Tourette Syndrome and Other Tic Disorders
Definitions of Tic Disorders
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 vocalizatins are less
common and include various throat sounds, 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 and 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 (TS), 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:
While the criteria appear basically valid, they are not absolute. First,
there have been rare cases of TS which have emerged later than age 18. Second,
the concept of "involuntary" may be hard to define operationally,
since many individuals experience their tics as having 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 individuals with TS, such as attentional problems,
compulsions and obsessions.
Table 1: Range of Symptoms
Motor
- Simple motor tics: fast, darting, and meaningless
- Complex motor tics: slower, may appear purposeful (includes copropraxia
and echopraxia)
Vocal
- Simple vocal tics: meaningless sounds and noises.
- Complex vocal tics: linguistically meaningful utterances such
as words and phrases (including coprolalia, echolalia, and palilalia).
Behavioral and Developmental
Attention deficit hyperactivity disorder, obsessions and compulsions,
emotional lability, irritability, impulsivity, aggressivity, and self-injurious
behaviors; varied learning disabilities.
Differential Diagnosis
Today the full-blown case of TS is unlikely to be confused with any other
disorder. In the past, however, TS was frequently misdiagnosed or undiagnosed.
The differentiation of TS from other tic syndromes may be no more than semantic,
especially since recent genetic evidence links TS with multiple and transient
tics of childhood and can only be defined in retrospect.
At times it may be difficult to distinguish children with extreme attention
deficit hyperactivity disorder (ADHD) from those with TS. On close examination,
many ADHD children have a few phonic or motor tics, grimace, or produce
noises similar to those with TS. Since at least half of individuals with
TS also have attention deficits and hyperactivity as children, a physician
may well be confused. However, the treating doctor should be aware of the
potential complications of treating a possible case of TS with stimulant
medication.
On rare occasions, the differentiation between TS and a seizure disorder
may be difficult. The symptoms of TS sometimes occur in a rather sharply
separated paroxysmal manner and may resemble automatisms. Individuals with
TS, however, retain a clear consciousness during such paroxysms. If the
diagnosis is in doubt, an EEG may be useful.
We have seen TS 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 TS symptoms. Whether
an autistic or retarded individual require the additional diagnosis of TS
may remain an open question until testing (biological or otherwise) is available
for a definitive diagnosis of TS.
In older individuals, conditions such as Wilson's disease, tardive dyskinesia,
Meige's syndrome, chronic amphetamine abuse, and the stereotypical movements
of schizophrenia must be considered in the differential diagnosis. The distinction
can usually be made by taking a good history or by blood tests.
Since more physicians are now aware of TS, there is a growing danger of
over-diagnosis or over-treatment. Prevailing diagnostic criteria would require
that all children with suppressible multiple motor and phonic tics, however
minimal, of at least one year, should be diagnosed as having TS. It is up
to the clinician to consider the effect that the symptoms have on the individual's
ability to function as well as the severity of associated symptoms before
deciding to treat with medication.
REPRINTED WITH PERMISSION FROM:
Wang, C., & Curry, L. (Eds.) Tourette Syndrome A Continuing Education
Course for Registered Nurses, Tourette Syndrome Association - Southern California
Chapter. TSA-SC Reseda, CA 1993.
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