[Surgical management and prognosis of iatrogenic peripheral facial nerve injury following middle ear surgery].

OBJECTIVE: To discuss the causes, sites, management strategies and curative effects of accidental facial nerve paralysis in the middle ear surgery.

METHODS: Forty two cases with peripheral facial nerve paralysis following middle ear surgery who underwent surgical exploration and reanimation were analyzed. Facial nerve decompression, primary end-to-end anastomosis, interpositional nerve grafts with the great auricular nerve and nerve substitution of facial-hypoglossal anastomosis were applied to restoration of the facial nerve function. The facial nerve function was graded according to House-Brackmann (HB) Grade.

RESULTS: The most common operation complicating iatrogenic facial nerve injury was mastoidectomy, and the common sites of the injured facial nerve were the tympanic segment and pyramid segment. The facial nerve exploration showed facial nerve edema in nine cases (21.4%), injury of the facial nerve sheath was observed in 10 cases (23.8%), partial nerve fibers transection was found in four cases (9.5%), total nerve fibers transection was detected in 17 cases (40.5%) and two cases (4.8%) with facial nerve anatomical integrity. Facial nerve re-animation methods include facial nerve decompression in 24 cases (57.1%), end-to-end anastomosis in two cases (4.8%), end-to-end anastomosis after nerve transfer in two cases (4.8%), interpositional nerve grafts with the great auricular nerve in 10 cases (23.8%) and facial-hypoglossal nerve anastomosis in four cases (9.5%). The facial nerve function was graded according to House-Brackmann Grade before and after surgery. Twenty eight patients were followed up more than one year. For the 17 cases who received facial nerve decompression, four cases recovered to House-Brackmann Grade I, 11 cases recovered to House-Brackmann Grade II, two cases recovered to House-Brackmann Grade III. For the five cases who underwent the great auricular nerve grafting, three cases recovered to House-Brackmann Grade II, two cases recovered to House-Brackmann Grade III. For the four cases who received facial-hypoglossal nerve anastomosis recovered to House-Brackmann Grade III. For the two cases who underwent the end-to-end anastomosis recovered to House-Brackmann Grade II.

CONCLUSIONS: The tympanic segment and pyramid segment are more vulnerable to be injured during mastoid surgery. The injured facial nerve should be explored and repaired. The methods include facial nerve decompression, end-to-end anastomosis, end-to-end anastomosis after nerve transfer, interpositional nerve grafts with the great auricular nerve and facial-hypoglossal nerve anastomosis.