Neuroendoscopic anatomy and surgery of the cerebellopontine angle.

To probe the feasibility and utility of neuroendoscopic inspection of the anatomy of the cerebellopontine angle (CPA) and of neuroendoscopic assisted microneurosurgery (NEAMN) for CPA lesions via a retrosigmoid approach, we used retrosigmoid NEAMN in 28 patients with CPA lesions. Prior to this, we undertook anatomical observation of bilateral CPA in two adult cadaver heads using the neuroendoscope. NEAMN tumour resection was performed in eight acoustic neuromas, one meningioma and 14 cholesteatomas and NEAMN vascular decompression was performed in five patients with trigeminal neuralgia. Both the neurovascular structures of the CPA and the ventral surface of the pons, as well as the clivus, can be inspected using the neuroendoscope through a retrosigmoid approach with a 2-3 cm diameter bony opening. Complete excision of the tumour with preservation of the facial nerve was achieved in all eight acoustic neuromas. Likewise, total resection of the tumour was possible in the 14 cholesteatomas and one meningioma. Paroxysmal facial pain resolved after NEAMN vascular decompression in the five patients with trigeminal neuralgia. There were no postoperative complications or deaths in this series. The CPA can be divided into three levels - the cranial, medial, and caudal, and each level contains specific neurovascular structures as seen through the neuroendoscope. Knowledge of these divisions is useful to master the common NEAMN procedures of the CPA. NEAMN for CPA lesions via a retrosigmoid approach is a useful adjunct to standard microneurosurgical techniques effect and may decrease the operative risk.