Author: John Whittaker / Editor: Taj Hassan / Reviewer: Eugene Henry / Codes: HAP33 / Published: 19/11/2018 / Review Date: 19/11/2021
Isolated facial muscle weakness is an uncommon presentation to the ED and may be quickly diagnosed by the unwary as Bells palsy. The Emergency Physician must be aware of two potential pitfalls when presented with a patient with facial weakness:
- Central facial weakness must be differentiated from a peripheral palsy
- A diagnosis of Bells palsy should only be made after exclusion of other causes for a peripheral facial muscle weakness
Bells palsy is defined as an acute idiopathic peripheral facial nerve paresis and is the most common cause of acute peripheral facial weakness . It has an incidence in the UK of approximately 20 cases per 100,00 person years , in other words around 50 cases per year will occur in an average ED catchment area. Although named after the Scottish anatomist Sir Charles Bell, the palsy was first described 23 years earlier by Nicolaus Friedreich , grandfather of the more famous neurologist.
In 70% of cases of Bells palsy, facial paralysis is complete and if untreated almost of patients will recover fully and 84% will recover near normal function . Common sequelae found in those that fail to recover are:
- Residual partial facial weakness
- Facial contracture
- Ageusia loss of taste function of the tongue
- Motor synkinesis involuntary muscle movement accompanying a voluntary movement e.g. eye closure when smiling
- Autonomic synkinesis e.g. Crocodile tears syndrome when lacrimation occurs with salivation
84% of patients with Bells palsy will recover full or near normal function, without any treatment
Right sided facial nerve palsy (Reproduced with permission from CDC)
An appreciation of the anatomy of the facial nerve is essential in understanding the clinical features and complications of facial paralysis. The course and connections of the facial nerve are complex but the particular anatomy of clinical relevance to the Emergency Physician (EP) is:
- The central connections of the facial nuclei each facial nucleus is bilaterally supplied by upper motor neurones from the cerebral cortex. Lesions within the brain therefore result in sparing of the muscles of the upper half of the face.
Bilateral innervation of the upper half of the face results in sparing of the forehead muscles in an upper motor neurone lesion
- The geniculate ganglion and greater petrosal nerve provide secretomotor fibres to the lacrimal glands
- The chorda tympani carries taste fibres from the anterior 2/3 of the tongue and secretomotor fibres to the submandibular and sublingual glands
- Nerve to the stapedius the stapedius muscle damps down sounds transmitted by the stapes and reduces auditory acuity
- Five branches of the terminal facial nerve to the muscles of the face- these arise within the parotid gland
The cause of Bells palsy has long been debated but only recently has evidence started to accumulate for a viral origin. Reactivation of latent herpes simplex or zoster virus is the most likely scenario. Herpes virus DNA has been isolated from facial nerve endoneural fluid , however attempts to isolate herpes simplex DNA from CSF and saliva in facial palsy patients have been less successful [6,7].
Herpes simplex virions
The most common presenting complaint in acute facial palsy is of unilateral facial weakness which may have been noticed by the patient themselves or a family member. Numbness or altered sensation to the same side of the face are also often described although formal testing should reveal normal sensory function. Other symptoms such as fever, headache or other neurological or systemic upset suggest an alternative cause other than Bells palsy.
Although facial numbness is a common presenting symptom in acute peripheral palsy, formal testing of the trigeminal nerve should be normal. Subjective reduced sensation is caused by reduced facial muscle tone
Approximately 50% of patients with Bells palsy experience facial pain, aural fullness or postauricular pain and in 25% of cases this precedes the paresis by 2-3 days 8
Facial palsy (Reproduced with permission from Wellcome Images)
Other symptoms which are commonly found in Bells palsy are attributable to individual branches of the facial nerve:
Dry eye due to weakness of the orbicularis oculi muscle and reduced tear production by the lacrimal gland
Altered taste 1/3 patients will notice this but when tested 4/5 have a reduced sense of taste .
