Bell’s palsy

Overview of Bell’s palsy

Neurological disorders arise from problems of the central and the peripheral nervous system. Brain damage or brain injury can also lead to these conditions. These disorders may be congenital or may develop at a later stage. Bell’s palsy is one such disorder that mainly affects the facial muscles. It is characterized by a number of sensory disorders and is easily identifiable. The incidence rate of the disease is about 1 to 4 per 10,000 people each year.

What is Bell’s palsy?

Bell’s palsy is a form of facial nerve paralysis that leads to involuntary movements of the facial muscles. The disease is named after Charles Bell, the doctor who first described the condition. It is usually unilateral in nature, that is, it affects the muscles on any one side of the face. The patients may exhibit muscle twitching, drooping of the eyelids and photosensitivity. The condition is more prevalent in people aged 15-45. However, there are instances where the disease has been seen in infants and aged people as well. Abnormal functioning of the cranial nerve is believed to be responsible for the disease. Other conditions associated with the disease are stroke, brain tumor, and Lyme disease. Bell’s palsy is responsible for 70% of the cases of one-sided facial nerve paralysis.

What are the main causes of Bell’s palsy?

In many cases, Bell’s palsy is idiopathic in nature. But in most of the cases, the following factors are identified-

• Dysfunctions of the cranial nerve VII (facial nerve)
• Upper respiratory tract infection
• Metabolic diseases like Diabetes
• Viral infections (cause swelling)
• A history of a brain tumor, stroke, Lyme disease or Ramsay Hunt syndrome

How does Bell’s palsy occur?

The pathophysiology of Bell’s palsy is quite complex. It mainly arises due to dysfunctions of the facial nerve (VII cranial nerve) that regulates the facial muscles. The paralysis, in this case, is of intranuclear or lower motor neuron type.

Studies have traced the origin of this paralysis to an inflammation of the facial nerve. Pressure is exerted on the nerve at the point of exit from the skull within the bony canal. This inhibits the transmission of neural signals and results in damage to the nerves. In certain cases of a bilateral facial palsy, acute HIV infection has been found to be responsible.

In some other cases, the Herpes Simplex Virus (HSV-1) has been found to be associated with demyelination of nerves. This results in edema, swelling, and compression of the nerve in the narrow bone canal. This is often seen as an unknown immune system response.

What are the main signs and symptoms of Bell’s palsy?

Bell’s palsy is mainly characterised by paralysis of the muscles on one side of the face. There are a number of additional symptoms of the disease which are given below-

• Sudden onset of muscle failure and paralysis
• Involuntary movement of the facial muscles
• A lopsided expression or smile
• Unilateral paralysis and loss of control (occur only on one side of the face)
• A feeling of heaviness in the face
• Difficulty talking, smiling, chewing or raising the eyebrows
• Drooling from one side of the mouth
• Alteration in the amount of saliva produced
• Trouble closing one eye (usually the affected eye)
• Irritation and dryness of the eye(s)
• Bad taste in the mouth (to due dysfunctions of the chorda tympani nerve)
• Alteration of taste sensation (on the affected side of the tongue)
• Pain around the ear
• Lack of facial expression
• Incomplete closure of the upper eyelid
• Reduced blinking
• Drooping of the lower eyelid
• Soreness and redness of the eyes
• Impaired vision since the tears are not spread uniformly over the eye(s) (the affected eye)
• Watering of the affected eye (due to loss of movement of the tear to the tear drainage ducts)
• Alteration in the amount of tear produced
• Facial tingling
• Loss of sensation on the affected side
• Sensitivity to loud noise (hyperacusis)
• Headache
• Memory problems

How can Bell’s Palsy be diagnosed?

Bell’s Palsy can be diagnosed through a few simple laboratory examinations. These are given below-

• Cranial ultrasound: Used for high-risk premature infants.
• CT scan: Detects brain injury.
• MRI scan: Studies the brain tissues and structures.
• Blood tests: To detect infections.
• Physiological and neurological examination: Checks the facial nerve functions.

Differential diagnosis should be carried out to rule out other neurological diseases like Lyme disease, brain tumour, and stroke.

Treatment & Care

Bell’s palsy is usually treated with Aciclovir for 10 days and steroid tablets for 16 days. Given below are some of the short-term treatment techniques for the disease.

• Drops and Ointments: Eye-drops like Liquifilm, Tears Naturale, and Hypromellose can maintain moisture and comfort in the eyes. Lacrilube eye ointment should be used at night in order to protect the eye. If the condition is serious, the patient is usually advised to apply the drops during the day as well.
• Taping: A sticky tape can be used at night to keep the eye shut or to uplift a drooped eyelid.
• Wrap-around sunglass: It helps protect the eye from wind, dust, and sunlight when the patient is outdoors.
• Moist chamber: It helps in moisture retention in the eyes.
• Punctal plugs: These are tiny stoppers inserted into the tear ducts to prevent an excess drainage of tears.
• Botox: It is applied as a small injection into the upper eyelid. It weakens the muscle that opens the eye.

There are some extreme cases of Bell’s palsy where the eyelids do not close fully. Hence it becomes very difficult to protect the eyes from drying up. Surgical procedures like lateral tarsorrhaphy, medial canthoplasty or drooping eyebrow surgery are recommended in such cases. Proper care and medical attention are necessary after these surgeries in order to avoid post-operative complications.

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