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Synonym: Bell's palsy (lower motor neurone facial palsy)
Damage to the facial nerve (either upper motor neurone (UMN) or lower motor neurone (LMN)) produces weak muscles of facial expression.
The VIIth cranial (facial) nerve is largely motor in function (some sensory fibres from external acoustic meatus, fibres controlling salivation and taste fibres from the anterior tongue in the chorda tympani branch). It also supplies the stapedius (so a complete nerve lesion will alter auditory acuity on the affected side). From the facial nerve nucleus in the brainstem, fibres loop around the VI nucleus before leaving the pons medial to VIII and passing through the internal acoustic meatus. It passes through the petrous temporal in the facial canal, widens to form the geniculate ganglion (taste and salivation) on the medial side of the middle ear, whence it turns sharply (and the chorda tympani leaves), to emerge through the stylomastoid foramen to supply all the muscles of facial expression, including the platysma.
Weakness of the muscles of facial expression and eye closure. The face sags and is drawn across to the opposite side on smiling. Voluntary eye closure may not be possible and can produce damage to the conjunctiva and cornea.
- In partial paralysis, the lower face is generally more affected.
- In severe cases, there is often demonstrable loss of taste over the front of the tongue and intolerance to high-pitched or loud noises. It may cause mild dysarthria and difficulty with eating.
The most common system used for describing the degree of paralysis is the House-Brackmann scale, where 1 is normal power and 6 is total paralysis.
It is important to identify whether the patient has an upper motor neurone (UMN) or lower motor neurone (LMN) lesion, to assist in identifying the cause.
- In an LMN lesion, the patient can't wrinkle their forehead - the final common pathway to the muscles is destroyed. The lesion must be either in the pons, or outside the brainstem (posterior fossa, bony canal, middle ear or outside skull).
- In an upper motor neurone (UMN) lesion, the upper facial muscles are partially spared because of alternative pathways in the brainstem, ie the patient can wrinkle their forehead (unless there is bilateral lesion) and the sagging of the face seen with LMN palsies is not as prominent. There appear to be different pathways for voluntary and emotional movement.
Cerebrovascular accidents usually weaken voluntary movement, often sparing involuntary movements (eg, spontaneous smiling). The much rarer selective loss of emotional movement is called mimic paralysis and is usually due to a frontal or thalamic lesion.
Lower Motor Neurone (LMN) = Bell's Palsy
- Cerebrovascular disease (eg brainstem stroke)
- Iatrogenic (dentists using local anaesthetic)
- Herpesvirus (type 1)
- Herpes zoster (Ramsay Hunt syndrome)
- Lyme disease
- Otitis media or cholesteatoma
- Trauma - eg, fractures of the skull base, haematoma after acupuncture
- Guillain-Barré syndrome
- Mononeuropathy - eg, due to diabetes mellitus, sarcoidosis or amyloidosis
- Posterior fossa tumours, primary and secondary
- Parotid gland tumours
- Sjögren's syndrome
- Hypertension and eclampsia
- Inactivated intranasal influenza vaccine - although this has been disputed
- Melkersson's syndrome (recurrent facial palsy, chronic facial oedema of the face and lips, and hypertrophy/fissuring of the tongue)
Upper Motor Neurone (UMN)
- Cerebrovascular disease
- Intracranial tumours, primary and secondary
- Multiple sclerosis
- If bilateral, particularly consider Guillain-Barré syndrome or Lyme disease.
- If recurrent, particularly consider lymphoma, sarcoidosis and Lyme disease.
- In children, particularly consider Lyme disease and middle ear disease.
Acute LMN palsy
Acute LMN palsy can present at any age but is most frequently seen at age 20-50 years, affecting both sexes equally. Incidence is around 30 cases per 100,000 per year, and is slightly higher in pregnant women (45 per 100,000). There is usually a rapid onset of unilateral facial paralysis. Aching pain below the ear or in the mastoid area is also common and may suggest middle ear or herpetic cause if severe. There may be hyperacusis and patients with lesions proximal to the geniculate ganglion may be unable to produce tears and have loss of taste.
- Originally described by Sir Charles Bell in 1821. Incidence is 20 per 100,000 between the ages of 10-40 years but 59 per 100,000 over the age of 65 years.
