Prognosis
The extent of facial palsy following complete evolution of Bell's palsy (i.e., within 72 hours of onset) is the parameter most predictive of ultimate recovery outcome. Of those who present with incomplete flaccid paralysis on clinical examination, 94% will fully recover, compared with 61% of those who present with complete flaccid paralysis (i.e., one-sided full paralysis).[3] Further evidence has demonstrated that spontaneous return of normal or near-normal facial function (i.e., HBS I or II) following Bell's palsy is reduced by 50% when electroneuronography (ENoG) reveals a >95% difference between sides within 14 days of symptom onset.[32] Other poor prognostic factors include advanced age, diabetes mellitus, and taste disturbance on presentation.[37]
By 6 months, all patients with Bell’s palsy will demonstrate some degree of recovery. Failure to demonstrate any return of hemi-facial tone or movement within 4-6 months suggests an alternative diagnosis. Without treatment, 70% of patients with Bell’s palsy will recover to completely normal function, while 13% will recover with minor degrees of synkinesis and 16% will recover with severe facial synkinesis with significant impairment in meaningful facial expression.[1][2] However, recovery rate is lower in patients with recurrent Bell’s palsy.[2]
There is some evidence to suggest that Bell's palsy associated with pregnancy has worse long-term outcomes than Bell's palsy not associated with pregnancy and that pregnant women who develop Bell's palsy should be closely monitored for the development of hypertensive disorder of pregnancy.[84][85]
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