Bell, Sir Charles
(bel 
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Scottish physiologist and surgeon, 1774–1842.
Variant: Bell-Magendie law
The fact that anterior spinal nerve roots contain only motor fibers and posterior roots only sensory fibers. SYN: law of Magendie.B. nerve Long thoracic nerve; nervus thoracicus longus.
B. palsy Paralysis of the facial nerve. SYN: Bell paralysis; facial palsy; facial nerve palsy; facial nerve paralysis; facial paralysis; idiopathic facial neuropathy.
Approx. 25 people out of 100,000 experience an episode of facial nerve paralysis yearly.
Bell palsy is usually caused by a reactivation of herpes simplex virus, but other infections such as syphilis or Lyme disease are sometimes implicated.
Paralysis of the facial nerve typically results in an asymmetrical facial appearance. Either side of the face may be affected. The affected patient is unable to raise one side of the mouth to smile or to wrinkle or raise the eyebrow on the same side. This peripheral nerve dysfunction is distinguished from strokes that alter facial movement by the involvement of both the forehead and the mouth. Paralysis of the face caused by strokes usually only limits movement of the oral muscles.
SEE: illus.
Bell palsy is diagnosed by physical examination. It should be distinguished from ischemic or hemorrhagic stroke, complicated migraine, brain tumors, central nervous system infections, Lyme disease and Guillain-Barré syndrome.
Tapering doses of prednisone without antiviral drugs provide the most effective results. In addition, the affected eye should be protected from drying with artificial tears or unmedicated ointments. Some practitioners advise wearing sunglasses during the palsy or patching the eye to protect it from foreign bodies or drying.
Partial facial paralysis is usually resolved within several months. The likelihood of complete recovery after total paralysis varies from 20% to 90% and is best in the young patient. Attacks recur in about 10% of cases. Complications that may arise from inability to close the eye include corneal drying and ulceration. Mild slurring of speech may occur because of paralysis of the muscles of the lower part of the face.
To protect the affected eye, patients should be advised to use lubricating eye drops or prescribed ointments. Patching the eye or taping it shut at night prevents drying. Patients who experience unilateral sensitivity to loud noises may try ear plugs.
Bell phenomenon Rolling of the eyeball upward and outward when an attempt is made to close the eye on the side of the face affected in peripheral facial paralysis.