Bell's palsy is characterised by an acute, unilateral, partial, or complete paralysis of the face (i.e., lower motor neurone pattern). The weakness may be partial (paresis) or complete (paralysis), and may be associated with mild pain, numbness, increased sensitivity to sound, and altered taste. Bell's palsy remains idiopathic, but a proportion of cases may be caused by reactivation of herpes viruses from 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 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 question: What are the effects of treatments in adults and children? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2010 (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).
We found 14 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
In this systematic review we present information relating to the effectiveness and safety of the following interventions: antiviral treatment, corticosteroids (alone or plus antiviral treatment), hyperbaric oxygen therapy, facial nerve decompression surgery, and facial retraining.
Bell's palsy is an idiopathic, unilateral, acute paresis or paralysis of facial movement caused by dysfunction of the lower motor neurone. Up to 30% of people with acute peripheral facial palsy have an alternative cause diagnosed at presentation or during the course of their facial palsy. Alternative causes are higher in children (>50%), warranting specialist evaluation at presentation. Severe pain, vesicles (ear or oral), and hearing loss or imbalance, suggest Ramsay Hunt syndrome caused by herpes zoster virus infection, which requires specialist management.
Most people with paresis (partial weakness) make a spontaneous recovery within 3 weeks. Up to 30% of people, typically people with paralysis (complete palsy), have a delayed or incomplete recovery.
Corticosteroids alone improve rate of recovery and the proportion of people who make a full recovery, and reduce cosmetically disabling sequelae, motor synkinesis, and autonomic dysfunction compared with placebo or no treatment.
Antiviral treatment alone is no more effective than placebo and is less effective than corticosteroid treatment at improving recovery of facial motor function and at reducing the risk of disabling sequelae.
For people with paresis at presentation (about 70%), there is no evidence of a clinically important additive effect of adding antivirals to corticosteroid therapy.
For people who develop paralysis (about 30%), and may demonstrate a trend towards complete degeneration on electrophysiological testing, it is unknown whether adding antiviral treatment to corticosteroid therapy has a significant additive or synergistic effect.
Hyperbaric oxygen may improve time to recovery and the proportion of people who make a full recovery compared with corticosteroids; however, the evidence for this is weak.
We don't know whether facial nerve decompression surgery is beneficial in Bell's palsy.
Facial retraining may improve 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 conclusions.
Good evidence exists that corticosteroid therapy improves facial palsy in people with Bell's palsy independent of severity at presentation. Treatment is likely to be more effective when started within 72 hours of onset, and less effective after 7 days. Contraindications to corticosteroid therapy exist and adverse effects are more likely following 7 days of treatment. Combination therapy with a corticosteroid and antiviral is no more effective than corticosteroid therapy alone for Bell's palsy; however, combination therapy should be considered when there is evidence of viral infection with herpes zoster, such as zoster sine herpete and Ramsay Hunt syndrome. People presenting with complete facial paralysis should be offered a choice of combination therapy with a corticosteroid and antiviral, because the evidence for therapy without antivirals is not yet definitive for this group and antivirals have few adverse effects. In people presenting with mild facial paresis from Bell's palsy, there is a high rate of spontaneous resolution without treatment. Bell's palsy is a diagnosis of exclusion and clinicians should remain mindful of the causes of facial palsy, including tumour and infection. All children presenting with facial palsy and adults with delayed recovery should be referred for assessment by an otolaryngologist - head and neck surgeon or other appropriate specialist. The authors believe that facial palsy should not be treated only by protocol-driven practice. Bell's palsy is a diagnosis of exclusion, although a search for other causes of facial palsy must not delay treatment of likely Bell's palsy. Patients should have the opportunity to participate in an informed choice in their management where relevant.