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Bell's palsy is characterised by an acute, unilateral, partial, or complete paralysis of the face. Bell's palsy occurs in a lower motor neurone pattern. The weakness may be partial or complete, and may be associated with mild pain, numbness, increased sensitivity to sound, and altered taste. Bell's palsy is idiopathic, but a proportion of cases may be caused by re-activation of herpes virus at the geniculate ganglion of the facial nerve. Bell's palsy is most common in people aged 15 to 40 years, with a 1 in 60 lifetime risk. Most people make a spontaneous recovery within 1 month, but up to 30% show delayed or incomplete recovery.
Methods and outcomes
We conducted a systematic review to answer the following clinical questions: What are the effects of drug treatments for Bell's palsy in adults and children? What are the effects of physical treatments for Bell's palsy in adults and children? We searched: Medline, Embase, The Cochrane Library, and other important databases up to October 2013 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 13 studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review, we present information relating to the effectiveness and safety of the following interventions: antiviral treatment, corticosteroids (alone or with antiviral treatment), hyperbaric oxygen therapy, and facial re-training.
Bell's palsy is an idiopathic, unilateral, acute paresis (partial weakness) or paralysis (complete palsy) of facial movement caused by dysfunction of the lower motor neurone of the facial nerve. Bell's palsy is a diagnosis of exclusion of other causes of facial nerve palsy.
Most people with paresis make a spontaneous recovery within 3 weeks. Up to 30% of people, typically those with paralysis, have a delayed or incomplete recovery.
Corticosteroids alone improve the rate of recovery and the proportion of people who make a full recovery, and reduce cosmetically disabling sequelae compared with placebo or no treatment.
Antiviral treatment alone is no more effective than placebo at improving facial motor function and reducing the risk of disabling sequelae.
We found no good evidence of significant benefit of combination corticosteroid-antiviral therapy over corticosteroid alone. However, there is a lack of data on people presenting with complete paralysis and any potential benefit of combination corticosteroid-antiviral therapy cannot be excluded.
Hyperbaric oxygen may improve the time to recovery and the proportion of people who make a full recovery compared with corticosteroids. However, the evidence for this is weak and comes from one small RCT.
Facial re-training may improve the recovery of facial motor function scores, including stiffness and lip mobility, and may reduce the risk of motor synkinesis in Bell's palsy, but the evidence is too weak to draw reliable conclusions.
About this condition
Definition
Bell's palsy is an idiopathic, unilateral, acute weakness of the face in a pattern consistent with peripheral facial nerve dysfunction, and may be partial or complete, occurring with equal frequency on either side of the face. Bell's palsy is idiopathic but there is weak evidence that Bell's palsy is cased by herpes simplex virus. Additional symptoms of Bell's palsy may include mild pain in or behind the ear, oropharyngeal or facial numbness, impaired tolerance to ordinary levels of noise, and disturbed taste on the anterior part of the tongue. Severe pain is more suggestive of herpes zoster virus infection and Ramsay Hunt syndrome. Bell's palsy is a diagnosis of exclusion. Other causes of lower motor neurone weakness include middle ear infection, parotid malignancy, malignant otitis externa, and lateral skull base tumours. Features such as sparing of movement in the upper face (central pattern), or weakness of a specific branch of the facial nerve (segmental pattern), suggest an alternative cause. Bell's palsy is less commonly the cause of facial palsy in children aged under 10 years (<50%).
Incidence/ Prevalence
The incidence is about 20 in 100,000 people a year, with about 1 in 60 lifetime risk. Bell's palsy has a peak incidence between the ages of 15 and 40 years. Men and women are equally affected, although the incidence may be higher in pregnant women.
Aetiology/ Risk factors
The cause of Bell's palsy is uncertain. It is thought that re-activated herpes virus at the geniculate ganglion of the facial nerve may play a key role in the development of Bell's palsy. Herpes simplex virus (HSV)-1 has been detected in up to 50% of cases by some researchers. However, one study demonstrated the replication of HSV, herpes zoster virus [HZV], or both, in <20% of cases. Herpes zoster-associated facial palsy more frequently presents as zoster sine herpete (without vesicles), although 6% of people develop vesicles (Ramsay Hunt syndrome). Infection of the facial nerve by HZV initially results in reversible neuropraxia, but irreversible Wallerian degenerationmay occur. Treatment plans for the management of Bell's palsy should recognise the possibility of HZV infection.