Is facial nerve integrity monitoring of value in chronic ear surgery?review
Аннотация: Facial nerve injury is a potential complication of otologic surgery as its dissection within the region of the tympanic and mastoid segments is an integral component of middle ear and mastoid surgery. The tympanic segment of the facial nerve is vulnerable as it can be normally dehiscent, and the incidence of dehiscence increases in the presence of chronic otitis media and cholesteatoma. Additionally, during mastoidectomy and posterior tympanotomy, the descending portion of the facial nerve is at risk for iatrogenic injury. Although there is no substitute for knowledge of normal facial nerve anatomy, potential aberrations in the course of the facial nerve, anatomic identification of the facial nerve, and surgical experience, the use of facial nerve integrity monitoring (NIM) during middle ear and mastoid surgery has been advocated as a means to reduce the surgical risk of facial nerve injury. In contrast to neurotologic procedures where it has been widely accepted as standard of care, routine use of facial NIM in otologic surgery remains controversial. In this Triological Society Best Practice review, we examined the evidence regarding the use of facial NIM in otologic surgery. Several studies have been conducted to investigate the utility of facial NIM in otologic surgery. Although facial nerve monitoring in neurotologic and skull base surgery has been well established for a number of decades, one of the earliest publications to address the use of facial NIM in otologic surgery was by Silverstein et al.1 The authors performed a review of facial nerve monitoring in 246 otologic surgeries (120 tympanomastoidectomies, 73 tympanoplasties, and 53 stapedectomies). Within this article, an early facial nerve integrity monitoring device was described in which facial contraction was detected by a strain gauge sensor in the corner of the mouth that produced an audible signal and was stimulable by a sterile probe. Although this study was mainly descriptive, it revealed vital information regarding facial NIM and the currents necessary to stimulate the various anatomic portions of the facial nerve (Table I). This study asserted that facial nerve monitoring was of great value in the early identification of dehiscent and aberrant facial nerve anatomy assisting in the maintenance of it integrity and functionality postoperatively. Since that time the technology for facial nerve integrity monitoring has advanced. More recent studies investigated the utility of facial NIM using the more advanced technology currently available for otologic surgery. Pensak et al. performed a prospective study of 260 consecutive chronic ear procedures performed by resident surgeons with faculty participation were facial nerve integrity monitoring was utilized (106 tympanomastoidectomies, 86 tympanoplasties, and 68 modified radical mastoidectomies).2 Within this study, a commercially available two-channel facial nerve monitoring system was utilized. Thresholds of 100 to 150 mV were used to eliminate background electromyographic activation and to minimize artifact. The facial nerve was identified in 100% of cases by gross anatomic visualization. Dehiscent facial nerves were identified in 38% of cases. The auditory signal from the monitor alerted the surgeon to the presences of an exposed facial nerve in 93% of cases prior to the surgical anatomic identification of the nerve (Table II). In 7% of cases, the monitor failed to passively identify an exposed nerve until after it had been identified anatomically. Pensak et al. concluded that facial NIM aided in heightening surgical cognizance of the presence of exposed facial nerves and thus is advantageous particularly in the training setting. It was asserted that facial nerve monitoring should be performed in all chronic ear cases in which the facial nerve may be at risk. Noss et al. examined the voltages producing facial nerve stimulation in patients with observed facial nerve dehiscence.3 A total of 262 otologic surgeries utilizing facial NIM were examined. In their series, the surgeon judged the nerve to be dehiscent in 35 patients or 13% of the cases; 89% of these cases had monitoring event with mechanical stimulation of the nerve being the most common (Table II). However, they suggested that electrophysiological dehiscence (facial nerve stimulation threshold <1 V), present in 53% of primary and 96% among revision surgery (62% overall), was a more reliable marker for identification of a nerve at surgical risk of injury. Thus, the use of facial NIM during middle ear and mastoid surgery can enhance the safety of the facial nerve by providing critical information regarding its surgical risk, thereby aiding in effecting a safe and complete surgical cure. More recently, Choung et al. also evaluated surgical dehiscence versus electrical dehiscence in 100 patients, prospectively.4 In 43% of cases, surgical dehiscence was noted. Among these patients, electrical stimulation was elicited with stimulation of 0.7 mA or less (Table II). Electrical dehiscence (stimulation with ≤0.7 mA with or without corresponding surgical findings) was present in 73% of patients, a number that is similar to the 62% found in Noss's series. Of these patients, 82% elicited a response with 0.4 mA or less. The mean threshold for electrical stimulation was 0.29 mA for tympanic segments and 0.41 mA for mastoid segments. This study further expanded on the thresholds described by Silverstein et al. utilizing their prototypical NIM device and identified similar threshold values. Given the higher percentage of electrically dehiscent facial nerves as compared to surgically apparent dehiscent facial nerves, this study further confirms the utility of the NIM in identifying vulnerable facial nerves in middle ear and mastoid surgery. Wilson et al. evaluated the cost-effectiveness of intraoperative facial NIM in middle ear and mastoid surgery.5 Historical data from the literature were used to estimate probabilities of complete versus incomplete, temporary versus permanent, facial paralysis in primary and revision middle ear/mastoid surgery with or without facial NIM use. Their study strongly favored the used of intraoperative facial NIM in all patients undergoing middle ear and mastoid surgery; their findings were robust across a wide range of cost and probabilities. Routine monitoring had the greatest effectiveness and lowest cost; it was associated with an average quality-adjusted life years (QALY) of 45.68 at an average cost of $238. Not monitoring was associated with the lowest QALY and the highest cost ($449.80). The authors concluded that facial NIM was cost-effective, and thus its routine use should be adopted to reduce the risk of facial nerve injury during middle ear and mastoid surgery. The current evidence suggests that intraoperative facial NIM is of value in identifying the facial nerve that is at surgical risk during middle ear and mastoid surgery, and it is also cost-effective. In this review, level 4 studies (randomized controlled trials) were examined.
Год издания: 2012
Авторы: Selena E. Heman‐Ackah, Sachin Gupta, Anil K. Lalwani
Издательство: Wiley
Источник: The Laryngoscope
Ключевые слова: Facial Nerve Paralysis Treatment and Research, Ear Surgery and Otitis Media, Ear and Head Tumors
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Том: 123
Выпуск: 1
Страницы: 2–3