Management of petrosal veins during microvascular decompression for trigeminal neuralgia.

OBJECTIVE Venous compression might be the main cause of incomplete decompression and symptom recurrence after microvascular decompression (MVD) in patients with trigeminal neuralgia. Although it can be killed in most cases, cutting the vein sometimes has the potential risk arising from venous congestion. To maneuver the vein safely, we introduced a temporary occlusion test of the vein. METHODS Among 407 consecutive MVD cases, 48 (11.8%) offending and 157 block veins were encountered. The vein was cut directly in 147 (71.7%). Owing to the potential risk following killing of the vein, 58 (28.3%) patients underwent venous occlusion test with neurophysiologic monitoring during the operation. The temporal occlusion should be ceased immediately as soon as any changes in brainstem auditory evoked potential (BAEP) or trigeminal evoked potential (TEP) wave figuration turn up; otherwise, it would last for 15 minutes. RESULTS The occlusion test was negative in 53 (91.4%), while positive in five patients (8.6%). According to the results, we cut the vein in test-negative patients, which made the operation easy and offered a satisfactory decompression. Among the five positive cases, the vein was finally saved in two and cut in three cases. Yet, all the three patients developed a severe ipsilateral cerebellar edema and brainstem shift after the vein was sacrificed. Despite those patients were reoperated on immediately for posterior fossa decompression, they remained equilibrium disorder with numbness in ipsilateral face and mind hemiparesis in contralateral extremities post-operatively. The residual two patients had an incomplete pain relief. CONCLUSION This venous occlusion test could help the surgeon in making a right decision before manipulation of the petrosal veins during MVD.