Mirror Movements Might Reflect ADHD in Kids
Simple Finger Tapping Test Could Aid in Diagnosis, Researchers Say
By KATIE MOISSE ABC News Medical Unit
Feb. 15, 2011
The cause of attention deficit hyperactivity disorder, which affects roughly 5.4 million kids in the United States alone, remains unknown. But new research into "mirror movements" sheds light on the mysterious neurobehavioral disorder and might even aid in its diagnosis.
Researchers at the Kennedy Krieger Institute in Baltimore studied 50 children between the ages of 8 to 13 who had been diagnosed with ADHD, and 25 who hadn't, as they tapped the fingers of one hand while resting the other in their laps. The ADHD kids showed increased mirror movements, meaning the voluntary finger taps in one hand were involuntarily reflected in the other.
Boys with ADHD had more than twice as many mirror movements than children without ADHD when they tapped with their nondominant hands. The difference was not seen in girls.
The study was published Feb. 14 in Neurology.
In an accompanying editorial, Dr. Jonathan Mink, professor of neurology and pediatrics at the University of Rochester Medical Center, wrote that the study provides "important evidence for impaired inhibitory function in ADHD."
Although ADHD has long been linked with motor symptoms, such as poor handwriting, the study suggests that measuring hand movements could become a useful test in diagnosing ADHD.
"This would be quite valuable," said Michael Manos, who directs the pediatric behavioral health department at the Cleveland Clinic Children's Hospital. "Even more important is the possibility that the methods, once developed, would assist us to monitor response to the medical treatment of ADHD." But Manos urges parents to not use motor movements to diagnose ADHD in their children.
"Parents who want to test their own children for ADHD using this method are only asking for worry and frustration added o their existing worry and frustration. The only advice is: Don't do it. More work must be done."
Exciting Results, More Work Needed
Dr. David Rosenberg, chairman of child psychiatry at Wayne State University School of Medicine, said the finger tapping test emphasized that ADHD is a brain disease that can be detected and treated. But he, too, cautions that the diagnosing of ADHD should be left to trained medical professionals.
"Such tests may be of interest and ultimately help identify more objective measures of illness, but at present this requires replication and cannot be considered diagnostic," he said.
Quantifying excessive mirror overflow in children with attention-deficit/hyperactivity disorder
1. L.K. MacNeil, AB,
2. P. Xavier, MS,
3. M.A. Garvey, MB, BCh,
4. D.L. Gilbert, MS, MD,
5. M.E. Ranta, BS,
6. M.B. Denckla, MD and
7. S.H. Mostofsky, MD
+ Author Affiliations
From the Kennedy Krieger Institute (L.K.M., P.X., M.E.R., M.B.D., S.H.M.), Baltimore, MD; Division of Developmental Translational Research (M.A.G.), National Institute of Mental Health, National Institutes of Health, Bethesda, MD; Division of Neurology (D.L.G.), Cincinnati Children's Hospital Medical Center and University of Cincinnati School of Medicine, Cincinnati, OH; and Departments of Neurology (M.B.D., S.H.M.), Psychiatry (M.B.D., S.H.M.), and Pediatrics (M.B.D.), Johns Hopkins University School of Medicine, Baltimore, MD.
1. Address correspondence and reprint requests to Dr. Stewart H. Mostofsky, Laboratory of Neurocognitive and Imaging Research, Center for Autism and Related Disorders, Kennedy Krieger Institute, Johns Hopkins University School of Medicine, 716 North Broadway, Baltimore, MD 21205 firstname.lastname@example.org
Objectives: Qualitative observations have revealed that children with attention-deficit/hyperactivity disorder (ADHD) show increased overflow movements, a motor sign thought to reflect impaired inhibitory control. The goal of this study was to develop and implement methods for quantifying excessive mirror overflow movements in children with ADHD.
Methods: Fifty right-handed children aged 8.2--13.3 years, 25 with ADHD (12 girls) and 25 typically developing (TD) control children (10 girls), performed a sequential finger-tapping task, completing both left-handed (LHFS) and right-handed finger sequencing (RHFS). Phasic overflow of the index and ring fingers was assessed in 34 children with video recording, and total overflow in 48 children was measured by calculating the total angular displacement of the index and ring fingers with electrogoniometer recordings.
Results: Phasic overflow and total overflow across both hands were greater in children with ADHD than in TD children, particularly during LHFS. Separate gender analyses revealed that boys, but not girls, with ADHD showed significantly more total phasic overflow and total overflow than did their gender-matched control children.
Conclusions: The quantitative overflow measures used in this study support past qualitative findings that motor overflow persists to a greater degree in children with ADHD than in age-matched TD peers. The quantitative findings further suggest that persistence of mirror overflow is more prominent during task execution of the nondominant hand and reveal gender-based differences in developmental neural systems critical to motor control. These quantitative measures will assist future physiologic investigation of the brain basis of motor control in ADHD.
Study funding: Supported in part by NIH grants R01 MH078160 and R01 MH085328 and the Johns Hopkins University School of Medicine Institute for Clinical and Translational Research (NIH/National Center for Research Resources Clinical and Translational Science Award program, UL1 RR025005). The views expressed in this article do not necessarily represent the views of the NIH.
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