Lamotrigine for cognitive deficits associated with neurofibromatosis type 1: A phase II randomized placebo-controlled trial

Aim: To find proof-of-principle evidence for short-term treatment with lamotrigine to improve cognitive functioning of adolescents with neurofibromatosis type 1 (NF1). Method: This was a double-blind, parallel-group, randomized, placebo-controlled clinical trial (the NF1-EXCEL trial: Examining the Cognitive and Electrophysiological benefit of Lamotrigine in Neurofibromatosis type 1; identifier NCT02256124), with the aim of enrolling 60 adolescents with NF1 aged 12 to 17 years 6 months. The short-term study intervention was 200 mg of lamotrigine taken orally for 26 weeks. The primary outcome was performance IQ tested with the Wechsler Intelligence Scale for Children, Third Edition, complemented with secondary outcomes for visuospatial learning efficacy, visual perception, visual sustained attention, fine motor coordination, attention-deficit/hyperactivity problems, and executive functioning. Results: We screened 402 adolescents with NF1, of whom 31 (eight females) entered the study. Complete-case analysis showed no effect of lamotrigine on either performance IQ (-0.23, 95% CI -6.90 to 6.44) or most secondary outcomes. Visual sustained attention showed a trend towards better performance in the lamotrigine group (-0.81, 95% CI -1.67 to 0.04). Interpretation: Lamotrigine did not improve cognitive functioning in adolescents with NF1. The small treatment effects make it unlikely that a larger sample size could have changed this conclusion.