Choroid plexus cyst causing acute hydrocephalus and transtentorial herniation: report of a rare case and its successful neuroendoscopic treatment.

Choroid plexus cysts (CPC) are a frequent incidental neuroimaging finding and completely asymptomatic in the vast majority of cases. We hereby describe a rare case of acute hydrocephalus secondary to a CPC, atypical in size, location and presentation, which required urgent neuroendoscopic management. There are very few reported cases of CPC causing obstructive hydrocephalus. The authors present the case of a previously healthy 2-year-old boy with severe symptoms of acute intracranial hypertension, triventricular hydrocephalus, and left ventricle exclusion after placement of a right external ventricular drain. Magnetic resonance imaging (MRI) showed a very subtle gadolinium enhancement in the anterior region of the third ventricle and foramen of Monro (FM). An emergency neuroendoscopic exploration was performed, where a big cyst was found in the choroid plexus near the FM. The foramen was completely unblocked by thoroughly fenestrating and coagulating the cyst, and a preventive endoscopic septum pellucidotomy was done in the same procedure. The patient completely resolved his symptoms, without neurological morbidity or requirement of a cerebrospinal fluid shunt placement. It is important to consider this infrequent presentation in cases of acute or intermittent obstructive hydrocephalus without apparent cause, bearing in mind its difficult detection in neuroimaging studies and the possibility of effective neuroendoscopic treatment.