Atlas of pathophysiology, 2 Edition
Part II - Disorders
Bell's palsy is a disease of the facial nerve (cranial nerve VII) that produces unilateral or bilateral facial weakness. Onset is rapid. In 80% to 90% of patients, it subsides spontaneously and recovery is complete in 1 to 8 weeks. If recovery is partial, contractures may develop on the paralyzed side of the face. Bell's palsy may recur on the same or opposite side of the face.
Although Bell's palsy affects all age-groups, it occurs most commonly in people between ages 20 to 60. Recovery may be slower in elderly patients.
· Infection such as herpes simplex virus
· Local trauma
· Lyme disease
Bell's palsy reflects an inflammatory reaction around the seventh cranial nerve, usually at the internal auditory meatus where the nerve leaves bony tissue. The characteristic unilateral or bilateral facial weakness results from the lack of appropriate neural stimulation to the muscle by the motor fibers of the facial nerve.
Signs and symptoms
· Unilateral face weakness
· Aching at jaw angle
· Drooping mouth
· Distorted taste or loss of taste
· Impaired ability to fully close the eye on the affected side
· Excessive or insufficient eye tearing on the affected side
· Hypersensitivity to sound on the affected side
When the patient attempts to close the affected eye, it rolls upward (Bell's phenomenon) and shows excessive tearing.
Diagnostic test results
Diagnosis is based on clinical presentation (see clinical tip, page 127). Other studies include:
· nerve conduction studies and electromyography to determine the extent of nerve damage
· blood tests to establish the presence of sarcoidosis or Lyme disease.
· Oral corticosteroids such as prednisone
· Lubricating eyedrops or eye ointments
NEUROLOGIC DYSFUNCTION IN BELL'S PALSY
Diagnosing Bell's palsy