Surgical interventions for the early management of Bell's palsy
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
This review aims to determine the evidence for surgery in the management of Bell's palsy and the effectiveness of surgery compared with outcomes of medical management.
Background
Bell's palsy is an acute paralysis of one side of the face due to a lesion of the facial nerve first described by Sir Charles Bell, a Scottish surgeon (1774 to 1842). Its cause is not known and it should only be used as a diagnosis in the absence of any other pathology. It was proposed in 1919 (Antoni 1919) that the underlying pathology was that of a viral neuropathy. Herpes simplex virus has been suggested as the likely pathogen (McCormick 1972) and animal studies have suggested that reactivation of the virus may lead to demyelination of the nerve leading to reduced function (Adour 1975, Stjernquist 2006).
The condition affects 25 to 35 people per 100 000 of the population per year and is most common in the 30 to 45 age group. It is also more common in pregnant women, people with diabetes or people with a respiratory tract infection (Theil 2001). Recovery in most patients can be expected to be good. It has been shown in a large review (Peitersen 2002) that over 70% of patients will have normal function restored and of the remainder 25% will have slight or mild sequelae and only 4% will have severe sequelae. Contractures, facial disfigurement, with associated psychological difficulties, and facial pain (Morgenlander 1990) remain the most common long‐term problems.
A number of studies have looked into identifying which population might benefit most from surgery. In addition to simple clinical assessment of disease using the House‐Brackmann scale or similar, many studies have tried to assess the electrical function of the facial nerve. Electroneurography (ENOG) has been the most popular technique employed (Esslen 1977; Fisch 1984). In this the degree of muscle response to an electrically evoked stimulus is assessed. It was shown (Esslen 1977; Fisch 1984) that when 95% of the nerve had degenerated the patient had a 50% chance of a poor outcome, that is stood a less than 50% chance of recovery to House‐Brackmann grade 1 or 2 and would potentially benefit from surgical intervention (Sillman 1992).
Although it is a common condition, in the absence of an established aetiology, treatment continues to be based upon the presumed pathophysiology of swelling and entrapment of the nerve. There is however continued controversy and variation in management. The most common management involves a combination of prednisolone with aciclovir although up until recently the evidence was weak and two recent Cochrane reviews found insufficient evidence to support either or both treatments (Salinas 2004; Allen 2004). A more recent double blinded randomised controlled study (Sullivan 2007) has shown that early treatment with prednisolone significantly improves the chances of complete recovery at three and nine months. At three months 83% had recovered facial function whilst this figure rose to 94% at nine months. Patients who did not receive prednisolone had recovery of 64% and 81% over similar time scales. This study also showed that there was no benefit in giving aciclovir either alone or in combination with prednisolone.
As the proposed pathophysiology involves entrapment of the nerve, this has led some surgeons to suggest that surgical decompression of the nerve is a suitable management option. The first recorded attempt at surgical decompression of the facial nerve for Bell's palsy was in 1932 (Ballance 1932). They recommended slitting the sheath in the distal descending segment of the nerve. This was consistent with theories of the site of the lesion at that time. Over the next few decades the proposed site for the surgery has migrated from the distal 1 cm at the stylomastoid foramen (Ballance 1932) to the entrance of the fallopian canal medially (Fisch 1972). The timing also varied from three months to immediately on onset (May 1972). In the early 1970s it was proposed that the most likely site of compression was at the entrance to the fallopian canal (Fisch 1972). Intraoperative evoked electromyography (EMG) and an oedematous swelling at this point proximal to the geniculate ganglion was noted in up to 94% of their patients. In this study transmastoid/middle cranial fossa approaches were used to allow decompression of the nerve and geniculate ganglion. Other studies (May 1984) suggested that a transmastoid approach to decompression of the labyrinthine segment was of benefit. Two further studies published around the same time gave evidence both for (Giancarlo 1970) and against (McNeill 1974) surgery. Given the natural history of the condition and the good outcomes of the condition without treatment and with medical management and also the potential for damage to the facial nerve and other ear structures during surgery, there has been a continued debate as to whether surgery has a role in the management of Bell's palsy (Adour 2002; Friedman 2000).
Despite the debate on different surgical approaches there is a paucity of level one evidence regarding facial nerve decompression surgery for acute Bell's palsy. Few large studies have been carried out. Of these one (May 1985) convinced many surgeons that surgery did not have a place in the management of Bell's palsy. More recently (Gantz 1999) found that when selected using ENOG, those patients who would have had a bad outcome as predicted by ENOG had a better outcome if surgically managed compared with those who were not. Currently most patients are managed medically with steroids with or without aciclovir as discussed above. Surgery, certainly in the UK, is rarely undertaken (Sullivan 2007).
Objectives
This review aims to determine the evidence for surgery in the management of Bell's palsy and the effectiveness of surgery compared with outcomes of medical management.
