A developmental disorder of the brain characterized by abnormal slits, or clefts, in the cerebral hemispheres. Schizencephaly is a form of porencephaly. Children with clefts in both hemispheres, or bilateral clefts, are often developmentally delayed and have delayed speech and language skills and corticospinal dysfunction. Individuals with smaller, unilateral clefts (clefts in one hemisphere) may be weak on one side of the body and may have average or near-average intelligence. Patients with schizencephaly may also have varying degrees of microcephaly, mental retardation, hemiparesis , or quadriparesis, and may have hypotonia. Most patients have seizures and some may have hydrocephalus.