- There may be a familial component.
- In the past no cause was found in the majority of cases of LMN facial nerve palsy and these were labelled as idiopathic (ie Bell's palsy).
- The incidence is higher in people with diabetes than in those without diabetes.
- Approximately 7% of patients have a recurrence.
- Recent work suggests that a large number of these cases may be due to herpetic viral infection - particularly herpes simplex type 1, or varicella (herpes) zoster.
Ramsay Hunt syndrome
LMN facial nerve palsy is specifically due to varicella (herpes) zoster in Ramsay Hunt syndrome. Pain is often a prominent feature and vesicles are seen in the ipsilateral ear, on the hard palate and/or on the anterior two thirds of the tongue. It can include deafness and vertigo and other cranial nerves can be affected. When the rash is absent it is known as zoster sine herpete. Immunodeficiency is a risk factor.
- Serology - Lyme, herpes and zoster (paired samples 4-6 weeks apart). It may not influence management but may reveal aetiology.
- Check blood pressure in children with Bell's palsy (two case reports of aortic coarctation presenting with facial nerve palsy and hypertension).
- The following tests are rarely done but, combined with a good understanding of the neuroanatomy, can determine the level of the palsy:
- Schirmer's tear test (reveals a reduced flow of tears on the side of a palsy affecting the greater palatine nerve).
- Stapedial reflex (an audiological test, absent if the stapedius muscle is affected).
- Electrodiagnostic studies (generally a research tool) reveal no changes in involved facial muscles for the first three days but a steady decline of electrical activity often occurs over the next week and will identify the 15% with axonal degeneration.
Ideally this should be a multidisciplinary approach, encompassing ophthalmologists, ENT surgeons, plastic surgeons, physiotherapists and psychologists.
- Reassurance - the majority of cases resolve spontaneously - see 'Prognosis', below.
- Eye care:
- Ophthalmologists play an important role in preventing irreversible blindness from corneal exposure. This may be successfully achieved by using lubricating drops hourly and eye ointment at night ± an eye patch.
- Botulinum toxin or surgery (upper lid weighting or tarsorraphy) may also be required temporarily.
- After the cornea has been protected but recovery is thought to be unlikely, longer-term management of eyelid and facial re-animation may be arranged.
Idiopathic facial palsy management
- High-quality evidence showed no significant benefit from anti-herpes simplex antivirals compared with placebo in producing complete recovery from facial nerve palsy.
- Physiotherapy may be beneficial for treating idiopathic facial nerve palsy but there is no high-quality evidence to support significant benefit or harm.
- Referral - will depend on clinical assessment. A patient may need immediate hospital referral, eg when there is any clinical suspicion of an underlying stroke.
- Refer urgently to neurology or to ear, nose, and throat (ENT) if there is:
- Any doubt regarding the diagnosis.
- Recurrent Bell's palsy.
- Bilateral Bell's palsy.
- If the cornea remains exposed after attempting to close the eyelid, refer urgently to ophthalmology.
- If the paralysis shows no sign of improvement after 1 month, or there is suspicion of a serious underlying diagnosis (e.g. cholesteatoma, parotid tumour, malignant otitis externa), refer urgently to ENT.
- If there is residual paralysis after 6–9 months, consider referral to a plastic surgeon with a special interest in facial reconstructive surgery.
- Refer urgently to neurology or to ear, nose, and throat (ENT) if there is:
- Surgical options for patients with facial palsy not responding to medical treatment include facial nerve decompression.
- Where the nerve fails to regenerate, cosmetic surgery to elevate the mouth or anastomosis of the hypoglossal nerve to the facial nerve may help.
Facial palsy in children
- Facial palsy in children is often idiopathic but an underlying cause is increasingly being identified after thorough investigations.
- Radiological investigation is required if there is a history of trauma.
- If no cause is found, prednisolone treatment can be used. If used, prednisolone treatment should be begun as early as possible after the onset of symptoms.
- The prognosis is variable but usually good.
Full recovery occurs in about 80% of the cases, 15% experience some kind of permanent nerve damage and 5% remain with severe sequelae.
Poor prognostic features:
- Complete palsy or severe degeneration (electrophysiology).
- No signs of recovery by three weeks.
- Age >60 years.
