ORIGINAL CONTRIBUTION Striatal volume deficits in children with ADHD who present a poor response to methylphenidate A. Moreno • L. Dun ˜o ´ • E. Hoekzema • M. Picado • L. M. Martı ´n • J. Fauquet • Y. Vives-Gilabert • A. Bulbena • O. Vilarroya Received: 25 July 2013 / Accepted: 22 December 2013 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Methylphenidate (MPH) is the first choice of medical treatment for attention-deficit/hyperactivity disor- der (ADHD). Its mechanism of action is to inhibit the re- uptake of dopamine and noradrenaline mainly in the region of the striatum. It has been estimated that 10–30 % of patients with ADHD do not respond adequately to MPH. The aim of this study was to evaluate whether striatal differences exist between good and poor responders to MPH. The sample included 27 treatment-naı ¨ve children with ADHD between the ages of 6 and 14. MPH admin- istration started 1 day after the MRI acquisition. After a month, psychiatrists established the good or poor response to treatment according to clinical criteria. MRI images were analyzed using a technique based on regions of interest applied specifically to the caudate and accumbens nuclei. Sixteen patients showed good response to MPH and 11 a poor one. Regions of interest analysis showed that good responders had a higher concentration of gray matter in the head of both caudate nuclei and the right nucleus accumbens. Furthermore, a significant correlation was found between caudate and accumbens nuclei volume and the Conners’ Parent Rating Scale and Continuous Perfor- mance Test improvement. These results support the hypothesis of the involvement of the caudate and accum- bens nuclei in MPH response and in ADHD pathophysiology. Keywords ADHD Á Methylphenidate Á Caudate nucleus Á Nucleus accumbens Á MRI Introduction Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopment disorder of childhood, affecting approximately 5 % of school-aged children [34]. The core symptoms of ADHD are inattention, impulsivity and hyperactivity. Methylphenidate (MPH) is the most widely used drug in the treatment of ADHD, because of its efficiency in improving patients’ symptoms. Although it is not exactly known what its mechanism of action is, posi- tron emission tomography and functional MRI studies suggest that MPH inhibits the reuptake of dopamine (DA) and noradrenaline (NA), mainly in the striatum, and nor- malizes the activity and the connectivity between the fronto-cortical and cerebellar regions [31, 37, 50]. How- ever, it has been estimated that 10–30 % of patients with ADHD do not respond adequately to MPH [16]. The rea- sons for this unresponsiveness are still unknown, although several studies have examined different variables that A. Moreno Á E. Hoekzema Á M. Picado Á O. Vilarroya Unitat de Recerca en Neurocie `ncia Cognitiva (Departament de Psiquiatria i Medicina Legal), Universitat Auto `noma de Barcelona, Campus de Bellaterra, 08193 Barcelona, Spain A. Moreno (&) Á E. Hoekzema Á M. Picado Á O. Vilarroya Fundacio ´ IMIM, Grup de Recerca en Neuroimatge (GREEN), C/Dr. Aiguader 88., 08003 Barcelona, Spain e-mail: ana.moreno.alcazar@gmail.com L. Dun ˜o ´ Á L. M. Martı ´n Á A. Bulbena Institut de Neuropsiquiatria i Addiccions (INAD), Hospital del Mar, 08003 Barcelona, Spain J. Fauquet Departament de Psicobiologia i Metodologia, Universitat Auto `noma de Barcelona, Campus de Bellaterra, 08193 Barcelona, Spain Y. Vives-Gilabert Port d’Informacio ´ Cientı ´fica (PIC), Universitat Auto `noma de Barcelona, Campus de Bellaterra, 08193 Barcelona, Spain 123 Eur Child Adolesc Psychiatry DOI 10.1007/s00787-013-0510-y