Surgical treatment of intratemporal lesions of the facial nerve

The article provides a brief literature data analysis on intratemporal facial nerve lesions of different etiology. The article describes the improved methods of surgical treatment of patients with intratemporal facial nerve lesions, such as end-to-end neurorrhaphy, as well as using the sural nerve autograft. The preliminary results of the rehabilitation of patients with this pathology are presented. According to world literature, facial nerve lesions (injuries, tumors, inflammations) rank second in the peripheral nervous system pathology frequency and rank first in the cranial neuropathy (number of cases varies from 8 to 240 patients per 100,000 population), equally among men and women.

According to authors’ monitoring results, the main causes of facial nerve dysfunction are: fractures of the petrous part of temporal bone (road traffic accident, home accident, criminal act), iatrogenic injuries (as a result of previous sanitizing operations), tumor lesions of the nerve and of the adjacent anatomical structures, destructive processes in the temporal bones (cholesteatoma, cholesterol granuloma, etc.). In treating facial nerve dysfunction, both conservative and surgical methods should be considered.

All patients, without exception, underwent examination according to generally accepted otorhinolaryngological methods, which also included an audiological examination in order to clarify the state of the auditory function; to diagnose the condition of the facial nerve and facial muscles, electromyography and electroneuromyography were performed among objective research methods. Mandatory in the diagnosis of the causes of damage to the facial nerve is to carry out radiological research methods, including MSCT of the temporal bones and MRI of the head in the modes T1, T2, DWI, T1 with contrast enhancement.

Surgical treatment in the amount of decompression at the present stage of otosurgery does not cause difficulties, it is relatively easy to perform, provided that the otosurgeon has the appropriate skills and good knowledge of the microanatomy of the temporal bone. But the issue of performing FN plasty, especially with its extended lesions of 5–7 (for example, from labyrinth to mastoid segments) mm or more in the temporal bone, has not yet been properly covered in the available domestic literature.

Objective: to improve the treatment effectiveness in patients with intratemporal facial nerve lesions.

Material and methods. During the period from 2014 to 2020, 115 patients with peripheral MM paresis caused by intratemporal lesion of the FN were examined and treated in the FSBI NMRCO FMBA of Russia (Ear Diseases Department), which included: benign tumors of the temporal bone – 64 (55.7%) patients, of which 23 (36%) patients with temporal bone paraganglioma and 41 (64%) with schwannoma of the facial nerve; chronic suppurative otitis media (CHS) complicated by cholesteatoma – 32 (27.8%) patients; traumatic injuries of FN due to fracture of the temporal bones – 8 (6.9%) patients; iatrogenic injuries of the FN during sanitizing operations on the ear – 11 (9.6%) patients, of which 4 (36.4%) cases had a tympanic segment trauma and 7 (63.6%) cases – mastoidal segments trauma. Depending on the location and extent of the FN lesion, patients underwent surgical treatment in the amount of FN decompression, end-to-end plasty, or using an autograft of the sural nerve. FN decompression was performed in 60 (52.2%) patients, end-to-end neurorraphy of the nerve was performed in 37 (32.2%) patients, reconstruction of the sural nerve autograft was performed in 18 (15.6%) patients.

Results and discussions. During the follow-up period of 12 months or more, no patient had a single complication associated with surgical treatment. The results obtained in different groups differed and directly depended on the degree of nerve damage and on the duration of the disease. When performing FN decompression, an improvement in nerve function was noted as early as a month after surgery. In 43 (71.7) patients, FN function recovered completely, in 8 (13.3%) patients, FN function improved to grade II in HB, in 6 (10%) patients, FN function improved to grade II in HB, and only in 3 (5%) patients had no result from the operation. With endto-end nerve plasty, improvement in function was noted after 6 to 9 months. In 12 (32.4%) patients, FN function improved to grade III in HB, in 16 (43.3%) to IV in HB, in 7 (18.9%) to grade V, in 2 (5.4% ) patients had no effect from the operation for 15 months or more. When using the insertion of the sural nerve graft during FN plasty, improvement in function was observed after 9–15 months. Good results (improvement of function to grade III) were observed in 6 (33.3%) patients, satisfactory results (improvement in function to grade IV–V) – in 5 (27.8%) patients, unsatisfactory (no result) – in 7 (38.9%). Unsatisfactory results were mainly associated with the duration of MM paralysis in the history of the disease for more than 2–3 years.

Conclusion. The success of surgical treatment of intratemporal facial nerve lesions depends on an early pathological process detection based on X-ray methods of diagnostics, as well as the nerve lesion extension and the paralysis duration. Determining the correct tactics of surgical treatment allows to get the satisfactory results in the post-surgical period. Functional results directly depend on the mimic muscles paresis duration (severe muscle atrophy and partial deterioration of the terminal segments of the motor neurons appear after 2 years).

Key words: facial nerve, decompression of the facial nerve, end-to-end facial nerve neurorraphy,  sural nerve graft

Conflicts of interest. The authors have no conflicts of interest to declare.

Funding. There was no funding for this study.