RESUMO
AIMS: To present nine cases of unilateral cerebellar hypoplasia and to show the clinical alterations and the possible etiology. CASE REPORTS: A retrospective analysis of the clinical, radiological and perinatal features of a series of nine infantile cases with unilateral cerebellar hypoplasia was made. The unilateral cerebellar hypoplasia was demonstrated in all patients after computarized tomography or magnetic resonance (MR) studies. Angiographic study was performed in six patients, in most of them by MR arteriography, with demonstration of vascular anomalies in the cerebellar and/or vertebral arteries in most of the patients. However, other types of malformations of the posterior fossa were also observed: retrocerebellar cyst associated with obstruction of the aqueduct (two cases), cutaneous hemangioma or vascular malformation (two cases), and psychomotor retardation (five cases), being this last disturbance the most frequent clinical alteration. CONCLUSIONS: The unilateral cerebellar hypoplasia is a relatively rare malformation and it is more frequently associated with psychomotor retardation than with cerebellar symptomatology. Hypoplasia or aplasia of the cerebellar arteries, of probable early intrauterine origin, would be the cause of this malformation.