The Retrosigmoid Keyhole Craniotomy as a Minimally Invasive Approach to Cerebellopontine Angle Lesions: A Systematic Review

Introduction: The retrosigmoid keyhole craniotomy (RSKC) was developed in the early 2000s through efforts to reduce OR time and surgical morbidity while providing excellent access to the ventrolateral brainstem and CPA. A well-planned RSKC circumvents the need to expose neural elements that might otherwise be desiccated.

Methods: Per PRISMA guidelines, we performed a three-database systematic review to accomplish our objective of identifying all studies reporting outcomes associated with surgical resection of CPA lesions via the RSKC.

Results: Eight studies reporting 778 patients met inclusion criteria. Among the 221 patients for whom sex was reported, 104 (47.1%) were female. The mean age across studies was 34.5 years. The most common CPA lesions were vestibular schwannomas (n=683, 87.8%) and epidermoids (n=57, 7.3%), while other lesions included CPA meningiomas and arachnoid cysts. Rates of GTR were high, ranging from 94.0% to 94.6%, with rates of near-total resection approaching 100%. Postoperative residual occured only when tumor was strongly adherent to cranial nerves (enabling important objectives such as hearing preservation). Otherwise, superior [relative to rates obtained using conventional approaches] total resection rates in addition to comparable hearing and facial nerve functional preservation were obtained. Overall, surgical morbidity was minimized. Further, the biological properties of CPA epidermoids are perfectly suited for neuroendoscopic resection via the RSKC, and the flexibility afforded by this approach enables MIS resection of large (> 4 cm) vestibular schwannomas with excellent outcomes.

Conclusion : The RSKC is perfectly suited for obtaining GTR of vestibular schwannomas, epidermoids, and other CPA lesions while sparing damage to adjacent neurovascular structures. Nonetheless, special care must be taken to avoid thermal injury from the endoscopic tip and to prevent hemorrhage at all costs. Bleeding within the narrow operative keyhole corridor can quickly obscure visualization of the operative field, making it difficult to identify the source and resulting in potentially devastating neurological deficits.