Use of supramaximal stimulation to predict facial nerve outcomes following vestibular schwannoma microsurgery: results from a decade of experience

Abstract

In a large cohort of patients, the authors found that interrogating intraoperative FN function with SMS is safe and technically simple. It is useful for predicting which patients will ultimately have good facial function, but is very limited in identifying patients destined for long-term facial weakness. This test may prove helpful in the future in tailoring less than gross-total tumor removal to limit postoperative facial weakness.

Surgical salvage of recurrent vestibular schwannoma following prior stereotactic radiosurgery

“…Intraoperative facial nerve electroprognostic testing was performed using proximal minimum stimulation thresholds or the supramaximal stimulation technique described previously . Facial nerve dissection was noted to be subjectively more difficult secondary to adherent and or poorly defined surgical planes at the nerve–tumor interface.…”

The intermedius nerve as a confounding variable for monitoring of the free-running electromyogram

“…All contemporary means of facial nerve monitoring in vestibular schwannoma patients (like corticobulbar motor evoked potentials and direct electrical stimulation) are universally, at least to some degree, flawed by false positive monitoring results, which lead to positive predictive values of only 46-61% (Dong et al, 2005;Fukuda et al, 2008;Liu et al, 2007;Matthies et al, 2011;Schmitt et al, 2013). For quantitative monitoring of the free-running EMG by realtime-assessment of traintime, a positive predictive value of 64% (Prell et al, 2010) has been calculated, which is in the same unfavorable range.…”

Supramaximal neurostimulation with laryngeal palpation to predict postoperative vocal fold mobility

“…Supramaximal stimulation is usually used when the maximal response is needed for peripheral nerve conduction studies in which all measurements are based on the assumption that all axons are depolarized by supramaximal stimulation . In parotid surgery, supramaximal stimulation during intraoperative electromyographic facial nerve monitoring was suggested as a reliable method to predict early functional outcome of facial muscles, and in other types of facial nerve surgeries, supramaximal stimulation had better predictive values than other neuromonitoring methods . Recently, advances in IONM for prediction of immediate postoperative VF function using EMG‐equipped endotracheal tubes have been reported, with most studies showing a high NPV (>99%) and a low PPV (11% to 62%) .…”