Related articles: Bell's palsy
Definition
Bell's palsy is an acute hemifacial paresis, manifested by a sense of heaviness or numbness in the face. The patient can also complain of retroauricular pain, hyperacusis, loss of taste sensitivity and salivation and lacrimation changes.
The side of the affected face becomes expressionless; the ability to wrinkle the forehead, to wink and to make faces is limited or absent. In severe cases, the patient cannot close the eye.
Bell's palsy is due to a sudden peripheral paralysis of the 7th cranial nerve and is usually self-limiting (resolves in a few weeks or months). The exact underlying causes of paresis have not yet been identified, but dysfunctions of the 7th cranial nerve are probably implicated. The intervention of immunological mechanisms, inflammatory processes or reactivation of latent infections (eg by varicella-zoster virus) has been hypothesized. Lyme disease can produce this type of facial paralysis as a neurological complication; in this case the diagnosis is confirmed with the search for specific antibodies in the blood or with the identification of the migrating erythema.
Commonly, subjects who exhibit facial paralysis for which it is possible to define a triggering cause are not considered to be suffering from a real Bell's palsy. For example, Bell's palsy must be distinguished from a central lesion of the 7th cranial nerve, due to a stroke or a brain tumor; the latter, in fact, causes weakness especially in the lower part of the face.
Other causes of facial paralysis that must be excluded include: meningitis, head trauma, diabetes mellitus, sarcoidosis, middle ear infections and inflammatory pathologies of the cranial nerves.
Possible Causes * of Bell's Palsy
- Herpes simplex
- Lyme disease
