-IBIS-1.5.0-
tx
nervous system
Bell's palsy
diagnoses

definition and etiology

definition:
The sudden occurrence of unilateral paralysis of the facial nerve (cranial nerve VII). It is the most common form of facial paralysis (around 1 in every 60-70 persons in a lifetime).

etiology: The cause of the disease is unknown. The pathology involves swelling of the seventh nerve from viral or immune disease, leading to ischemia and compression of the nerve where it traverses through the narrow area of the temporal bone. The scattered cases that have been autopsied showed nondescript differences in the normal appearance of the nerve and no inflammatory changes.

signs and symptoms

principal signs and symptoms:
Onset is abrupt: often full paralysis is evident within hours and usually by two days.
• Pain behind the ear or at jaw angle on the involved side may precede paralysis.
• The involved side is expressionless and sags, and patients may complain more about the normal side which seemingly feels tight and twisted.

associated signs and symptoms: (relate to position of lesion)
• A lesion proximal to the nerve branches may cause problems with salivation, gustation, tearing, and hearing (hyperacusis).
• In the worst cases, the patient has a wide palpebral fissure and cannot close his eye.
• Physical examination may show a decrease in pinprick sensitivity behind the ear along the distribution of Arnold's nerve.
• X-rays are negative but may uncover a bony erosion from infection or cancer, a fracture line or internal auditory canal growth from cerebellopontine angle tumor.

course and prognosis

Over 80% of afflicted patients will recover fully within a few weeks or months. Incomplete paralysis during the first week is the most favorable sign for recovery. If electromyography indicates denervation after 10 days, pointing to axonal degeneration, then there will be a long delay before regeneration occurs, and it still might not totally reverse pathology (20% of patients). If the nerve retains full excitability to electrical stimulation, complete recovery is around 90%. Facial muscle contractions may follow a long-term weakness. If the regrowth of nerve tissues is incorrect, lower facial muscles may be come innervated by periocular muscle nerves, or vice versa, causing contraction of unexpected muscles during voluntary facial movements (synkinesia).

Conventional treatment is prednisone daily with rapid tapering.

differential diagnosis

• Supranuclear lesions: weakness focused below the eye, not the entire side of the face.
• Ramsay-Hunt Syndrome (geniculate herpes).
• Middle ear and/or mastoid infections.
• Fractures of the petrous portion of the temporal bone.
• Carcinomatous or leukemic invasion of the facial nerve.
• Cerebellopontine angle or glomus jugulare tumors.
• Any invasive cranial nerve disease.


footnotes