Abstract
Objectives:
The aim of this study was to assess the relationship between the stimulation amplitude and the distance to the facial nerve.
Methods:
This study was designed as a prospective clinical study. A total of 20 patients (12 males, 8 females) were included. Partial superficial parotidectomy was performed in all patients with intraoperative facial monitoring. Measurements were made on the main trunk and major branches. Stimulation was started at 1 mA and incrementally increased to 2 and 3mA’s. The shortest distance creating a robust response (>100mV) was recorded.
Results:
At 1 mA, 2 mA and 3 mA stimulation intensity, the average distance between the tip of the stimulation probe and the main trunk was 2.20±0.76 mm (range 1-3 mm), 3.80±0.95 mm (range 2-5 mm), 4.80±1.05 mm (range 3-7 mm) respectively. The stimulus intensity was inversely proportional in respect to the distance between the nerve and the tip of the stimulus probe (P < .00). The same relation was present in the facial nerve major branch measurements (P < .00).
Conclusion:
The proportional stimulation amplitude and distance to the facial nerve is thought to be a reliable auxillary method to assist the surgeon by facilitating the estimation of the distance to the facial nerve during extracapsular dissection and minimally invasive cases where the facial nerve isn’t routinely dissected.
Level of evidence: Level 3.
KEYWORDS
Parotid surgery; Facial nerve; Intraoperative facial monitoring; Electromyography
HIGHLIGHTS
The facial nerve may not be routinely dissected in minimally invasive parotid surgery.
Facial nerve stimulator might be used as a navigation tool to estimate the distance to the nerve.
The distance to the nerve can be predicted by increasing the stimulus intensity.
The facial nerve is stimulated from an average of 2.20 ±0.76 mm (range 1-3 mm) when the stimulus intensity is 1 mA.
Distance to the major branches of the facial nerve can also be predicted with the stimulator.
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