gms | German Medical Science

Objective: Facial nerve function can be continuously monitored by transcranial facial nerve motor evoked potentials (FNMEPs) during neurosurgical interventions. Despite their advantages, FNMEPs are not yet widely used. While there are several publications of FNMEP in adults, the feasibility and safety of FNMEP in children has not yet been documented.

Method: We included 10 consecutive procedures involving 10 patients (median age 2.5 y, range 1-15 y, 7 male) that were operated by the senior author in 2013 and in whom FNMEPs were monitored. A threshold increase greater than 20 mA for eliciting FNMEPs in the most reliable facial nerve target muscle was considered a prediction of reduced postoperative facial nerve function, and subsequently a warning was issued to the surgeon. Preoperative and early postoperative function was documented using the House-Brackmann (HB) grading system.

Results: Monitoring of FNMEPs was feasible in all 10 surgeries in at least one facial nerve target muscle. The mentalis muscle yielded the best result (89% of trials), followed by orbicularis oris (85%) and orbicularis oculi muscles (80%). The median stimulation threshold was initially 69 mA (range 40-100 mA) for FNMEP and 60 mA (15-95 mA) for MEP of the thenar muscles. The initial FNMEP threshold exceeded the MEP threshold in 5/10 patients (median difference 5 mA). FNMEP deterioration showed a specificity for HB deterioration of 88% CI [47-100%].

Conclusions: Intraoperative FNMEP monitoring is feasible and safe also in young children. We found no evidence that procedures and thresholds should differ from FNMEP in adults.