The "Bell's smile" is characterized by an asymmetry caused by paralysis of one side of the face.
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Bell's palsy

Bell's palsy (facial palsy) is characterised by facial drooping on the affected half, due to malfunction of the facial nerve (VII cranial nerve), which controls the muscles of the face. Named after Scottish anatomist Charles Bell, who first described it, Bell's palsy is the most common acute mononeuropathy (disease involving only one nerve), and is the most common cause of acute facial nerve paralysis. The paralysis is of the infranuclear/lower motor neuron type. Bell’s palsy affects about 40,000 people in the United States every year. It affects approximately 1 person in 65 during a lifetime. Until recently, its cause was unknown in most cases, but it has now been related to both Lyme disease and Herpes simplex. more...

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Additional symptoms that may accompany the condition are pain around the ear and loss of taste. In the great majority of patients, only one side of the face is affected. Detection of sensory loss, hearing loss, or ataxia during examination militates against the diagnosis of Bell's palsy and suggests the need for further evaluation.


Clinicians should determine whether all branches of the facial nerve are involved, or whether the forehead muscles are spared. Since these receive innervation from both sides of the brain, the forehead can still be wrinkled by a patient whose facial palsy is caused by a problem in the brain rather than in the facial nerve itself.


Bell's palsy is a diagnosis of exclusion; in many cases, no specific cause can be ascertained.


It is supposed to be the result of inflammation of the facial nerve, which produces pressure on the nerve as it exits the skull within its bony canal. Patients with facial palsy for which an underlying cause can be readily found are not generally considered to have Bell's palsy per se. These underlying problems include tumor, meningitis, stroke, diabetes mellitus, head trauma and inflammatory diseases of the cranial nerves (sarcoidosis, brucellosis, etc). In these conditions, the neurologic findings are rarely restricted to the facial nerve. Babies can be born with Facial palsy, and they exhibit many of the same symptoms as people with Bell's palsy; this is often due to a traumatic birth which causes irrepairable damage to the facial nerve, i.e.acute facial nerve paralysis.

One disease that may be difficult to exclude in the differential diagnosis is involvement of the facial nerve in infections with the herpes zoster virus. The major differences in this condition are the presence of small blisters, or vesicles, of the external ear and hearing disturbances, but these findings may occasionally be lacking.

In recent years, two new suspects have been added to the possible causes of Bell's palsy. Lyme disease may produce the typical palsy, and may be easily diagnosed by looking for Lyme-specific antibodies in the blood. In endemic areas Lyme disease may be the most common cause of facial palsy. The subsequent observation of an increased incidence of antibodies to the Herpes simplex virus in patients with Bell's palsy has led many specialists to believe that this agent is the most likely underlying cause in areas where Lyme disease is uncommon.


Bell's Palsy is three times more likely to strike pregnant women than non-pregnant women . It is also considered to be four times more likely to occur in diabetics than the general population, and it is more common in the elderly than children .


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Are drug therapies effective in treating Bell's palsy? - Clinical Inquiries
From Journal of Family Practice, 2/1/03 by Scott Shannon

* Photocopy for your patients "Bell's palsy" on page 160.


Early use of corticosteroid therapy results in less autonomic synkinesis and possibly improved rates of recovery in adults (strength of recommendation: C); there is no proven benefit in children (SOR: B).

Adding acyclovir (Zovirax) to prednisone therapy may improve recovery rates compared with prednisone alone (SOR: C).

The results of 1 nonblinded study indicate that intramuscular methylcobalamin (vitamin [B.sub.12]) used alone or in combination with prednisone may shorten time to recovery (SOR: C).


Bell's palsy is a lower motor neuron disease of the facial nerve characterized by a transient paralysis. Healing is occasionally incomplete, resulting in residual nerve dysfunction, including partial palsy and motor synkinesis (involuntary movement accompanying a voluntary one) and autonomic synkinesis (involuntary lacrimation after a voluntary muscle movement). Bell's palsy is associated with significant edema and ischemia of the facial nerve as it passes through its bony canal.

Herpes simplex reactivation has been shown to be associated with a large proportion of cases.

Corticosteroids are the most studied form of therapy for Bell's palsy (Table). Early work in England culminated in 1971 with a well-performed study demonstrating lower rates of incomplete recovery with prednisolone compared with corticotropkin. (1) A potentially definitive randomized controlled trial in 1970 was stopped prematurely because of investigators' subjective impression that prednisone markedly reduced postauricular pain. (2) Subsequently, the highest-quality study had few patients (n=51) and reported no difference in outcomes between patients receiving 10 days of oral prednisone plus vitamins and those receiving vitamins alone. (3)

One open randomized controlled trial demonstrated shorter mean recovery times with intramuscular methylcobalamin (1.95 weeks) and methylcobalamin plus prednisone (2.0 weeks) compared with prednisone alone (9.6 weeks). (4) Another trial of 239 patients showed improved rates of autonomic synkinesis after treatment with 16 days of prednisone compared with placebo. (5)

A randomized, controlled trial of children 2 to 6 years of age found no significant differences in short-term recovery after treatment with methylprednisolone compared with untreated controls. (6) Eventually, all these children recovered normal facial nerve function within 12 months.

