Hearing preservation after removal of small vestibular schwannomas by retrosigmoid approach: comparison of two different ABR neuromonitoring techniques
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Background and objective
Goals of small vestibular schwannoma (VS) microneurosurgery are as follows: radical resection, facial nerve (FN) preservation, and hearing preservation (HP). Microsurgical advances make HP possible in many patients with preoperative socially useful hearing (SUH). We evaluated postoperative HP in VS with maximum diameter < 2 cm monitored with two different auditory brainstem response (ABR) techniques.
Materials and methods
Twenty-eight consecutive non-randomized patients with SUH suffering from small VS underwent keyhole microneurosurgery by retrosigmoid (RS) approach. Selection criteria are as follows: speech discrimination > 50%, pure tone audiogram < 50 dB loss (50/50 criterion; AAO-HNS classes A–B), maximum diameter < 2 cm. HP was attempted with intraoperative ABR, evoked by classical Click (16 cases, group 1) and LS-CE-Chirp® stimulus (12, group 2).
Mean age was 47.5 years (16–75); average maximum diameter was 1.35 cm (0.5–1.9 mm). Total and nearly total resection (> 95%) was obtained in all, as confirmed by 24–48-h postoperative enhanced MRI. Mortality and major morbidity were 0. In all cases, FN was preserved; in 3, incomplete deficit recovered within few weeks. Socially useful HP (pre- and postoperatively) was 64.3% (18 of 28): 56.25% group 1 and 75% group 2 (p = NS). Postoperative ipsilateral deafness was observed in 5 cases of group 1 (p < 0.0001). Preoperative tinnitus had negative impact on HP (p < 0.05).
Microsurgery can cure small growing VS with SUH. Our limited experience confirms that keyhole RS removal assisted by intraoperative ABR monitoring leads to valuable rates of SUH. LS-CE-Chirp–evoked ABRs allow a safe, effective, and clear neurophysiological feedback and are faster and, thus, more useful than the Click-ABR.
KeywordsABR LS-CE-Chirp Hearing preservation Facial nerve preservation Microsurgery Retrosigmoid approach Vestibular schwannoma
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (name of institute/committee) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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