The aim of this study was to investigate trigeminal nerve involvement in patients with peripheral facial palsy. In total, 25 patients with facial nerve palsy and 19 controls were tested by electrophysiological methods regarding their facial and trigeminal nerve functions within 1 month after disease onset. The presence of an abnormal blink reflex was determined in patients with peripheral facial palsy by comparing paralytic and non-paralytic sides (12.3 +/- 1.1 and 10.8 +/- 1.3, respectively: p = 0.001). However, the average masseter inhibitory reflex difference between the paretic and non-paralytic sides of patients compared with the corresponding side-to-side comparison for controls was not statistically significant. The masseter inhibitory reflex response was abnormal in some cases. These findings suggest that the masseter inhibitory reflex, a trigemino-trigeminal reflex, was normal in most of our patients with peripheral facial palsy, but may be abnormal in individual cases. Our study showed that subclinical disorders affecting the trigeminal pathways occur in individual patients with idiopathic facial palsy, while the majority of patients have no trigeminal nerve involvement. (C) 2010 Elsevier Ireland Ltd. All rights reserved.