Bell’s palsy
Bell’s palsy is an acute, idiopathic lower motor neurone (LMN) lesion of the facial nerve (CN VII) producing unilateral facial weakness that affects all divisions of the face, including the forehead. Diagnosis is clinical and one of exclusion.
Emergency management aims to confirm an uncomplicated LMN palsy, exclude red flags that require urgent investigation or specialist input, protect the eye and offer early corticosteroids when appropriate (NICE NG127).
Presentation
- Rapid onset over hours, often maximal within 72 hours and sometimes noted on waking.
- Improvement often begins within 2-3 weeks; recovery may continue for months.
- Complete hemifacial weakness including inability to raise the eyebrow or wrinkle the forehead (LMN pattern).
- Common associated symptoms: ipsilateral ear/postauricular pain (~50%), taste disturbance (~35%), dry mouth or difficulty chewing (~20%), incomplete eye closure with dry eye or tearing, and occasional perioral/cheek numbness.
- Hyperacusis is uncommon.
- Bilateral facial palsy is rare and suggests alternative diagnoses (Lyme disease, sarcoidosis, Guillain-Barré variants).
Examination essentials
- Perform a full cranial nerve examination.
- Confirm LMN pattern: weakness of the whole hemiface including the forehead (UMN lesions typically spare the forehead).
- Observe resting symmetry, nasolabial fold, eyebrow position, smile, and ability to close the eye tightly.
- Test the corneal reflex (afferent V1, efferent VII). Reduced or absent blink on the affected side supports facial nerve dysfunction.