Tourette Theory In Hot Dispute

January 15, 1989|By Peter Gorner.

A startling new theory about a bizarre childhood disorder-Tourette syndrome-has shaken the field of medical genetics, as scientists probe ever more deeply into the role inheritance plays in brain disease.

Tourette syndrome affects at least 100,000 Americans, striking children between the ages of 2 and 15. Symptoms include uncontrollable muscle tics and vocalizations-compulsive swearing, barking or yelping.

But the syndrome also has been associated with a wide range of problems, such as hyperactivity, dyslexia, stuttering, phobias, hallucinations, aggression and the inability to concentrate in school.

The new theory by California researchers suggests that the syndrome actually represents the extreme end of a broad spectrum of ailments caused by a single abnormal gene.

As much as 20 percent of the American population carries the gene, and it may contribute to a wide range of psychiatric and behavioral disorders, according to Dr. David Comings, chief of genetics at the City of Hope National Medical Center in Duarte, Calif.

Comings and his wife, Brenda, a clinical psychologist, theorize that when children inherit one copy of the abnormal gene from a parent, they are predisposed to errors in brain chemistry that result in a loss of inhibitions. Such children may, for example, overeat compulsively.

But when youngsters inherit copies of the gene from both parents, the result is Tourette syndrome.

Although other genes may protect carriers against the influence of the Tourette gene, half the carriers ``have some of the Tourette syndrome spectrum of disorders,`` such as alcoholism, drug abuse and severe obesity, said Comings, who also serves as president of the American Society for Human Genetics.

``I don`t mean that the Tourette gene is solely responsible for all such problems,`` he stressed. He is not saying that genetic problems afflict every alcoholic, drug addict or obese person, nor that every child with a tic has Tourette syndrome.

``But I do believe that this one bad gene contributes to a lot of difficulties,`` Comings said.

Comings has been sharply criticized by some colleagues, especially Dr. David Pauls, an assistant professor of human genetics at Yale University`s Child Study Center. The two have been engaged in a running feud over Comings` research methods that recently spilled into several professional journals.

The Comingses studied more than 1,200 Tourette patients and their families for eight years. In addition to diagnosing, counseling and medically treating these families, the researchers drew up questionnaires seeking detailed information about several generations of relatives.

According to a 166-page analysis published last year in the American Journal of Human Genetics, mania and severe anxiety are 20 times more common in Tourette families than in the general population.

Attention-deficit disorder-inability to concentrate, with or without hyperactivity-is 10 times more common; obsessive-compulsive behavior is 5 times more common.

Chronic unruly behavior is 17 times more common, the Comingses found. Stuttering is 5 times more common; dyslexia, 6 times. Tourette family members are 13 times more prone to panic attacks, 11 times more likely to develop episodes of depression, and 3 times as vulnerable to multiple phobias.

On the other hand, Pauls and his Yale team interviewed 86 Tourette patients, as well as 338 of their immediate relatives. The Yale findings directly contradict the Comingses.

``Our data do not support the hypothesis that other psychiatric and behavioral abnormalities are associated with Tourette syndrome,`` Pauls has said.

Too much of the Comings data is anecdotal, based on questionnaires, while his findings are based on direct interview information, he claims.

Comings called most of Pauls` objections ``personal nitpicking`` and said, ``The study was reliable, controlled, and had a large number of patients.``

The academic dispute has been commanding extraordinary attention in genetics research because of Comings` contention that a single common gene can contribute to so many behavioral disorders.

Biologists in at least six laboratories are in hot pursuit of the Tourette gene because it almost certainly will shed light on one of the most mysterious and misunderstood of human diseases. Its discovery would also test Comings` theory.

Parisian neurologist George Gilles de la Tourette formally described the syndrome that bears his name in 1885, although case histories of people exhibiting the strange symptoms of this disease have been described since medieval times.

Tourette reported on nine patients in whom tics were accompanied by vocalizations, many of them offensive.

Modern researchers have tracked the disorder to the basal ganglia, structures deep within the brain believed to control anger, sexual behavior and other emotions.

One theory, said Comings, is that Tourette patients lack sufficient amounts of the powerful brain chemical called serotonin, and without it, they lose their inhibitions.

``That disinhibition can take the form of tics,`` Comings said, ``or obsessive-compulsive behavior, mood swings, or many other behavioral difficulties.``