Destructive lesions of the brain.

The congenital destructive lesions of the brain include focal lesions (porencephaly) and diffuse lesions (micrencephaly, hydranencephaly). According to the time the injury occurred and following the assumption of Yakovlev and Wadworth (1946), they are classified as agenetic porencephalies, either - bilateral (schizencephaly) or unilateral, when the injury occurs early enough in gestation (before 6 months) to disturb the growth of the cerebral mantle: abnormal sulcal pattern and heterotopic gray matter are then observed. They are classified as encephaloclastic when the destruction affects an otherwise normal cerebrum (last trimester). The porencephalies should be differenciated from post natal lesions (multicystic encephalomalacia, focal cavitations). By showing the fluid cavity and the cortical distortion, neuroradiology permits precise diagnosis of the defect itself and the associated cortical disorder, as well as an evaluation when they occurred.