BELL’S PALSY: The Definition, It’s Causes, Clinical Features, Diagnosis, Treatment, & Prognosis

DEFINITION

BELL’S PALSY is an idiopathic demyelinating disease. It is characterized by acute isolated unilateral lower motor neuron facial paralysis.

• It accounts for over 50% of acute facial palsies.
• Both sexes are equally affected.
• There is no age bar but incidence rises with increasing age.
• Risk factors include diabetes (angiopathy) and pregnancy (retention of fluid).

ETIOLOGY

1. Viral infection: Many reports suggest viral infections due to Herpes simplex, Herpes zoster and Epstein-Barr virus. Some consider Bell’s palsy a part of the polyneuropathy. Other cranial nerves may also be involved.
2. Vascular ischemia: Primary ischemia may be induced by cold or emotional stress. It causes increased capillary permeability that leads to exudation of fluid, edema and compression of microcirculation of the nerve (secondary ischemia).
3. Hereditary: About 10% of patients give positive family history. The narrow fallopian canal (may be due to hereditary predisposition) can make the nerve susceptible to early compression at the slightest edema.
4. Autoimmunity: T-lymphocyte changes have been seen.

CLINICAL FEATURES

This sudden onset of complete or incomplete isolated unilateral lower motor neuron facial palsy may present with following features:

1. Inability to close eye.
2. Bell’s phenomenon: When patient tries to close the eye, eyeball turns up.
3. Dribbling of saliva from the angle of mouth.
4. Asymmetrical face.
5. Epiphora: Tears flowing down from the eye.
6. EARACHE: Ear pain may precede or accompany the facial palsy.
7. Hyperacusis: Sensitivity to loud sounds due to stapedial palsy.
8. Diminished taste sensation: It may occur due to the involvement of chorda tympani.
9. Recurrence: Bell’s palsy is recurrent either ipsilateral or contralateral in 12% of patient.

DIAGNOSIS

Diagnosis of Bell’s palsy is usually clinical and by exclusion.

Patient requires careful history and examination to exclude other known causes of facial paralysis.

• Laboratory tests: Some patients need radiological studies, complete blood count (CBC), peripheral blood smear, sedimentation rate, blood sugar and serology.

• Nerve excitability tests: They are done daily or on alternate days to monitor nerve degeneration.

• Topodiagnostic tests: They help in establishing the cause and site of lesion.

DIFFERENTIAL DIAGNOSES

The presence of any of the following features rule out the diagnosis of Bell’s palsy:

• Preceding history of temporal bone trauma or surgery.
•  Presence of acute suppurative otitis media (ASOM), cholesteatoma, vesicles in and around ear, glomus tumors, malignant tumors of ear and CPA, CNS diseases (such as strokes).
• Multiple cranial nerve palsies.
• Bilateral facial nerve paralysis.
• Facial palsy at birth.
• Gradual onset of facial paralysis.
• Failure to recover within 6 months.

TREATMENT

Regular electrophysiological assessment is important to know the extent of nerve damage and determine the need of surgical decompression.

A) General Measures

B) Medical Treatment

C) Surgical Treatment

A. General Measures INCLUDES —

1. Reassurance.

2. Analgesics: For the relief of ear pain.

3. Eye Care         

Eye must be protected against exposure keratitis. The preventive measures for EYE CARE include–

a) Artificial tears (methylcellulose drops) every 1–2 hours and 4–5 times per day.

b) Eye ointment followed by patching or taping the eye.

c) Cover for the eye in night.

d) Protect the eye from wind, foreign bodies and drying with glasses and moisture chambers.

e) Temporary tarsorrhaphy (surgical partial closure of eyelids) may be needed in some cases.

4. Physiotherapy

The facial muscles massage though does not influence recovery, gives psychological support. Active facial movements should be encouraged.

B. Medical Treatment includes —

1. Steroids:

If patient reports within 1 week, steroids have been reported to prevent incidence of synkinesis and crocodile tears and shorten the recovery time.

Prednisolone, 1 mg/kg/day divided into morning and evening doses for 5–10 days depending upon whether the paralysis is incomplete or is recovering.

Thereafter the doses are tapered in next 5–10 days.

Contraindications for STEROIDS:

Pregnancy, diabetes, hypertension, peptic ulcer, pulmonary tuberculosis and glaucoma.

2. Acyclovir or Valacyclovir

Steroids are generally combined with acyclovir or Valacyclovir.

3. Other drugs:

Vasodilators, vitamins, mast cell inhibitors, and antihistaminics have not been found useful.

C. Surgical Facial Nerve Decompression

It relieves pressure on the nerve fibers and improves their microcirculation.

Both the vertical and tympanic segments of nerve are decompressed.

Some favor decompression of the whole fallopian canal including labyrinthine segment.

The approaches include postaural and middle fossa.

PROGNOSIS

• Majority of the patients (85–90%) recover fully.
• Ninety five percent patients of incomplete Bell’s palsy recover completely.
• The chances of complete recovery are better when clinical recovery begins within three weeks of onset.
• Some of the patients (10–15%) do not recover completely and some stigmata of regeneration remain.
• Recurrent facial palsy may not recover fully

THANK YOU

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