Introduction
Background
Bell palsy is an acute, idiopathic, unilateral, peripheral, lower-motor-neuron facial-nerve paralysis that gradually resolves over time in 80-90% of cases. Its cause is unknown, though it appears to be a polyneuritis with possible viral, inflammatory, autoimmune, and ischemic etiologies. Increasing evidence implicates herpes simplex type I and herpes zoster virus reactivation from cranial-nerve ganglia.
Determining whether facial-nerve paralysis is peripheral or central is a key step in the diagnosis. A lesion involving the central motor neurons above the level of the facial nucleus in the pons causes weakness of the lower face alone. Thorough history taking and examination, including the ears, nose, throat, and cranial nerves, must be performed. If the clinical findings are doubtful or if paralysis lasts longer than 6-8 weeks, further investigations, including gadolinium-enhanced MRI of the temporal bones and pons, should be considered.
Bell palsy is more common in adults, in people with diabetes, and in pregnant women than in others. Bell palsy recurs in 3-10% of patients, either on the same side or on the opposite side of the face. Recurrent or bilateral disease should suggest myasthenia gravis.
Treatment overview
Treatment of Bell palsy should be conservative and guided by the severity and probable prognosis in each particular case. However, the relationship with the herpes simplex virus has become even more apparent, and antiviral treatment combined with corticosteroids has become accepted for treating patients with milder degrees of Bell palsy. Electrodiagnostic tests (eg, stapedius reflex test, evoked facial-nerve electromyography [EMG], audiography) may help improve the accuracy of prognosis in difficult cases.
Topical ocular therapy is useful in all cases, except for those in which the condition is severe or prolonged. In these cases, surgical management is best. Several procedures are aimed at protecting the cornea from exposure and achieving facial symmetry. These procedures help eliminate the need for constant use of lubrication drops or ointments, they improve cosmesis, and they preserve vision on the affected side.
Anatomy
The facial nerve travels a 30-mm interosseous course through the internal auditory canal (with the eighth cranial nerve) and through the internal fallopian canal in the petrous temporal bone. This bony confinement limits the amount that the nerve can swell and thereby cause acute paralysis.
The facial nerve arises from its nucleus in the pons and exits at the cerebellopontine angle, where the nervus intermedius (which is responsible for lacrimation, salivation, and taste) and the nerve to the stapedius muscle joint are. The facial nerve travels with the vestibulocochlear nerve through the internal auditory canal and the facial (fallopian) canal in the temporal bone. The parasympathetic fibers directed toward the pterygopalatine ganglion and lacrimal gland exit at the geniculate ganglion as the greater petrosal nerve.
While coursing through the temporal bone, a branch leaves to the stapedius and proceeds distally as the chorda tympani to supply the salivary glands.
The facial nerve exits the stylomastoid foramen and divides into 5 branches in the parotid gland to innervate the facial muscles.
Pathophysiology
By definition, Bell palsy is idiopathic. Possible etiologies include infections, particularly herpes simplex (but also herpes zoster, Lyme disease, syphilis, Epstein-Barr viral infection, HIV, and mycoplasma); inflammation alone; and microvascular disease (diabetes mellitus and hypertension).
Frequency
United States
The rate is 20-30 cases per 100,000 population.
International
The rate worldwide is approximately 10-30 cases per 100,000 population.
Mortality/Morbidity
- This condition is 4.5 times more common in people with diabetes, 3.3 times more common in pregnant women, and more common in people with immunocompromise or preeclampsia than in others.
- Indicators of a poor prognosis are age older than 60 years, no recovery by 3 weeks, complete facial palsy, severe pain, and severe degeneration of the facial nerve (as assessed by means of evoked EMG testing).
Sex
The incidences are roughly equal in men and women.
Age
Bell palsy is rare in children. Peak ages are 20-40 years. The disease also occurs in elderly persons aged 70-80 years.
Clinical
History
See Physical.
