On the Surgical Implications of Peritrigeminal Perforating Vessels in Microvascular Decompression

BACKGROUND: Perforating branches arising from the superior cerebellar artery (SCA) or anterior inferior cerebellar artery (AICA) that pierces the brainstem within 5 mm of the trigeminal root may limit offending vessel transposition during microvascular decompression for trigeminal neuralgia. OBJECTIVE: To investigate the microsurgical anatomy of peritrigeminal perforators and evaluate their effect on the mobility of the SCA and AICA. Additionally, we propose strategies for mitigating the potential complications caused by the presence of short peritrigeminal perforators. METHODS: Retrosigmoid approaches and exposure of the upper cerebellopontine angle were performed on 11 cadaveric heads (22 sides). The number, origin, and course of perforators were recorded and each was classified as either type I, short straight (<3 mm); type II, long straight perforators (>3 mm); or type III, long circumflex (>3 mm). Transposition of each SCA and AICA away from trigeminal nerve was performed, and degree of mobilization was evaluated and graded. RESULTS: A total of 123 perforators were identified, of which 44 were considered peritrigeminal. Of these, 19 arose from the AICA, 18 from the SCA, and 7 from the basilar artery. Type I peritrigeminal perforators were the most common at 77.3%. Transposition or interposition of the parent vessel was not possible in 8 (47.1%) instances. CONCLUSION: Identification of inhibiting perforators is essential before performing microvascular decompression to avoid ischemic injury to the brainstem. The presence of type I perforators may necessitate extensive arachnoid dissection and use of an interpositioning technique with minimal repositioning of the offending vessel.