Bell's Palsy

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In medicine, Bell's Palsy is "A syndrome characterized by the acute onset of unilateral facial paralysis which progresses over a 2-5 day period. Weakness of the orbicularis oculi muscle and resulting incomplete eye closure may be associated with corneal injury. Pain behind the ear often precedes the onset of paralysis. This condition may be associated with human herpesvirus 1 infection of the facial nerve."[1]


Most cases of Bell's Palsy are caused by Herpes simplex virus type 1[2] Some cases are caused by Herpes zoster virus.[3]


Two meta-analyses reach conflicting conclusions.[4][5] While both agree that corticosteroids improve recovery, one analysis supported antivirals[5] while the other did not[4]. The negative meta-analysis by Quant noted that the two factorial trials[6][7] that Quant interpreted as having the highest quality were negative.

Do antimetabolite antivirals add to corticosteroids in improving Bell's Palsy?
Sutdy Design Result
Meta-analysis of 6 trials† OR: 0.67‡ (95% CI, 0.37-1.20)
de Almeida[5]
Meta-analysis of 8 trials RR: 0.75 (95% CI, 0.56-1.00)
† Quant excluded the trial of Antunes[8] and the negative trial of Vazquez[9]
‡ The original publication reported the odds ratio for increase in good outcomes. This table uses the reciprocal in order to report the reduction in adverse outcomes.

Of the two best randomized controlled trials, one was by Sullivan who studied 496 patients in a factorial design within 3 days after the onset of symptoms using 25 mg of prednisolone twice a day for 10 days.[7]Sullivan found improved facial function at 3 months from 64% to 83.0%.[7] This means that the drug benefits one out of every five patients treated (number needed to treat is 5). Acyclovir 400 mg five times daily for 10 days was also studied in this trial and found an absolute 8% increase in benefit but the study was underpowered to show significance for this difference.

A second high quality factorial trial was by Engström who studied with three of less days of symptoms and found that valaciclovir 1000 mg three times per day for 7 days added only 1% absolute benefit which had no statistical significance.[6]

This trial contradicts a previous randomized controlled trial of 99 patients in which acyclovir was better than prednisone at improving electroneurography evidence of volitional muscle motion and in preventing partial nerve degeneration.[10]

  1. Anonymous (2023), Bell's Palsy (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. Murakami S, Mizobuchi M, Nakashiro Y, Doi T, Hato N, Yanagihara N (1996). "Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle". Ann. Intern. Med. 124 (1 Pt 1): 27–30. PMID 7503474[e]
  3. Peitersen E (2002). "Bell's palsy: the spontaneous course of 2,500 peripheral facial nerve palsies of different etiologies". Acta oto-laryngologica. Supplementum (549): 4–30. PMID 12482166[e]
  4. 4.0 4.1 4.2 Quant, Eudocia C; Shafali S Jeste, Rajeev H Muni, Alison V Cape, Manveen K Bhussar, Anton Y Peleg (2009-09-07). "The benefits of steroids versus steroids plus antivirals for treatment of Bell's palsy: a meta-analysis". BMJ 339 (sep07_1): b3354. DOI:10.1136/bmj.b3354. Retrieved on 2009-09-10. Research Blogging.
  5. 5.0 5.1 5.2 de Almeida JR, Al Khabori M, Guyatt GH, Witterick IJ, Lin VY, Nedzelski JM et al. (2009). "Combined corticosteroid and antiviral treatment for Bell palsy: a systematic review and meta-analysis.". JAMA 302 (9): 985-93. DOI:10.1001/jama.2009.1243. PMID 19724046. Research Blogging.
  6. 6.0 6.1 Engström M, Berg T, Stjernquist-Desatnik A, Axelsson S, Pitkäranta A, Hultcrantz M et al. (2008). "Prednisolone and valaciclovir in Bell's palsy: a randomised, double-blind, placebo-controlled, multicentre trial.". Lancet Neurol 7 (11): 993-1000. DOI:10.1016/S1474-4422(08)70221-7. PMID 18849193. Research Blogging. Review in: Ann Intern Med. 2009 Mar 17;150(6):JC3-12
  7. 7.0 7.1 7.2 Sullivan FM, Swan IR, Donnan PT, Morrison JM, Smith BH, McKinstry B et al. (2007). "Early treatment with prednisolone or acyclovir in Bell's palsy.". N Engl J Med 357 (16): 1598-607. DOI:10.1056/NEJMoa072006. PMID 17942873. Research Blogging. Review in: ACP J Club. 2008 Mar-Apr;148(2):29 Review in: Evid Based Med. 2008 Apr;13(2):44 Review in: J Fam Pract. 2008 Jan;57(1):22-5
  8. Antunes ML, Fukuda Y, Testa JRG. Clinical treatment of Bell's palsy. Acta AWHO. 2000;19(2):68-75.
  9. Vazquez MC, Sanchez N, Calvo J. Eficacia de los antivirales en la parálisis de Bell. Rev Med Urug. 2008;24(3):1-8.
  10. Adour KK, Ruboyianes JM, Von Doersten PG, et al (1996). "Bell's palsy treatment with acyclovir and prednisone compared with prednisone alone: a double-blind, randomized, controlled trial". Ann. Otol. Rhinol. Laryngol. 105 (5): 371–8. PMID 8651631[e]