This longitudinal study aims at assessing the predictive value of facial nerve high-resolution ultrasound (HRUS) for incomplete clinical recovery in patients with Bell’s palsy, the most common facial nerve disease.

We prospectively enrolled 34 consecutive patients with Bell’s palsy. All patients underwent neurophysiological testing (including facial nerve conduction study) and HRUS evaluations 10–15 days (T1), one month (T2), and three months (T3) after the onset of Bell’s palsy. Patients who did not experience complete recovery within three months were also evaluated after six months (T4). We have then compared the accuracy of HRUS with that of the facial nerve conduction study in predicting incomplete clinical recovery at three and six months.

At T1, the facial nerve diameter, as assessed with HRUS, was larger on the affected side than on the normal side, particularly in patients with incomplete recovery at T2, T3 and T4. ROC curve analysis, however, showed that the facial nerve diameter at T1 had a lower predictive value than the facial nerve conduction study for an incomplete clinical recovery at three (T3) and six (T4) months. Still, the facial nerve diameter asymmetry, as assessed with HRUS, had a relatively high negative predictive value (thus indicating a strong association between normal HRUS examination and a good prognosis).

Although HRUS shows abnormally increased facial nerve diameter in patients in the acute phase of Bell’s palsy, the predictive value of this technique for incomplete clinical recovery at three and six months is lower than that of the nerve conduction study.

Nerve ultrasound has a low predictive value for incomplete clinical recovery in patients with Bell’s Palsy.