This month, Hannah Hook discusses the importance of knowing the signs of facial nerve palsy and the impact it could have on the oral cavity.
Facial nerve palsy often has a rapid onset and can cause great deal of worry to patients experiencing it.
There are various causes of facial nerve palsy, each of which have slightly different presentations and management.
Dentists are not expected to treat a facial palsy. However, being aware of the signs and symptoms will allow for identification and, where appropriate, prompt referral and treatment.
Furthermore, a facial nerve palsy may also have implications on the oral cavity.
Causes of facial nerve palsy:
- Idiopathic – Bell’s palsy
- Infectious – Ramsy Hunt syndrome
- Iatrogenic – Local anaesthetic
- Tumours – Acoustic neuroma, adenocarcinoma
- Vascular – Stroke
- Trauma
- Congenital – Mobius syndrome.
Idiopathic
Bell’s Palsy
- What: Acute unilateral facial weakness or palsy with a rapid onset
- Why: The cause of Bell’s palsy is currently unknown. However, it has been speculated that inflammation and oedema could cause compression of the facial nerve
- Who: It is the most common type of facial nerve palsy and accounts for approximately 80% of cases. Men and women are equally affected
- Symptoms: Rapid onset, usually less than 72 hours. The affected side may include the ear and post-auricular regions. People may also experience dry mouth, taste disturbances and an inability to close the eye of the affected side
- Treatment: Initiation of steroids within 72 hours of the onset of symptoms.
Infectious
Ramsay Hunt Syndrome
- What: Acute unilateral facial weakness or palsy paired with blistering of the ear canal or mouth on the affected side
- Why: Infection of the facial nerve by varicella-zoster virus (VZV). It is thought that following primary infection by VZV, the virus enters a latent period where it remains dormant in the geniculate ganglion of the facial nerve. When VZV in the geniculate ganglion is reactivated, it can lead to facial nerve palsy
- Who: It is more common in females than males. Also, it is often seen in adults over 60 years of age
- Symptoms: Ear pain, tinnitus or hearing loss may be experienced. As well as this, blistering of the ear canal or mouth on the affected side can occur
- Treatment: Initiation of antivirals and steroids within 72 hours of onset of symptoms.
Iatrogenic
Local anaesthetic
- What: Rapid unilateral facial palsy following administration of local anaesthetic, such as an inferior alveolar block
- Why: Local anaesthetic is misplaced and injected into the area of the facial nerve, most commonly for a dental procedure
- Symptoms: Immediate or delayed onset of facial palsy to the same side that the local anaesthetic was administered. This results in temporary unilateral paralysis of the facial nerve
- Treatment: No treatment is required; the anaesthetic will gradually wear off over a few hours. Inform the patient of what has occurred, apologise and reassure. Also, surgical tape may be used to close the eye on the affected side if the patient is unable to close it.
Tumours
Acoustic Neuroma
- What: Unilateral hearing loss and facial paralysis which shows no signs of improvement over a number of months
- Why: Rare benign brain tumour of the eighth cranial nerve. Tumour growth leads to compression of the facial nerve, causing facial weakness as a result
- Symptoms: Initially tinnitus, unilateral hearing loss and vertigo. Facial palsy then follows this
- Treatment: Surgical removal of the tumour. However, this could result in permanent traumatic damage to the facial nerve.
Adenocarcinoma
- What: Progressive unilateral facial nerve weakness and eventually palsy. This is most likely accompanied by a mass in parotid gland
- Why: Adenocarcinomas are malignant tumours of the parotid gland. Infiltration of malignant cells into the facial nerve causes facial palsy as a result. Benign tumours are unlikely to cause facial nerve paralysis
- Symptoms: Unilateral mass in the parotid gland which is increasing in size (either slowly or rapidly). As well as this, development on pain in the parotid lump and progressive unilateral weakness of the facial nerve
- Treatment: Surgical removal of the tumour. However, this could result in permanent traumatic damage to the facial nerve.
Vascular
Stroke
- What: Unilateral facial palsy with a rapid onset
- Why: Either haemorrhagic or ischaemic in nature. In a haemorrhagic stroke bleeding results in excess pressure on the facial nerve and surrounding tissues. An ischaemic stroke causes restriction of oxygen to the facial nerve and surrounding tissues, resulting in ischaemia
- Symptoms: Unilateral facial weakness. Unilateral weakness of an arm or leg (or both). Headache, confusion, dizziness or unsteadiness. Individuals may experience numbness in an area of the body. Loss of consciousness may occur in severe cases
- Treatment: Strokes are a medical emergency and require urgent treatment. There are different methods of treating strokes based on the type. This may include medications or surgery.
Dental Implications
- Xerostomia: Dry mouth possibly due to decreased salivary secretion from the submandibular or sublingual glands. The inability of an individual to close their mouth can also result in xerostomia. High fluoride toothpaste and salivary substitutes should be considered
- Speech: Reduced innervation to the muscles of facial expression may result in speech difficulties. Speech may also be affected by xerostomia
- Eating and drinking: Decreased innervation to the buccinator muscle may result in difficulty chewing. It can also lead to food collecting in the buccal sulcus. Reduced innervation to the orbicularis oris can cause a poor lip seal. Therefore, the patient may have difficulty drinking.
Key points:
- There are multiple causes of facial nerve palsy
- The most common type is Bell’s palsy, the cause of which is currently unknown
- Facial palsy as a result of an inferior alveolar nerve block may initially seem concerning. However, it will resolve over a few hours
- Aside from a facial palsy caused by local anaesthetic, all other types mentioned above will need referral for further assessment and treatment
- A facial palsy may have implications on speech, eating and drinking
- Xerostomia may also be a complication of facial palsy
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