Surgical Management of Internal Acoustic Canal Stenosis Due to Exostoses and Osteomas

Background: Exostoses and osteomas are benign, insidious lesions of the skull base bone. Although histologically distinct, both of these lesions can present with hyperostotic growth adjacent to the IAC resulting in compression of neurovascular structures. Patients with such lesions often present with progressive sensorineural hearing loss, vertigo, and tinnitus. Surgical decompression of the IAC can result in satisfactory radiographic results; however, clinical outcomes following surgical decompression have not been previously reviewed.

We present our clinical experience treating two patients with IAC exostoses with surgical decompression, and we review the existing literature to summarize expected clinical outcomes for vertigo, tinnitus, and hearing loss.

Methods: We reviewed the clinical presentation, surgical management, and outcomes of two patients with IAC stenosis managed with retrosigmoid craniotomy for surgical decompression. A literature search was also conducted using PubMed Central, Web of Science Core Collection, and Google Scholar databases to identify previous reports of IAC exostoses and osteomas. We summarize the clinical presentation, medical and surgical management strategies, and patient outcomes in this series of patients with IAC stenosis due to exostosis or osteoma.

Results: Both patients in our institutional series experienced significant improvement in tinnitus and vertigo following surgical decompression. Hearing remained stable immediately after surgery, although one patient experienced progressive hearing loss during the long-term follow-up period. Our literature review identified 26 previous cases of IAC stenosis, of which 21 were due to osteomas and 5 were due to exostoses. Detailed treatment and outcome data were available for 23 of these patients. Most patients in this series presented with symptoms of vertigo, tinnitus, and/or hearing loss ([Table 1]). Treatment strategies included surgical decompression of the IAC (n = 13) or medical treatment (n = 10).

Of the 13 patients who underwent surgical decompression, all experienced significant improvement in vertigo and tinnitus while maintaining their preoperative hearing function. Of the 10 patients in the literature treated with medical management alone, only 3 cases reported complete clinical outcomes: two patients having resolution of vertigo symptoms, and one patient having improved hearing function.

Conclusion: Internal acoustic canal exostoses and osteomas are rare lesions that lead to insidious onset of debilitating symptoms from vestibulocochlear nerve dysfunction due to IAC stenosis. Patients presenting with vertigo and tinnitus may experience significant improvement following surgical decompression, with low risk of hearing loss. Medical treatment may be prudent for asymptomatic patients or those with unsalvageable hearing. Further studies are necessary to better understand the role of surgery in management of patients with IAC stenosis due to exostoses and osteomas.