| disease | Tic Disorder |
| alias | Tic Disorder |
Tic disorder refers to a condition that begins in childhood and adolescence, primarily characterized by involuntary, purposeless, repetitive, and rapid motor tics or vocal tics in one or multiple muscle groups. It may also be accompanied by other behavioral symptoms, including inattention, hyperactivity, self-injury, and obsessive-compulsive disorder. The cause of tic disorder remains unclear, and its course varies. If persistent over a long period, it can develop into a chronic neuropsychiatric disorder.
bubble_chart Epidemiology
The most common condition in childhood is transient tic disorder, also known as tics or habitual spasms, with a prevalence of about 1–7%. It is more common in boys than girls, with the majority of cases occurring between the ages of 5 and 7. Foreign literature reports the prevalence of Tourette syndrome (i.e., tic-coprolalia syndrome) at 0.1%–0.5%. In recent years, domestic case reports have gradually increased, but epidemiological survey data remain limited. Gao Qingyun (1984) surveyed 17,727 children aged 8–12 and identified 43 cases of tic-coprolalia syndrome, with a prevalence rate of 2.42%. The condition was found to be more prevalent in urban areas than rural ones, and a significant difference was observed between polluted and non-polluted environments.
1. Genetic Factors Numerous studies indicate that tic disorders are associated with genetic factors, with a relatively high concordance rate among twins. First- and second-degree relatives of children with tic disorders are more likely to exhibit tics, Tourette syndrome, or other psychiatric disorders compared to the general population. It is generally believed that the inheritance pattern may involve autosomal dominant or polygenic inheritance.
2. Neurochemical Factors Research on neurotransmitters, behavior, and the mechanisms of psychotropic drugs suggests that this disorder is related to alterations in neural generation and transformation. Some scholars propose that the condition arises from excessive dopaminergic activity in the striatum or hypersensitivity of postsynaptic dopamine receptors. Others argue that tic disorders are associated with dysregulation of norepinephrine and serotonin (5-HT) or reduced inhibitory function of gamma-aminobutyric acid (GABA) in the brain. Additionally, recent studies on endorphins indicate that imbalances in multiple neurotransmitters, such as dopamine, serotonin, and GABA, may be secondary to dysfunction of the endogenous opioid system. Thus, endorphins are believed to play a significant role in the pathological mechanism of Tourette syndrome. However, further research is needed to elucidate the changes in neural generation and transformation.3. Organic Factors Tic disorders may be linked to perinatal injuries (e.g., birth trauma, asphyxia). Approximately 50–60% of children with Tourette syndrome exhibit abnormal electroencephalogram (EEG) findings, primarily characterized by increased slow or spike waves, though these changes are nonspecific. A small number of cases show abnormal head CT scans, and neurological soft signs are relatively common. Some researchers suggest that the abnormal motor behaviors in Tourette syndrome are related to dysfunction in the amygdalo-striatal pathway, while involuntary vocalizations may be associated with irregular discharges in the cingulate gyrus, basal ganglia, and brainstem. Therefore, this disorder is considered an organic disease.
5. Other Factors Infectious diseases or the use of certain medications (e.g., central nervous system stimulants and antipsychotic drugs) may contribute to the onset of tic disorders.
bubble_chart Clinical Manifestations
Based on different clinical features and disease courses, tic disorders are classified into the following categories:
1. **Transient Tic Disorder** (also known as tic disorder or childhood habitual spasm), the most common clinical type. It primarily manifests as simple motor tics, such as involuntary movements like blinking, forehead wrinkling, lip biting, teeth baring, nose twitching, head shaking, nodding, or shrugging. A few cases involve simple vocal tics, such as repeated coughing, grunting, or throat clearing.
2. **Combined Vocal and Multiple Motor Tic Disorder**, also known as **Tourette Syndrome (TS)** or **Tic-Coprolalia Syndrome**. This is a complex and severe type. The symptoms of TS were first described by Itard in 1825. In 1885, George Gilles de la Tourette systematically reported nine cases, hence the name. The clinical features of TS include multi-site, diverse motor tics, often starting from the eyes and face, then progressing to the limbs and even multiple muscle groups throughout the body. These may present as simple motor tics (e.g., blinking, eyebrow raising, eye rolling, grimacing, tongue protrusion, head turning, shrugging, abdominal thrusting, or inhaling) or complex motor tics (e.g., impulsively touching others or objects, poking, stomping, spinning while walking, squatting, kneeling, or performing a series of meaningless actions). Most cases also exhibit or develop vocal tics, such as simple sounds (e.g., throat clearing, coughing, sniffing, grunting, or barking) or complex vocalizations (e.g., repeating words or phrases, monotonous tones, or stereotyped coprolalia).
The course of TS progresses slowly, with symptoms fluctuating—new symptoms replacing old ones—and varying in severity. Most affected children have normal intelligence and are aware of their condition.
3. **Chronic Motor or Vocal Tic Disorder** is more common in adults. It shares features of tic disorders, but motor and vocal tics do not occur simultaneously, and symptoms remain relatively stable, persisting for years or even a lifetime.
4. **Other Unspecified Tic Disorders**.
The diagnosis primarily relies on medical history and clinical examination, with meticulous and direct observation of tic symptoms and general behavioral manifestations playing a crucial role. Children with tic disorders may temporarily suppress their tics in the presence of a physician, making them easily overlooked and misdiagnosed as fistula disease. Additionally, due to accompanying behavioral symptoms, misdiagnosis is common, necessitating the identification of primary and secondary symptoms to clarify the nature of the disorder.
