Background: Bell’s palsy is an idiopathic peripheral facial palsy and no readily identifiable cause. There
are still controversies regarding the enhancement of the facial nerve on magnetic resonance image
(MRI) and its correlation with disease severity, electrophysiological tests, and prognosis. This study
is conducted to investigate the correlation between the facial nerve enhancement on MRI, abnormality
of electrophysiologic studies and prognosis of Bell’s palsy.

Methods: This prospective study includes 391 patients of Bell’s palsy. The severity of facial palsy was
assessed by House-Blackmann facial nerve grading scale. Follow-up physical examination and
electrophysiologic test were conducted about 12 weeks after the initial assessment.

Results: Brain MRI showed that 255 of them had facial nerve enhancement. Patients with facial nerve
enhancement had more severe facial palsy than patients without enhancement at the initial
assessment (p=0.025). After 12 weeks, House-Blackmann grade between the two group were statistically
significant (p=0.042). Patients with abnormality on blink reflex had more severe facial palsy than with
normal at time of diagnosis (p<0.01). At the 12 weeks after diagnosis, group of abnormal in blink reflex
had higher House-Blackmann grade (p=0.017). Patients with low amplitude in facial nerve conduction
study also had more severe facial palsy at time of diagnosis (p=0.010) and at the 12 weeks after
diagnosis (p<0.01).

Conclusions: Facial nerve enhancement on brain MRI have more severe facial weakness and poor
prognosis. Facial nerve conduction study, blink reflex also reflect severity and prognosis of Bell’s palsy.
Brain MRI and electrophysiologic test are an effective tool in predicting severity and prognosis of Bell’s
palsy.