Muscular alteration in agyria with pyramidal tract anomaly.

A 4-year-old boy with a history of muscular hypotonia, mental retardation, microcephaly, and generalized convulsions was found at autopsy to have agyria, agenesis of the anterior commissure and posterior corpus callosum as well as an abnormal decussation of pyramidal tracts which descended in the spinal dorsal columns. Postmortem muscular alterations included type IIc fiber hypertrophy and type I fiber grouping, variably expressed in individual muscles and intramuscular fascicles. This may represent a developmental delay compatible with a gestational age between the 34th and 40th week. These studies also indicate the importance of examining multiple samples of postmortem muscles and muscles from patients afflicted with cerebral malformations.