TRAUMATIC DILATATION OF THE CEREBRAL VENTRICLES.

or meningo-cerebral cicatrix which may result from focal contusion and laceration of the brain rest upon a firm foundation of fact, of unequivocal observation. 2. The enlargement involves the whole of one lateral ventricle; it may occur on that side of the head which received the blow, or on the opposite side. These cases may provide a link connecting the processes leading to local bulging, and those causing general symmetrical dilatation. It is tempting to assume that a large focal contusion can lead to cedema of the whole hemisphere. If this were proven, and if the cedema alone, as opposed to any vascular disturbances which cause cedema were sufficiently severe and enduring, then doubtless gliosis and atrophy would lead to ventricular enlargement. Although such an explanation is accepted by many, an cedema of this extent has not yet been satisfactorily proven. The occurrence of contralateral enlargement seems related to contrecoup effects, but the precise mechanism of dilatation is not thereby explained. Raised intracranial pressure by itself cannot be the cause, unless a softened state of one hemisphere allows its ventricle to dilate. 3. General symmetrical enlargement of the lateral ventricles; rarely the third and fourth ventricles are involved, although not to any considerable extent. Two questions immediately present themselves. What is an abnormally large ventricle, and what is the incidence of the condition? Davidoff and Dyke (1937) measure the distance between the outermost limits of the bodies at the lateral angles as seen in the antero-posterior projection and regard 3*5-4*5 cm. as normal. Robertson (1941) proposed