Botulinum toxin type A commonly referred to as Botox is an injectable compound that produces temporary muscular weakness. In addition to its role in anti-aging therapy, Botox has proven effective in treating some of the side effects of facial paralysis (synkinesis, hemifacial spasm, blepharospasm).
During the recovery phase of Bell’s palsy, the regenerating nerve fibers initially migrate through a common channel (main nerve trunk). Eventually the facial nerve will start to divide into a series of branches bound for either the brow, eye, cheek, lips or neck and migrating nerve fibers will be forced to select a path. Unfortunately, some nerve fibers that the brain has earmarked for a particular function may ultimately grow to the wrong location.
For example, a collection of nerve fibers the brain has deemed responsible for smiling may grow to the muscles at the corner of the mouth and eyelid. In this case an attempt to smile will produce movement of the lips and closure of the eye. These abnormal facial movements are referred to as synkinetic function. Hyperactivity and synkinetic function of the facial muscles often responds favorably to Botox injections.