Hyperacusis (oversensitivity to sound) caused by paralysis of the stapedius muscle which attenuates sound transmitted by the stapes
Two questions must be asked by the clinician when assessing a patient who presents with an acute facial weakness:
Is this an upper or lower motor neurone lesion ?
Is this an idiopathic peripheral facial muscle weakness (Bells palsy) or is there another cause for the problem ?
1. Is this an upper or lower motor neurone lesion ?
The key to differentiating a central (upper motor neurone) from a peripheral (lower motor neurone) facial palsy is to identify the extent of facial muscle weakness. The muscles of the upper half of the face (frontalis, corrugator and orbicularis) are innervated bilaterally by corticobulbar fibres. Weakness of the forehead muscles indicates a peripheral facial nerve problem whereas sparing of the forehead muscles is diagnostic of a central lesion. Asking the patient to close their eyes tightly or wrinkle their forehead will quickly identify the source of the problem.
A patient with facial weakness who cannot close their eye tightly or raise their eyebrow has a peripheral facial palsy
A lesion in the facial nerve resulting in weakness of all the facial muscles
1. Is this an idiopathic peripheral facial muscle weakness (Bells palsy) or is there another cause for the problem ?
Having identified a peripheral facial muscle weakness, the clinician must then exclude other causes before diagnosing an idiopathic palsy (Bells palsy).
General examination of the patient should be normal in Bells palsy. Derangement of vital signs, fever, rash or other abnormality on examination all point to an alternative cause for facial weakness such as:
- Lyme disease
- HIV infection
Erythema migrans in a woman with Lyme disease (Reproduced with permission from CDC)
In addition acute peripheral facial weakness may either be found in known diabetics or be a presenting feature of previously undiagnosed diabetes 9. Mononeuropathy in diabetes is most commonly caused by vascular occlusion and therefore has a poorer prognosis than facial weakness from other causes.
Head and Facial examination
It is important to examine the face and head carefully as most of the alternate causes for peripheral facial weakness arise from involvement of the facial nerve in its extracranial course.
Ear Nose and Throat
Examine the ear for evidence of otitis media, cholesteatoma, or malignant otitis externa (spread of infection from ear canal eroding into skull base, most commonly seen in immunocompromised and elderly diabetics). The mastoid may also appear inflamed as a consequence of chronic ear infection.
Careful examination of the parotid gland may reveal swelling suggesting parotitis or tumour which compress the facial nerve as it passes between the deep and superficial lobes of the gland.
Tumour of the parotid gland (reproduced with permission from Wellcome Images)
Strictly speaking Bells palsy is an isolated facial nerve paresis but there is some evidence that other cranial nerves, particularly trigeminal, glossopharyngeal and hypoglossal may very occasionally be involved 10. Altered sensation, such as heaviness or numbness, is commonly described by patients with facial weakness and is thought to be due to reduced muscle tone. Formal sensory testing of the trigeminal nerve should be normal.
If additional cranial nerve deficits are identified, the patient must be further investigated to exclude a likely alternative cause for facial weakness.
Post traumatic facial nerve paralysis is most commonly caused by fracture of the temporal bone and may be immediate or delayed 11. If delayed, the weakness appears, on average, 4-5 days after the injury and is caused by oedema, delayed arterial spasm or external compression by haematoma.
The commonest cause of peripheral facial weakness is Bells palsy, but a careful history and examination must be performed to exclude other rarer causes
As Bells palsy is an idiopathic condition, there is no currently available diagnostic test which will confirm the diagnosis. Although the aetiology is felt to be related to herpes virus infection, serum tests for rising antibody titres to herpes simplex are not reliable .
Serological testing will be required if other causes for peripheral facial weakness, such as Lyme disease or HIV, are suspected.
