The laryngeal adductor reflex (LAR) monitoring technique, elicited by electrical stimulation of the vocal fold mucosa with endotracheal tube surface based electrodes, has been proved to be a reliable and robust method for intraoperative monitoring of the integrity of the Vagus nerve in thyroid and cervical spine surgery. It is based on the recording of the contralateral R1(cR1) and R2(cR2) motor responses using the endotracheal tube electrode contralateral to the stimulating electrode. Its utility however is still to be validated for posterior fossa surgery, especially when lower cranial nerves, such as the Vagus, are at risk of injury such as in oncological surgery near the cerebello-pontine angle.
We are presenting a case series of 4 patients who underwent cerebello-pontine angle surgery using the aforementioned technique along with a multimodal setting for intraoperative monitoring (IOM) including free run EMG and corticobulbar MEPs for cranial nerves. In all of our patients, the LAR was 100% reliably elicited and could predict changes even before the appearance of alterations in the other more traditional modalities of IOM. No peri-operative complications or adverse outcomes were observed.
We therefore conclude that the LAR is a reliable method to monitor the entire vagus nerve reflex arc and shows a promising utility in posterior fossa surgery.