Prenatal porencephaly: the pattern of secondary lesions.

Two cases of prenatal porencephaly in young adults are reported with the aim of studying retrograde and trans-synaptic degeneration and comparing the findings with similar situations developing postnatally. The thalamic nuclei with cortical projections and the nuclei of the basal forebrain complex showed hypoplasia rather than typical retrograde degeneration, while the locus ceruleus was unaffected. The nuclei pontis and the cerebellum were essentially normal in spite of severe loss of corticopontine fibers. These striking differences between the effects of prenatal and postnatal lesions are ascribed to the greater plasticity of the developing, as opposed to the mature, brain.