Intellectual impairments are a significant cause of morbidity in children with birth defects along with long term implication on academic and occupational functioning. Long lasting functional changes in the brain occur when children learn new things or memorise new information. Enhancing this and learning is a key objective inneurodevelopment and neuro-rehabilitation. This is pilot study aimed at testing a experimental neuroscience technique, Transcranial Direct Current Stimulation (tCDS) on the cognitive functioning of the brain in children with Neurofibromatosis type 1 (NF1). tDCS is an established research tool and has the potential for ameliorating the cognitive impairments associated with NF1. There is a growing interest in the use of tDCS in children but to our knowledge there have been no reported studies using tDCS intervention in NF1. 16 children aged 11-16 years will be recruited through the Manchester Centre of Genomic Medicine NF1 database. Participants will be randomised to receive active or sham tDCS. The treatment will be delivered for 20 minutes for 3 days. In the experimental group a 1mA current will be applied for 20 mins ; in sham tDCS the electrodes will be placed in an identical spot but the current is ramped down to 30 seconds to prevent stimulation. The aim of the study is to look into the acceptability and feasibility of using tDCS intervention within the NF1 group, obtain pilot data on the effect of tDCS on EEG (Electroencephalogram), cognitive and behavioural measures.