From the Guidelines
Bell's palsy is primarily caused by inflammation and swelling of the facial nerve, with a suspected viral etiology, although the exact mechanism is currently unknown. The condition is characterized by acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours and without identifiable cause 1. According to the clinical practice guideline, Bell's palsy is a diagnosis of exclusion, requiring the careful elimination of other causes of facial paresis or paralysis 1.
Key Points
- The facial nerve inflammation and edema lead to nerve compression, resulting in temporary or permanent nerve damage 1.
- The condition can cause a range of symptoms, including dryness of the eye or mouth, taste disturbance or loss, hyperacusis, and sagging of the eyelid or corner of the mouth 1.
- Most patients with Bell's palsy show some recovery without intervention within 2 to 3 weeks after onset of symptoms and completely recover within 3 to 4 months 1.
Treatment and Recovery
- Corticosteroids and antiviral medications are the most commonly used medical therapies for Bell's palsy 1.
- The benefit of surgical decompression of the facial nerve remains relatively controversial 1.
- Even without treatment, facial function is completely restored in approximately 70% of Bell's palsy patients with complete paralysis within 6 months and as high as 94% of patients with incomplete paralysis 1.
From the Research
Causes of Bell's Palsy
- The exact cause of Bell's palsy is not fully understood, but it is believed to be related to inflammation of the facial nerve, which may be caused by viral reactivation, such as herpes simplex virus (HSV) type 1 or Varicella Zoster virus (VZV) 2, 3, 4.
- Some studies suggest that reactivation of herpes viruses from the geniculate ganglion of the facial nerve may be a contributing factor in a proportion of cases 2.
- The condition is characterized by an acute, unilateral, partial, or complete paralysis of the face, which may be associated with mild pain, numbness, increased sensitivity to sound, and altered taste 2.
Viral Associations
- Herpes simplex virus (HSV) type 1 has been implicated as a potential causative pathogen in Bell's palsy, with some studies suggesting that antiviral therapy may be beneficial in treatment 3, 4.
- Varicella Zoster virus (VZV) reactivation, also known as Ramsay Hunt syndrome, is a less common cause of Bell's palsy, but may appear without skin lesions and be indistinguishable from Bell's palsy 3.
- The use of antiviral agents, such as acyclovir, may be effective in treating Bell's palsy, particularly when used in combination with corticosteroids 3, 5.