Tuesday, May 16, 2017

Introduction to Bell’s palsy

Bell’s palsy
is a neurologic disorder that affects the seventh cranial (facial) nerve, producing unilateral facial weakness or paralysis. Onset is rapid. Although it affects all age-groups, it’s most common in persons younger than age 60. In 80% to 90% of patients, it subsides spontaneously, with complete recovery in 1 to 8 weeks; however, recovery may be delayed in older adults. 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.

The seventh cranial nerve is responsible for motor innervation of the facial muscles. With Bell’s palsy, the nerve is blocked by an inflammatory reaction around the nerve (usually at the internal auditory meatus). This is commonly associated with infections (most likely herpes simplex) and can result from hemorrhage, tumor, meningitis, or local trauma.

Signs and symptoms
Bell’s palsy usually produces unilateral facial weakness, occasionally with aching pain around the angle of the jaw or behind the ear. On the weak side, the mouth droops (causing the patient to drool saliva from the corner of his mouth), and taste perception is distorted over the affected anterior portion of the tongue. In addition, the forehead appears smooth, and the patient’s ability to close his eye on the weak side is markedly impaired. When he tries to close this eye, it rolls upward (Bell’s phenomenon) and shows excessive tearing. The patient also has hypersensitivities to sound.
Although Bell’s phenomenon occurs in those without Bell’s palsy, it isn’t apparent because the eye closes completely and covers this eye motion. In Bell’s palsy, incomplete eye closure makes this upward motion obvious.

Patients with Bell’s palsy typically have a distorted facial appearance and inability to raise the eyebrow, close the eyelid, smile, show the teeth, or puff out the cheek. After 10 days, electromyography helps predict the level of expected recovery by distinguishing temporary conduction defects from a pathologic interruption of nerve fibers.

With Bell’s palsy, treatment consists of prednisone, an oral corticosteroid that reduces facial nerve edema and improves nerve conduction and blood flow. In some cases, prednisone may be combined with acyclovir. After the 14th day of prednisone therapy, electrotherapy may help prevent atrophy of facial muscles

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