Tourette Syndrome: The Neurology of a Tic
From the Point of View of the Scientist
Gilles de la Tourette Syndrome (TS) is one of the most common neurological movement disorders of childhood onset, present in up to 3% of children. TS is characterized by motor and phonic tics that fluctuate in distribution, severity, and frequency, often exacerbated by anxiety and stress.
Tics are abrupt, brief, repetitive movements of one or more muscle groups, frequently preceded by an urge to move, stretch, or apply pressure on the affected area until it feels "just right." Although tics are classified as involuntary movements, many patients report that tics are voluntary motor responses to involuntary sensations.
In 1825, Itard described one of the earliest cases of TS in a French woman, the Marquise de Dampierre who exhibited barking, involuntary utterances of obscene words (coprolalia), and motor tics. Sixty years later, an additional eight patients were diagnosed by Georges Gilles de la Tourette, a French neurologist and student of Charcot, considered by most to be the father of neurology. All eight patients had tics, some with involuntary repetition of others' words (echolalia), others' gestures (echopraxia), as well as coprolalia. Prior to the use of drugs that block the neurotransmitter dopamine (neuroleptics) for the treatment of motor tics in the 1960s, TS was considered a disorder of psychological origin.
Not until this past decade have associated anxiety disorders, language and learning disorders, mood disorders, and other co-morbidities, particularly attention deficit disorder (ADD), and obsessive compulsive disorder (OCD), been suspect as a feature of TS. However, often these co-morbidities may be more troublesome than the motor tics.
Language and communication disorders have not been commonly recognized by clinicians as an associated feature of TS. However, language and speech abnormalities have been previously reported in the TS population. TS patients may suffer from a variety of speech and voice abnormalities, some more disabling than others.
TS patients exhibit motor tics involving the oral and nasal passageways that are commonly referred to as "vocal" or "phonic" tics. Since not all noises made by TS patients involve the passage of air through vocal cords, the term "phonic" tic is preferred. The mechanisms for "phonic" tics do not differ from motor tics, except that the muscular contractions producing "phonic" tics involve the oral-nasopharyngeal area. Simple phonic tics may include persistent throat clearing, coughing, squealing, barking, grunting, screaming, or other noises. Complex phonic tics include semantically meaningful vocalizations such as repeating one's own words (palilalia), repeating others' words (echolalia), or blurting out obscene words or other socially inappropriate words or phrases (coprolalia).
Coprolalia, perhaps one of the most recognizable and disabling symptoms of TS, often impairs normal socialization and sometimes even leads to trouble with the law. The frequency of coprolalia varies from study to study, but the symptom is present in less than half of U.S. patients. However, the frequency of "mental" coprolalia (merely thinking of the obscene word or phrase) may be higher. Coprolalia, which is culturally determined, is thought to be one of several involuntary, disinhibitive type symptoms seen in TS patients. When describing the distress caused by his severe coprolalia, one of our patients remarked that immediately after shouting an obscenity he reaches out with his hand in an attempt to "catch the word and bring it back before others can hear it."
Phonic tics may interfere with job security, self-esteem, and socialization. Quite often, parents and teachers misconstrue vocalizations (and other motor tics) as means of gaining attention. However, the child usually experiences embarrassment, rather than any secondary gain. One TS patient who suffered from a phonic tic of sporadic screaming was dismissed from his job, experienced public embarrassment, and developed agoraphobia.
Another speech disturbance present in some TS patients is "blocking" tics, manifested by either start hesitation or a sudden interruption in the normal flow of speech. The mechanism of blocking tics may be partly related to underlying OCD or caused by an isometric contraction of the abdominal muscles producing a Valsava maneuver (forcible exhalation against a closed glottis) that results in a sudden interruption and cessation of speech. When the cause is OCD, a specific thought (an obsession) may suddenly interfere with the normal processing of language and speech. TS patients may also have a need to state a phrase in a certain way to an attempt to formulate a certain idea or a thought until it sounds "just right" before spoken.