Methods
Criteria for considering studies for this review
Types of studies
We will assess randomised and quasi‐randomised controlled trials in the main review. Other studies, including case series will be included in the discussion section of the final review. Case series must have three consecutive cases with follow‐up for one year using similar outcome measures.
Types of participants
We will include any participant (adult or child) who presented with an idiopathic facial palsy which was diagnosed as Bell's palsy. Those who were diagnosed as having herpes zoster, who had a traumatic aetiology or other identified aetiology will be excluded from the review. This includes any cases of recurrent and familial Bell's palsy or Melkerson‐Rosenthal syndrome, which will be excluded.
Types of interventions
We will include any surgical intervention carried out for Bell's palsy within the acute phase (within 3 weeks of presentation). The outcomes and evidence for different surgical interventions will be considered. Any concurrent medical management will be assessed.
Types of outcome measures
Primary outcomes
The primary outcome measure will be the degree of recovery of facial nerve function and resolution of symptoms at 12 months as measured using the House‐Brackmann scale, the Sunnybrook scale, the Yanigahara scale or other similar scale. The results from studies using different follow‐up periods will be standardised to their six month equivalents for meta‐analyses including them all.
Secondary outcomes
Secondary outcome measures are:
1. Complete recovery at three and six months.
2. Synkinesis and contracture at 12 months.
3. Psychosocial outcomes at 12 months.
4. Side effects and complications of treatment.
Search methods for identification of studies
Electronic searches
See: Cochrane Neuromuscular Disease Group methods used in reviews.
We will search the Cochrane Neuromuscular Disease Group Trials Register using the following search terms 'Bell's palsy' 'facial palsy' or 'idiopathic facial paralysis'. We will also search the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 3 2008). We will adapt this strategy to search MEDLINE (from January 1950 to the present) and EMBASE (from January 1947 to the present).
The following phrases, adapted to each database as appropriate, will be used:
#1 (Bell's palsy) OR (Bell palsy) OR (idiopathic facial paralysis) OR (facial paralysis) OR (facial palsy) OR (facial nerve)
AND
#2 (surgery) OR (surg*) OR (operative) OR (operat*) OR (decompression) OR (decompres*).
See Appendix 1 and Appendix 2.
Searching other resources
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We will review the bibliographies of all trials identified.
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We will contact the authors of all included trials for further additional information or information on unpublished trials.
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We will perform a search for conferences regarding latest research in this area and, if appropriate, contact known experts in this field for clarification on latest unpublished data.
Data collection and analysis
Selection of studies
Two review authors (Walker, McAllister) will review titles and abstracts identified by the search strategy. The review authors will obtain full text for all relevant studies and will assess them independently. Two review authors (Walker, McAllister) will assess whether each trial meets the inclusion criteria. Disagreement between the review authors will be resolved by discussion with the lead author (Swan) if required.
Assessment of risk of bias in included studies
An assessment of risk of bias will be made on all included studies included and a risk of bias table will be completed according to Cochrane guidelines. If randomised controlled trials are identified we will assess for randomisation sequence generation, allocation concealment, blinding (participants, personnel and outcome assessors), incomplete outcome data, selective outcome reporting and other sources of bias. We will then make a judgement on each of these criteria relating to the risk of bias using 'Yes' indicating low risk of bias, 'No' high risk of bias and 'Unclear' unclear or unknown risk of bias. Two authors (Walker, McAllister) will assess quality independently. Disagreement between the authors will be resolved by discussion with the lead author (Swan) if required.
Data extraction and management
The data extracted will include study participants, methods, interventions used, outcomes along with 95% confidence intervals and results. The main outcome measure is degree of recovery of facial function and residual disability. Two authors will extract these data independently and enter them onto a specifically designed form. We will obtain missing data where possible from the authors.
Measures of treatment effect
We will enter data into the Review Manager (RevMan) software and will analyse data using the standard statistical methods. For continuously measured outcomes we will use means to obtain mean differences (MDs) with 95% confidence intervals (CI), for dichotomous outcome data the pooled relative risk with 95 % CI will be estimated from study log relative risks.The number needed to treat (NNT) will be calculated if possible. If little trial evidence is found observational relative risks will be combined.
Assessment of heterogeneity
A Chi2 test for homogeneity will be carried out. If significant heterogeneity is found, then an attempt will be made to find the cause of this based on the characteristics of the studies included.
Assessment of reporting biases
Publication bias will be assessed through a funnel plot.
Data synthesis
Initially, a fixed‐effect model will be used and the test for heterogeneity carried out. Random‐effects models such as DerSimonian and Laird account for more uncertainty and these will also be utilised, especially if there is heterogeneity (DerSimonian 1986).
Subgroup analysis and investigation of heterogeneity
A sensitivity analysis will be performed omitting studies of lower quality of methodology. In addition, quality could be incorporated into mixed models simultaneously allowing for differences in quality using Bayesian methods, utilised in WinBUGS (Spiegelhalter 2000).
Economic issues
If there is inadequate information from the trials identified, adverse events and cost effectiveness will be considered in the discussion in the full review taking into account observational studies.