Physical
- Early symptoms
- Weakness of the facial muscles
- Poor eyelid closure
- Aching of the ear or mastoid (60%)
- Alteration of taste (57%)
- Hyperacusis (30%)
- Tingling or numbness of the cheek/mouth
- Epiphora
- Ocular pain
- Blurred vision
- Early ocular complications
- Lagophthalmos
- Paralytic ectropion of the lower lid
- Corneal exposure
- Brow droop
- Upper eyelid retraction
- Decreased tear output/poor tear distribution
- Loss of nasolabial fold
- Corneal erosion, infection, and ulceration (rare but may occur)
- Late ocular manifestations
- Mild, generalized mass contracture of the facial muscles, rendering the affected palpebral fissure narrower than the opposite one (after several months)
- Aberrant regeneration of the facial nerve with motor synkinesis
- Reversed jaw winking (ie, contracture of the facial muscles with twitching of the corner of the mouth or dimpling of the chin occurring simultaneously with each blink)
- Autonomic synkinesis (ie, crocodile tears-tearing with chewing)
- Rare, permanent, disfiguring facial paralysis
- Classification for facial nerve deficits
- Normal
- Mild dysfunction (normal symmetry at rest, ability to close lids with minimal effort and slight asymmetry, ability to move mouth with maximal effort)
- Moderate dysfunction (mild asymmetry, no functional impairment, ability to close lids and move mouth with maximal effort)
- Moderately severe dysfunction (obvious asymmetry, no movement of brows, unable to close lids completely, inability to move corner of mouth)
- Severe dysfunction (only barely perceptible motion, obvious asymmetry with droop of mouth and absent nasolabial fold, slight movement of eyelids)
- Total paralysis
Causes
By definition, Bell palsy is idiopathic. Possible etiologies include infections (herpetic, Lyme disease, Epstein-Barr viral infection, HIV, and mycoplasma), inflammation, and microvascular disease (diabetes mellitus and hypertension).
More on Bell Palsy |
 Overview: Bell Palsy |
| Differential Diagnoses & Workup: Bell Palsy |
| Treatment & Medication: Bell Palsy |
| Follow-up: Bell Palsy |
| References |
| Next Page » |
References
Adour KK, Byl FM, Hilsinger RL Jr, Kahn ZM, Sheldon MI. The true nature of Bell's palsy: analysis of 1,000 consecutive patients. Laryngoscope. May 1978;88(5):787-801. [Medline].
Bauer CA, Coker NJ. Update on facial nerve disorders. Otolaryngol Clin North Am. Jun 1996;29(3):445-54. [Medline].
Chua CN, Quhill F, Jones E, Voon LW, Ahad M, Rowson N. Treatment of aberrant facial nerve regeneration with botulinum toxin A. Orbit. Dec 2004;23(4):213-8. [Medline].
Davies R. Facial nerve palsy. In: Levine M, ed. Manual of Oculoplastic Surgery. 2003. Butterworth-Heinemann: Boston, MA; 197-202.
English JB, Stommel EW, Bernat JL. Recurrent Bell's palsy. Neurology. Aug 1996;47(2):604-5. [Medline].
Grogan PM, Gronseth GS. Practice parameter: Steroids, acyclovir, and surgery for Bell's palsy (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. Apr 10 2001;56(7):830-6. [Medline].
Halperin JJ, Golightly M. Lyme borreliosis in Bell's palsy. Long Island Neuroborreliosis Collaborative Study Group. Neurology. Jul 1992;42(7):1268-70. [Medline].
Holland NJ, Weiner GM. Recent developments in Bell's palsy. BMJ. Sep 4 2004;329(7465):553-7. [Medline].
Jackson CG, von Doersten PG. The facial nerve. Current trends in diagnosis, treatment, and rehabilitation. Med Clin North Am. Jan 1999;83(1):179-95, x. [Medline].
Julian GG, Hoffmann JF, Shelton C. Surgical rehabilitation of facial nerve paralysis. Otolaryngol Clin North Am. Oct 1997;30(5):701-26. [Medline].
Lee V, Currie Z, Collin JR. Ophthalmic management of facial nerve palsy. Eye. Dec 2004;18(12):1225-34. [Medline].
Murphy TP. MRI of the facial nerve during paralysis. Otolaryngol Head Neck Surg. Jan 1991;104(1):47-51. [Medline].
Olver JM. Raising the suborbicularis oculi fat (SOOF): its role in chronic facial palsy. Br J Ophthalmol. Dec 2000;84(12):1401-6. [Medline].
Seiff SR, Chang J. Management of ophthalmic complications of facial nerve palsy. Otolaryngol Clin North Am. Jun 1992;25(3):669-90. [Medline].
Williamson IG, Whelan TR. The clinical problem of Bell's palsy: is treatment with steroids effective?. Br J Gen Pract. Dec 1996;46(413):743-7. [Medline].
Further Reading
Keywords
Bell's palsy, facial nerve paralysis, idiopathic facial palsy
