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Facial Nerve Palsy & Bell’s Palsy


Introduction
The facial nerve is a complex nerve which originates from the brainstem (junction between the brain and spinal cord), exits the skull by going through the middle ear and then supplies most of the muscles of facial expression.

The term Bell’s palsy describes a sudden weakness of the facial muscles due to paralysis of facial nerve. Gradual resolution occurs in the vast majority of cases. Although its cause has never been found, various causes have been suspected including viral infection or a mini-stroke like event.

Facial nerve palsy is a wider term describing weakness of the face due to loss of function of the facial nerve. The causes of facial nerve palsy are therefore many and include tumours, strokes, infections, trauma, surgery but the vast majority of facial nerve palsies are sudden, self resolving and without apparent cause i.e. Bell’s palsy.

Bell’s palsy is:
  • Relatively uncommon with 10-30 cases per 100000
  • Commoner in diabetics, pregnancy and in immunocompromised patients.
  • Thought to affect 2 age groups of patients (20-40 years old and 70-80 years old)

Symptoms and Signs
Patients often complain of:
  • Weakness of the facial muscles
  • Problems closing the eye
  • Watering eye
  • A painful eye
  • Blurred vision

Because the facial nerve is a nerve which supplies the muscles of the facial expression and the tear gland of the eye. Loss of function of the facial nerve can have quite marked consequences on the face.

Problems which can arise include:
-Lagophthalmos - the inability to close the eye due to paralysis of the upper eyelid
-Ectropion- an out-turning eyelid due to paralysis of the lower eyelid
-Corneal exposure - the corneal surface may start to ulcerate due to poor wetting
-Brow ptosis - drooping of the eyebrow due to paralysis of the forehead muscles
-Midface/Cheek ptosis - a drooping descended cheek due to paralysis of the cheek muscles
-Abnormal spasms of the muscles due to abnormal healing of the damaged nerve
-Crocodile tears- tearing of the eye due to excess tear production associated with chewing

Bells palsy: 2 weeks after onset (left) and 6 weeks later (right). Notice the patient's difficulty in trying to close his right eye in the early stages of the palsy (the eyelid shows 10mm of non-closure). Although this has improved dramatically 6 weeks later, the patient still complains of a sore right eye since the eye still cannot close completely and shows 5mm of non-closure

Early management of facial nerve palsy >>