A blocking tic may also be part of a sequential complex tic. Many TS patients may not respond to answers until they complete a set of ritualistic behaviors, such as producing a motor tic, followed by tapping, and then communicating the answer as the last component of the complex tic. The completion of the thought from the time it is mentally formulated to the time it is communicated verbally is delayed due to the obsessive mechanisms, and is often misunderstood as cognitive delay, mutism, extreme shyness, or stuttering.
One patient, whom we initially determined to be extremely shy, had difficulty verbalizing his responses when questioned in the clinic. He had extreme co-morbid OCD. Upon further examination, he was noted to have a marked delay in his responses due to an obsessive need to complete a specific thought pattern before verbalizing his response. In addition, he had a need to complete a stereotypic motor tic of rocking at least six times before he was able to complete any other task, including speaking. However, when asked to answer through a non-verbal form of communication (1 finger = yes, 2 fingers = no), he was able to answer questions promptly and accurately, without signs of cognitive compromise.
Besides phonic and blocking tics, coprolalia, and echolalia, patients with TS often also exhibit palilalia, manifested by repetition of the last syllable, word, or phrase. Developmental stuttering (DS) has also been reported to be more common in the TS population than any other movement disorder. In a study of 246 TS patients, these individuals had a significantly increased frequency of DS compared to normal; another study of 22 people who stuttered revealed that 11 had motor tics (see Comings & Comings and Abwender et al., in the references). The pathology of DS and TS may share a basal ganglia dysfunction. Case reports of other voice discrepancies in TS patients include spasmodic dysphonia, slurred speech secondary to pimozide, a dopamine-blocking medication to treat tics, and falsetto.
Management of TS may range from simple education and counseling to concerted efforts of experienced neurologists, psychiatrists, psychologists, social workers, educators, and other allied health care professionals. Medical therapy should be tailored to the individual with TS and should be focused on the most disabling or bothersome symptom, whether motor or behavioral. For some, inappropriate vocalizations or stuttering may affect socialization and result in the greatest morbidity.
Tics respond best to dopamine-blocking drugs such as haloperidol, fluphenazine, pimozide, or other pharmacological agents, such as tetrabenazine, that disrupt the release of dopamine. The prescribing physician must openly discuss with patients and their families potential side effects of these drugs including sedation, weight gain, school phobia, potential liver or cardiac toxicity, and, except for tetrabenazine, tardive dyskinesia. Central nervous system stimulants such as dextroamphetamine and methylphenidate are used to treat ADHD, although these medications may exacerbate tics. OCD symptoms are best managed with antidepressants, specifically selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, fluvoxetine, paroxetine and sertraline. Botulinum toxin (BTX) injections are yet another option for tics isolated to one body region (focal tics) such as the eyes, neck, or vocal cords.
Treatment for Speech Disorders in TS
The appropriate speech treatment is dependent upon recognition and accurate diagnosis of the specific condition. If anti-dopaminergic drugs are not sufficient to control phonic tics, botulinum toxin injections directly into the vocal cords have resulted in marked improvement and have abated social embarrassment often produced by coprolalia, echolalia, and palilalia. TS patients have reported improvement of coprolalia, resulting not only in attenuation of phonic tic severity but also the urge to vocalize the tic. SSRIs should be prescribed for blocking tics, particularly if the underlying mechanism is presumed to be obsessive thoughts. Speech treatment should be considered for TS patients with stuttering. Anti-TS medications may also contribute to speech problems as side effects include dysarthria and discontinuation of the drugs has been associated with improvement in speech. Concomitant neurological disorders such as dystonia (spasmodic dysphonia) in TS patients should be treated accordingly.
In conclusion, TS is a multi-faceted neurological disorder requiring the understanding of the individual symptoms and integration of the co-morbidities. Recognition of the complexity of the underlying mechanisms and targeting treatme nt for the most troubling symptom, such as speech and voice problems, should substantially improve the quality of life of the individual with TS.