Effect of two fascial incision options for access to the temporomandibular joint on facial nerve function: objective investigation

This study was performed to compare the effects on facial nerve (FN) function of the deep supra-temporalis muscle subfascial approach (DSFA) and traditional fascial approach (TFA) for access to the temporomandibular joint (TMJ), via qualitative and quantitative evaluations. Thirty patients requiring open TMJ surgery were randomly allocated to one of two groups: group A patients underwent the DSFA approach, while group B patients underwent the TFA approach. The TMJ was accessed via modified endaural incision with temporal extension. Clinical examinations, FN conduction tests, and electromyography (EMG) of the frontalis and orbicularis oculi muscles were used to assess FN function. A FN function deficit was noted in 50% of the whole sample population immediately after surgery, with no statistically significant difference between the groups (P = 0.082). Overall, 37.5% of the total study population experienced temporary loss of frontalis muscle activity, while zygomatic nerve injury was seen only in 25% of group A. Within 2-6 months, normal function returned in both groups. Nerve conduction studies showed no statistically significant difference between the groups in terms of nerve amplitude or latency after surgery. However, EMG of orbicularis oculi activity showed a significant difference between the groups after 6 months (P = 0.010). The results suggest that the traditional dissection approach is more protective of the FN, especially the zygomatic branch, than the deeper dissection technique.