Clinico-Radiological Manifestations of Cochlear Schwannomas

Cochlear schwannomas, which are categorized into intracochlear and intravestibulocochlear schwannomas (ICs and IVCs, respectively) are rare and may cause hearing loss (HL). The affected region is invariably correlated with tumor location, which can be detected on magnetic resonance imaging (MRI). We describe the cochleovestibular manifestations of ICs and IVCs.

The study included 31 patients with ICs or IVCs. Tumor extent and exact locations were delineated using MRI. Types of HL were subcategorized into the low-to-mid frequency (250 Hz to 1 kHz), mid-to-high frequency (>1 kHz), and all-frequency (universal) HL groups.

The tumors involved the entire cochlear turn (two ICs) or extended beyond the cochleae (nine IVCs) in 11 patients, and 20 ICs were located in specific locations as follows: 14 in the basal, 3 in the middle, and 3 in the middle and apical turns. No patient showed tumor invasion of the internal auditory canal or middle ear. The pattern of HL usually reflects the location or extent of a tumor. We observed HL at all frequencies, at low-to-mid frequencies, and at mid-to-high frequencies in 13, 4, and 14 patients, respectively. Dizziness or tinnitus was observed in >50% of patients. Surgical tumor removal was performed in 10 patients, and the remaining patients are undergoing annual monitoring.

Cochlear schwannomas may be associated with HL, which may worsen over time and reflect tumor location. Therefore, these lesions should be considered in the differential diagnosis in patients who present with idiopathic, fluctuating, progressive or sudden HL.