Despite the common misconception that Tourette's syndrome is defined by uncontrollable and socially inappropriate cursing, only 10 percent of Tourette's patients actually exhibit that symptom. Most have milder tics like rapid blinking , shoulder-shrugging and throat-clearing. Coprolalia, the involuntary utterance of obscenities, profanities and derogatory remarks, is an extreme example of a vocal tic experienced by some people with Tourette's.
When the compulsion overcomes them, sufferers of the condition cannot help yelling inappropriate or culturally taboo remarks or phrases. A coprolalia sufferer might even blurt out ethnic slurs, even if they aren't racist an embarrassing and distressing situation for all involved.
Aside from Tourette's, brain injuries, strokes, dementia , seizures and many other forms neurological damage can usher the onset of coprolalia as well. It is known to be caused by brain dysfunction, but the details are, as yet, hazy. One hypothesis, described by psychologist Timothy Jay in his book "Why We Curse" (John Benjamins Pub Co. 2000), suggests that it's caused by damage to the amygdala, a region of the brain that normally mitigates anger and aggression. Because cursing is a form of verbal aggression, amygdala damage could result in the inability to control aggression, including verbal aggression, or cursing.