The only other investigations required are those to exclude a secondary cause for facial weakness. All patients must have their capillary blood glucose measured and routine observations performed. In the presence of either a central facial weakness or a peripheral weakness with other features (e.g. history of trauma, systemic upset or co-existing neurological deficit), radiological imaging will be required.
Bells Palsy (Reproduced with permission from Wellcome Images)
Bells palsy can be diagnosed when there is peripheral facial muscle weakness in the absence of an apparent cause. As facial muscle weakness can vary from mild to complete, grading it can help in prognosis and follow-up. The modified House-Brackmann classification is the most commonly used scale:
Normal facial function
Slight weakness noticeable on close inspection. May have slight synkinesis
Obvious but not disfiguring difference between two sides. Compete eye closure with effort. Noticeable but not severe synkinesis, contracture or hemifacial spasm
Moderately severe dysfunction
Obvious weakness or disfiguring asymmetry. Normal symmetry or tone at rest. Incomplete eye closure.
Only barely perceptible motion. Asymmetry at rest.
Management of Bells palsy can be divided into;
- treatment directed at the facial nerve
- treatment of the consequences of the facial nerve palsy
Treatment directed at the facial nerve
This has been a controversial area for many years but recent high quality studies have clearly established the benefits of steroids in Bells palsy.
Two recent large high quality studies 13,14 and subsequent systematic reviews and meta-analyses 15,16 have all shown a reduction in time to complete recovery and an increased chance of complete recovery at 3 and 9 months in patients treated with steroids (NNT 6 (95% CI, 4 to 9) for complete recovery at 3 months).
Both of the large studies were restricted to patients with Bells palsy who presented within 72 hours and both used prednisolone at a dose of 50 or 60mg for a total of 10 days, one of the studies tapering the dose after 5 days.
Subgroup analysis from both systematic reviews and meta-analysis 16 suggests that steroids may also be associated with improved recovery even when started more than 3 days after onset of symptoms.
Treatment of patients with Bells palsy with corticosteroids has been proved to have beneficial effects on recovery time and to increase the chances of a complete recovery
The effects of antiviral agents on recovery were also studied in the above trials and further systematic reviews. No positive benefit was demonstrated with the use of antiviral agents either used alone or in combination with prednisolone. A meta-analysis 17 directly comparing the use of steroids with and without antiviral agents confirmed this conclusion.
The addition of an antiviral agent to steroid treatment in Bells palsy has not been shown to provide any additional benefit
Treatment of the consequences of facial muscle weakness.
The most common problem associated with facial muscle weakness is incomplete closure of the eyelid. This may lead to exposure keratitis and corneal ulcers. Two strategies should therefore be employed;
- hourly lubricating eye drops during the day and eye ointment at night
- eye taping at night.
In addition, patients must be told to report new eye symptoms such as pain, discharge and change in vision. Patients with incomplete eye closure should be referred for ophthalmology follow-up as further options include temporary tarsorrhaphy or botulinum toxin tarsorrhaphy are available.
Eye care is extremely important in the management of Bells palsy as ophthalmological complications are common
Attempts have been made to reduce facial muscle weakness by physiotherapy, electrical stimulation and acupuncture. Physiotherapy has been shown to be potentially useful in patients with long standing paralysis 18but there are no high quality trials showing benefit in the acute phase.
The benefits of acupuncture have been repeatedly claimed but a Cochrane review 19 failed to confirm a positive effect mainly due to poor study design. There is no good evidence that electrical stimulation of facial muscles in the acute setting is of value either 20.
