TOURETTE’S SYNDROME

By Denise Ribeiro


	Tourette’s Syndrome (TS) is a chronic neuropsychological 
disorder characterized by involuntary motor and vocal tics, 
(Singer, 1993).  A tic is an uncontrolled, spasmodic muscular 
contraction.  It may also be a persistent, repetitive postural 
or verbal response without apparent meaning (Reber, 1985). A 
vocal tic usually consists of words or sounds such as clicks, 
grunts, yelps, barks, sniffs, snorts and coughs.  Coprolia is a 
vocal tic that involves uttering obscenities. Simple motor tics 
are abrupt isolated movements such a shoulder shrugs, head 
jerks, or nose twitching, (Cohen, Bruun, Lechman, 1988). Complex 
motor tics involves touching, squatting, skipping, doing knee 
bends and retracing steps.  Individuals may also engage in 
echolalia or echopraxia.  Echolalia is the compulsive and 
apparently meaningless repetition of a word or phrase or word 
spoke by another person. Echopraxia is compulsive repetition of 
gestures made by others, (Reber, 1985). Initial symptoms include 
tongue protrusion, grimacing, eye blinking and stuttering, 
(American Psychiatric Association, 1997).	
According to the Diagnostic and Statistical Manual of 
Mental Disorders, Fourth Edition (DSM IV), in order to be 
diagnosed with TS, the tics must occur several times a day, 
nearly every day for more then a year.  During this period a tic 
free period never exceeds three consecutive months. The onset of 
the symptoms needs to occur before 18 years of age in order to 
meet the criteria for TS. The tics must cause significant 
distress and impairment in the individuals functioning. Males 
are affected three to four times more then women, (American 
Psychiatric Association, 1997).
	Aretaeus of Cappadocia first recorded Tourette’s Syndrome 
2,000 years ago. Apparently Prince de Conde was affected by it, 
whenever he was in the presence of Louis XIV, he would have to 
stuff his mouth with any nearby object, even a curtain in order 
to prevent barking. It was not until 1885 when George Gilles de 
la Tourette, a French neurologist published his classic paper 
describing the motor and vocal tics that eventually came to be 
known as Tourette’s Syndrome, (Sacks, 1995; Shapiro, et al, 
1988).
	The basal ganglia and the substantia nigra are thought to 
be the neurological regions that are associated with Tourette’s 
Syndrome, (Leckman, Riddle, Cohen, 1988). The basal ganglia is 
involved in the integration, and execution of movement.  It is 
made up of the striatum and the globus pallidus (pallidus, 
“pale”). The striatum includes the caudate nucleus (caudate, 
“tail”), ventrally located nucleus accumbens, and the putamen, 
which is the largest part of the striatum.  The striatum has a 
high concentration of neurotransmitters such as acetylcholine, 
dopamine, serotonin, and gamma-aminobutyric acid (GABA). Tracts 
which convey impulses from the substantia nigra (black 
substance) to the caudate and putamen store dopamine in their 
terminals.  This represents the most important source of 
dopamine in the striatum.  Failure of dopamine synthesis in the 
substantia nigra results in the progressive depletion of this 
critical neurotransmitter in the caudate and putamen 
(consequently which develops in Parkinson’s disease, (Martin, 
1999; Diamond, Scheibel, Elson, 1985; Lechman, et al., 1988).
	There are three major dopamine nerve pathways in the brain. 
The first leads from the substantia nigra, which is in the brain 
stem to the caudate and striatum, is called the nigro-striatal 
pathway. The striatum inhibits movement; the substantia nigra 
stimulates movement. When the dopamine neurons in this pathway 
are under-stimulated, it produces muscle rigidity and tremors 
seen in Parkinson’s disease. However when the dopamine neurons 
in the pathway are over-stimulated, it produces the spontaneous, 
jerky movements seen in Tourette’s Syndrome, (Comings, 1990).
	Receptors are proteins that bind to different 
neurotransmitters. Receptors determine which neurotransmitters a 
