Atypical meningioma in the posterior fossa associated with colpocephaly and agenesis of the corpus callosum.

Colpocephaly is an abnormal enlargement of the occipital horns, i.e., the posterior or rear portions of the lateral ventricles of the brain, and is associated with several other brain abnormalities. Colpocephaly is occasionally misdiagnosed as hydrocephalus, and various etiologies have been postulated, including genetic disorders and errors of morphogenesis. Meanwhile, chromosomal losses including 22q and rarely 21q are observed in malignant and atypical meningiomas. We report an uncommon case of a 67-year-old woman with colpocephaly and an atypical meningioma in the posterior fossa. There were no neurological deficits or family history of hereditary neuropsychiatric disorders. Brain magnetic resonance (MR) images showed bilateral enlarged occipital horns, agenesis of corpus callosum, and a cerebellar mass in the right cerebellar hemisphere. Right suboccipital craniotomy was performed, and the tumor was resected totally. Pathological study of the surgical specimen showed findings of atypical meningioma, and the postoperative course was uneventful until hydrocephalus developed. At 36th day after tumor removal, the patient undertook an external ventricular drainage followed by replacement of the ventriculoperitoneal shunt. We discuss the importance of colpocephaly in terms of the differential diagnosis for hydrocephalus and review the pertinent literature.