1081 Re-Do Microvascular Decompression (MVD) Surgery for Recurrent/Persistent Trigeminal Neuralgia (TN): Pattern of Failure (POF) Analysis and Operative Findings in 164 Re-Do MVD’s Over 18 Years

INTRODUCTION: As more neurosurgeons perform MVD, persistent/recurrent TN after first MVD attempt is becoming more common. METHODS: 164 sequential re-do MVD’s for persistent/recurrent TN from prospective database over 18 years, retrospectively analyzed. Retrosigmoid craniectomy (RSC) with intra-operative ABR, monitoring. Endoscope assisted (EA) in 59 (25%). Temporal bone dissection (TBD) in 7 (0.6%). Our re-do 23 [14% - 2/23 (35%) pediatric, 16y-22y at re-do]. 141 (86%) initial operation elsewhere. Intra-operative findings carefully documented & photographed. Clinical evaluations, 3m, 1y, & annually. Pain relief for typical neuralgic pain (TNP) & atypical neuralgic pain (ATNP), 0-10 scale. RESULTS: Shredded Teflon felt (TF) found in 75.6%, non-shredded TF (15.9%), no material (8%), Ivalon 2 patients & Cellulose, Telfa, Dacron & Gortex in 1 each. Two patients material on cranial nerves (CN) 7/8. Only 6 negative explorations (all our own). Multiple vessels identified 146 (89%). Arteries & Veins 139 (84.8%). Veins only 16 (9.8%), Artery +/- unnamed artery Branch(es) (UAB) only 8 (4.9%). 135 vessels dorsal/lateral proximal third under Cerebellar Ala (CA). 95 vessels ventral/medial middle third, 76 vessels ventral/medial distal third. Failure to mobilize the CA was the proximate cause in 78/164 (47.6%0 of patients. Re-do from elsewhere 70% pain-free (PF) TNP and 50% =50% improved ATNP. Our own re-do MVD only 30% pain-free (PF) TNP and =50% improved ATNP. CONCLUSIONS: Not releasing tethering veins to mobilize the CA is the major cause of technical failure of MVD for TN with failure to adequately expose/explore the dorsal/lateral proximal third of the CN 5 shoulder-nerve root-brainstem junction, followed by failure to appreciate the potential causal nature of veins &/or UAB’s, followed by failure to explore the ventral medial aspect of the nerve root, followed by poor distal exposure due to failure to remove obscuring bone. Endoscopic assistance & TBD are useful adjuncts.