Bell’s palsy is a disorder that results from the dysfunction of cranial nerve VII, the facial nerve. It involves weakness or paralysis, typically on one side of the face. The onset of the condition is rapid, usually progressing to maximum severity within 72 hours.
While there can be a number of causes of facial weakness or paralysis, the cause of Bell’s palsy is unknown, and diagnosis is made by ruling out other potential causes like Lyme disease, trauma, tumors, etc. In other words, Bell’s palsy is only diagnosed when there is not another identifiable cause of the facial paralysis. The symptoms of Bell’s palsy can vary from case to case in both form and severity, but the most common symptom is rapidly developing weakness on one side of the face.
There can be a number of other symptoms that emerge from facial nerve dysfunction, including drooping of the eyelid, drooping of one side of the mouth, drooling, an inability to completely close the eye, excessive tearing and pain in the eye, facial pain, loss of taste, hypersensitivity to sound on the affected side, and other symptoms depending on the case. Although the cause of Bell’s palsy is unclear, there is evidence that many cases may have a viral origin. Reactivation of latent viruses such as the herpes simplex virus has been hypothesized to be an important factor in many cases of Bell’s palsy, but how exactly viruses might damage the facial nerve is still uncertain.
Other factors potentially involved in the development of Bell’s palsy include reduced blood supply to the facial nerve and damage to the facial nerve caused by inflammation. Most cases of Bell’s palsy start to improve without any medical intervention within a few weeks, and recover completely within 3 to 4 months. Less commonly, symptoms may last longer, never completely disappear, or fade away and then reoccur.
