Definitions of Tic Disorders

by Ruth Dowling Bruun, M.D., Donald J. Cohen, M.D., James F. Leckman, M.D.

Tics are involuntary, rapid, repetitive and stereotyped movements of individual muscle groups. They are more easily recognized than precisely defined. Tic disorders are generally categorized according to age of onset, duration of symptoms, severity of symptoms and the presence of vocal and/or motor tics.

Transient tic disorders often begin during the early school years and can occur in up to 18% of all children. Common tics include eye blinking, nose puckering, grimacing and squinting. Transient vocalizations are less common and include various throat sounds, humming or other noises. Childhood tics may be bizarre - palm licking, poking and/or pinching the genitals are examples. Transient tics last only a few weeks or months and are usually not associated with specific behavioral or school problems. They are especially noticeable during times of heightened excitement or fatigue. As with all tic syndromes, boys are three to four times more often affected than girls. While transient tics by definition do not persist for more than a year, it is not uncommon for a child to have recurrent episodes of transient tics over the course of several years.

Chronic tic disorders are differentiated from transient tic disorders not only by their duration over many years, but by their relatively unchanging character. While transient tics come and go (sniffing may be replaced by forehead furrowing and the furrowing may become finger snapping), chronic tics - such as facial contortions or blinking - may persist unchanged for years.

Chronic multiple tics suggest that an individual has several chronic motor tics (or, in rare cases, several chronic vocal tics). Often it is not an easy task to draw distinctions between transient tics, chronic tics, and chronic multiple tics.

Tourette Syndrome (Tourette Syndrome), first described by Gilles de la Tourette, can be the most debilitating tic disorder and is characterized by multiform, frequently changing motor and phonic tics. The current diagnostic criteria, as defined by the Diagnostic and Statistical Manual of Mental Disorders IV are as follows:

1. Both multiple motor and one or more vocal tics have been present at some time during the illness, although not necessarily concurrently.
2. The tics occur many times a day (usually in bouts) nearly every day or intermittently throughout a period of more than 1 year, and during this period there was never a tic-free period of more than 3 consecutive months.
3. The disturbance causes marked distress or significant impairment in social, occupational, or other important areas of functioning.
4. The onset is before age 18.
5. The disturbance is not due to the direct physiological effects of a substance (e.g. stimulants) or a general medical condition (e.g. Huntington's disease or postviral encephalitis).

While the criteria appear basically valid, they are not absolute. First, there have been rare cases of Tourette Syndrome which have emerged later than age 18. Second, the concept of "involuntary" may be hard to define operationally, since many patients experience their tics as having a volitional component - either a capitulation to an internal sensory urge for motor discharge, or a more generalized psychological tension and anxiety, or both. Finally, the diagnostic criteria do not adequately portray the full range of behavioral difficulties that are commonly observed in patients with Tourette Syndrome, such as attention problems, compulsions, and obsessions.

Differential Diagnosis

Today, the full-blown case of Tourette Syndrome is unlikely to be confused with any other disorder. In the past, however, Tourette Syndrome was frequently misdiagnosed or undiagnosed.

The differentiation of Tourette Syndrome from other tic syndromes may be no more than semantic, especially since recent genetic evidence links Tourette Syndrome with multiple and transient tics of childhood and can only be defined in retrospect.

On rare occasions, the differentiation between Tourette Syndrome and a seizure disorder may be difficult. The symptoms of Tourette Syndrome sometimes occur in a rather sharply separated paroxysmal manner and may resemble automatisms. Patients with Tourette Syndrome, however, retain a clear consciousness during such paroxysms. If the diagnosis is in doubt, an EEG may be useful.

Tourette Syndrome has been seen in association with a number of developmental and other neurological disorders. It is possible that central nervous system injury from trauma or disease may cause a child to be vulnerable to the expression of the disorder, particularly if there is a genetic predisposition. Autistic and retarded children may display the entire gamut of Tourette Syndrome symptoms. Whether an autistic or retarded individual requires the additional diagnosis of Tourette Syndrome may remain an open question until testing (biological or otherwise) is available for definitive diagnosis of Tourette Syndrome.

In older patients, conditions such as Wilson's disease, tardive dyskinesia, Meige's syndrome, chronic amphetamine abuse and the stereotypic movements of schizophrenia must be considered in the differential diagnosis. The distinction can usually be made by taking a good history or by blood test.

Since more physicians are now aware of Tourette Syndrome, there is a growing danger of over-diagnosis or over-treatment. It is up to the clinician to consider the effect that the symptoms have on the patient's ability to function (as well as the severity of associated symptoms) before deciding to treat with medication or other approaches.

The Authors

Tourette Syndrome Association
Ruth Dowling Bruun, M.D. is Clinical Associate Professor of Pyschiatry, Cornell University Medical School, New York, N.Y.
Donald J. Cohen, M.D. is Director and Irving B. Harris Professor of Child Psychiatry, Pediatrics and Psychology, Yale Child Study Center, New Haven, CT.
James F. Leckman, M.D. is Neison Harris Associate Professor of Child Psychiatry and Pediatrics, Yale Child Study Center, New Haven, CT.

More information can be obtained from:

Tourette Syndrome Association
42-40 Bell Boulevard
Bayside, New York 11361
718/224-2999

next: Co-Morbid Conditions

top . send to friend . tourette's site map

Reviewed: 09/2006