A Novel Strategy of Transvenous Embolization of Anterior Condylar Confluence Dural Arteriovenous Fistulas Under Hypoglossal Nerve Monitoring to Prevent Postoperative Nerve Palsy: A Technical Note Regarding 2 Cases

BACKGROUND AND IMPORTANCE: Dural arteriovenous fistula (dAVF) of the anterior condylar confluence (ACC) is often treated with transvenous embolization (TVE), but postoperative hypoglossal nerve palsy is a critical complication. We report herein 2 cases of ACC dAVF treated with TVE under motor evoked potential (MEP) monitoring of the hypoglossal nerve. We used transcranial MEPs for hypoglossal nerve monitoring with corkscrew electrodes inserted in C3 and C4. Constant current stimulation was set with short trains, a pulse duration of 0.2 ms and an interstimulus interval of 1.5 ms. We also recorded transcranial MEPs of the upper and lower limbs and compound muscle action potentials of the tongue. A >50% reduction in MEP amplitude during the procedure was regarded as the warning criterion. Only coils were used for TVE. CLINICAL PRESENTATION: In Case 1, no reduction in hypoglossal nerve MEPs was observed during TVE. Conversely, Case 2 showed a transient reduction in MEPs during coil embolization. When the operator immediately repositioned the coil, this reduction normalized. Finally, each patient achieved complete obliteration without hypoglossal nerve palsy. During the procedure, the operator obtained real-time feedback from monitoring and could check whether nerve palsy because of coil migration or balloon inflation was occurring. This feedback was helpful for achieving complete occlusion while preserving hypoglossal nerve function. CONCLUSION: Real-time information from hypoglossal nerve monitoring is very useful for operators and may lead to safer TVE procedures for ACC dAVF.