- almost 75% of patients recover normal function and just over a tenth have minor sequelae (1)
- about one sixth of patients are left with either moderate to severe weakness, hemifacial spasm, contracture or synkinesis
- patients with a partial palsy fair better
- 94% making a full recovery
- in partial palsy, outcome is worse when herpes zoster virus infection is involved
- in patients who recover without treatment
- in the majority, major improvement occurs within three weeks
- if recovery does not occur within this time
- recovery is then unlikely to be seen until four to six months - this is when nerve regrowth and reinnervation have occurred
- it is clear by six months who will have moderate to severe sequelae
- indicators of poor prognosis in Bell's palsy include: (2)
- a complete facial palsy
- no recovery by three weeks
- if there are associated conditions
- hypertension, diabetes, pregnancy
- if the patient is aged over 60 years
- if there is severe pain associated with the facial palsy
- Ramsay Hunt syndrome (herpes zoster virus)
- if electrophysiological testing shows severe degeneration of the facial nerve
- in facial palsies caused by herpes simplex virus or herpes zoster virus there remains a strong correlation between the peak severity of the palsy and the outcome
- there is currently no reliable investigation or test at presentation that can indicate who will make a full recovery
- 80% of patients with Bell's palsy have a conduction block in the facial canal which is probably caused by segmental demyelination
- in this group, recovery occurs within about 4 weeks
Reference:
1. Dong SH, Jung AR, Jung J, et al. Recurrent Bell's palsy. Clin Otolaryngol. 2019 May;44(3):305-12.
2. Gilden DH. Clinical practice. Bell's palsy. N Engl J Med. 2004 Sep 23;351(13):1323-31.