Dopamine transporter genotype influences the physiological response to medication in ADHD.

Attention deficit hyperactivity disorder (ADHD) is a complex, multifactorial disorder characterized by physical hyperactivity and behavioural disinhibition. Short interval cortical inhibition (SICI), measured in motor cortex with transcranial magnetic stimulation, is reduced in ADHD and correlates with symptom severity. However, ADHD medication-induced changes in SICI vary widely among normal individuals and have not been well studied in children with ADHD. Therefore, we undertook this study to measure and compare effects of two ADHD medications, methylphenidate (MPH), a psychostimulant, and atomoxetine (ATX), a selective norepinephrine reuptake inhibitor, on SICI in children with ADHD. In addition, we wished to determine whether a genetic variation in the dopamine transporter (DAT1), a site of action of MPH, could influence the effects of MPH or ATX on SICI. We performed a randomized, double-blind, single-dose, crossover study comparing 0.5 mg/kg MPH with 1.0 mg/kg ATX in 16 children with ADHD, aged 8-17. Seven were homozygotes and 9 heterozygotes for the DAT1 variable number of tandem repeats 10-repeat allele. Medication and genotype effects on SICI were estimated with repeated measures, mixed model regression. We found that MPH and ATX had similar effects on SICI. However, medication effects differed significantly by DAT1 genotype [F(2,13) = 13.04, P = 0.0008]. Both MPH and ATX increased SICI in heterozygotes but not in 10-repeat homozygotes. In conclusion, MPH and ATX have similar effects on SICI in children with ADHD. A genetic variation in DAT1, previously linked to ADHD risk and MPH behavioural responses, influences the neurophysiological effects of both MPH and ATX.

Comparison of the inhibitory and excitatory effects of ADHD medications methylphenidate and atomoxetine on motor cortex.

Stimulant and norepinephrine (NE) reuptake inhibitor medications have different effects at the neuronal level, but both reduce symptoms of attention deficit hyperactivity disorder (ADHD). To understand their common physiologic effects and thereby gain insight into the neurobiology of ADHD treatment, we compared the effects of the stimulant methylphenidate (MPH) and NE uptake inhibitor atomoxetine (ATX) on inhibitory and excitatory processes in human cortex. Nine healthy, right-handed adults were given a single, oral dose of 30 mg MPH and 60 mg ATX at visits separated by 1 week in a randomized, double-blind crossover trial. We used paired and single transcranial magnetic stimulation (TMS) of motor cortex to measure conditioned and unconditioned motor-evoked potential amplitudes at inhibitory (3 ms) and facilitatory (10 ms) interstimulus intervals (ISI) before and after drug administration. Data were analyzed with repeated measures, mixed model regression. We also analyzed our findings and the published literature with meta-analysis software to estimate treatment effects of stimulants and NE reuptake inhibitors on these TMS measures. There were no significant pretreatment differences or effects of treatment order. Both agents produced a significant increase in facilitation and a decrease in inhibition. Effects of ATX and MPH did not differ significantly. Pooled estimates from published studies show similar results for stimulants and NE reuptake inhibitors. In conclusion, in healthy adults, both stimulant and nonstimulant medications for ADHD decrease cortical inhibition and increase cortical facilitation. Cortical inhibition, shown previously to be abnormal in ADHD, may play a key role producing behavioral pathology.

An updated review of the long-term neurological effects of galactosemia.

Classical galactosemia is an autosomal recessive condition in which there is near total absence of the activity of galactose-1-phosphate uridyltransferase. Patients with this condition have substantial motor, cognitive, and psychiatric impairments despite dietary treatment. A characteristic pattern of biochemical abnormalities is observed in patients with this disorder. Galactose-1-phosphate, the substrate of galactose-1-phosphate uridyltransferase, accumulates within cells, and surplus galactose is reduced to galactitol or oxidized to galactonate. Using sophisticated mass spectrometry, these compounds as well as free galactose can be measured in plasma and in urine. It is clear that initiation of dietary restriction of galactose in the newborn period produces reversal of hepatic, renal, brain, and immune dysfunction, along with reduction of the accumulated galactose metabolites. However, the neurologist should be aware that chronic and progressive neurologic impairments occur even in patients spared these neonatal symptoms. The purpose of this review is to summarize current information about neurologic complications of galactosemia and what is known, and still unknown, about its pathophysiology.

Views of recently first-certified US child neurologists on their residency training.

We surveyed child neurologists first certified in "Neurology with Special Qualification in Child Neurology" by the American Board of Psychiatry and Neurology (ABPN) between 2001 and 2010 using a 24-item questionnaire. Respondents (n = 204, 54% response rate) were between the ages of 30 and 59 years (54% male), and 68% completed adult neurology training in a 10- to 12-month, primarily inpatient block. Sixty-two percent of the sample completed subspecialty fellowship training and 82% currently reported practicing within a hospital or hospital-based/owned clinic. Current practice data showed just 3% provide general neurology services to adults. A majority reported using adult neurology residency training "less than weekly" and believed the ideal model for residency training in diagnosis and management of both common and rare neurologic conditions would involve less time in adult neurology and more time (mean 6 months) in child neurology, most prominently in genetics and developmental and behavioral areas.

Child neurology: past, present, and future: part 3: the future.

This is the last of a 3-part series exploring the past, present, and future of the field of child neurology. This article addresses the 2 fundamental challenges facing child neurology. The most important challenge is our inadequate workforce; based on current numbers, recruitment patterns, and projected retirement, the child neurology clinical and research workforce shortage will likely worsen. The second challenge involves adapting our training to prepare child neurologists for changes ahead. We propose that these 2 issues are related, and that solutions need to include consideration of career options in research, education, and patient care.

The prevalence of neuropsychiatric disorders in Sydenham's chorea.

Sydenham's chorea is a rare movement disorder associated with streptococcal infection. The co-occurrence of neuropsychiatric symptoms has raised the question of whether streptococcal infection could trigger these symptoms without chorea. This study evaluated the prevalence of behavioral diagnoses before, during, and after the onset of chorea in a cohort of children with a history of Sydenham's chorea for whom demographic and clinical data were available. In all, 28 Sydenham's chorea patients were evaluated, with a mean age of 10.3 years. Retrospective analysis was performed for subject demographics, streptococcal titers, and presence of arthritis and carditis. Structured diagnostic interviews were performed on 14 available patients and parents. Streptococcal titers and duration of treatment for chorea were compared between groups. The prevalence of attention deficit hyperactivity disorder before and after chorea was 30 and 37%, respectively. The proportion of children meeting combined, subthreshold, and suprathreshold criteria before, during, and after Sydenham's chorea was 71, 79, and 79% for anxiety and 19, 69, and 44% for depression. Streptococcal antibody titers and duration of treatment did not correlate with attention deficit hyperactivity disorder, depression, or anxiety disorders. During and after the diagnosis of Sydenham's chorea, clinicians should be vigilant for signs and symptoms of anxiety, depression, and attention deficit hyperactivity disorder.