Facial Palsy

 Introduction
This condition usually occurs due to either permanent or temporary damage to the facial nerve generally leading to the weakness of the facial muscles. Sometimes lower half of the face is affected, or sometimes whole one side of the face gets affected or either both sides of the face gets affected and it occurs as the facial nerves are not functioning properly so the muscles of the face are not receiving appropriate signals for normal functioning 1 . 

It is also known as Bell's palsy.

 

Causes

Although the most commonly known cause of facial paralysis is Bell’s palsy, there are actually many different causes of facial palsy.. Some of the main causes of facial palsy are listed below² :

• Viral infections such as Bell’s palsy and Ramsay Hunt syndrome.

• Surgical causes: for example during removal of acoustic neuroma or facial nerve tumour, or when operating on the parotid gland.

• Bacterial causes such as Lyme disease or following a middle ear infection.

• Neurological conditions such as Neurofibromatosis 2, or Guillain-Barré syndrome.

• Traumatic injury such as fractures to the brain, skull or face.

• Birth trauma: for example caused by forceps or facial presentation delivery.

• Congenital conditions such as an abnormal development of the facial nerve or muscle in the womb.

• Rare genetic syndromes such as Moebius syndrome or CHARGE syndrome.

• Stroke: although a stroke can cause facial palsy it is slightly different in that the problems are not caused by direct damage to the facial nerve. The paralysis in this case is caused by brain damage and the messages not being transferred properly to the facial nerve.

Kinds of facial nerve injury

There are three different kinds of facial nerve injury³ :

1. First degree injury – when the facial nerve is just concussed or bruised and recovers within eight weeks.

2. Second degree injury – where the facial nerve is more severely damaged but still retains its outer layer. The nerve begins to show the first signs of recovery at about four months as it slowly repairs itself at the rate of around one millimetre per day.

3. Third degree injury – when the facial nerve is more severely damaged, any recovery is much slower and always incomplete. Sometimes the nerve is completely severed and surgical repair is needed to restore facial function.

 

Diagnosis

There's no specific test for Bell's palsy. Your doctor will look at your face and ask you to move your facial muscles by closing your eyes, lifting your brow, showing your teeth and frowning⁴ , among other movements or may recommend tests such as;

• Electromyography (EMG). This test can confirm the presence of nerve damage and determine its severity. An EMG measures the electrical activity of a muscle in response to stimulation and the nature and speed of the conduction of electrical impulses along a nerve.

• Imaging scans. Magnetic resonance imaging (MRI) or computerized tomography (CT) may be needed on occasion to rule out other possible sources of pressure on the facial nerve, such as a tumor or skull fracture.

Treatment

Mostly people recover without any treatment but sometimes medications are prescribed which includes;

Commonly used medications to treat Bell's palsy include ⁵:

• Corticosteroids, such as prednisone, are powerful anti-inflammatory agents. If they can reduce the swelling of the facial nerve, it will fit more comfortably within the bony corridor that surrounds it. Corticosteroids may work best if they're started within several days of when your symptoms started.

• Antiviral drugs. The role of antivirals remains unsettled. Antivirals alone have shown no benefit compared with placebo. Antivirals added to steroids are possibly beneficial for some people with Bell's palsy, but this is still unproved.

However, despite this, valacyclovir (Valtrex) or acyclovir (Zovirax) is sometimes given in combination with prednisone in people with severe facial palsy.

By Zoha Khan

References

1.      Cawthorne, T. & Haynes, D. R. Facial palsy. Br. Med. J. 2, 1197 (1956).

2.      Odebode, T. O. & Ologe, F. E. Facial nerve palsy after head injury: case incidence, causes, clinical profile and outcome. J. Trauma Acute Care Surg. 61, 388–391 (2006).

3.      Roob, G., Fazekas, F. & Hartung, H.-P. Peripheral facial palsy: etiology, diagnosis and treatment. Eur. Neurol. 41, 3–9 (1999).

4.      May, M. & Klein, S. R. Differential diagnosis of facial nerve palsy. Otolaryngol. Clin. North Am. 24, 613–645 (1991).

5.      Adour, K. K. & Hetzler, D. G. Current medical treatment for facial palsy. Otol. Neurotol. 5, 499–502 (1984).