Third ventricular colloid cyst and organic hypomania

(also called neuroepithelial cysts) are relatively rare i n t r a c r a n i a l lesions located in the rostral aspect of the third ventricle. They comprise approximately 0.5–1% of primary brain tumours. They occur with equal frequency in men and women. Most reported cases occur in the third to fifth decades of life.1 Although colloid cysts are histologically benign, they may obstruct the foramina of Monro, causing obstructive hydrocephalus involving only the lateral ventricles. These lesions are a recognised cause of sudden death.2 Overall mortality has been described as between 58% and 77%.3 While the pathogenesis remains unclear, there are four tissues from which third ventricle colloid cysts may originate. These are the choroidal epithelium, ependymal cells, paraphysis and endoderm.4 Genetic inheritance has been suggested in familial cases.5 Colloid cysts can present with or without hydrocephalus. Headache occurs in 68–100% of patients and is often the presenting symptom.6 Other symptoms can include nausea, vomiting, seizures, vertigo, visual disturbances, drop attacks, gait disorder, insomnia, memory loss and mental status changes. This usually occurs when the cyst is 1–2cm in size.4 Colloid cysts frequently cause psychiatric manifestations including psychosis,7 depression,8 anxiety episodes, Korsakoff type presentations,9 and dementia.10 In a large proportion of these cases there was no hydrocephalus present. Surgical excision resolved the psychiatric manifestations. Discovery is often coincidental as many of these tumours are asymptomatic. MRI is the optimal diagnostic investigation.5 We report a case of a man with a hypomanic presentation to clinic following a psychotic episode associated with a third ventricular colloid cyst which remitted after surgical intervention.