Intraoperative Mapping of the Sensory Root of the Trigeminal Nerve in Patients with Pontocerebellar Angle Pathology

-OBJECTIVE: The aim of the present study was to deter-mine the position of the 3 sensory branches of the tri-geminal nerve in the preganglionic tract using intraoperative neurophysiological mapping.-METHODS: We included consecutive adult patients who u nderwent neurosurgical treatment of cerebellopontine angle lesions. The trigeminal nerve was antidromically stimulated at 3 sites along its circumference with different stimulus intensities at a distance of 1 pound cm from the brainstem. The sensory nerve action potentials (SNAPs) were recorded from each main trigeminal branch (V1 [ophthalmic branch], V2 [maxillary branch], and V3 [mandibular branch]).-RESULTS: We analyzed 13 patients. The stimulation points at which we obtained the greatest number of congruous and exclusive SNAPs (SNAPs only on the stimulated branch) was the stimulation point for V3 (20.7%). The stimulation intensity at which we obtained the highest n umber of congruent and exclusive SNAPs with the stim-u lated branch was 0.5 mA.-CONCLUSIONS: Using our recording conditions, tri-geminal stimulation is a reliable technique for mapping the V3 and V1 branches using an intensity not exceeding 0.5. However, reliable identification of the fibers of V2 is more difficult. Stimulation of the trigeminal nerve can be a reliable technique to identify the V3 and V1 branches if rhizotomy of these branches is necessary.

Automated summary

The study shows that using intraoperative neurophysiological mapping to determine the position of the sensory branches of the trigeminal nerve is reliable for mapping the V3 and V1 branches with a stimulation intensity not exceeding 0.5 mA. Reliable identification of the fibers of V2 branch is more challenging. Stimulation of the trigeminal nerve can be a reliable technique to identify the V3 and V1 branches if rhizotomy is necessary.