MRI of the head in the evaluation of microcephaly.

Fifty-five patients with microcephaly (head circumference < -2SD) were identified. The 55 patients were divided into two groups, consisting of group 1 (34 cases) in which genetic causes were considered primary, and group 2 (21 cases) in which intrauterine and/or postnatal acquired factors were thought to be responsible. MRI abnormalities were present in 80% of the total series: 68 and 100% in groups 1 and 2, respectively. In group 1, migration abnormalities were the most prominent and mental retardation was the major neurological handicap, while in group 2, hydranencephaly and infarction secondary to brain circulatory derangements were the most frequently observed abnormalities, with severe multiple handicaps such as cerebral palsy, epilepsy and mental retardation seen. Head MRI was considered indispensable in the investigation of the causes of microcephaly and in determining the neurological prognosis of affected patients.