Central conduction time of magnetic brain stimulation in attention-deficithyperactivity disorder

Twenty-seven children and adolescents aged 4 to 18 years, fulfilling the Di agnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) c riteria for attention-deficit hyperactivity disorder, were included in this study. The diagnosis was determined by a pediatric neurologist and a psych ologist examined all 27 subjects with tests that included the Wechsler Inte lligence Scale for Children-Revised (WISC-R) and reading, writing, handedne ss, personality, and anxiety scores. Subjects with histories of epilepsy, h ead injury, drug abuse, or psychotic disorders were excluded. Culturally ba sed causes or emotional disorders were also excluded. Transcranial magnetic stimulation was performed on all subjects, with recording of the motor evo ked potential at the biceps brachii. Central motor conduction time was calc ulated by cervical root stimulation. Due to shape variability, the amplitud e of the motor responses was not measured in the study. The mean value of c entral conduction time in the subjects was very significantly increased (P < .001) compared to that in a group of normal controls, case-matched for IQ , age, and sex. A central motor conduction time greater than 12 ms indicate s abnormality. A second finding in the subjects was the significant differe nce of central conduction time on the side-to-side stimulation (P = .03). T hese findings are correlated with delay in the maturation of the corticomot oneuronal system and might provide neurophysiologic data for diagnosis.