"These tics may be a sign of an underlying brain developmental disorder that contributes to academic difficulties," said study author and neurologist Roger Kurlan, MD, of the University of Rochester School of Medicine in Rochester, NY.
Tics are involuntary, repetitive brief movements (motor tics), such as eye blinking or head jerking, or sounds (vocal tics), such as throat clearing. Tourette syndrome is diagnosed when both motor and vocal tics have been present for at least one year.
Tourette syndrome is linked to abnormalities in the basal ganglia area of the brain, which controls movement. Attention deficit hyperactivity disorder, obsessive-compulsive disorder and some learning disabilities are also linked to abnormalities in this area, and patients with Tourette syndrome often have one or more of these other disorders.
"While most cases of tics are mild and eventually resolve on their own, in some cases tics may be a first sign of an underlying disturbance in basal ganglia development which, in turn, can lead to Tourette syndrome or one of these other disorders that can interfere with success in school," Kurlan said. "It may be important to train physicians, teachers and parents to recognize tics early in young children, because they may benefit from early intervention, or at least careful monitoring.
"It may also be important to look for tics in children with problems in school, because many of the symptoms are treatable. Using the proper treatment could improve performance in school and even social and emotional development."
For the study, researchers interviewed 1,596 school children in Rochester and the surrounding county. Of those in special education classes, 27 percent had tics, compared to 20 percent of those in regular classes. Eight percent of the special education students met the criteria for Tourette syndrome, compared to three percent of the regular education students.
"For both types of students, these numbers are larger than most studies have found previously," Kurlan said. "But most previous studies were based largely on reviews of medical records and data taken from questionnaires without direct examinations, and these approaches are likely to lead to gross underestimates."
Kurlan also said that most cases are mild and do not come to the attention of health care professionals. "People with tics are themselves often unaware that they have them," he said.
But Kurlan cautioned that the results could overestimate the number affected, due to selection bias. After students were randomly selected for the study, parents were mailed information about the study and asked to return a signed form giving their consent for their child to participate. Eleven percent of those contacted agreed to participate. Students in special education classes were more likely to participate than students in regular classes.
"It's possible that parents who suspected that their children had tics were more likely to give their consent to participate," Kurlan said.
Kurlan said prospective, long-term observational studies are needed to determine exact numbers. "Nevertheless, our estimates suggest that previously reported numbers are underestimates," he said.
For a copy of the study, contact Cheryl Alementi, 651-695-2737 calementi@aan.com
The study was supported by the National Institute of Neurological Disorders and Stroke.
The American Academy of Neurology, an association of more than 17,500 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. For more information about the American Academy of Neurology, visit its web site at www.aan.com.
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Neurology