Bell's Palsy Flashcards
What is Bell’s palsy?
Bell’s palsy is an acute unilateral peripheral facial nerve palsy in patients for whom physical examination and history are otherwise unremarkable. It consists of deficits affecting all facial zones equally that fully evolve within 72 hours.
To date, it remains a clinical diagnosis of exclusion.
Briefly recap the pathway of the facial nerve and its branches
The facial nerve exits the brainstem at the cerebellopontine angle. On its journey to the face, it passes through the temporal bone and parotid gland.
It then divides into five branches that supply different areas of the face:
- Temporal
- Zygomatic
- Buccal
- Marginal mandibular
- Cervical
What is the motor function of the facial nerve?
It supplies the muscles of facial expression, the stapedius in the inner ear and the posterior digastric, stylohyoid and platysma muscles in the neck.
What is the sensory function of the facial nerve?
It carries taste from the anterior 2/3 of the tongue.
What is the parasympathetic function of the facial nerve?
It provides the parasympathetic supply to the:
- Submandibular and sublingual salivary glands
- Lacrimal gland (stimulating tear production)
How can an upper and lower motor neurone facial nerve palsy be differentiated?
A common exam task is to distinguish between an upper motor neurone and lower motor neurone facial nerve palsy. It is essential to make this distinction because, in a patient with a new-onset upper motor neurone facial nerve palsy, you should be referring immediately with a suspected stroke. In contrast, patients with a lower motor neurone facial nerve palsy can be managed with less urgency.
Each side of the forehead has upper motor neurone innervation by both sides of the brain. However, each side of the forehead only has lower motor neurone innervation from one side of the brain.
In an upper motor neurone lesion, the forehead will be spared, and the patient can move their forehead on the affected side.
In a lower motor neurone lesion, the forehead will NOT be spared, and the patient cannot move their forehead on the affected side.
You can differentiate between an upper and lower motor neurone lesion by asking the patient to raise their eyebrows. If they can raise both eyebrows and wrinkle both sides of the forehead, the patient has an upper motor neurone lesion. If the eyebrow on the affected side cannot be raised and the forehead remains smooth, the patient has a lower motor neurone lesion.
What causes unilateral and bilateral upper motor neurone facial nerve palsies?
Unilateral upper motor neurone lesions occur in:
- Cerebrovascular accidents (strokes)
- Tumours
Bilateral upper motor neurone lesions are rare. They may occur in:
- Pseudobulbar palsies
- Motor neurone disease
Briefly describe the pathophysiology of Bell’s palsy
It presents as a unilateral lower motor neurone facial nerve palsy
What are the risk factors of Bell’s palsy?
- Black or Hispanic ancestry
- Arid/cold climate
- Hypertension
- Diabetes
- Pregnancy
- Intranasal influenza vaccination
- Positive family history
What are the clinical features of Bell’s palsy?
- Single episode
- Unilateral
- Absence of constitutional symptoms e.g. fever, general malaise, myalgia, arthalgia or headache
- Involvement of all nerve branches
- Keratoconjunctivitis sicca
- Pain
- Synkinesis
How is Bell’s palsy diagnosed?
Diagnosis is clinical, based on history and physical examination alone.
Briefly describe the treatment of Bell’s palsy
If patients present within 72 hours of developing symptoms, NICE clinical knowledge summaries recommend considering prednisolone as treatment, either:
- 50mg for 10 days
- 60mg for 5 days followed by a 5-day reducing regime of 10mg a day
Patients also require lubricating eye drops to prevent the eye on the affected side from drying out and being damaged. If they develop pain in the eye, they need an ophthalmology review for exposure keratopathy. The eye can be taped closed at night.
How long does recovery from Bell’s palsy take?
The majority of patients fully recover over several weeks, but recovery may take up to 12 months.
What differentials should be considered for Bell’s palsy?
- Ramsay Hunt Syndrome
- Lyme disease
- Benign facial nerve tumour
- Malignant facial nerve tumour
- Blunt force trauma to face or temporal bone
What is Ramsay Hunt Syndrome?
How does it present?
Ramsay-Hunt syndrome is caused by the herpes zoster virus.
It presents as a unilateral lower motor neurone facial nerve palsy. Patients stereotypically have a painful and tender vesicular rash in the ear canal, pinna and around the ear on the affected side. This rash can extend to the anterior two-thirds of the tongue and hard palate.
