TMS and ADHD
Attention Deficit Hyperactivity Disorder (ADHD) is primarily characterised by the co-existence of attentional problems and hyperactivity, with each behaviour occurring infrequently alone and symptoms starting before seven years of age (Biederman 1998).
Early tests using TMS to try and find the cause of the disorder (Uclés et al. 1996) suggested delayed myelination at the brain stem reticular formation where the alpha rhythm is activated and at the corticospinal pathway as parts of a widespread involvement. Later studies seem to support this theory, Buchmann et al. (2003) found that iSP-latencies were significantly longer and their duration shorter in ADHD. The authors go on to describe that shortened duration of iSP in ADHD children could be explained by an imbalance of inhibitory and excitatory drive on the neuronal network. The longer iSP-latencies might be the result of defective myelination of fast conducting transcallosal fibers in ADHD. iSP may be a useful supplementary diagnostic tool to discriminate between ADHD and normal children (Buchmann et al. 2003).
Niederhofer (2008) wanted to verify the therapeutic effectiveness of rTMS, applied on the impending scalp additional motor area, in a subject affected by ADHD. The results showed a significant improvement that lasted for at least 4 weeks. Placebo control did not show any improvement (Niederhofer 2008).
Another study by Bloch et al. (2010) was based on the premise that ADHD may involve dopaminergic prefrontal abnormalities and the fact that rTMS affects dopaminergic secretion in the prefrontal cortex. This was a crossover double-blind randomised, sham-controlled pilot study, patients diagnosed as having adult ADHD received either a single session of high-frequency rTMS directed to the right prefrontal cortex (real rTMS) or a single session of sham rTMS. The authors reported a specific beneficial effect on attention 10 minutes after a real rTMS course. The post-real rTMS attention score improved significantly compared to the pre-real rTMS attention score. The sham rTMS had no effect whatsoever. They concluded that their findings should encourage future research on the possibility of amelioration of attention difficulties in patients suffering from ADHD by using high frequency rTMS directed to the right dorsolateral prefrontal cortex (Bloch et al. 2010).
References
- Biederman, Psychiatr Danub, 2008.
- Bloch et al., World J Biol Psychiatry, 2010.
- Buchmann et al., Clin Neurophysiol, 2003.
- Uclés P, Childs Nerv Syst, 1996.