nerve will respond to. If there is a dopamine receptor on a 
nerve, a nerve can respond to dopamine, if there isn’t a 
dopamine receptor, the nerve can’t respond to dopamine. There 
are two major types of dopamine receptors, called D1 and D2; 
their major location is in the striatum. However, stimulation of 
D2 causes hyperactivity and stereotyped moves. The drug most 
often prescribed to individuals with TS is Haloperidol. 
Haloperidol acts as an antagonist to dopamine, it blocks the D2 
receptor, which is why it is most often prescribed to 
individuals suffering from TS. Unfortunately, some of the side 
effects associated with Haloperidol are muscular rigidity, 
drooling, tremors, lack of facial expression, slow movement, 
restlessness, fatigue, depression, anxiety, weight gain, and 
difficulties in thinking, (Comings, 1990).
	Postmortem studies on individuals with Tourette’s syndrome 
have reported a large number of presynaptic dopamine sites in 
the caudate nucleus and putamen of adults (Singer and Walkup, 
1991).  It is unclear if this abnormality is due to the long 
term effects of drug treatments or the variable time between 
death, freezing and actually being able to examine the brain 
tissue. As a result researchers have started employing positron 
emission tomography (PET) to measure the amount of presynaptic 
dopamine activity.  Brain imaging techniques such as the PET and 
single photon emission computed tomography have shown the 
availability of dopamine transporters especially in the caudate 
nucleus (Malison, McDougle, Van Dyck, 1995). In a recent study 
that looked at children with TS, used the PET in order to 
measure the presynaptic dopamine activity in the basal ganglia, 
(Ernst, Zametkin, Jons, Matochik, Pascualvaca, Cohen, 1997). 
Children were used in order to rule out the long-term effects of 
having the disorder or any of the drug effects. Using Fluoradopa  
(FDODA) as the tracer, the found abnormally elevated 
accumulation of FDOPA in the left caudate nucleus and at a trend 
level in the right midbrain (p=.08), (Ernst, Zametkin, Matochik, 
Jons, Cohen,1999). This supports the theory that TS may be 
caused by “dopamine receptor supersensitivity,” (Friedhoff, 
1997; Leckman & Cohen, 1983; Singer, 1981, Singer et al., 1982). 
	Electroencephalogram (EEG) studies have examined the 
comorbidity of obsessive-compulsive disorder (OCD) with TS.  
Research has found that OCD like symptoms are due to frontal 
lobe disturbances, (Drake, Pakalnis, Newwll, Sharon, 1996). TS 
has also been known to co-exist with Attention Deficit 
Hyperactivity Disorder (ADHD). A recent study that looked at TS, 
OCD and ADHD proposed that the co-morbidity rates are due to the 
TS gene, (Sheppard, Bradshaw, Purcell, Pantelis, 1999). 
	There is genetic evidence for TS.  A person with TS has a 
50/50 chance of passing it on to their offspring.  A person with 
a TS gene may not develop full-blown Tourette’s Syndrome, but 
OCD, ADHD or mild tics. Approximately 100,000 Americans have 
full-blown TS, (NIH, 1999).
	In conclusion, Tourette’s Syndrome is a disorder 
distinguished by tics, echolalia and echopraxia. Neurological 
evidence shows that the neurotransmitters in the substantia 
nigra, caudate and the striatum are involved in Tourette’s 
Syndrome. Haloperidol is most often prescribed to individuals 
with TS, however it has unpleasant side effects. PET studies 
have supported the theory that TS is caused by a “dopamine 
receptor supersensitivity.” Tourette’s Syndrome has been known 
to co-exist with OCD and ADHD, it has been proposed that the TS 
gene is responsible for the comorbidity rates. Huntington's 
chorea has similar symptoms of Tourette’s.  It is characterized 
by involuntary jerky movements, however unlike TS; Huntington’s 
chorea is associated with personality changes, and progressive 
mental deterioration. 

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Copyright © 1999, Dr. John M. Morgan, All rights reserved - This page last edited 19 - November, 1999
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