[A case of quadrigeminal cistern arachnoid cyst associated with hydrocephalus].

A case of quadrigeminal cistern arachnoid cyst associated with hydrocephalus is reported. A 1-year-old girl was admitted to our service on July 31, 1984, because of mental retardation and an enlarged head. She was born of a full-term pregnancy and normal vaginal delivery without prenatal complications. Progressive increase in her head circumference was noticed at the age of 6 months by her family physician. On admission she was found to be a well-nourished infant with a head circumference of 56 cm, bulging anterior fontanelle and mental retardation. Marked dilatation of the lateral ventricles and a large cyst in the quadrigeminal cistern were demonstrated on plain CT. There were no findings of communication between the ventricular system and the cyst on metrizamide CT ventriculography. The extension of the cyst from the quadrigeminal cistern to the right cerebello-pontine angle was demonstrated on reconstructed coronal CT. Reconstructed sagittal section revealed huge hydrocephalus caused by aqueductal stenosis. A vertebral angiography demonstrated opening of the para-mesencephalic segments of the bilateral posterior cerebral arteries and downward displacement of the right superior cerebellar artery. Accordingly, a large quadrigeminal cistern arachnoid cyst with hydrocephalus caused by aqueductal stenosis was suspected. Following V-P shunt operation for hydrocephalus, right temporo-parietal craniotomy was performed. The inner wall of the lateral ventricle was thin and an expanding cyst was observed through it. A partial resection of the cyst wall with the ventricular wall was performed to obtain communication between the cyst and lateral ventricle. The content of the cyst was watery clear fluid like CSF.(ABSTRACT TRUNCATED AT 250 WORDS)