Table 1.
Proposals for standardization of intraoperative FNM in parotid surgery.
| Phases | Procedures | Remarks |
|---|---|---|
| Pre-operative | Pre-operative video recording of facial expression | Four dynamic facial movements: wrinkling foreheads, tightly closing eyes, whistling and a wide smile |
| Intra-operative | FNM setup | Recording electrodes are inserted into the muscles over lower forehead, infraorbital area, superolateral upper lip and inferolateral lower lip |
| General anesthesia (NMBA use) | (1) A small dose of non-depolarizing NMBA (rocuronium, 0.3 mg/kg or mivacurium, 0.2 mg/kg), (2) standard dose of rocuronium combined with reversal agent (sugammadex, 1–2 mg/kg) |
|
| FNM procedures (V-L-F1-F2) | ||
| V—Verification (10 mA) | Stimulus for mandibular angle area and verification of the functional FNM system before parotid gland dissection | |
| L—Localization (5 mA) | Stimulus for FN trunk during parotid gland dissection and facilitate the identification of the FN trunk | |
| F1—Pre-dissection FN signal (3–5 mA) | Signals were obtained when the FN trunk is first identified | |
| F2—Post-dissection FN signal (3–5 mA) | Signals were obtained after dissecting the FN branches and resecting the parotid tumor | |
| Interpretation of EMG signals (F1/F2 ratio) | Prediction of facial expression outcome | |
| Unchanged or Increased | Intact FN branch function | |
| Decreased (>20%↓) | Neural injury point mapping procedure—Mapping the injured area of the corresponding FN branch from the distal to proximal end with 1 mA | |
| Post-operative | Post-operative video recording of facial expression | The dynamic movements of individual muscle groups over four separate facial regions are recorded and the total score of the patient’s facial function was 12, registered as T(0–3)Z(0–3)B(0–3)M(0–3) |
| 0 (Severe facial dysfunction) | A complete lack of dynamic movement | |
| 1 (Moderate facial dysfunction) | Obvious asymmetrical dynamic movement, but movement is observable | |
| 2 (Mild facial dysfunction) | Slightly asymmetrical dynamic movement, but symmetrical expression can be achieved after the movement is completed | |
| 3 (Normal facial function) | Fully symmetrical dynamic movement of the facial area |
FN: facial nerve; FNM: facial nerve monitoring; EMG: electromyography; NMBA: neuromuscular blocking agents.