DESCRIPTION

• Tics are sudden, rapid, recurrent, nonrhythmic motor movements or vocalizations.
• According to their semiology, they can be classified as simple and complex.
  • Blinking, nose twitching, shoulder shrugging, and grimacing are examples of simple motor tics, and coughing, humming, grunting, and throat clearing are examples of simple vocal tics.
  • Complex tics include a combination of movements or noises, such as shouting words or phrases, barking, coprolalia (involuntary use of obscene words), copropraxia (involuntary use of obscene gestures), or repetitive execution of complex nonfunctional motor gestures (jumping, hand gesturing).
• Tics tend to follow a waxing and waning course, in which old tics disappear and new tics emerge. Location, type, frequency, severity, and complexity of tics often also changes over time.
• An important characteristic of tics is that they are, unlike other types of movement disorders, suppressible and can be interrupted.
  • They tend to diminish with concentrated engagement in performance and in sleep, and they tend to worsen with stress, anxiety, fatigue, or excitement. Tics are suggestible: When attention is given to them, they tend to worsen; mere discussion of tics can provoke their occurrence.
  • Although tics may appear intentional, they are not. They typically do not disrupt purposeful movements.
• In many individuals, tics are associated with a premonitory urge—a sensory feeling or urge to move that is frequently uncomfortable (eye itching that precedes blinking, throat discomfort that precedes throat clearing). The urge is relieved by tic execution. A person may be able to suppress a tic for a short time, but the tic movement or sound will recur as the urge becomes stronger.
• Tics are not harmful, but because they occur repetitively and in inappropriate situations, they may lead to development of secondary symptoms (embarrassment, stigmatization, and issues with self-esteem) that are often more harmful to the well-being of a child than tics themselves.
• Tic disorders differ from each other in terms of the type of tic present (motor, vocal or combination of both), and how long the symptoms have lasted.
• The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) requirements for diagnosis of any of the primary tic disorders are the following:
  • Tic onset is before the age of 18 years.
  • Symptoms are not attributable to the physiologic effects of a substance (e.g., cocaine) or another medical condition (e.g., postviral encephalitis).
• Tourette disorder (also Tourette syndrome [TS])
  • Both, multiple motor tics and one or more vocal tics, have been present at some time during the illness (although not necessarily concurrently).
  • Tics have persisted for >1 year since the first tic onset (although they may wax and wane in frequency).
• Persistent (chronic) motor or vocal tic disorder
  • Single or multiple motor or vocal tics have been present but not both motor and vocal.
  • Tics have persisted for >1 year since the first tic onset (although they may wax and wane in frequency).
• Provisional tic disorder
  • Single or multiple and/or vocal tics
  • Tics have been present for <1 year since the first tic onset.
  • Criteria have never been met for other tic disorders (above).
• All tics classified in DSM-5 are primary tics. Secondary tics which are caused by another etiology (infections, medications, etc.) are much rarer in children.
• Diagnosis of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) remains controversial and disputed by some neurologists. The main clinical features are the following:
  • Pediatric age of onset (age 3 years to puberty, with average age of 6 to 7 years)
  • Very abrupt onset of obsessive-compulsive disorder (OCD), tics, or both
  • Relapsing, remitting, episodic course of symptom severity
  • Presence of neurologic abnormalities (hyperactivity, unusual jerky movements)
  • Temporal association between symptom onset and group A Streptococcus infection

EPIDEMIOLOGY

• Tics occur in children of all racial and ethnic groups and socioeconomic backgrounds.
• Males are affected more frequently than females (3:1 ratio).
• Onset of tics is typically between ages 4 and 8 years. Peak severity occurs between ages 10 and 12 years.
• Prevalence of tics in school-aged children is 6–12%.
• Transient tic disorder is the most common tic disorder in children, occurring in up to 20% at some time during childhood.
• Prevalence of TS is 0.5–1% in school-aged children.

RISK FACTORS

Tic disorders are multifactorial. They develop due to a combination of genetic predisposition, environmental processes, and social and unknown age- and sex-dependent factors.

GENERAL PREVENTION

Tics cannot be prevented. There is nothing children or parents do that “causes” tics.

PATHOPHYSIOLOGY

Increasing evidence supports involvement of the cortical-basal ganglia-thalamocortical circuit; however, the primary location and neurotransmitter remains controversial. Dysfunction of cortical-basal ganglia-thalamocortical projects affect sensorimotor, language and limbic cortical circuits, and may explain why patients have difficulty in inhibiting unwanted behaviors and impulses.

COMMONLY ASSOCIATED CONDITIONS

Most patients with tic disorders will have at least one additional neuropsychiatric disorder, most commonly ADHD, which occurs in up to 60% of individuals, or OCD (which occurs in 30–60%).

• Less common, but still more frequent than the general population, are autism spectrum disorders, depression, anxiety, and behavioral disorders.
• Of the patients with TS who present for clinical care, about 85% have at least one comorbid psychiatric disorder. These comorbidities are a major source of psychosocial distress and impairment to quality of life.