Tourette's, Other Tic Disorders Far More Common Than Once Thought
October 31, 2001
One out of four students in special-education classes has a tic-related disorder like Tourette syndrome, and the rate of Tourette's among students in the general population is 50 to 75 times higher than has been traditionally thought by doctors, according to a study published in the Oct. 23 issue of the journal Neurology.
The neurologists who did the study say that Tourette's comes in many forms, including variations much milder than the profanity-spewing, limb-jerking characters seen on TV shows like Ally McBeal and LA Law. Doctors say the findings should raise awareness among teachers and doctors that children who are performing poorly in school and who have tics may need medical treatment, and that such treatment could ease school difficulties for these students.
"Most people view Tourette's as a very rare, unusual disorder with bizarre symptoms, but it's really very common, usually with mild symptoms," says Roger Kurlan, M.D., a professor of neurology at the University of Rochester Medical Center and lead author of the Neurology paper. "The cases you see on TV are the most severe cases, and they're just the tip of the iceberg. Most cases of Tourette's are much milder and don't progress to the severe form."
In the study of 1,596 children in Rochester, N.Y., 8 percent of children in special education met the criteria for Tourette's, and about 27 percent had some tic disorder. In the general population, 3 percent had Tourette's, and 20 percent had a tic disorder. The rate of 3 percent in the general population is about 50 to 75 times higher than typical estimates.
While tics like barking obscenities or jerking one's head are easy to spot, there are a slew of other repetitive and involuntary movements or vocalizations - tics - that are usually overlooked by family, friends and co-workers as strange or annoying habits, Kurlan says. Common tics include rapid eye-blinking, scrunching up one's nose, little jerks of the head, facial twitches, or even constant sniffing or clearing one's throat repeatedly.
"The fact that a child has tics probably signifies a subtle brain developmental disorder. It's like a window into the brain: When you see a child with tics, it's a sign that the wiring isn't quite right," says Kurlan, chief of the Cognitive and Behavioral Neurology Unit at the university's Strong Memorial Hospital, where he treats more than 400 Tourette's patients regularly. "Tics are observable markers that this person is more likely to have problems in school."
Researchers have linked Tourette syndrome to an area of the brain known as the basal ganglia, which is involved in controlling movement and plays an important role in attention, concentration, and decision-making. The same part of the brain is affected in people with obsessive-compulsive disorder, attention deficit-hyperactivity disorder (ADHD), and some learning disabilities.
So it's no surprise that the same factors that affect children with ADHD and these other disorders are also stumbling blocks for children with Tourette's. Students with the disorder are five times as likely as others to end up in special education. People with Tourette's typically are impulsive, have trouble concentrating and are easily distracted; friends or colleagues might say they're filled with nervous energy or seem to fidget continually.
Kurlan says that with a little training, teachers should be able to recognize most tics and thus identify some students more likely than their peers to have difficulty in school.
"A good proportion of these kids has a recognized medical condition that's amenable to treatment. Many of the symptoms of Tourette's are treatable, so that if you recognize it, you can treat it and perhaps improve the child's school performance and their ability to make friends.
"If a child is doing well, there certainly wouldn't be much to do in terms of intervening," Kurlan says. "On the other hand, maybe a child isn't doing all that well. If the child is struggling in school or having trouble making friends, perhaps causes like ADHD or Tourette's should be evaluated, and treatment should be considered for that student."
Kurlan first became aware of the possible extent of the disorder in 1983, when a man who had been diagnosed with Huntington's disease hitchhiked more than 2,000 miles to seek a second opinion from Kurlan. The man actually had Tourette's, and within an hour - the most astonishing moment in his career, Kurlan recalls - the patient had described 20 relatives with similar symptoms.
Kurlan put together a research team to visit the isolated village in northern Alberta which the patient called home, for a study of the genetic roots of Tourette's. The Mennonite community of 700 was made up heavily of descendants of a single Russian ancestor, and tales of Tourette's-like behavior were rife.
"After several flights, we arrived at the six-room hotel in town, and the very first person we met, the man checking us in at the hotel, had obvious Tourette's. We looked at each other in total amazement. We knew we had come to the right place," Kurlan says. Through interviews and exams of the man's relatives, the team ultimately found about 200 members of the extended family of 2,500 people with the disorder.
Kurlan thinks that the rate of Tourette's has been underestimated because the patients who seek out treatment in a doctor's office are usually those with the most severe symptoms. In past studies, doctors have relied on questionnaires and a review of medical records to identify patients without conducting direct interviews or exams.
"Our eyes were opened by going out into the community, when we explored what Tourette's is like in the real world. It's not a severe illness with bizarre symptoms; most people had relatively mild symptoms and did not go to their doctors for help. Most live a pretty normal life and are not disabled by tics."
Using his experience in northern Alberta as a springboard, Kurlan returned to Rochester and conducted a series of studies indicating that the disorder is much more common in the general population than previously thought. The Neurology study, funded by the National Institute of Neurological Disorders and Stroke, was done in the city of Rochester and in 10 suburban school districts and included students ages 8 to 17. Teachers and parents answered questions about the students, and then students were interviewed for an hour by technicians trained to assess tics and separate out possible causes like boredom, hyperactivity, or simple restlessness.
His results back the findings of two recent smaller studies which estimated Tourette's in about 1 percent of people, significantly higher than previous estimates.
Every day - in airports, at the office, and in the hospital - Kurlan sees people who likely have Tourette's, just like anyone with a trained eye would see among any large group of people, he says. He likes to tell the story of famed neurologist and author Oliver Sacks, who often said that on the day he recognized his very first patient with Tourette syndrome, he saw several more cases on the way home from work.
Other authors on the paper include biostatistician Michael McDermott, Ph.D.; nurse Cheryl Deeley; neuropsychologist Peter Como, Ph.D.; child psychiatrist Bruce Miller, M.D.; epidemiologist Elaine Andresen, Ph.D.; and programmer Christine Brower and statistician Sarah Eapen.