Bell's Palsy
You are a foundation doctor on your GP placement. Charles, a 67 year old builder woke up this morning with a right sided facial droop. On examination, he has paralysis of the right side of his face and is unable to raise his eyebrow on the right side. Marion, his wife, is concerned he has had a mini stroke. What do you tell her?
The facial nerve, cranial nerve VII, is a mixed motor and sensory nerve arising from the brainstem. The nerve exits the cranium via the temporal bone and passes through the parotid gland where it splits into 5 branches that supply the muscles of facial expression.
The facial nerve has several functions
Motor
-
Muscles of facial expression
-
Stapedius – a muscle in the inner ear responsible for contracting during loud sounds (stapedius reflex) to protect the inner ear
Sensory
-
Taste sensation to anterior 2/3 of the tongue (via chorda tympani branch)
Other
-
Supplies salivary (saliva) and lacrimal (tears) glands
The upper and lower parts of the facial muscles are supplied by the facial nerve.
The upper part of the face is supplied by the left and right sides of the brain (as seen by the yellow and orange line)
Therefore, a lesion of the facial nerve (lower motor neuron lesion) would cause paralysis to both upper and lower parts of the face
Whereas a lesion in the brain (upper motor neuron lesion), such as a stroke, would only cause paralysis of the lower part of the face (orange line).
The upper part of the face is spared due to dual supply to the upper part of the face from both sides of the brain – this is often called central facial palsy
You are a foundation doctor on your GP placement. Charles, a 67 year old builder woke up this morning with a right sided facial droop. On examination, he has paralysis of the right side of his face and is unable to raise his eyebrow on the right side. Marion, his wife, is concerned he has had a mini stroke.
Since Charles has paralysis of both upper and lower parts of his face, you can reassure Marion that he is not having a TIA. He is suffering from Bell’s palsy – an acute idiopathic peripheral facial nerve palsy. There is no known cause, but it is thought to be caused by viral induced inflammation.
Since the facial nerve has several functions, features may include:
-
Drooping of mouth corner, inability to close eyelid, and smoothing of forehead – due to facial muscle paralysis
-
Hyperacusis: intolerance to everyday sounds – due to loss of the stapedius reflex which dampens loud sounds
-
Loss of taste to anterior 2/3 of tongue – due to loss of chorda tympani innervation, a branch of the facial nerve
-
Decreased production of tears – due to loss of greater petrosal nerve innervation, a branch of the facial nerve
Some patients may experience crocodile tears - tears from the affected side when eating/smelling food during recovery of Bell's palsy due to misdirected salivary fibres innervating the lacrimal gland
If patients present within several days of onset of symptoms , they are often prescribed high doseprednisolone for that is tapered over 5-10 days.
It is very important to stress the importance of eye care:
-
prescribe artificial tears to prevent exposure keratitis
-
tape eye shut at night if unable to fully close eyelid
-
advise the patient to seek help if their eye becomes red, dry, or painful (will need urgent referral to eye clinic)
