Clinical and electrophysiological prognostic factors in predicting poor outcomes in patients with idiopathic facial nerve paralysis.

OBJECTIVE

This study was designed to verify whether one or more clinical and neurophysiological parameters could predict a poor prognosis in idiopathic facial paralysis.

METHODS

Seventy-three outpatients with unilateral idiopathic facial nerve paralysis who visited our hospital within 7 days of onset. All patients received treatment according to a standard therapy protocol and ocular care. Patients' baseline characteristics were assessed before initiating treatment, including demographic characteristics, facial nerve function assessment and previous medical history. House-Brackmann (H-B) grading system was performed at baseline and six months after the onset. Electroneurography (ENoG) and blink reflex tests were conducted 7-10 days after the onset of paralysis. Sunnybrook Facial Grading System (SFGS) was conducted at baseline, days 7-10 post-onset when the electrophysiological tests were performed, and one month after the onset.

RESULTS

According to the H-B grade at 6 months following the onset, 58 patients (79.5 %) had a good prognosis, while 15 patients (20.5 %) had a poor prognosis. The CMAP amplitudes in three facial muscles (frontalis, orbicularis oculi, and orbicularis oris) were decreased, and ENoG values were increased in the poor prognosis group compared with the good prognosis group (all p < 0.01). The results of the blink reflex study showed that the group with a poor prognosis had a longer R1 latency compared to the group with a good prognosis. Additionally, the group with a poor prognosis exhibited a higher rate of R1 absence on the affected side (both p < 0.01). The findings of conditional logistic regression indicated that the absence of R1 on the affected side, frontalis ENoG, orbicularis oculi ENoG, and orbicularis oris ENoG were predictive factors of a poor prognosis for facial nerve palsy. The receiver operating characteristic (ROC) curves showed that the SFGS at 1 month after onset of 55 is considered a critical cutoff value for poor prognosis, with a sensitivity of 86.7 % and specificity of 91.4 %.

CONCLUSION

Electroneurography (ENoG) and blink reflex tests acquired within 7-10 days after the onset of paralysis are significant and highly valuable for predicting the prognosis of idiopathic facial nerve paralysis. Higher ENoG values of the muscles innervated by the facial nerve and the absence of R1 on the affected side of the blink reflex are predictive factors for a poor prognosis. The SFGS is a clinical tool that plays an important role in evaluating the prognosis of idiopathic facial paralysis, particularly one month after onset.