A Contribution to the Histopathology of Porencephalus

Porencephalus is always of interest, partly because of the striking disproportion between the great loss of brain substance and the mild degree of functional disturbance. Unfortunately, however, almost all studies of such brain lesions have been limited to gross anatomic observations. It is hoped that this study adds a few facts to our knowledge of the histopathology of porencephalus. Incidentally it emphasizes the close relationship of such defects to the inflammatory encephalitides. The term porencephalus was first adopted by Heschl,¹in 1859, to designate such defects in the brain substance as are characterized by cavity formation in the cerebral hemispheres. Such cavities, to be within the limits of his definition, must communicate either with the subarachnoid or ventricular space. Moreover, the defect might be so pronounced as to lead to intercommunication between the subarachnoid space and the ventricular cavity. Heschl assumed that this loss of brain substance was the