1

Introduction

Although uncommon in and of themselves, schwannomas are the most common tumor to cause sensorineural hearing loss. Schwannomas are derived from Schwann cells of the vestibulocochlear nerve (cranial nerve VIII), most often arising at the transition of central myelin to peripheral myelin near the medial opening of the internal auditory canal . Rarely, these tumors may originate at the terminal end of the nerve including the vestibule, semicircular canal, or cochlea. This case presentation reports sensorineural hearing loss attributed to an intracochlear schwannoma as the cause of hearing loss, which was surgically resected via a transcanal/transotic approach.

2

Case report

A 34-year-old African American female presented to the clinic with a 5-week history of decreased hearing and tinnitus in the right ear. The patient denied any trauma or exposure to loud noise. Physical examination was noncontributory, and facial nerve function was normal bilaterally. A hearing test performed showed decreased hearing in the right ear. A magnetic resonance imaging (MRI) with and without contrast demonstrated a focal region of enhancement 1.1 × 2.6 mm within the medial turn of the right cochlea. No extra-axial fluid collection, intraparenchymal hemorrhage, mass, or mass effect was identified. These findings were felt to be consistent with a small cochlear schwannoma. The patient was placed on hydrochlorothiazide and a low-salt diet with marked improvement in symptoms. The patient was followed up over the next 2 years with serial MRIs, which showed no expansion of the enhancement.

The patient presented to the clinic 3 years post diagnosis of a right intracochlear schwannoma with a 4-day history of dizziness after cleaning her ears. The patient stated that the room felt like it was spinning and also complained of nausea. The patient was prescribed meclizine, and a repeat MRI was performed. The MRI demonstrated a lesion measuring 4.8 × 0.9 mm indicating growth of the tumor ( Fig. 1 ). There was no apparent extension through the modiolus into the apex of the internal auditory canal. Because of the progression of the lesion, an elective excision was planned.

The right cochlea enhancement is a signature finding of an intracochlear schwannoma.

A transcanal/transotic approach was used to achieve removal of the schwannoma. A wide tympanometal flap was raised, and the incus, stapes, short head of the malleus, and chorda tympani were removed to allow sufficient access to the cochlea. The facial nerve was identified and preserved. A wide cochleostomy was made from the oval window niche to the round window, and the otic capsule was sequentially exteriorized from the basal and apical turn, exposing the schwannoma. The schwannoma was noted to extend medially necessitating the resection of the modiolus. An abdominal fat graft was used to reconstruct the cochleostomy defect, covered with DuraSeal, and the tympanometal flap was repositioned back into place. The patient’s initial postoperative course was unremarkable; however, the patient was briefly admitted 10 days later for a community acquired pneumonia that resolved uneventfully.

The resected lesion’s histologic features included random proliferation of spindle-shaped cells with tapering nuclei and bland nuclear morphology with a fine fibrillary background. Immunohistochemisty showed positivity for S-100 and negativity for neurofilament. These findings were morphologically consistent with a Schwann cell neoplasm.