Choroid plexus cyst of the third ventricle presenting as acute triventriculomegaly

Introduction Cystic lesions in and around the third ventricle have been known to cause intermittent and acute obstruction of the foramen of Monroe with rapid onset symptoms. Most of these lesions are seen on routine investigations, whereas some are not so obvious resulting in mistaken diagnosis. Symptomatic choroids plexus cysts have only been infrequently reported, predominantly in the lateral ventricle. Case report A 3-year-old female child presented with rapid loss of consciousness for the first time. Computed tomography and magnetic resonance imaging scans only showed triventriculomegaly. Endoscopy revealed a cyst of the third ventricle, which was excised, leading to good recovery. Biopsy of the wall revealed a choroid plexus cyst. Conclusion Choroid plexus cysts are rare causes for symptomatic obstruction of the third ventricle and may be difficult to detect on routine investigations and may lead to the wrong choice of treatment. Endoscopic fenestration or excision is a good option to manage such lesions.