Bell’s palsy is an acute, sudden-onset, unilateral facial palsy of probable viral aetiology.
Clinical diagnosis of exclusion.
High-dose corticosteroids should be administered in all patients in the absence of significant contraindications.
Other treatment options include concomitant antiviral agents, physiotherapy, and, in severe cases, surgical decompression.
Eye protection should always be considered.
Failure to demonstrate any return of hemi-facial tone or movement within 4 to 6 months suggests an alternative diagnosis.
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. Complete recovery to normal facial function occurs in approximately 70% of cases, with permanently impaired facial function occurring to a minor degree in 13% and to a major degree in 16% of cases. However, recovery rate is lower in patients with recurrent Bell's palsy. Onset of clinical recovery is nearly always demonstrated within 4 to 6 months of symptom onset; absence of any return of hemi-facial tone or movement by this time is highly suggestive of an alternative diagnosis. Facial palsy of an otherwise known aetiology (e.g., Lyme disease-associated facial palsy), or facial palsy that is progressive, waxing and waning, or affects facial zones in an uneven fashion, is not Bell's palsy.
History and exam
Key diagnostic factors
- single episode
- absence of constitutional symptoms
- involvement of all nerve branches
- keratoconjunctivitis sicca
Other diagnostic factors
- presence of risk factors
- any age
- intranasal influenza vaccination
- upper respiratory tract infection
- arid/cold climate
- family history of Bell's palsy
- dental procedures
1st investigations to order
- clinical diagnosis
- electroneuronography (ENoG) (evoked electromyography - eEMG)
- needle electromyography (EMG)
- serology for Borrelia burgdorferi
Investigations to consider
- pure-tone audiometry
- tympanometry and stapedius reflex
- MRI (gadolinium-enhanced fine-cut of facial nerve course)
- CT (fine-cut, non-enhanced)
- Herpes zoster oticus (Ramsay Hunt syndrome)
- Lyme disease
- Benign facial nerve tumour (e.g., facial nerve schwannoma)
- ACR appropriateness criteria: cranial neuropathy
- Facial palsy (Bell's palsy)
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