Facial Nerve Palsy

• Facial nerve palsy refers to isolated dysfunction of the facial nerve and presents with unilateral facial weakness.
• The facial nerve exits the brainstem at the cerebellopontine angle.
• On its journey to the face, the facial nerve passes through the temporal bone and parotid gland.
• The facial nerve divides into five branches: temporal, zygomatic, buccal, marginal mandibular, and cervical.
• The facial nerve has motor function for facial expression, stapedius in the inner ear, and posterior digastric, stylohyoid, and platysma muscles.
• The facial nerve has sensory function for taste from the anterior 2/3 of the tongue.
• The facial nerve receives parasympathetic supply to the submandibular and sublingual salivary glands and lacrimal gland, stimulating tear production.
• It is essential to distinguish between upper motor neurone and lower motor neurone facial nerve palsy.
• Patients with new-onset upper motor neurone facial nerve palsy need immediate management as a possible stroke.
• In contrast, patients with lower motor neurone facial nerve palsy can be managed less urgently.
• Each side of the forehead has upper motor neurone innervation by both sides of the brain.
• The forehead will be spared in an upper motor neurone lesion so the patient can move their forehead on the affected side.
• Treatment for Ramsay-Hunt syndrome is with aciclovir and prednisolone.
• Ramsay-Hunt Syndrome is caused by the varicella zoster virus (VZV) and presents as a unilateral lower motor neurone facial nerve palsy.
• Bell’s palsy presents with a unilateral lower motor neurone facial nerve palsy.
• Trauma that can cause lower motor neurone facial nerve palsy includes Direct nerve trauma, Surgery, Base of skull fractures.
• Patients also require lubricating eye drops.
• Each side of the forehead only has lower motor neurone innervation from one side of the brain.
• Bilateral upper motor neurone lesions are rare and may occur in Pseudobulbar palsies, Motor neurone disease, Bell’s Palsy, and Bell’s palsy is a relatively common condition.
• A third are left with some residual weakness.
• Unilateral upper motor neurone lesions occur in Cerebrovascular accidents (strokes) and Tumours.
• If patients present within 72 hours of developing symptoms, NICE clinical knowledge summaries (updated 2023) recommend considering prednisolone as treatment, either: 50mg for 10 days or 60mg for 5 days followed by a 5-day reducing regime, dropping the dose by 10mg per day.
• Patients also require lubricating eye drops to prevent the eye from drying out and being damaged.
• If they develop pain in the eye, they need an ophthalmology review for exposure keratopathy.
• Infections that can cause lower motor neurone facial nerve palsy include Otitis media, Otitis externa, HIV, Lyme disease, Systemic diseases such as Diabetes, Sarcoidosis, Leukaemia, Multiple sclerosis, Guillain–Barré, and Tumours such as Acoustic neuroma, Parotid tumour, Cholesteatoma.
• In a lower motor neurone lesion, the forehead is not spared, and the patient cannot move their forehead on the affected side.
• Most patients fully recover over several weeks, but recovery may take up to 12 months.
• Patients stereotypically have a painful and tender vesicular rash in the ear canal, pinna and around the ear on the affected side.