Progression of Contralateral Hearing Loss in Patients With Sporadic Vestibular Schwannoma

Abstract

Background and Introduction: Vestibular schwannomas (VSs) are the most common tumors of the cerebellopontine angle, typically presenting unilaterally with ipsilateral sensorineural hearing loss (SNHL). The mechanism of tumor-induced hearing loss has recently been shown to be related to secreted tumor factors, in addition to mechanical compression of the adjacent auditory nerve, and these factors may percolate through CSF or blood to affect contralateral hearing as well. Methods: This is a retrospective study of medical records for patients treated for VS at Mass Eye and Ear from January 1994 through October 2018. Included patients had unilateral VS and sequential audiometry allowing for longitudinal assessment of hearing over time. Mass Eye and Ear's audiology database was used to select age- and sex-matched case controls, also with sequential audiometry, from the non-VS population. Subgroup analysis was performed by age, sex, baseline hearing, and tumor size at initial diagnosis. Hearing loss progression was performed using Kaplan-Meier analysis to account for variable follow-up times. Results: A total of 661 patients were identified with VS and sequential audiometry. The population was predominantly female vs. male (368 vs. 293, p = 0.0035), driven primarily by younger patients with Koos 4 tumors (76 female vs. 49 male, p = 0.016). Patients with normal baseline hearing bilaterally (N = 241) demonstrated no significant difference in hearing loss progression in VS-contralateral vs. control ears. Patients with abnormal baseline VS-ipsilateral hearing (N = 190), however, demonstrated significantly higher likelihood of reaching moderate SNHL in VS-contralateral ears. Subgroup analysis by age, sex, and baseline tumor size did not yield any subgroup-specific trends for hearing loss progression. Discussion and Conclusion: This is the largest study to date tracking long-term bilateral hearing outcomes in patients with VS, and demonstrates that, in patients with abnormal hearing in the VS-ipsilateral ear, there exists a long-term risk of progression to moderate hearing loss in the contralateral ear as well. Combined with the absence of significant changes in word understanding in the affected ears, these findings may provide clues to the nature of tumor-secreted factors involved in VS-associated hearing loss. Female predominance within the VS patient population is confirmed, driven mostly by younger female patients with Koos 4 tumors.

Keywords: contralateral; hearing loss; outcomes; secreted factors; vestibular schwannoma.

Figure 1

Screening approach from Mass Eye and Ear audiology database for VS patients to include in study, as described in methods.

Figure 2

Kaplan-Meier curves for HL progression in patients with baseline normal hearing bilaterally (WRS ≥ 92% and PTA ≤ 25 dB bilaterally); see Table 3 for demographics. Analysis uses three-tone PTA to assess baseline hearing in (A,D), as well as endpoint in (A), while four-tone PTA used, respectively in (B,C,E,F). Endpoint bone three-tone PTA > 40 dB (moderate HL); (B) Endpoint bone four-tone PTA > 40 dB (moderate HL); (C) Endpoint word understanding <78%; (D) Endpoint bone three-tone PTA > 55 dB (moderately severe HL); (E) Endpoint bone four-tone PTA > 55 dB (moderately severe HL); (F) Endpoint word understanding <60%. All control ears with normal baseline hearing defined by same criteria as for VS-ipsilateral and contralateral ears.

Figure 3

Kaplan-Meier curves for HL progression in patients with baseline abnormal hearing in VS-ipsilateral ear (WRS < 92% and PTA > 25 dB) and baseline normal hearing in VS-contralateral ear (WRS ≥ 92% and PTA ≤ 25 dB); see Table 3 for demographics. Analysis uses three-tone PTA to assess baseline hearing in (A,D), as well as endpoint in (A), while four-tone PTA used, respectively in (B,C,E,F). (A) Endpoint bone three-tone PTA > 40 dB (moderate HL); (B) Endpoint bone four-tone PTA > 40 dB (moderate HL); (C) Endpoint word understanding <78%; (D) Endpoint bone three-tone PTA > 55 dB (moderately severe HL); (E) Endpoint bone four-tone PTA > 55 dB (moderately severe HL); (F) Endpoint word understanding <60%. All control ears with normal baseline hearing defined by same criteria as for VS-ipsilateral and contralateral ears.