Ramsay Hunt Syndrome and Zoster Sine Herpete
Ramsay Hunt syndrome is defined as a peripheral facial nerve weakness accompanied by a vesicular rash. It is caused by herpes zoster infection of the facial nerve and geniculate ganglion although the exact pathophysiological processes involved are still unclear 21. Presentation is with a classic peripheral facial nerve weakness but close examination will reveal an ipsilateral rash which may be evident in one of a number of areas dependant on the sensory ganglion(s) involved:
- In the ear canal or behind the ear
- Over the lateral neck
- On the tongue or buccal mucosa
- On the palate, uvula and/or pharynx
Ramsay Hunt Syndrome with a vesicular rash in the right ear (Reproduced with permission from Wellcome Images)
It is important to note that the rash may be initially erythematous only, with vesicles developing later. Ramsay Hunt syndrome is commonly accompanied by associated symptoms such as hearing loss and vestibular disturbance due to involvement of structures adjacent to the facial nerve 8. It is associated with a poorer prognosis than Bells palsy and sequelae such as persistent synkinesis and hearing loss, are more common ,.
Although high quality studies are lacking, best evidence suggests that a combination of high dose steroids and acyclovir (e.g. prednisolone 60mg once daily for 10 days and acyclovir 800mg five times a day for 7 days) are associated with improved rates of recovery 23,24. Other treatment and follow-up for the sequelae of facial muscle weakness are also be required, as for Bells palsy. In addition the patient must be counselled on the infectivity of the rash and potential risk to the non-immune and immunocompromised.
It is important to examine a patient with apparent Bells palsy very carefully as evidence of the vesicular rash may be difficult to see and management of the patient is significantly altered
Zoster sine herpete is a term for Ramsay Hunt syndrome without apparent vesicles or when there is a delayed presentation of the rash. In 15% of patients with Ramsay Hunt syndrome vesicles develop after the onset of facial weakness 8 and therefore patients diagnosed with Bells palsy must be instructed to return or see their GP should a rash develop later.
Prognosis & Followup strategies:
Although the great majority of patients with Bells palsy will regain normal or near normal facial function there are certain prognostic indicators that predict a poorer outcome 25;
- Increased age
- Impairment of taste
- Pain other than in the ear
- Complete facial weakness
Follow-up of a patient with Bells palsy who attends the ED, should be arranged either through the GP or ENT clinic, according to local policy. Recurrence of Bells palsy is very rare and if it does occur an alternative diagnosis should be considered e.g. myasthenia gravis or brain stem lesion 25.
Safety pearls and Pitfalls:
The following are potential pitfalls the unwary clinician may fall into when assessing and managing a patient with an acute facial palsy:
- Failure to differentiate an upper from a lower motor neurone lesion, thereby missing a potentially significant central lesion.
- Inadequate examination missing an alternate cause for a lower motor neurone palsy e.g. parotid gland pathology.
- Failure to prescribe early high dose steroids in a patient diagnosed with Bells palsy.
- Failure to manage the sequelae of facial palsy, in particular, adequate eye care.
- Failure to identify a rash and miss a diagnosis of Ramsay Hunt syndrome.
Key Learning Points
- Bells palsy is an acute idiopathic peripheral facial nerve paresis.
- If untreated, 84% of patients with Bells palsy will recover full or near normal facial function. (level of evidence 4)
- Intact forehead muscle function, revealed by an ability to raise the eyebrow or close the eye tightly, is a sign of a central (upper motor neurone) lesion.
- Bells palsy is the commonest cause of a peripheral facial muscle weakness, but a careful history and examination must be completed to exclude one of the many other causes of this problem. (level of evidence 5)
- The use of high dose steroids in Bells palsy has been shown to shorten recovery time and increase the chances of a complete recovery. (level of evidence 1a)
- Antiviral drugs do not have any beneficial effects on the time to recovery or incidence of complete recovery in Bells palsy. (level of evidence 1a)
- Eye care is extremely important in the management of patients with facial muscle weakness in the ED as ophthalmological complications are common in these patients. (level of evidence 5)
- Best evidence suggests that patients with Ramsay Hunt syndrome treated with a combination of high dose acyclovir and prednisolone have improved recovery rates. (level of evidence 4)
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- Kanerva M, Mannonen L, Piiparinen H et al. Search for herpesviruses in cerebrospinal fluid of facial palsy patients by PCR. Acta Otolaryngol 2007;127:775-9
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