Bell's Palsy

Bell's Palsy: Definition, Pathophysiology, Clinical features, Treatment

Definition:
Bell's palsy is a weakness or paralysis of the muscles of one side of the face mainly due to injury of facial nerve (7th Cranial nerve).

Pathophysiology:
It is due to acute onset of inflammation of the facial nerve within the facial canal above stylomastoid foramen, producing a unilateral lower motor neuron type of facial palsy.
   - Etiology: Unknown
   - Associated with Diabetes Mellitus, Hypertension and viruses like HSV and Varicella Zoster Virus which can cause inflammatory response.

Clinical features:
   - Onset: Acute
   - Complete weakness up to 48 to 72 hours
   - Generally unilateral
   - Upper and lower facial muscles are usually involved
   - Characterized by
       1. No frowning: Inability to wrinkle brow
       2. Drooping eyelid: Inability to close eye
       3. No muscle tone: Inability to puff chicks
       4. Dropping mouth: Inability to smile or pucker or whistle

Treatment: 
Spontaneous recovery within 2 to 12 weeks, if there is partial involvement of facial muscles. If not, then:
    1. Physiotherapy of affected facial muscles
    2. Drugs: Dexamethasone 2 mg three times a day or
                    Prednisone 60 to 80 mg/day for 5 days

Associated Syndromes:
   1. Ramsay Hunt Syndrome
   2. Mimic paralysis
   3. Melkersson Rosenthal Syndrome

Differential Diagnosis:
   1. Borella syndrome
   2. Leprosy
   3. Guillain B syndrome
   4. Sarcoidosis (Bilateral facial palsy)
   5. Ramsey Hunt Syndrome
   6. Multiple sclerosis

Poor prognostic features:
   1. Age > 60 years
   2. Associated hypertension and DM
   3. Decreased lacrimation
   4. Hyperacusis
   5. No return of voluntary power

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