Bell's palsy is a paralysis of cranial nerve VII (the facial nerve) resulting in inability to control facial muscles on the affected side. Several conditions can cause a facial paralysis, e.g, brain trauma, stroke and Lymes disease. However, if no specific cause can be identified, the condition is known as Bell's palsy. Named after Scottish anatomist Charles Bell, who first described it. Bell's palsy is the most common acute mononeuropathy (disease involving only one nerve) and is the most common cause of acute nerve paralysis.
Bell's palsy is defined as an idiopathic unilateral facial nerve paralysis, usually self-limiting. The trademark is rapid onset of partial or complete palsy, usually in a single day.
It is thought that a inflammatory condition leads to swelling of the facial nerve. The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to lead to nerve inhibition, damage or death. No readily identifiable cause for Bell's palsy has been found.
Doctors may prescribe anti-inflammatory and anti-viral drugs. Early treatment is necessary for the drug therapy to have effect. The effect of treatment is still controversial. Most people recover spontaneously and achieve near-normal to normal function. Many shows signs of improvement as early as 10 days after the onset, even without treatment. Yet a small percentage continue to suffer from the many symptoms of the paralysis for many years. There is evidence to suggest that for some this is an irrecoverable situation and the paralysis remains with them throughout their lives.
Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea may be permanently damaged resulting in impaired vision. In some cases the whole side of the face sags and lack control of the lower facial muscles results in a drool and difficulty in speech and eating. Hearing on the affected side becomes greatly enhanced, especially in the higher audible frequencies. After several months from onset alternative methods of controlling the various movement and function of the facial muscles is almost automatically "self taught" by the brain in an attempt to return to normality. This results in an achievement that is not normal operation of the nerve and muscle system and is referred to as "Synkinesis". Although this process assists the patient to recover in part normality of facial function, it also incurs frequent cramping of muscles, odd sensations running throughout the head and facial regions and often severe pain.
Further significant symptoms include the uncontrollable facial twitching. This, although sometimes invisible to the onlookers' eye; has a severe effect upon eyesight and can provoke extremely severe headache on a regular basis. This twitching can, in some cases, be indicative of recovery. However, this actually cannot be relied upon since random and hitherto unexplained twitching and other facial and cranial aberration may continue throughout the affliction.