Diagnostic criteria:
Diagnostic criteria for tic disorder (transient tic disorder): ① Onset in childhood; ② Presence of motor tics or vocal tics; ③ Tics can be voluntarily suppressed for a short period (minutes to hours); ④ Intensity of symptoms or location of tics may vary; ⑤ Duration of at least 1 month but no more than 1 year; ⑥ Exclusion of extrapyramidal system neurological diseases and other causes of muscular rigidity.
Diagnostic criteria for Tourette syndrome: ① Onset before the age of 21, mostly between 2 and 15 years; ② Recurrent, involuntary, repetitive, rapid, and purposeless tics affecting multiple muscle groups; ③ Multiple motor tics and one or more vocal tics, occurring concurrently at times but not necessarily simultaneously; ④ Tics can be voluntarily suppressed for minutes to hours; ⑤ Fluctuation in symptom intensity over weeks or months; ⑥ Tics occur multiple times daily, nearly every day, with a duration exceeding 1 year and symptom remission not exceeding 2 months within the same year; ⑦ Exclusion of Sydenham's chorea, Wilson's disease, epileptic myoclonus, drug-induced involuntary movements, and other extrapyramidal disorders.
Diagnostic criteria for chronic motor or vocal tic disorder: (1) Must meet the first three criteria listed for transient tic disorder; (2) Motor tics or involuntary vocalizations occur multiple times daily, nearly every day or intermittently, with generally consistent intensity, and a duration exceeding 1 year.
bubble_chart Treatment Measures
First, for tic symptoms, drug therapy is selected. The commonly used clinical medications are as follows:
(1) Haloperidol: The initial dose is 1–2 mg daily, taken orally in 2–3 divided doses, and then gradually increased. The total daily dose ranges from 1.5 to 8 mg. Anti-tremor paralysis medication (such as Artane) can be taken simultaneously to reduce side effects. Common side effects include drowsiness, lack of strength, dizziness, constipation, difficulty urinating, and extrapyramidal reactions. The dose can be appropriately reduced, and symptomatic treatment can be applied.
(2) Pimozide: Its therapeutic effects are similar to haloperidol, but its sedative effects are milder, while cardiac side effects are more common than with haloperidol. It is taken once daily, with an initial dose of 0.5–1 mg/d, increased gradually. The daily dose for children is 3–6 mg. Electrocardiogram changes must be monitored during treatment.
(3) Tiapride: It is effective in treating tic disorders, with milder side effects than haloperidol, but the onset of action is slightly slower, usually taking effect 1–2 weeks after administration. The dose is 50–100 mg, taken 2–3 times daily. The main side effects include dizziness, weakness, and drowsiness.
(4) Clonidine: This is an α-adrenergic blocker that can directly act on central dopamine neurons and belongs to the category of antihypertensive drugs. Clinical use has proven its effectiveness in treating tic disorders, and it can also improve accompanying behavioral symptoms. The usual initial dose is 0.05 mg/d, taken orally in 2–3 divided doses daily. For children, the dose ranges from 0.0375 to 0.075 mg per dose, taken 2–3 times daily. The main side effects of clonidine include drowsiness, dry mouth, dizziness, lowered blood pressure, and insomnia. A few cases may show ECG changes. Blood pressure and ECG should be monitored regularly during treatment.
Other medications, such as inosine, sulpiride, clonazepam, penfluridol, levo-japanese honeysuckle stem lidine, and tetrahydropalmatine, have shown efficacy in treating tic disorders, but further controlled studies are needed.
Regarding the treatment of behavioral symptoms accompanying tic disorders: ① For comorbid attention deficit hyperactivity disorder, haloperidol, tricyclic antidepressants, or oral clonidine can be used; ② For those with comorbid obsessive-compulsive disorder, oral clomipramine can be effective. The dose for children is 3 mg/kg·d, usually 12.5–25 mg, taken 1–2 times daily. Recently, fluoxetine has been reported to effectively control obsessive symptoms.
Psychotherapy: The severity of tic disorders varies, causing interference and harm to the affected child and their family. The tic symptoms themselves are also a source of psychological distress. Therefore, in addition to drug therapy, psychotherapy should be incorporated, and parents and teachers should be helped to understand the characteristics and nature of the child’s involuntary tic symptoms to gain their cooperation and support. Furthermore, daily activities should be appropriately arranged to avoid excessive stress and fatigue, nutritional imbalances should be corrected, and recreational and sports activities should be appropriately conducted.
The prognosis for tic disorders is generally good. Tourette syndrome is a chronic neuropsychiatric disorder with a prolonged course. Medication can control symptoms in most cases, but long-term maintenance therapy is required. Follow-up observation is also necessary.
Tic disorders generally need to be differentiated from the following diseases:
1. Sydenham's chorea caused by wind-dampness infection, which is also common in children but characterized by choreiform abnormal movements, absence of vocal tics, signs of wind-dampness infection, and positive laboratory results, with effective anti-wind-dampness treatment.
2. Hepatolenticular degeneration (Wilson's disease) is caused by copper metabolism disorder, presenting with liver damage, extrapyramidal signs, and mental disorders. The presence of K-F pigment rings in the cornea and reduced serum ceruloplasmin levels can help distinguish it.
3. Myoclonus is a type of epileptic seizure, each episode is brief and often accompanied by impaired consciousness, with highly abnormal EEG rhythms, and is responsive to antispasmodic drugs.
4. Other extrapyramidal disorders such as acute dyskinesia, tardive dyskinesia, athetosis, Huntington's chorea, etc., should also be differentiated.
