Typical Symptoms of Normal-Pressure Hydrocephalus Caused by Choroid Plexus Papilloma in the Cerebellopontine Angle

Choroid plexus papillomas (CPPs) are rare benign intracranial tumors. We report a rare case of CPP manifesting with typical symptoms of normal-pressure hydrocephalus rather than obstructive hydrocephalus. A 45-year-old woman presented with a 6-year history of headache and typical symptoms of normal-pressure hydrocephalus, including gait disturbance, urinary incontinence, and cognitive dysfunction, in addition to the more common symptoms of CPP, such as lower cranial nerve dysfunctions and ataxia. The CPP arose from the right lateral recess of the fourth ventricle and extended to the cerebellopontine angle. Magnetic resonance imaging did not show any radiographic evidence of obstruction of aqueduct, foramen of Magendie, or foramen of Luschka on the contralateral side. We speculated that hydrocephalus was associated with cerebrospinal fluid overproduction by the CPP originating from the choroid plexus of the lateral recess and extending laterally into the cerebellomedullary fissure (CMF). Surgical excision was performed with a trans-CMF approach. The symptoms of normal-pressure hydrocephalus disappeared. In addition to improved clinical symptoms, radiographic findings showed mitigation of ventricular dilatation. The hydrocephalus was of a communicating type and caused by CSF overproduction. The lateral route of the trans-CMF approach is useful for the dissection of tumors that extend into the unilateral cerebellomedullary cistern through the CMF. This approach not only enables sufficient exposure for resection but also avoids damage to the surrounding structures.