Dear Editor,
We pleasantly read the recent paper “Hearing preservation in vestibular schwannoma surgery via retrosigmoid transmeatal approach” by Matsushima et al. [4] who describe their technique in vestibular schwannoma surgery.
The respect of integrity of the inner ear structures during the drilling of the petrous bone is essential in order to preserve the hearing. Indeed a technique for the safe opening of internal acoustic meatus (IAM) is not generally agreed upon [1].
In literature, different techniques for preservation of the inner ear structures were reported. Tatagiba [8] and Yokoama [9] introduced the concept of a “safety line” for estimating the risk of labyrinth injury; others [2, 3, 5] used purely anatomical landmarks. Recently, studies integrating anatomical and neuronavigation data were published [6, 7].
In the paper by Matsushima et al.1, drilling area is routinely measured on preoperative CT scans. We would be glad to know which kind of measures were taken and how they were intraoperatively used.
In our experience, labyrinth injury cannot always be avoided during surgery, but we identified a safer area of drilling within a distance of 5 mm laterally from the posterior lip of IAM. The integration of the basic anatomic knowledge and new tools, such as a very precise navigation and finer instruments, should allow developing a trough that will lead to exposure of the IAM without entering inner ear structures.
Dr. G. Trevisi
Dr. G. Beggio
Dr. F. Raneri
References
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Trevisi, G., Beggio, G. & Raneri, F. Hearing preservation in vestibular schwannoma surgery. Acta Neurochir 162, 71 (2020). https://doi.org/10.1007/s00701-019-04140-8
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DOI: https://doi.org/10.1007/s00701-019-04140-8