Description
Facial Nerve Monitoring For All?
Intraoperative monitoring of neural function is not a new concept. It has been with us for decades although it originally gained popularity in the field of Spinal Surgery and Neurosurgery1,2 In the mid 1980s these techniques found their way into Otolaryngology-Head and Neck surgery, particularly through the efforts of Neurotologists within the specialty. The auditory brain stem response is now widely used during posterior fossa and acoustic neuroma surgery as this is relatively resistant to anaesthetic effects.3 The use of monitoring has now also spread to peri-operative monitoring of facial nerve function4 in skull base surgery, not only for acoustic neuroma surgery, but for vestibular nerve section, micro vascular decompression etc.
The question needs to be asked whether the knowledge and experience of these techniques, particularly facial nerve electromyographic recordings, should be extended into routine use for middle ear surgery and in particular surgery for cholesteatoma. At a recent meeting in London (CME Update 1998) attended by nearly 100 Specialists (representing approximately one fifth of the total accredited workforce in Otolaryngology Head and Neck Surgery), a show of hands demonstrated quite clearly that the majority of Specialists present did not routinely use intraoperative facial nerve monitoring for mastoid surgery. In addition, at the recent American Academy meeting on Facial Nerve Disorders (Washington 1999), the consensus view was expressed that VII monitoring for middle ear surgery was still not mandatory. In view of the known risks to facial nerve function when operating on cholesteatomatous disease, we must ask whether this is justifiable.
For example, even in the best hands, facial nerve palsy rates of between 0.5 and 0.8% are being recorded.5 A national audit report from the Royal College of Surgeons in England in 19956 demonstrated a facial palsy rate of 0.8% in a series of over 600 cholesteatoma operations. Complication rates of 0.5 to 1% of facial paralysis in cholesteatoma surgery could be reduced by intraoperative monitoring. Strong reasons need to be advanced if this is not to become mandatory.
The technology is no longer expensive. A commercial nerve integrity monitor can be purchased for approximately ??5,000 and the use of disposable recording electrodes adds only ??15 – ??20 per operation. This compares very favourably with, for example, the cost of disposable equipment during a laparoscopic cholecystectomy. The machines themselves do not represent any added burden to an operation and application of the electrodes etc. takes less than 5 minutes at the start of the procedure.
Why are so many Specialists reluctant to introduce this straightforward procedure? There are a number of reasons, but one clue may be found in the audit report mentioned above6 in which it was discovered that the average number of mastoid operations performed per year by Specialists in the UK was 11. Given a complication rate of just under 1%, it seems that each Specialist is likely to be able to practice for approximately 10 years before he experiences one such complication. Over a working lifetime, he can only expect to see approximately 2 – 3 such cases.
This may help to diminish the importance of this complication but the magnitude of the impact on the patient cannot be underestimated, even if each Specialist only has 2 – 3 such patients in his entire working lifetime. Even if a patient undergoes successful nerve re-construction following a traumatic injury, the results are often disappointing and although grading scales such as that recommended by the American Academy of Otolaryngology of Head and Neck Surgery give the impression of good function, patients themselves continue to complain bitterly about such things as synkinesis which are an almost inevitable consequence of a post traumatic facial nerve injury.
Twenty five years ago, physiological monitoring of the patient during general anaesthesia was in its infancy; nowadays, real-time monitoring of oxygen and carbon dioxide levels and cardiovascular status is compulsory in the developed world. Intraoperative monitoring is of course no substitute for detailed anatomical study coupled with high quality training in the operating room. However, it is time that Otologists pulled together and demanded facial nerve monitoring for all, without exceptions. Our watch word should be ‘if it can be monitored then it should be monitored’. Let us do it voluntarily before the lawyers force it upon us. The benefits of mandatory intra-operative facial nerve monitoring regime would be to the Specialists themselves as a discipline, to trainees, as an example and most of all to our patients, as a service.
References
1. Barber C and Blum T. Evoked Potentials 3. Butterworth 1987
2. Lueders H, Gurd A, Hahan J, Andrish J, Weigner G, Clem G. A new technique for intraoperative monitoring of spinal cord function. Spine 1982; 7: 110-115.
3. Grundy B L, Jannetta P J, Procopio P T et al. Intraoperative monitoring of brain stem audiometry evoked potentials. Journal of Neurosurgery1982; 57: 647-681.
4. Kartush J M, Niparko J K, Bedsoe S C, et al; Intraoperative facial nerve monitoring; A comparison of stimulating electrodes. Laryngoscope 1985; 95: 1536-1540.
5. Wayof M Charachon R, Roulleau P, Lacher G, Degurne C H. Advances in Otorhinolaryngology, volume 36 1987. Karger
6. Harkness P, Brown P, Fowler S, Grant H, Ryan R, Topham J. Mastoidectomy audit, results of the Royal College of Surgeons of England comparitve audit of ENT surgery. Clinical Otolaryngology 1995; 20: 89-94.
