Overview
The facial nerve (CN VII) has motor and sensory functions in the muscles of the face and the anterior tongue. It also supplies the stapedius muscle and has parasympathetic fibres to lacrimal and salivary glands.
Damage to the facial nerve can cause weakness in the muscles of facial expression – either upper motor neurone (UMN) or lower motor neurone (LMN) lesions. It can also cause dysfunction in the other structures it supplies.
It is essential to differentiate between UMN and LMN lesions, as a UMN can be the presenting feature of a stroke.
Causes
Lower motor neurone lesions
- Idiopathic (Bell’s palsy) – more common in pregnancy/diabetes mellitus
- Infective causes:
- Herpes simplex type 1
- Herpes zoster (Ramsay Hunt syndrome)
- HIV
- Epstein-Barr virus
- CMV
- Lyme disease – can be bilateral
- Otitis media
- Cholesteatoma
- Basal skull fractures
- Guillain-Barré syndrome – can be bilateral
- Parotid gland tumours
- Sarcoidosis – can be bilateral
- Sjögren’s syndrome
Upper motor neurone lesions
- Cerebrovascular disease i.e. strokes
- Intracranial tumours e.g. acoustic neuroma
- Multiple sclerosis
- Vasculitis
- HIV
- Syphilis
Presentation
It is critical to distinguish whether the patient has signs of a UMN or LMN. In general:
- UMN lesions spare the forehead and upper face
- LMNs include the forehead and affect all facial muscles
Referral
Refer patients with facial nerve palsy any of the following urgently to secondary care:
- Features of a UMN lesion
- Worsening or new neurological findings
- Features suggestive of cancer
- Systemic of severe local infection
- Trauma
