A Case–Case Analysis of Intralabyrinthine versus Intracanalicular Vestibular Schwannomas

Intralabyrinthine schwannomas (ILSs) are rare benign tumors originating from the Schwann cell sheath of the intralabyrinthine portion of the eighth cranial nerve. We describe a retrospective chart review of a case-to-case analysis comparing 18 cases of ILSs with 280 small (<15 mm in maximal axial dimension) intracanalicular vestibular schwannomas (VS) to better understand the difference in presentation and outcomes between these two groups. Variables studied included age, gender, presenting signs and symptoms, imaging findings, pure tone average (PTA, average of hearing thresholds at 500, 1,000, and 2,000 Hz) at presentation and change over time, and treatment. Among them, 27.8% of patients in the ILS group were male, while 45.7% of the intracanalicular VS patients were male. The average age at presentation was 58.7 years in the intracanalicular VS group and 54.2 years in the ILS group. Kennedy classification for the ILSs demonstrated six intracochlear tumors, eight intravestibular tumors, one intravestibular-cochlear tumor, one transmacular tumor, and two translabyrinthine tumors. Interestingly, 22.2% of ILSs were missed on initial radiology report. Examination of presenting signs and symptoms (hearing loss, sudden hearing loss, vertigo, imbalance, facial nerve weakness, tinnitus, facial paresthesia or numbness, and headache) demonstrated no significant difference between the two groups. The incidence of vertigo was similar in both groups, 30.1% in the VS group and 33.3% in the ILS group. The amount of hearing loss at presentation was statistically worse in the ILS group compared with the intracanalicular VS group (p = 0.0003). The average PTA at presentation in the ILS group was 79.7 dB compared with the intracanalicular VS PTA of 41.9 dB. The change in PTA over time was also compared between the two groups and no statistically significant difference was found (p = 0.83). In the intracanalicular VS group 40.7% of patients underwent intervention (surgery or radiation) and 22.2% of ILS patients underwent surgical intervention (three for recalcitrant vertigo and one for tumor growth). This study demonstrates the similarities in terms of presentation between the two groups; however, the ILSs have significantly worse hearing at initial presentation. Physicians should keep a high level of suspicion for ILS in the setting of hearing loss, tinnitus, and vertigo, particularly given the ease in overlooking this diagnosis on imaging.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021