Tics

TICS

DEFINITION

A tic is an involuntary movement or vocalization that is usually of sudden onset, brief, repetitive, and stereotyped, but nonrhythmic. Tics frequently imitate normal behavior, often occurring during normal activity and without alteration of consciousness. A tic is usually associated with a premonitory “buildup” sensation or feeling of discomfort that is often localized to the affected area. Usually, the individual experiences a sensation of relief once the tic has occurred. Unlike most movement disorders, tics can persist during sleep.

Tics can be classified as motor or vocal. Motor tics are associated with movements, whereas vocal tics are associated with sounds. Sometimes, the distinction between a motor tic and a vocal tic may be difficult because the noise may result from a muscle contraction.

Tics can also be categorized as simple or complex, depending on the manifestation (Table 9.1).

Simple motor tics involve only a few muscles, usually restricted to a specific body part. They can be clonic (abrupt in onset and rapid), tonic (isometric contraction of the involved body part), or dystonic (sustained abnormal posture).¹ Examples of simple motor tics include the following:

Eye blinking

Shoulder shrugging

Facial grimacing

Neck stretching

Mouth movements

Jaw clenching

Simple vocal tics consist of sounds that do not form words, such as these:

Throat clearing

Grunting

Table 9.1
Simple Versus Complex Tics

Type	Characteristics	Examples
Simple motor tics	Only one body region involved, only a few muscles used	Eye blinking, shoulder shrugging, facial grimacing, neck stretching, spitting, hair combing
Simple vocal tics	Sounds that do not form words	Throat clearing, grunting, coughing, sniffing
Complex motor tics	Multiple body regions involved	Jumping, kicking, squatting, abnormal body posturing, echopraxia, copropraxia
Complex vocal tics	Pronunciation of words or sentences, repetition of other people’s words	Coprolalia, palilalia, formed words, echolalia

Coughing

Sniffing

Blowing

Squeaking

Complex motor tics consist of movements involving multiple muscle groups and have a deliberate character, frequently resembling normal movements or gestures. They usually last longer than simple tics. Examples of complex motor tics include these:

Jumping

Kicking

Squatting

Holding the body in an atypical position

Imitating other people’s gestures (echopraxia)

Vulgar or obscene gesturing (copropraxia)

Complex vocal tics consist of pronounced words or sentences. Examples include the following:

Repetition of other people’s words (echolalia)

Repetition of a last word or parts of a word (palilalia)

Verbalizing profanities (coprolalia)

CHARACTERISTICS OF TICS

Tics are commonly associated with a premonitory sensation or feeling of discomfort that is usually relieved by performing a specific activity.

Tics can be suppressed, but suppression usually requires concentration on the part of the affected individual and results in a buildup of an uncomfortable sensation that is relieved when the tic occurs.

Typically, tics do not disrupt volitional movement, unlike other abnormal movements, such as those of chorea and myoclonus, which may share some of the features of tics.

There can also be tic blocking, during which there is a sudden stoppage of movement.

The severity of tics usually waxes and wanes, and the affected individual experiences episodes of repeated tics alternating with tic-free periods that may last from minutes to hours.²

Involvement in activities that require a great deal of attention or concentration usually diminishes the frequency of tics, whereas tics tend to occur more often during periods of stress or fatigue.

The classification of tic disorders is based on the type(s) of tics and duration of symptoms. The Tourette Syndrome Classification Study Group classification of idiopathic tic disorders appears in Table 9.2.³

However, there are many behavioral/psychiatric manifestations of Tourette syndrome (TS), and these are often more disabling than tics.

Two behavioral features commonly associated with TS are attention-deficit/hyperactivity disorder (ADHD) and obsessive–compulsive disorder (OCD).

The incidence of ADHD in TS ranges from 50% to 75%, and ADHD is the most commonly reported comorbidity. OCD may be seen in 30% to 60% of patients with TS.

The symptoms of ADHD begin aproximately 2.5 years before the onset of TS, whereas OCD generally appears after the onset of tics.⁴

Other symptoms seen in TS are listed in Table 9.3.

EPIDEMIOLOGY, PATHOGENESIS, AND PATHOPHYSIOLOGY

Tics usually begin during childhood. The average age at the onset of symptoms ranges from 5.6 to 6.4 years. On average, tics become most severe at the age of 10 years and then decrease in frequency to the point that by age 18, half of patients who have had tics are free of them.⁵ The incidence of TS is higher in males, with a male-to-female ratio of 4.3:1.⁶ Tics rarely begin in adulthood, and when they do, they are most frequently recurrences of tics that occurred during childhood.⁷ Underlying causes must be strongly considered in adult-onset tics.