In contrast to acute EPS, TD is insidious in onset, arises only after prolonged treatment and is often masked by ongoing treatment. In addition, TD is irreversible in most cases but usually mild, whereas acute EPS are transient but unmistakable and incapacitating. Even so, TD can become socially disfiguring and severe enough to compromise eating, speaking, breathing or ambulation.
TD presents as a polymorphous involuntary movement disorder.32, 87, 88 In its most common form, TD is characterized by involuntary, non-rhythmic, repetitive, purposeless hyperkinetic movements. Most often, TD affects orofacial and lingual musculature (“buccolinguomasticatory syndrome”) with chewing or bruxism of the jaw, protrusion, curling or twisting of the tongue, lip smacking, puckering, sucking and pursing, retraction, grimacing or bridling of the mouth, bulging of the cheeks, or eye blinking and blepharospasm. Choreoathetoid movements of the fingers, hands, upper or lower extremities are common. Axial symptoms affecting the neck, shoulders, spine or pelvis may be observed. Dyskinesias can affect breathing, swallowing or speech.
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