Pathology
Facial nerve lesion
This may result in paralysis of the facial muscles and/or abnormal taste sensation.
Facial Paralysis
Facial paralysis usually occurs unilaterally and is often a consequence of Bell's palsy, stroke or trauma. In addition to total loss of voluntary movement to the affected side of the face the patient will also have drooping of the face and ptosis (as shown in the image to the right) along with drooling from the mouth and excessive tear production.
Bell’s palsy
Bell’s palsy is the most commonly diagnosed condition related to facial nerve dysfunction. It is a non-life threatening condition, thought to be caused by a viral infection that leads to damage and inflammation of the facial nerve. Patients present with symptoms ranging from unilateral paralysis of the facial muscles to numbness of the ear or tongue, around 60% of patients have a preceding viral infection. Patients may also be hypersensitive to sound and have a watery eye. These symptoms may arise within 24 hours but usually only persist for around 6-8 weeks.
Treatment isn’t necessary in all cases although painkillers and steroids may be used to reduce inflammation and pain.
See the bottom of the page for a video on Bell's palsy.
This cultural model represents a person with facial paralysis
Tumours
Acoustic neuroma – is a benign tumour resulting from abnormally excessive schwann cell production. Cells cluster together putting pressure on the facial nerve and interfering with normal function. Tumours of the parotid gland may also have a similar affect.
Facial nerve schwannoma – is a rare form of neurofibromatosis, also caused by over-production of schwann cells leading to tumour formation around the facial nerve. The patient will present with symptoms that correspond to the location of the tumour. For example loss of hearing may indicate a tumour near the internal acoustic meatus.
The diagnosis of tumours can be aided by MRI scans and treatment usually involves surgery.
Trauma
A petrous bone fracture or surgery to the parotid gland or middle ear can cause trauma at differing extents to the facial nerve. Injuries that specifically damage either the facial nerve directly or surrounding tissue will prevent normal function and may cause muscle paralysis.
Hemifacial spasm
This is a neuromuscular disorder that most commonly, although not exclusively affects older women. Symptoms include involuntary contractions known as spasms of the muscles of one eye. Stress and fatigue can trigger spasms.
Treatment depends on the extent of the spasms and the duration of symptoms. Many people suffer for a temporary period at some point in their lives with infrequent eye spasms or twitches in response to stress and fatigue. However in the case of hemifacial spasm, microvascular decompression surgery can relieve pressure on the facial nerve easing symptoms. Other treatments include Botox injections and muscles relaxant pharmaceuticals.
Congenital disorders
Bulbopontine paralysis with progressive sensorineural hearing loss is a congenital condition commonly causing facial paresis and in some cases causing complete facial paralysis. This disorder is autosomal dominant and more frequent in females.
Acknowledgement
Video courtesy of youtube https://www.youtube.com/