Uncommon syndromes of cerebellar vermis aplasia. II: Tecto-cerebellar dysraphia with occipital encephalocele.

Two new cases are reported of a rare syndrome of malformation consisting of occiptal encephalocele, aplasia of the vermis and deformity of the tectum. Less consistent components are aplasia of mammillary bodies, fusion of thalami, anomalies of cerebral gyral patterns, bifid atlas or bifid occipital squame, elevation of torcular, and cervical hydromyelia. One of the present cases had survived to the age of eight years with a ventricular shunt. This syndrome, of which five cases are known, is thought to be a tandem malformation in which either an occipital dysraphia or an encephalocele induces aplasia of the vermis. A classification of aplasias of the cerebellar vermis is proposed.