Special Feature
New Therapy is Warranted for Bell’s Palsy
By David J. Karras, MD, FACEP
The sudden appearance of facial weakness is, understandably, exceptionally disturbing to a patient. After performing a history and examination, the physician often makes a diagnosis of Bell’s palsy without performing any tests. The physician then may try to put a favorable "spin" on the diagnosis for the distraught patient. The good news, we tell the patient, is that you’re not having a stroke and your symptoms will probably improve with time. The bad news, we go on to say, is that we don’t know what caused it, we don’t have an effective treatment, and it may recur.
Fortunately, the bad news is getting better. There is new strong evidence that the etiologic agent for Bell’s palsy has been identified as the herpes simplex virus. Furthermore, specific antiviral therapy appears to be of benefit. A brief review of Bell’s palsy is indicated before further discussion of recent advances in its management.
Presentation of Bell’s Palsy
Bell’s palsy is acute paralysis of the peripheral portion of the seventh cranial nerve, which, until recently, was considered idiopathic. Twenty people per 100,000 are affected each year, with neither gender being preferentially involved. Pregnant women have more than three times the risk of the general population, diabetics have greater than a fourfold risk, and the incidence increases steadily with age. The greatest risk factor for Bell’s palsy is a history of the disease: 10% of affected patients will develop a recurrence, which occurs equally on either side.1
Symptoms of Bell’s palsy are ipsilateral and involve structures innervated by the seventh nerve, including the muscles of facial expression, the lacrimal gland, and taste in the anterior two-thirds of the tongue. A viral syndrome precedes the illness in the majority of patients and may be associated with transient, mild ipsilateral facial numbness. Facial motor deficits are the hallmark of Bell’s palsy and may present with anything from mild facial asymmetry to profound facial weakness with drooling and inability to fully close the eyelid. Because this is a peripheral nerve lesion, the patient loses the ability to wrinkle the forehead on the affected side. Hyperacusis results from paralysis of the stapedius muscle. The majority of patients experience dysgeusia and either hyperlacrimation or decreased tearing.
More than 90 diseases are listed in the differential diagnosis of facial paralysis.2 The potential etiologies of acute facial paralysis are a bit more limited and are listed in the Table. The most common causes of acute facial paralysis are Bell’s palsy, trauma, and herpes zoster oticus (Ramsay Hunt’s syndrome). Lyme disease also should be considered if the patient has been in areas where the disease is endemic; Lyme titers are then indicated, although empiric therapy is not. Bell’s palsy can usually be diagnosed without special testing. The presence of characteristic signs and symptoms and the absence of any other neurologic deficit or evidence of other acute illness are sufficient to make a diagnosis. Eighty-five percent of patients will have complete recovery within six months, and most of the remainder will have minor residual deficits.3 Treatment is supportive, with artificial tears if needed. Corticosteroid therapy has been both widely advocated and widely disparaged but is considered by some to be a standard of care.
| Table | |
| Some Causes of Acute Facial Palsy | |
| Neurological
cortical CVA Infectious
|
Neoplastic
cerebellopontine angle tumor temporal bone tumor acoustic neuromas Trauma
Toxic
Iatrogenic Idiopathic
|
| _______________________________________________________ | |
Insights into Disease Etiology and Treatment
In the 1970s, the hypothesis first appeared that Bell’s palsy might be related to herpes simplex virus (HSV). Patients with Bell’s palsy were found to have higher HSV titers than matched controls.4 More weight was given to this conjecture when it was demonstrated that HSV can reside in latent form in nerve ganglia.5 Strong, direct evidence linking HSV and Bell’s palsy has been published in this decade. Facial paralysis has been induced in an animal model by inoculating HSV into mouse ears; in the same experiment, HSV was recovered from mice that developed paralysis, but not from those that did not develop paralysis.6
In 1996, Murakami and colleagues reported a four-year study of patients who had undergone nerve-decompression surgery for facial palsy. Fourteen patients had been diagnosed with Bell’s palsy and nine with Ramsay Hunt’s syndrome. Twelve controls undergoing surgery for trauma or bacterial otitis media were also included. Using polymerase chain reaction techniques, HSV was detected in the affected facial nerve of 70% of patients with Bell’s palsy. Strikingly, HSV was detected in none of the patients with Ramsay Hunt’s syndrome and none of the control patients.
Adding stronger evidence to the role of HSV in Bell’s palsy, Adour and colleagues published a placebo-controlled, double-blind study of acyclovir for patients with Bell’s palsy of less than three days’ duration.7 Ninety-nine patients were randomized to receive either acyclovir (400 mg 5 times a day) or placebo; all subjects were also treated with prednisone 1 mg/kg divided in two daily doses for five days and then in tapering doses over five more days. Patients receiving acyclovir and prednisone demonstrated better recovery in muscle function and less nerve degeneration than those receiving prednisone alone. The rate of recovery appeared better in the acyclovir-treated group, though incomplete follow-up information precluded formal testing of this difference. Adour et al conclude that HSV is the likely etiologic agent of Bell’s palsy and that acyclovir is indicated in the management of the disease.
While a causal relationship between HSV and Bell’s palsy has not been definitely established, the evidence to date is extremely compelling. Acyclovir therapy carries minimal risk. Most authorities, therefore, now recommend both prednisone and antiviral therapy for patients presenting with Bell’s palsy of recent onset.8 (Dr. Karras is Director of Emergency Medicine Research, Temple University School of Medicine, Philadelphia, PA.)
References
1. Jackson CG, et al. The facial curve. Med Clin North Am 1999;83:179-195.
2. May M, Klein SR. Differential diagnosis of facial nerve palsy. Otolaryngol Clin North Am 1991;24:613-645.
3. Knox GW. Treatment controversies in Bell’s palsy. Arch Otolaryngol Head Neck Surg 1998;124:821-823.
4. Adour KK, et al. Herpes simplex virus in idiopathic facial paralysis (Bell palsy). JAMA 1975;233:527-530.
5. Baringer JR. Herpes simplex virus and Bell palsy. Ann Intern Med 1996;124:63-65.
6. Murakami S, et al. Role of herpes simplex virus infection in the pathogenesis of facial paralysis in mice. Ann Otol Rhinol Laryngol 1996;105:49-53.
7. Adour KK, 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;105:371-378.
8. Knox GW. Treatment controversies in Bell palsy. Arch Otolaryngol Head Neck Surg 1998;124:821-823.
In patients with Bell’s palsy, acyclovir therapy:
a. often has severe side effects.
b. does not appear to speed the rate of initial recovery.
c. is not associated with better muscle function.
d. should be combined with corticosteroid therapy.
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