Objective Attention deficit/hyperactivity disorder (ADHD), whose definition, diagnosis and treatment has been the subject of debate in the scientific community for a long time, is the most common neurobehavioral disorder in childhood. There are many studies on the pathophysiology of attention deficit. However, there is no study in the literature based on direct or indirect measurement of cerebral ve-nous circulation in ADHD, and the effect of methylphenidate (MPH) treatment on cerebral venous circulation. Therefore, it was aimed to noninvasively measure superior vena cava (SVC) flow, which is an indirect indicator of cerebral venous flow, by transthoracic echocar-diography in patients with ADHD. Methods In the study, 44 healthy children, and 40 ADHD patients who were planned to start on osmotic-release oral system (OROS)-MPH were included. SVC flows were measured in healthy children and before and after drug therapy of ADHD patients. Results SVC flow was found to be higher in ADHD patients compared to healthy children. A significant decrease was found in SVC flow of ADHD patients after OROS-MPH treatment. There was no decrease in SVC flow of patients who did not respond adequately to MPH treatment. Conclusion This first study of SVC flow in children with ADHD showed that ADHD was associated with increased SVC flow and MPH treatment had a reducing effect on this increased SVC flow. We believe that noninvasive, easily measurable, and reproducible SVC flow may be a new focus of interest for future comprehensive studies as a biomarker to support clinical evaluation in the diagnosis and treat-ment follow-up of ADHD patients.
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