Intraoperative monitoring of trigemino-palatal responses

Our study aim was to describe the methodology for intraoperative recording of trigemino-palatal responses during posterior fossa surgeries.

Trigeminal nerve stimuli (2-4 pulses with 200-500 µs duration, 2 ms inter-stimulus interval, 25-50 mA) was applied to V3 under the zygomatic arch. Responses were recorded through needle electrodes inserted bilaterally in the soft palate, and through surface electrodes embedded in the endotracheal tube. Onset latency (L), duration (D) and peak-to-peak amplitude (A) were measured in each triggered response.

The trigemino-palatal responses were successfully recorded in 23 out of 38 patients, bilateral in 12 of them. Response data (mean and IC 95 %) were L: 42 ms [35-57 ms]; D:45 ms [23-61 ms]; A:67 µs [57-183 µs]. Vocal cords responses were also recorded to trigeminal V3 stimulation in six patients with L:40 ms [37-47 ms]; D:25 ms [18-65 ms], and A: 70 µs [37-96 µs].

Trigemino-palatal responses were obtained under general anesthesia and used for the monitorization of patients submitted to posterior fossa surgery. Further studies are needed to foster the use of these responses for intraoperative monitorization.

Trigeminal V2/V3 branches trigger brainstem palatal responses that remain obtainable after general anesthesia.