Differential Diagnosis (or, When Is a Tic Not a Tic?)
Tics are brief non-rhythmic “jerky” movements and vocalizations. Bear in mind the following types of abnormal movements, which can masquerade as tics:
- • Blepharospasm. Focal contraction of muscles around the eyes—commonplace involuntary movement, often incorrectly described as a tic.
- • Akathesia. A sense of inner restlessness, relieved by moving about, e.g., marching, rocking, or squirming. Akathesia can occur due to antipsychotic medication, especially at high doses or when newly introduced.
- • Tremor. An involuntary, rhythmic type of movement that can be primary (essential tremor) or secondary (e.g., due to medications/drugs, Parkinson’s Disease, or metabolic disturbance).
- • Athetosis. Slow, writhing, continuous movements (e.g., in cerebral palsy).
- • Dystonia. Continuous unwanted contractions of muscles, which are often painful (e.g., due to nerve compression, or as a reaction to antipsychotics).
- • Chorea. Irregular random “dance like” sets of movements, abrupt and un-sustained, but seeming to flow from one body part
to another. Unpredictable in timing, direction, and body part affected (e.g., Sydenham’s Chorea; e.g., Huntington’s Disease).
• Tardive dyskinesia. Repetitive movements occurring due to chronic antipsychotic use (especially first generation)— includes grimacing, smacking one’s lips, rapid eye blinks, and tongue protrusion
The differentiation of tics from these other types of movement is greatly aided by observation of abnormal movements themselves (where possible) and by taking a detailed psychiatric history, which should include questions about exacerbating and relieving factors, prescribed medications, past medical history (such as of childhood streptococcal infection), and any salient family history (neurologic and psychiatric conditions in first-degree relatives).