Tics represent the most common involuntary movement of childhood. Although no exact incidence figure is available, between 4% and 23% of children will have one or more tics during their lifetime.1 These movements are best described as frequent but irregularly occurring, non-rhythmic, rapid, highly stereotyped movements. A single tic may be present for a brief period of time or it may persist over many years or even the patient's lifetime. Other patients will have one tic replaced by another or develop multiple tics which occur simultaneously.
The tic disorders, their etiology, and treatment have generated a great deal of controversy. The traditional viewpoint is that they are primarily psychological in origin. The ability of the child to voluntarily suppress the tics for varying periods of time and the obvious worsening of symptoms under periods of emotional stress are used as evidence for this hypothesis. Neurochemical studies are now focusing on specific brain abnormalities in the disorders associated with multiple tics. Genetic and clinical evidence suggests that all tics may lie on the milder end of a spectrum of severity but are produced by the same basic process.2 If this is true, then all tic disorders would have a primary neurochemical basis.
Until a biological classification of tics is available, the following is a useful operational framework.
This refers to a condition in which the child has only one tic at any point in time although it may be replaced by other single tics in serial fashion. The abnormal movement is the only manifestation of the disorder. Prognosis is generally good.
Complex Tic Disorders
This refers to conditions in which multiple tics are present at any given time (chronic motor tic disorder); these may include vocal tics. The pattern may be stable over many years or change constantly. Prognosis is guarded in this disorder.
This is the most severe of the complex tic disorders.3 Defining criteria and associated symptoms are listed in the Table.
SIMPLE TIC DISORDER
Simple tics present at any age in childhood with a mean age of onset of seven years. Boys are affected two to three times as frequently as girls. The tics most frequently involve the eyes with unilateral or bilateral blinking or occasionally eye-rolling movements. The muscles around the nose and mouth are also commonly affected. Somewhat less frequent, but quite typical, are sudden turning movements of the neck or shoulder-shrugging. Tics involving the distal portion of the extremities or the trunk are much less common. An isolated vocal tic is occasionally present.
The onset of the tic is sudden and the parents may try to relate it to a stressful event in the child's life although little or no controlled data are available to support such a causal relationship. The average patient has tics for approximately three years before medical help is sought. Many parents are told that the tics are a sign of tension and thus should be ignored. Children are occasionally entered into psychotherapeutic treatment at this point, but the studies available suggest that this provides no primary benefit.4 There is some evidence that behavioral techniques such as massed practice may be useful, but this is largely from single case reports. Drug therapy is not generally indicated but an occasional patient finds the tics to be a major social handicap or source of conflict within the family. Haloperidol (Haldol) in doses of 0.5 mg one to three times a day is often effective. The lower dose is initiated and this is increased every five to seven days as necessary.
Prognosis of simple tics is good. At least 4ß% to 50% of children will lose their tics entirely.5 Most of the others will have a marked diminution in symptoms and less than 10% of patients will continue into adult life with a serious tic disorder.
COMPLEX TIC DISORDERS
The complex tic disorders, chronic motor tic disorder, and Tourette syndrome will be discussed together. Complex tics, like simple tics, have a mean age of onset of seven years and a male to female ratio of 3 or 4 to 1. The most common initial symptom is a tic indistinguishable from any other simple tic; the parts of the body most frequently involved are also identical.5 The eyes and facial muscles are most commonly affected with tics involving the neck, shoulders, and extremities, in that order. A changing pattern then becomes evident.
The initial vocal tics generally occur after the onset of motor tics, are often subtle, and diagnostic errors are common. Sniffing, coughing, and throat-clearing are the most typical. AU of the symptoms tend to wax and wane spontaneously and the pattern changes over time. There is almost always partial voluntary control, although some patients show a rebound phenomenon when they relax. Tics very commonly increase in frequency while the child is watching television, and there is now some evidence that movements continue during sleep.6
Many patients show no further progression of the disorder. Others may develop a number of unusual and dramatic symptoms.7 Motor manifestations include highly complex stereotyped movements such as jumping, squatting down in place, or twisting the trunk and pelvis. Compulsive touching of other people, oneself, or objects, often develops and may appear to be sexual in nature. Rituals such as arranging objects in a certain way, handwashing or rubbing one specific area of skin, or repetitively checking to see if a door is locked or a light has been turned off can be seen. Many patients report obsessional thinking which interferes with concentration, especially in school.
