Are breaches in the glia limitans the primary cause of the micropolygyria in Fukuyama-type congenital muscular dystrophy (FCMD)? Pathological study of the cerebral cortex of an FCMD fetus.

A light and electron microscopic study of the brain of an 18-week fetus with a prenatal genetic diagnosis of Fukuyama-type congenital muscular dystrophy revealed a widespread mantle of abnormal neurogliomesenchymal tissue that covered a dysplastic cerebral cortex. In this area alone, the glia limitans that adjoined the abnormal mantle via one or two layers of basal lamina had frequent breaches, through which neuroglial elements extruded. In the most severely affected cortical region, which had only a rudimentary and fragmentary glia limitans, the majority of cortical neurons had migrated into the neurogliomesenchymal tissue. The massive overmigrated neurons still maintained a somewhat columnar arrangement, and the marked dysplasia abruptly shifted to a neurogliomesenchymal tissue-free normal cortical structure with an intact glia limitans, thus indicating essentially vertical overmigration of neurons without significant tangential migration of them. Together the above findings imply that breaches in the glia limitans may be the primary cause of the micropolygyria seen in this genetic disorder.