Bell’s Palsy in Children
Bell’s palsy is an acute, unilateral weakness or paralysis of the facial muscles, caused by a lower motor neuron lesion of the seventh cranial nerve (facial nerve). It’s the most common cause of facial nerve palsy in children and is typically a self-limiting condition. In the UK, management guidelines focus on confirming the diagnosis, ruling out more sinister causes, and providing supportive care.
Aetiology and Clinical Presentation
Causes: The vast majority of cases are idiopathic. The underlying mechanism is thought to be an inflammatory response that causes swelling and compression of the facial nerve.
Infectious Triggers: Infections, particularly viruses, are a common trigger. Herpes simplex virus (HSV) is often implicated, but Varicella-Zoster virus can cause a more severe form known as Ramsay Hunt syndrome, which includes a vesicular rash in the ear canal and pain.
Lyme Disease: A key differential diagnosis, as it can cause a facial nerve palsy that is often bilateral.
History: The onset is typically sudden, with the child waking up with a facial droop. Other symptoms may include:
Difficulty with eye closure, eating, or drinking.
Loss of taste on the front two-thirds of the tongue.
Hypersensitivity to sound in the affected ear.
Pain behind the ear may precede the weakness.
Examination and Differential Diagnosis
Clinical Examination: The examination confirms a lower motor neuron (LMN) palsy, which affects the entire half of the face, including the forehead.
Ask the child to smile, show their teeth, close their eyes tightly, and raise their eyebrows.
In an LMN palsy, the child will be unable to wrinkle their forehead on the affected side.
A full neurological examination is essential to rule out other causes, such as a tumour, stroke, or Lyme disease.
Red Flags (Rule out):
Bilateral palsy: Highly suggestive of Lyme disease.
Multiple cranial nerve palsies: May suggest a brainstem lesion or a more widespread neurological condition.
History of trauma or a systemic illness.
Investigations
None required: For a typical, unilateral, isolated Bell’s palsy, no investigations are needed. The diagnosis is clinical.
Specific Tests: Investigations are only performed if a specific cause is suspected:
Lyme Serology: If the child has a history of a tick bite or has other signs of Lyme disease (e.g., migratory rash).
MRI Brain: If a tumour or stroke is suspected.
VZV Serology: If Ramsay Hunt syndrome is suspected.
Management
Corticosteroids: The primary treatment is a short course of oral prednisolone (2 mg/kg/day, up to a maximum of 60 mg/day) started within 72 hours of symptom onset. This can improve outcomes and should be given for about 7-10 days.
Supportive Eye Care: This is a critical component of management to prevent corneal damage. Advise parents to:
Administer artificial tears regularly throughout the day.
Use a protective patch or tape the eye closed at night to prevent corneal drying.
Referral to ophthalmology is recommended if there is any concern about corneal exposure or damage.
Antivirals: Antiviral medications like acyclovir are not routinely recommended for Bell’s palsy unless there is a strong suspicion of Varicella-Zoster virus infection (Ramsay Hunt syndrome).
Follow-up: Most children make a full recovery within a few weeks to months. The child should be reviewed regularly, and if there is no improvement after 3 months, they should be referred to a paediatric neurologist.