Neurological Disorders: Bells Palsy

What is this condition?

Bells palsy (Bell's palsy) is an acute unilateral facial droop resulting from an idiopathic 7th cranial nerve (facial nerve) paralysis or damage (a type of cranial neuropathy).

Idiopathic means the cause is not found. So the above term can be used only if the cause for 7th cranial nerve damage is not known. This condition is the commonest causer for acute 7th CN paralysis. It is also the commonest case for single nerve damage in the body called as mononeuropathy.

Some known causes for facial nerve damage include;

• Stroke
• Lyme disease
• Leprosy
• Sarcoidosis
• Trauma etc.

So all these above conditions are not called as Bell’s palsy because the cause is known for them..

Who gets this condition?

It can affect any race or ethnicity although the incidence is slightly higher in people from Japanese origin. Both sexes are affected almost equally. It is uncommon in young children (<10 years). Incidence is higher in patients with Diabetes.

What causes this condition?

What exactly triggers this type of facial nerve paralysis is still not known. Nevertheless it appears to be an inflammatory process involving this cranial nerve. There may be viral etiology? zoster virus for example but never proved.

The 7th cranial nerve emerges out from the brainstem part of brain and then passes through a narrow channel in the bone adjacent to inner ear and finally emerges out of the skull bone near to external ear then pierces through the parotid gland and supplies the muscles of the face. This nerve also is connected with salivary secretion and taste sensation.

How does patient manifest?

• Facial drooping (muscle weakness)
• Inability to close the eye on the affected side

Typically the patient will present with a somewhat rapid onset of one sided facial paralysis. This is expectedly frightening to the patient as even stroke can present like this.

There are two types of facial nerve paralysis; upper motor neuron (UMN) and lower motor neuron (LMN) types. UMN type occurs when the fibers controlling the facial nerve are affected within the brain, LMN type occurs when either facial nerve nucleus in the brain stem or the nerve itself out side the brain is affected.

A good clinical examination can always sort out whether the facial nerve paralysis is UMN or LMN type. If UMN type then it cannot be Bells palsy. If LMN type it can be Bell’s-palsy but there are other possibilities too. A thorough history and examination can almost always help in arriving to the correct diagnosis. If still confusion is there then an MRI of the brain can help.


Diagnosis is mostly clinical and in rare situations an MRI of the brain may be necessary.


There is still some controversy regarding the most appropriate therapeutic approach to these patients however majority of the physicians try a course of steroids. Some also give a course of acyclovir or drugs belonging to the same group.

Almost all Bells palsy patients generally require exercise therapy to facial muscles. Eye pad is used to protect the affected eye due to widened eye lids. Eye drops may be necessary for preventing dryness of eyes.

Some patients require surgical interventions especially of the eye lids.

A neurologist is frequently involved in the care of these patients.

Bells Palsy to Neurology Articles


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