Flocculus Herniation and Hearing Disturbance Induced by Remote Tentorial Meningioma: A Case Report.

Tentorial meningiomas, not involving the cerebellopontine angle cistern or cranial nerves, rarely cause symptoms of cranial nerve disturbance. We report a case of a patient with a paramedian tentorial meningioma who presented with hearing loss as a result of indirect compression of the vestibulocochlear nerve by the herniated cerebellar flocculus into the internal acoustic meatus. A 50-year-old woman had presented with hearing loss in her right ear. Magnetic resonance imaging (MRI) revealed a large tentorial meningioma in the right posterior cranial fossa. Constructive interference in steady-state (CISS) imaging demonstrated a non-enhanced solid structure at the ipsilateral cerebellopontine angle cistern and internal acoustic meatus. During surgery, after resection of the tumor, the herniated cerebellar flocculus into the internal auditory canal was observed at the ipsilateral cerebellopontine angle. MRI obtained following meningioma resection demonstrated the herniated flocculus regressing from the fundus of the internal acoustic meatus to the cerebellopontine angle cistern, and her hearing was improved as a result of decompression. This is a rare case report of flocculus herniation caused by remote tentorial meningioma. Patients with paramedian tentorial meningiomas rarely present with hearing loss. In these cases, the causes of the hearing loss (microvascular compression, transformed brainstem, and venous circulation disorders) have been described in the literature. In this report, a new mechanism became evident: a herniated flocculus into the internal acoustic meatus by a tumor can cause hearing loss. MRI, particularly CISS imaging, can clearly show the flocculus during the entire clinical course.