Ventral Compression of the Trigeminal Nerve by the Superior Cerebellar Artery: A Novel Intraoperative Classification...

The superior cerebellar artery (SCA) is the most common offending vessel in microvascular decompression (MVD) for trigeminal neuralgia (TN). Among its variations, ventral compression presents unique surgical challenges, yet systematic classification remains limited. This study aimed to establish a novel intraoperative classification of ventral SCA compression and to evaluate its surgical and clinical relevance.

We retrospectively reviewed patients with TN who underwent MVD by the senior author between February 2019 and February 2024. Intraoperative video recordings were analyzed to categorize ventral-type SCA compression into 4 subtypes, based on the anatomic relationship with the trigeminal nerve and the facial-vestibulocochlear nerve complex. Patient demographics, operative findings, decompression techniques, and postoperative outcomes were compared across subtypes.

Eighty-eight patients with SCA compression were identified and classified into 4 subtypes: type 0 (36.4%), SCA rostral to the trigeminal nerve; type I (35.2%), SCA ventral to the nerve without extending below its inferior border; type II (18.2%), SCA looping ventrally with its lowest point between the trigeminal and facial-vestibulocochlear nerves; and type III (10.2%), SCA extending ventrally beyond the superior border of the facial-vestibulocochlear complex. No statistically significant differences were observed in postoperative pain relief or complication rates across subtypes (P>0.05). However, surgical complexity varied considerably, with hidden compression at the trigeminal root entry zone and excessive vascular tortuosity contributing to greater intraoperative difficulty. Tailored surgical strategies, including the "push-and-flip" technique, enabled safe and effective decompression.

This study proposes a novel intraoperative classification of ventral SCA compression in TN. While short-term clinical outcomes were similar across subtypes, the classification emphasizes key anatomic variations that significantly affect surgical complexity. Recognition of these subtypes may facilitate operative planning, improve surgical safety, and reduce the risk of recurrence in patients undergoing MVD.