- Severe pain.
- Ramsay Hunt syndrome (herpes zoster virus).
- Associated with either hypertension, diabetes, or pregnancy.
Those with axonal degeneration may not show any re-innervation for three months and recovery may be partial or not at all. Synkinesis is often seen - eg, blinking causes the angle of the mouth to contract. Also aberrant parasympathetic re-innervation may cause symptoms such as gustatory lacrimation ('crocodile tears'). Symptoms can be helped by subcutaneous or intramuscular injections of botulinum toxin.
Further reading & references
- House JW, Brackman DE; House Brackman Facial Nerve Grading System 2010.
- Holland NJ, Weiner GM; Recent developments in Bell's palsy. BMJ. 2004 Sep 4;329(7465):553-7.
- Gilden DH; Clinical practice. Bell's Palsy. N Engl J Med. 2004 Sep 23;351(13):1323-31.
- Rosted P, Woolley DR; Bell's Palsy following acupuncture treatment - a case report. Acupunct Med. 2007 Jun;25(1-2):47-8.
- Mutsch M, Zhou W, Rhodes P, et al; Use of the inactivated intranasal influenza vaccine and the risk of Bell's palsy in Switzerland. N Engl J Med. 2004 Feb 26;350(9):896-903.
- Stowe J, Andrews N, Wise L, et al; Bell's palsy and parenteral inactivated influenza vaccine. Hum Vaccin. 2006 May-Jun;2(3):110-2. Epub 2006 May 11.
- Serrano P, Hernandez N, Arroyo JA, et al; Bilateral Bell palsy and acute HIV type 1 infection: report of 2 cases and review. Clin Infect Dis. 2007 Mar 15;44(6):e57-61. Epub 2007 Feb 8.
- Taylor DC et al; Bell Palsy, Medscape, Nov 2012
- Qin D, Ouyang Z, Luo W; Familial recurrent Bell's palsy. Neurol India. 2009 Nov-Dec;57(6):783-4.
- Goldani LZ, da Silva LF, Dora JM; Ramsay Hunt syndrome in patients infected with human immunodeficiency virus. Clin Exp Dermatol. 2009 Dec;34(8):e552-4. Epub 2009 Jun 1.
- Margabanthu G, Brooks J, Barron D, et al; Facial palsy as a presenting feature of coarctation of aorta. Interact Cardiovasc Thorac Surg. 2003 Mar;2(1):91-3.
- Rahman I, Sadiq SA; Ophthalmic management of facial nerve palsy: a review. Surv Ophthalmol. 2007 Mar-Apr;52(2):121-44.
- Bell's palsy; NICE CKS, October 2012
- Salinas RA, Alvarez G, Daly F, et al; Corticosteroids for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2010 Mar 17;(3):CD001942. doi: 10.1002/14651858.CD001942.pub4.
- Ashtekar CS, Joishy M, Joshi R; Best evidence topic report. Do we need to give steroids in children with Bell's Emerg Med J. 2005 Jul;22(7):505-7.
- Lockhart P, Daly F, Pitkethly M, et al; Antiviral treatment for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2009 Oct 7;(4):CD001869. doi: 10.1002/14651858.CD001869.pub4.
- Teixeira LJ, Valbuza JS, Prado GF; Physical therapy for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2011 Dec 7;(12):CD006283. doi: 10.1002/14651858.CD006283.pub3.
- Shargorodsky J, Lin HW, Gopen Q; Facial Nerve Palsy in the Pediatric Population. Clin Pediatr (Phila). 2010 Feb 4.
- Cha HE, Baek MK, Yoon JH, et al; Clinical features and management of facial nerve paralysis in children: analysis J Laryngol Otol. 2009 Dec 22:1-5.
- Lorch M, Teach SJ; Facial nerve palsy: etiology and approach to diagnosis and treatment. Pediatr Emerg Care. 2010 Oct;26(10):763-9; quiz 770-3. doi: 10.1097/PEC.0b013e3181f3bd4a.
- Finsterer J; Management of peripheral facial nerve palsy. Eur Arch Otorhinolaryngol. 2008 Jul;265(7):743-52. Epub 2008 Mar 27.
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Dr Huw Thomas
Dr Colin Tidy
Dr John Cox