neurological work, however, as is usually regarded as being more or less exclusively the province of the surgeon-the care of cases of head injuryit is characteristic of the conditions which have to be dealt with that the actual degree and kind of disturbance of function is no less variable and no less important than the situation of it. The surgery of head injuries furnishes in fact many instances of lesions closely similar in distribution, producing totally different clinical manifestations. Such cases make it clear that there must be some fnctor determining the effects of a given lesion other than its size, shape, and situation. This factor is to be found in the rate a t which the lesion develops.It is a principle of wide application in cerebral pathology, that the great majority of progressive lesions produce their effects on the brain through interference with its circulation rather than by destruction of its substance. This is clearly shown by the possibility of complete disappearance of symptoms after decompressive operations for tumoiir and after the evacuation of abscesses or hzmntomas, though well-defined paralytic focal symptoms may have been present bcforc the operation. The principle applies even more generally to the pathology of head injuries. Here actual destruction of the brain tissue plays a w r y small part in the causation of symptoms, while interferences with the circulation are all-important. Hzmorrhagc and edema are almost exclusively the causes of the cerebral disturbance in such cases, and they produce their cffect by pressing upon the neighbouring blood-vessels and limiting the circulation in the part affected.It is because the effects of the lesion are produced through the agency of the circulation that the rate of development of the lesion exerciscs so remarkable an influence upon the disturbance of function which results.Subdural hmnorrhage is of all pathological conditions the one which most perfectly illustrates the variety of clinical manifestations which arc produced by lesions developing a t different rates. It is well known that a large subdural hzmatonia may, and perhaps usually does, produce the profoilridest and least mistakable evidences of widespread compression of the brain. On thc other hand, a hscmatoma equally large .or even largcr may produce such slight and, according to currcnt teaching, atypical manifestations as not even to be suspected during Iifc. Such variability is somcwliat confusing a t first sight,

No abstract