A Case-Case Analysis of Intralabyrinthine Schwannoma Versus Intracanalicular Vestibular Schwannoma.

Objectives: Determine the differences in presentation of intracanalicular and intralabyrinthine schwannomas. Study

Design: Retrospective chart review at a single center. Setting: Tertiary academic referral center. Patients: Eighteen subjects with an intralabyrinthine schwannoma (ILS) and 216 patients with an intracanalicular vestibular schwannoma (VS). Main outcome measures: Variables collected included age at diagnosis, gender, presenting signs and symptoms, imaging findings, treatment modality, pure-tone average (PTA), and word recognition scores (WRS) at presentation and at follow-up visits.

Results: Incidence of subjective hearing loss was 100% in the ILS group and 80.6% in the intracanalicular VS group. The degree of hearing loss was significantly worse in the ILS group (average PTA of 83.9 dB; average WRS of 46.9%) compared with the VS group (average PTA of 38.7 dB; average WRS of 71.8%) (PTA p = 0.000006; WRS p = 0.007). Other subjective signs and symptoms, including vestibular symptoms, did not differ significantly between the two groups. Approximately one-third of both groups underwent microsurgical resection. 22.2% of ILSs were missed on initial imaging by radiologists.

Conclusion: Intralabyrinthine schwannomas differ from intracanalicular schwannomas in the severity of hearing loss at presentation. Otherwise, these two tumors present in a very similar fashion-age at presentation, presenting signs and symptoms-and are treated comparably. Otolaryngologists should maintain a high degree of suspicion for ILS in patients presenting with an asymmetric hearing loss, vertigo, and tinnitus.