Porencephaly

PORENCEPHALY, porencephalia (from Greek poros - pore, opening, and encephalon - brain), a malformation of the brain characterized by the presence of funnel-shaped depressions on its surface (see figure). The term porencephaly was introduced by Heschl in 1852, and the disease was described in more detail by Kundrat in 1882. Porencephaly depends on an arrest in the development of individual parts of the brain, which, according to a number of authors, occurs on the basis of occlusion of the corresponding arteries, most often in the region of the middle cerebral artery.

The defect can be unilateral or bilateral, in the form of a single focus or several, has the shape of a funnel, the base of which corresponds to the surface of the brain, while the apex goes into the depth and communicates for the most part with the lateral ventricles; the surrounding convolutions are located radially to the depression and sink into it; the base of the defect is covered by soft meninges, which are abundantly vascularized. It was noted by some authors (Gilyarovsky and others) that the cyst formed in this way is separated from the subarachnoid space by a very thin film, in the composition of which there are not only elements of the pia mater, but also nerve elements of the cerebral cortex. Histological changes in the surrounding convolutions amount to a strong rarefaction of ganglion cells and an irregular orientation of cellular layers.

Close in appearance to this so-called true porencephaly is false porencephaly, or pseudoporencephaly, which develops on the basis of a necrobiotic process or hemorrhage causing the destruction of certain areas on the surface of the brain, with the secondary formation of a cyst. Pseudoporencephaly differs from true porencephaly by its more extensive dimensions and mostly the absence of communication with the brain ventricles; the walls of the cavity in false porencephaly are very irregular, formed by white matter; the surrounding convolutions are irregularly transected by the process and do not have a correct radial arrangement. Traces of the main process are often found in the walls of the depression, e.g., hemosiderin in hemorrhages. The presence of porencephaly leads to disorders in the somatic and mental spheres, the character and intensity of which depend on the size and localization of the defect. Until recently, it was considered impossible to differentiate porencephaly during life from other congenital defects in brain development, and it was discovered only as an autopsy finding. However, recently (1928–1931), by means of encephaloventriculography, a number of authors (Salomon, Reiche, Dannebaum, Yuzhelevsky, Antonov) have managed to diagnose porencephaly during life as well. For prophylaxis and treatment, see Infantile paralysis, cerebral paralysis.