Expansion
Forehead sparing separates the two
Expansion
The forehead has bilateral cortical representation, so an upper motor neurone lesion on one side is compensated by the other hemisphere.
| Upper motor neurone | Lower motor neurone | |
|---|---|---|
| Forehead | Spared, can raise eyebrows | Involved, cannot raise eyebrow |
| Eye closure | Preserved | Weak, Bell’s phenomenon visible |
| Emotional movement | Often preserved | Lost |
| Common causes | Stroke, tumour | Bell’s palsy, Ramsay Hunt, parotid tumour |
Localising a lower motor neurone palsy by the branches given off along the course
- Above the geniculate ganglion: weakness plus reduced lacrimation, hyperacusis (stapedius) and loss of taste on the anterior two thirds of the tongue (chorda tympani)
- Between the ganglion and the stapedial branch: weakness, hyperacusis and taste loss, lacrimation intact
- Below the chorda tympani: weakness alone, which localises to the parotid or the distal nerve
Causes
- Bell’s palsy, a diagnosis of exclusion, of abrupt onset, treated with prednisolone within 72 hours plus meticulous eye care with lubricants and taping
- Ramsay Hunt syndrome: vesicles in the ear canal or palate, severe pain, often with vestibulocochlear involvement. Worse prognosis, and requires aciclovir plus steroid
- Parotid malignancy, cholesteatoma, trauma, Lyme disease, sarcoidosis, and bilateral palsy, which suggests Guillain-Barré, Lyme, sarcoid or HIV
A slowly progressive facial palsy over weeks is a tumour until proven otherwise, since Bell’s palsy is sudden and begins to recover within three weeks.