Cortical atrophy is due to a disturbance in the cerebrospinal fluid—eliminating mechanism, which permits an increase in the amount of supracortical fluid with varying degrees of pressure. The factors which may cause the pathologic intracranial condition are many: encephalitis following measles, chickenpox or whooping cough; congenital malformation of the brain; congenital internal hydrocephalus; tumor of the brain; meningitis, or trauma. The first response of the brain to edema is an accumulation of fluid with resulting pressure and progressive atrophy and dilatation of the ventricles or the accessory channels. Obstruction at any point causes dilatation of the ventricular system and cortical shrinkage.
The rapidity with which cortical atrophy may develop is strikingly illustrated in the following case, in which trauma was the only etiologic factor discovered. The condition gave rise to a syndrome similar to that seen in cerebral lesions due to infection or in congenital malformations of the brain.