Clinical Vignette

A 12-year-old boy presented to the neurology clinic with approximately 1 year of excessive eye blinking. He was accompanied by his parents. He was a full-term infant and reached all developmental milestones appropriately. Schoolwork has been average; he frequently loses pencils and articles of clothing. He also has difficulty finishing his homework. During the past year, his parents have noted increased frequency of eye blinking. The patient is aware of the blinking and has been told by his classmates that he “squints” and “makes funny faces.” He is embarrassed by the movements. His neurologic exam was notable for eye blinking, sniffing, nose wrinkling, and contraction of the platysma. He was able to suppress the movements volitionally. He was prescribed clonidine. After 8 weeks, he returned to the office with his parents. He reported lessening of his tics. His parents felt he was performing better at school.

Phenomenology and Classification

Tics are sudden, relatively quick, stereotyped movements (motor tics) or sounds (phonic tics) which are repeated at irregular intervals. Tics are often preceded by a premonitory urge or inner sensory stimulus, and can be suppressed at will. They are, therefore, referred to as semivoluntary, or unvoluntary, movements.

Tics are categorized as simple or complex (Box 39-1). Simple motor tics involve only one group of muscles and are characterized by quick, jerk-like movements. Usually they are abrupt in onset and brief (clonic tics) but they can also be slower and sustained (dystonic tics). Examples of simple motor tics include eye blinking, nose twitching, and shoulder shrugging. Simple phonic tics include sniffing, throat clearing, and grunting. Complex motor tics are sequenced and coordinated movements that can resemble gestures or fragments of normal behavior, e.g., kicking, jumping, and, rarely, inappropriate behavior, e.g., showing the middle finger. Complex phonic tics have a semantic basis, including words, parts of words, and obscene words (coprolalia).

It is important to distinguish tics from other hyperkinetic movement disorders. For example, simple motor tics can resemble myoclonus. However, clonic tics are stereotyped, rather than random, are suppressible, and are typically accompanied by a premonitory sensation.

The most common tic disorder is Tourette syndrome (TS), which is characterized by motor and phonic tics. The Tourette Syndrome Classification Study Group has formulated diagnostic criteria for TS that include the presence of both motor and phonic tics, though not necessarily concurrently; the presence of tics for at least 1 year; fluctuation in tic type, frequency, and severity; and onset before age 21 years. Tics of duration less than a year are classified as transient tic disorder. When only one category of chronic tics can be identified, the terms chronic motor tic disorder or chronic vocal tic disorder are used.