BS18. Reduced prepulse inhibition in trigeminal neuralgia

Abstract

We hypothesized that prepulse inhibition (PPI) may be decreased in trigeminal neuralgia (TN) if it leads hyperactivity of trigeminal nucleus and tested our hypothesis in a group of patients with classical TN. Consecutive nine patients with classical TN and 14 healthy subjects were enrolled in this study between January 2015 and August 2016. Diagnosis and classification were done according to the International Classification of Headache Disorders-3 (ICHD-3 beta version). Blink reflex and BR-PPI were recorded on both symptomatic and asymptomatic sides in patient group and on the right side in healthy subjects. Subthreshold conditioning stimulus was applied to the median nerve at second finger using an electrical stimulus at two different interstimulus intervals: 50 ms and 100 ms before the test stimulus to the supraorbital nerve. Standard BR recordings were normal in all groups. In healthy subjects, prepulse stimulus resulted in lower magnitude of BR-R2 (p = 0.000) and longer R2 latencies (p = 0.008) at ISIs of 50 ms and 100 ms in comparison to baseline recordings whereas no change after prepulse stimulation was observed on both symptomatic and asymptomatic sides of patients with TN. Our study provided evidence for the reduced PPI and thus, sensory gating of brainstem in classical TN. This finding was bilateral and present even on the asymptomatic side.