Additional vocal manifestations include yells, shrieks, or cries. The patient may make animal-like sounds such as those of a dog or rooster. Echolalia is quite common, as is palilalia, repeating the same word or phrase over and over. Approximately 20% of children develop coprolalia, the involuntary utterance of obscene or blasphemous statements. This can be seen in children as young as four years of age. Many patients, when asked directly, also admit to having coprolalia, obsessive thinking of obscene words without environmental provocation. A rare child has copropraxia, the making of obscene gestures. This is almost invariably associated with coprolalia. Coprolalia is not required for the diagnosis of Tourette syndrome.
Despite the dramatic nature of the symptoms, a correct diagnosis is not made until an average age of 11 years, four years after the onset of the disorder. In over 80% of cases, the diagnosis is first made by the patient's family, the patient, a teacher, or a friend. The knowledge has usually been obtained from presentations on television or in the lay press. Prior diagnoses, if any have been offered, are most commonly related to stress and psychological dysfunction on the part of the child and treatment appropriate to that hypothesis has often been unsuccessfully attempted.
Learning disability is associated in approximately onethird of cases. Although no entirely specific pattern of cognitive dysfunction has been found, many children have deficits in the areas of visual-motor coordination and arithmetic.8 Some of the children with learning disability carry a diagnosis of attention-deficit disorder.
No consistent features are present in the past medical history. Occasionally a patient is seen who has had the dramatic and rapid onset of symptoms following closed head trauma or a serious systemic illness. However, not enough data are available to prove a causal relationship.
There does appear to be an increased risk of developing Tourette syndrome following the use of stimulant drugs.9 These are often prescribed for the treatment of attentiondeficit disorder. Some of these patients show a sudden and full-blown onset of Tourette syndrome within a week or two after stimulants are begun. In other cases, the drugs had been used at some time in the past and are not currently being taken when the disorder develops. Any patient taking stimulant medication should be monitored carefully for the development of tics and the drug should be discontinued if these appear.
Genetic evidence indicates a familial incidence of tics in at least 50% of cases.10 In one-half of the familial group, other family members meet all the diagnostic criteria for Tourette syndrome. In the remaining pedigrees with a familial tic disorder, the propositus has Tourette syndrome and one or more additional family members have chronic motor tic disorder but does not meet all the diagnostic criteria of Tourette syndrome. This evidence strongly suggests that the disorders are basically the same, and only differ in severity and the presence of vocal tics. No clearly definable differences have been found when comparing those patients who have a positive family history and those who do not. The mode of transmission has not been rigorously defined, but vertical transmission suggests an autosomal dominant gene.
Physical and neurological examinations are normal except for the presence of the tics. Because of the ability of the child to control the tics under certain circumstances, their absence during the examination should not cause serious questioning of the disorder. The history is quite typical and provides the most important diagnostic information.
There are no specifically useful diagnostic tests. A major laboratory evaluation is required if the history and signs either are not consistent with the diagnosis or suggest the possibility of another neurological disorder. CT scans are normal. Electroencephalograms are abnormal in approximately one-half of the patients, but the findings are nonspecific and of no diagnostic value.
Treatment decisions should be made after full discussion of the options with the child and parents. Treatment has no effect other than suppressing symptoms, and in no way modifies the long-term outcome. The only regularly useful medication is haloperidol. This provides good or excellent relief of tics in 80% of cases. The recommended protocol is to start the medication in low doses and then gradually increase it to therapeutic levels. This strategy seems to minimize the somnolence produced by the drug. A dose of 0.5 mg can be started at bedtime and the daily dose increased by 0.5 mg every five to seven days. Medication is given two or three times a day. It is not unusual to initially have a good response on very low doses and then a breakthrough of symptoms. This may happen once or twice until a stable response is obtained. Those patients who respond well rarely require more than 2 to 2.5 mg/day. If the patient has not responded to a dose of 5 to 6 mg/day, the chance of responding to higher doses is extremely small.