Two randomized controlled trials have assessed the efficacy of acyclovir for treatment of Bell's palsy. One trial compared prednisone with acyclovir and found patients treated with prednisone had better complete recovery rates, 93.6% versus 77.7% (absolute risk reduction [ARR]=15.9%, 95% confidence interval [CI]=2.8%-29%], number needed to treat [NNT]=7). (7)

Another study demonstrated that the combination of prednisone and acyclovir had greater complete recovery rates compared with prednisone alone (92% vs. 76%, ARR=16%, 95% CI=1.7%-30.3%, NNT=7). (8)

Overall, the data suggest corticosteroid therapy may provide a small clinical benefit in adult patients with Bell's palsy. In many of these studies, patients who had contraindications to steroid therapy (peptic ulcer disease, uncontrolled diabetes, hypertension, or immunosuppression) were excluded.

If no contraindications to steroids exist, it is resonable to initiate treatment with corticosteroids for an adult patient with new-onset Bell's palsy. Most studies have started patients on steroids within 10 days of onset of symptoms.


A practice parameter from the American Academy of Neurology states that steroids are safe and probably effective (SOR: B), whereas acyclovir is safe and possibly effective (SOR: C). (9) Systematic reviews from the Cochrane Database report that available evidence from randomized controlled trials does not show significant benefit from treating Bell's palsy with corticosteroids and that clinical trials on acyclovir are inconclusive and therefore cannot be used to make recommendations regarding its use. (10,11)


My practice of neurology began before the era of corticosteroid treatment for Bell's palsy. Despite the lack of convincing evidenced-based data, it is my clinical impression that there are far fewer patients today with incompletely resolved Bell's palsy than before the widespread use of steroids. Permanent facial deformities seemed more common back then. Therefore, in the absence of harmful effects, I will continue treating with steroids.

Steven H. Horowitz, MD, University of Vermont College of Medicine, Burlington.


(1.) Taverner D, Cohen SB, Hutchinson BC. Comparison of corticotrophin and prednisolone in treatment of idiopathic facial paralysis (Bell's palsy). Br Med J 1971; 4:20-2.

(2.) Adour KK, Wingerd J, Bell DN, Manning JJ, Hurley JP. Prednisone treatment for idiopathic facial paralysis (Bell's palsy). N Engl J Med 1972; 287:1268-72.

(3.) May M, Wette R, Hardin WB, Jr., Sullivan J. The use of steroids in Bell's palsy: a prospective controlled study. Laryngoscope 1976; 86:1111-22.

(4.) Jalaludin MA. Methylcobalamin treatment of Bell's palsy. Methods Find Exp Clin Pharmacol 1995; 17:539-44.

(5.) Wolf SM, Wagner JH, Davidson S, Forsythe A. Treatment of Bell palsy with prednisone: a prospective, randomized study. Neurology 1978; 28:158-61.

(6.) Unuvar E, Oguz F, Sidal M, Kilic A. Corticosteroid treatment of childhood Bell's palsy. Pediatr Neurol 1999; 21:814-6.

(7.) De Diego JI, Prim MP, De Sarria MJ, Madero R, Gavilan J. Idiopathic facial paralysis: a randomized, prospective, and controlled study using single-dose prednisone versus acyclovir three times daily. Laryngoscope 1998; 108:573-5.

(8.) Adour KK, Rubayaines JM; Von Doersten PG, Byl FM, Trent CS, Quesenberry CP Jr. et al. Bell's palsy treatment with acyclovir and prednisone compared with prednisone alone: a double-blind, randomized, controlled trial. Ann Otol Rhinol Laryngol 1996; 105:371-8.

(9.) 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 2001; 56:830 6.

(10.) Salinas RA, Alvarez G, Alvarez MI, Ferreira J. Corticosteroids for Bell's palsy (idiopathic facial paralysis) (Cochrane Review). In: The Cochrane Library, Issue 2, 2002. Oxford: Update Software. Updated quarterly.

(11.) Sipe J, Dunn L. Aciclovir for Bell's palsy (idiopathic facial paralysis) (Cochrane Review). In: The Cochrane Library, Issue 2, 2002. Oxford: Update Software. Updated quarterly.

Scott Shannon, MD, Dept of Family and Community Medicine University of Missouri, Columbia. E-mail: Susan Meadows, MLS, Dept of Family and Community Medicine, University of Missouri, Columbia. E-mail:

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