NEUROPATHIC PAIN SECTION Original Research Article A fMRI Evaluation of Lamotrigine for the Treatment of Trigeminal Neuropathic Pain: Pilot Study

Using functional magnetic resonance imaging (fMRI) methods, we evaluated the effects of lamot- rigine vs placebo in a double-blind 1:1 randomized trial. Six patients with neuropathic pain were recruited for the study. All subjects had baseline pain >4/10 on a visual analog scale (VAS) and allo- dynia to brush as inclusion criteria for the study. Patients underwent two fMRI sessions, with half of the subjects receiving placebo first and half receiv- ing drug first (based on the blinding protocol). Lam- otrigine decreased their average pain intensity level from 5.6 to 3.5 on a VAS. All subjects had brush, cold, and heat applied to the affected and mirror- unaffected sides of their face. The results show: 1) in a small cohort, lamotrigine had a significant effect on heat VAS but not on the other stimuli; and 2) contrast analysis of fMRI results for heat stimuli applied to the affected face for lamotrigine vs placebo produced an overall decrease in blood oxygen dependent level signal, suggesting a poten- tial inhibitory effect of the drug on predominantly cortical regions (frontal, parietal, and temporal).