Unfortunately, one-half of patients will have troublesome side effects from the medication. The most common is lethargy, sometimes associated with depression and blunting of cognitive performance. Increased appetite can lead to unacceptable weight gain. Acute extrapyramidal reactions are rare and for this reason an antiparkinsonian drug is not begun unless they occur. An oculogyric crisis or dystonic reaction can be treated with diphenhydramine 25 to 50 mg intravenously and the patient then begun on benztropine mesylate 0.5 mg once or twice a day.
The risk of tardive dyskinesia in Tourette syndrome appears to be quite small, perhaps because of the low doses of haloperidol used or possibly because of the underlying neurochemistry of the condition. With concerns over longterm use of psychotropic medication, however, periodic attempts to lower the dose in well-controlled patients are warranted, and many families will accept drug holidays over the summer vacation or other school recesses. The drug should not be discontinued abruptly, especially if relatively high doses are used, as this may precipitate a withdrawal emergent syndrome accompanied by severe choreiform movements.
Although many other drugs have been used and seem to produce a response in occasional patients, none appear to be as reliable as haloperidol. Clonidine has been reported to ameliorate symptoms, especially verbal tics, although it is difficult to predict which patient will respond and the original study needs to be replicated. " This drug is begun at an initial dose of 0.05 mg/daily and increased weekly to a total dose of 0.15 mg/daily. Many patients will tolerate slightly higher doses. Lethargy following the institution of therapy is common, but this generally improves with time. Hypotension has not been a problem.
Prognosis of complex tic disorders has not been as welldefined as that for simple tics. Remissions clearly occur in some patients, most typically in the second half of adolescence. The evidence for this is derived from follow-up of patients with this disorder and information obtained from family interviews. Parents of children with Tourette syndrome often give a history of having had identical symptoms as a child but then losing them during adolescence. It is interesting that many of these individuals still note the occurrence of tics during periods of major stress. The remission rate is probably 20% to 30% although further studies are required. Other children will have a decrease in their symptoms during adolescence, even if a complete remission does not occur.
ETIOLOGY OF TIC DISORDERS
The tic disorders, especially those associated with additional complex and bizarre symptoms, provide a unique opportunity to study the interrelationship of psychological and organic factors. The psychological component is supported by the increase in symptoms during periods of stress, an increased incidence of other emotional and behavioral problems, and the apparent precipitation, in some patients, by a traumatic event.12
There have been many attempts to define an underlying organic substrate. No anatomical abnormalities are shown by CT scans. Electrophysiological abnormalities are restricted to non-specifically abnormal electroencephalograms. The most exciting area of research at this time involves central neurotransmitters. The specific response to haloperidol has always suggested a critical role for abnormalities of dopamine function.
The last five years has seen a number of studies in which the concentration of cerebrospinal fluid metabolites of biogenic amines is examined. By blocking the removal of these substances through the use of probenecid, the rate of turnover of the parent compound relative to that of agematched controls can be determined. A significantly decreased level of HVA, the major metabolite of dopamine, has been found.13 This increases, often returning to the normal range, following clinical improvement during treatment with haloperidol. The implication is that there is supersensitivity of central dopamine receptors. Feedback mechanisms lower the turnover rate of dopamine. Blocking the receptors with haloperidol allows dopamine metabolism to return to normal.
The finding that therapeutic responses occur with very low serum levels of haloperidol (1 to 4 ng/ml) supports this hypothesis.13 The small doses needed to achieve these blood levels may be associated with sedation. This is unlike the situation with the major psychotic disorders where treatment requires blood levels of 6 to 30 ng/ml . Additional support for dopaminergic dysfunction comes from the triggering or worsening of tics following administration of stimulant drugs.9 These substances are active on monoaminergic systems including dopamine.
The tic disorders represent a spectrum of disability ranging from simple transient tics of childhood to severe Tourette syndrome. Diagnosis depends on an awareness of their existence, willingness to accept the child and parents' histories, and appreciation of the broad range of symptoms. Although the etiology is not clear, some cases are familial. Environmental agents, especially psychostimulant drugs, may precipitate occasional cases. Treatment with haloperidol is useful for 80% to 85% of patients but associated with troublesome side effects in one-half of those treated. The long-term prognosis for complex tic disorders is not as bad as once thought, with improvement or remission often occurring in late adolescence. Abnormalities of central nervous system dopamine metabolism may be involved in the pathophysiology of the tic disorders.
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