Bell’s Palsy: What It Is, Causes, Symptoms & Treatment

Bell’s Palsy: What It Is, Causes, Symptoms & Treatment

Question 1. Discuss the etiology, clinical features, differential diagnosis, and management of Bell’s palsy. List the causes of facial nerve palsy. Write a short essay/note on Bell’s palsy.
Answer:

The most common form of unilateral isolated lower motor neuron type of facial paralysis is Bell’s palsy.

Bell’s palsy Pathophysiology

• The main cause of Bell’s palsy is thought to be latent herpes viruses (herpes simplex virus type 1 and herpes zoster virus), which are reactivated from cranial nerve ganglia.
• It causes swelling of a nerve within the tight petrous bone facial
  canal.
• Herpes zoster virus shows more aggressive biological behavior than herpes simplex virus type 1.
• Polymerase chain reaction (PCR) techniques have isolated herpes virus DNA from the facial nerve during acute palsy.
• Inflammation of the nerve initially results in reversible neuropraxia

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Bell’s palsy Clinical manifestations

• Race: Slightly higher in persons of Japanese descent. Familial incidence—4.1%.
• Age and gender: Highest in persons aged 15–45 years. It is rare below the age of 15 and above the age of 60. No gender difference exists.
• Onset is fairly abrupt, with pain around the ear preceding the unilateral facial weakness (maximal weakness by 48 hours). Patients often describe the face as “numb” and sometimes give a history of exposure to cold.
• Associated symptoms: Hyperacusis, decreased production of tears and saliva, altered taste, otalgia or aural fullness, and facial or retro auricular pain.
• Less common in pregnancy but prognosis is significantly worse in pregnant women.

Bell’s palsy Examination: Shows features of isolated lower motor neuron facial paralysis.

On the affected side following features are observed. These include:

• Paralysis of all the muscles of facial expression.
• Dropping of the corner of the mouth, effacement of creases, and skin fold.
• The involvement of the frontalis makes frowning difficult. Eye closure is weak because of the involvement of orbicularis oculi
• Drooling of saliva from the angle of the mouth.
• The action of the levator anguli oris on the normal side, makes the angle of the mouth to deviate to the opposite side of the lesion when the patient shows his teeth.
• When the closure of the eyelid is attempted, the eye on the paralyzed side rolls upward (Bell’s phenomenon).
• Due to exposure of the cornea, the patient may develop exposure keratitis and corneal ulceration.

Bell’s palsy Investigation

• No specific confirmatory diagnostic test.
• CSF may show mild lymphocytosis.
• MRI may reveal swelling and uniform enhancement of the geniculate ganglion and facial nerve and in some cases, entrapment of the swollen nerve in the temporal bone.
• The differences between upper motor and lower motor neuron facial palsy
• The differences between bilateral upper motor and bilateral lower motor neuron facial palsy

Bell’s palsy Treatment

• Severe facial weakness may produce an inability to blink and lead to exposure keratitis.
• Use of lubricating eye drops may be needed, and paper tape to close the eye during sleep.
• Massage of weekend muscles.

Medical treatment of Bell’s palsy:

• Steroids (Prednisolone) 1 mg/kg/day for 5–7 days and then tapered over the next 1 week.
• Antiviral agents: for 5–7 days.
• Famciclovir 500 mg BD.
• Valacyclovir 500 mg BD.
• Acyclovir 800 mg five times a day.
• Surgical decompression—only if no resolution of symptoms after 2 weeks.