Incidence of Iatrogenic Inner Ear Breaches from Vestibular Schwannoma Surgery: A Review of 1,153 Hearing Preservation Approaches

Background: Vestibular schwannoma (VS) surgery is a common procedure which often requires precise drilling close to the inner ear labyrinth. A breach of the vestibulocochlear system from drilling is correlated with hearing loss and third window symptoms such as vertigo, nystagmus, autophony, and Tullio’s phenomenon (sound induced vertigo), among others.[1] Inner ear breaches (IEB) have been reported as high as 30% in the patients undergoing retrosigmoid approaches to the internal auditory canal,[2] but these figures were reported in the early 1990s with small cohorts. Studies describing VS surgical complications commonly report CSF leak, hydrocephalus, wound infection, and hematoma, among others, all with incidences below 10%;[3] [4] but there remains a paucity of data regarding IEB from VS surgery in the recent literature.

Objective: The aim of the study is to assess the rate of iatrogenic injury to the inner ear labyrinth in VS resections via hearing preservation (retrosigmoid [RS] and middle cranial fossa [MCF]) approaches.

Methods: We performed a multi-institutional chart review of all operative cases of VS performed between 1993 and 2015 across three tertiary care centers. Only surgeries undergoing hearing preservation approaches were considered for analysis. Preoperative imaging, operative notes, and postoperative imaging were reviewed for each case. IEBs were confirmed by report in operative note or consensus opinion of two neuroradiologists reviewing the postoperative CT.

Results: A total of 1,153 patients underwent hearing preservation approaches for VS resection. One thousand seventy-five (93.2%) patients underwent RS, and 78 (6.8%) underwent MCF approaches. IEB was confirmed in 248 (21.5%) of all cases reviewed: operative notes reported IEB in 102 cases, of which 50 had no postoperative CT for review; postoperative CT confirmed an additional 146 cases of IEB. Postoperative CT was available in 378 patients (32.8% of total cases reviewed), of which 198 (52.4% of postoperative CTs) showed areas of inner ear dehiscence attributable to drilling. Of the patients with confirmed IEB on postoperative CT, 96 patients (38.7%) did not have a record of IEB mentioned in the operative note.

Conclusion: IEB was confirmed in 21.5% of VS surgeries utilizing hearing preservation approaches. IEB is correlated with hearing loss and its occurrence negates the intention of selecting a hearing preservation approach for tumor resection. Due to low rates of postoperative CT available and the lack of reporting IEB in operative notes, we postulate that our confirmed cases likely underestimate the true incidence of IEB sustained in VS surgery undergoing RS and MCF approaches.

• References

• Bartholomew RA, Poe D, Dunn IF, Smith TR, Corrales CE. Iatrogenic inner ear dehiscence after lateral skull base surgery: therapeutic dilemma and treatment options. Otol Neurotol 2019; 40 (04) e399-e404
• Tatagiba M, Samii M, Matthies C, el Azm M, Schönmayr R. The significance for postoperative hearing of preserving the labyrinth in acoustic neurinoma surgery. J Neurosurg 1992; 77 (05) 677-684
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