[A case of intraventricular cyst associated with normal pressure hydrocephalic condition].

A case of intraventricular cyst associated with normal pressure hydrocephalic condition (NPHC) is reported. A 72 year-old female, with 2-year-history of slowly progressing dementia and gait disturbance, was admitted to our hospital on September 19, 1989. On admission, she had mild dementia, unsteadiness of gait, and at times urinary incontinence. Cerebrospinal fluid (CSF) pressure was found to be 90mmH2O by lumbar tap. Plain computed tomographic (CT) scan and T1-weighted magnetic resonance image (MRI) showed asymmetrical enlargement of the trigon and posterior horn of the right lateral ventricle. CT cisternography showed a cyst in the trigon and in the posterior horn of the right lateral ventricle. T1-weighted MRI with Gd-DTPA demonstrated no enhancement of the cyst wall, and there was superior and posteromedial displacement of the choroid plexus at the trigon of the right lateral ventricle. The patient was diagnosed as having an intraventricular cyst in the right trigon with NPHC. Ventriculo-peritoneal shunt and partial removal of the cyst were performed. Histological examination of the cyst wall revealed collagenous strands and no epithelial cells. Developmental intracranial cysts, especially arachnoid or ependymal cysts, occasionally lack an epithelial layer, so their histological diagnosis is difficult. This case was considered to be an arachnoid cyst because there was adhesion between the cyst and the choroid plexus in the right trigon, and superior, posteromedial displacement of the choroid plexus, which indicated extension of the cyst from the extracerebral to the intracerebral region. NPHC was considered to be due to disturbance of CSF circulation caused by gradual expansion of the cyst.