What is Bell's palsy?
It is a weakness or paralysis of the muscles of one side of the face. The face droops on that side and there is inability to close the eye on the affected side. The problem is with the nerve that controls the muscles on that side of the face, rather than due to any pressure.
How does it occur?
The exact cause of Bell's palsy is not known. It is believed to be caused due to a viral infection of the facial nerve. This infection causes the nerve to swell and press against the bony canal through which it passes into the face. This leads to a failure in the transmission of signals to the facial muscles thus causing paralysis.
What are the symptoms?
It usually starts with an ache behind one of the ears followed by weakness or paralysis in the facial muscles on the same side. The paralysis or weakness generally starts in the lower face. There may be a decrease in taste, a change in hearing, tears in the eye and the inability to whistle or hold food in the mouth. The severity can vary from a mild weakness to complete paralysis. The severity of the illness is directly proportional to the speed of progression of the symptoms. The development of symptoms can take as little as a few hours (sometimes overnight) to a couple of days.
How is it diagnosed?
The doctor will review the symptoms and conduct an examination. Other causes of facial paralysis have to be excluded. The causes of facial paralysis other than Bell's palsy include an injury to the nerve (skull fracture), stroke, acute or chronic ear infection, tumour in the ear or in the parotid (salivary gland in front of the ear), and a viral illness such as shingles.
An ear, nose, throat, and a neurological exam will exclude most of the other causes of facial paralysis. A hearing test is done to check for an inner ear tumour. A CT scan of the head may be done to rule out a tumour in the ear or brain. Electrical testing on the nerve may be required to know the extent of damage.
What is the treatment?
A short oral course of steroids, if started early enough, can speed up recovery, even though most people recover completely even without treatment. It is very important to protect the eye on the affected side from dust and drying by either patching the eye or using artificial tears. In the few cases where recovery is very slow or not very imminent, various plastic surgical procedures can improve the cosmetic appearance of the face.
How long will the effects last?
The degree of weakness is important to predict whether nerve function will return completely or not though 80% of people recover completely. Patients with no movement of the facial muscles at all generally have less than full return of muscle movement. Mild cases with at least some muscle movement can usually expect a complete recovery.