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Major causes of acute facial palsy include Bell's palsy and Ramsay Hunt syndrome. These two diseases account for approximately two thirds of all cases. Although Ramsay Hunt syndrome is caused by reactivation of varicella zoster virus (VZV), the etiology of Bell's palsy has not been clarified until more recently. In 1996, we found viral genomes of herpes simplex virus type 1 (HSV-1) from endoneurial fluid of the facial nerve and auricular muscle using PCR. HSV-1 genomes were identified specifically in 79% of Bell's patients and VZV genomes were identified in 89% of Ramsay Hunt patients. In 1998, Furuta et. al. detected HSV-1 genomes from saliva in 50% of Bell's palsy patients. These studies have provided the conclusive evidence that Bell's palsy is caused by a reactivation of HSV-1. On the other hand, we know that atypical Ramsay Hunt's syndrome, zoster without auricular vesicles, is often diagnosed as Bell's palsy. Previous studies have demonstrated the prevalence of zoster without vesicles in Bell's palsy ranged from 8 to 25%. Accordingly, 50 to 80% of Bell's palsy may be caused by HSV-1, 8 to 25% by VZV, and others are still unknown.

Extensive studies by our group have demonstrated that the underlying pathophysiology of Bell's palsy and Ramsay Hunt syndrome is viral neuritis, edema and entrapment neuropathy. Therefore, combination treatment with steroids and anti-viral agents is rational and has been accepted as a standard treatment for Bell's palsy and Ramsay Hunt syndrome. For Bell's palsy (HSV-1), prednisone (1mg/kg/day) and valacyclovir (1000mg/day) are generally used. In cases of Ramsay Hunt' syndrome (VZV), a greater dose of 3000mg/day of valacyclovir is needed. Steroid and anti-viral agents must be administrated as soon as possible, hopefully within 3 days of the onset of facial palsy. However, as mentioned above, a considerable number of patients diagnosed with Bell's palsy actually suffer from zoster without vesicles. Moreover, in about one third of Ramsay Hunt patients, herpetic vesicles develop several days after the onset of facial palsy. We are not able to differentiate patients with acute facial palsy caused by VZV from those by HSV-1 at the initial visit. Patients who are diagnosed with Bell's palsy and treated without or with an insufficient dose of an antiviral agent may have a poorer prognosis. Detection of viral genomes from clinical samples by PCR is thought to be a powerful tool for early diagnosis of HSV-1 and VZV reactivation. However, it is not yet available for clinical use. For this reason, we designed a practical protocol of medical treatment that covers both HSV-1 and VZV infection. Basically, the dose of valacyclovir combined with prednisone is decided upon depending on the severity of facial palsy. The dosing is considered again on the third day of treatment because the palsy may be worse in some patients. Valacyclovir at 3000mg/day is used for severe cases for the first 3 days, but continued for an additional 4 days if herpetic vesicles and vestibulo-cochlear symptoms appear. We studied 172 patients with acute facial palsy using this protocol and obtained better results compared with previous studies.

The role of decompression surgery for Bell's palsy and Ramsay Hunt syndrome remains controversial. However, we believe the decompression operation is effective for reducing further nerve degeneration and brings better regeneration of the facial nerve because it eliminates edematous swelling of the facial nerve and entrapment neuropathy within the Fallopian canal. The facial nerve has two narrow portions, one located at the meatal foramen and the other at the pyramidal segment. Therefore, total decompression with the combination of middle cranial fossa and transmastoid approaches is recommended. The effects of facial nerve decompression using intraoperative electrical stimulation of the nerve will be demonstrated.

The final goal in the management of facial palsy is to prevent its development. VZV vaccine is known to be effective in preventing chicken pox in children. In 2005, VZV vaccine was also proven to reduce the incidence of herpes zoster in elderly adults. Usefulness of VZV vaccine in childhood for the prevention of Ramsay Hunt syndrome will be discussed.

Special Presentation