RESUMO
Using transcranial magnetic stimulation (TMS), disturbed facilitatory and inhibitory motor functions were recently found to correlate with motor hyperactivity in children with ADHD. Since hyperactivity seems to become reduced in ADHD during the transition to adulthood, a normalization of motor cortical excitability might be assumed. Therefore, we investigated the same inhibitory and facilitatory TMS paradigms in ADHD adults as we had previously examined in children. Motor cortical excitability was tested with TMS paired-pulse protocols in 21 ADHD adults and 21 age- and gender-matched healthy controls. In contrast to our results in ADHD children, no group-specific differences in amplitude changes of motor evoked potentials for inhibitory inter-stimulus intervals (ISI) (3, 100, 200 and 300 ms) or for facilitatory ISIs (13, 50 ms) could be detected. In ADHD adults, disturbed facilitatory and inhibitory motor circuits as found in ADHD children could not be shown, probably due to a development-dependent normalization of motor cortical excitability.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/complicações , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Córtex Motor/fisiopatologia , Transtornos dos Movimentos/etiologia , Transtornos dos Movimentos/fisiopatologia , Inibição Neural/fisiologia , Adulto , Fatores Etários , Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Campos Eletromagnéticos , Potencial Evocado Motor/fisiologia , Potencial Evocado Motor/efeitos da radiação , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciais Pós-Sinápticos Excitadores/efeitos da radiação , Feminino , Humanos , Potenciais Pós-Sinápticos Inibidores/fisiologia , Potenciais Pós-Sinápticos Inibidores/efeitos da radiação , Masculino , Córtex Motor/crescimento & desenvolvimento , Córtex Motor/efeitos da radiação , Movimento/fisiologia , Movimento/efeitos da radiação , Transtornos dos Movimentos/diagnóstico , Inibição Neural/efeitos da radiação , Vias Neurais/crescimento & desenvolvimento , Vias Neurais/fisiopatologia , Vias Neurais/efeitos da radiação , Tempo de Reação/fisiologia , Tempo de Reação/efeitos da radiação , Estudos Retrospectivos , Transmissão Sináptica/fisiologia , Transmissão Sináptica/efeitos da radiação , Estimulação Magnética Transcraniana , Adulto JovemRESUMO
Using transcranial magnetic stimulation (TMS) in children with ADHD, an impaired transcallosally mediated motor inhibition (ipsilateral silent period, iSP) was found, and its restoration was correlated with improvement of hyperactivity under medication with methylphenidate (MPH). Hyperactivity has been reported to decrease during transition into adulthood, although some motor dysfunction might persist. As one underlying neurophysiological process, a development-dependent normalization of motor cortical excitability might be postulated. In order to test this hypothesis, we measured the iSP in 21 adult ADHD patients and twenty-one sex- and age-matched healthy controls. In 16 of these patients, a second TMS was performed under treatment with MPH. Our results indicate a persistence of impaired transcallosally mediated motor cortical inhibition (shortened duration) in ADHD adults, which was correlated with clinical characteristics of hyperactivity and restlessness, and was restored by MPH. In contrast to ADHD in childhood, the iSP latency was not impaired, suggesting a partial development-dependent normalization of motor cortical excitability in ADHD adults. ISP duration appears to be a sensitive parameter for the assessment of disturbed intercortical inhibition in adults with ADHD.