From the Guidelines
Bell's palsy is a diagnosis of exclusion, characterized by acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours and without an identifiable cause.
Definition and Diagnosis
- Bell's palsy is defined as acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours and without an identifiable cause 1.
- The diagnosis of Bell's palsy is made by excluding other causes of facial paresis or paralysis, and is characterized by the sudden onset of unilateral facial weakness or paralysis 1.
Clinical Features
- Patients with Bell's palsy may experience dryness of the eye or mouth, taste disturbance or loss, hyperacusis, and sagging of the eyelid or corner of the mouth 1.
- Ipsilateral pain around the ear or face is not an infrequent presenting symptom 1.
Pathophysiology
- The exact mechanism of Bell's palsy is currently unknown, but facial paresis or paralysis is thought to result from facial nerve inflammation and edema 1.
- The facial nerve carries nerve impulses to muscles of the face and also to the lacrimal glands, salivary glands, stapedius muscle, taste fibers from the anterior tongue, and general sensory fibers from the tympanic membrane and posterior ear canal 1.
Treatment
- Oral corticosteroids are recommended for patients 16 years and older with new-onset Bell's palsy to decrease recovery time and improve facial nerve functional recovery 1.
From the Research
Definition and Characteristics of Bell's Palsy
- Bell's palsy, also known as "acute facial palsy of unknown cause", is a common cranial neuropathy leading to facial muscle paresis or complete paralysis characteristically on one side, occurring suddenly and may progress over 48 hours 2.
- It results from facial nerve dysfunction due to trauma or inflammation of the 7th cranial nerve or facial nerve or its branches along its course, primarily in the bony canal 2.
- Both sexes are equally affected, and though no age is immune, its incidence rises with increasing age 2.
Etiology and Pathogenesis
- The exact etiology of Bell's palsy is unknown, affecting its treatment 2.
- Viral infection or autoimmunity has been postulated as possible pathomechanisms 3.
- Bell's palsy may be caused when latent herpes viruses (herpes simplex, herpes zoster) are reactivated from cranial nerve ganglia 3.
- A cell-mediated autoimmune mechanism against a myelin basic protein has been suggested for the pathogenesis of Bell's palsy 3.
Clinical Features and Diagnosis
- Bell's palsy is characterized by unilateral facial weakness, which can result in the inability to close the eyelids, smile, or whistle 4.
- Diagnosis is primarily one of exclusion, and early treatment based on careful investigation of Bell's palsy can improve the patient's function and esthetics 4, 5.
- The natural history of Bell's palsy is favorable, with 84% showing satisfactory recovery without any treatment, however 16% suffer moderate to severe sequelae 5.
Treatment and Prognosis
- Steroids are generally agreed to be beneficial, and steroid application is the only evidence-based therapy to date with recovery rates >90% 5, 6.
- Acyclovir would seem to be a promising drug; however studies have not adequately assessed its use 5.
- Prognosis is influenced by degree of paresis, age of patient, and time until first signs of recovery, and more than 90% degeneration of the facial nerve carries a poor prognosis for recovery 5.