Tic
Tic
A tic is an abrupt, jerky repetitive movement involving discrete muscle groups, hence a less complex movement than a stereotypy. Vocal (phonic) tics are also described. Tics vary in intensity, lack rhythmicity, and are relatively easy to imitate. They may temporarily be voluntarily suppressed by will power (perhaps accounting for their previous designation as "habit spasms") but this is usually accompanied by a growing inner tension or restlessness, only relieved by the performance of the movement. The pathophysiology of tics is uncertain. The belief that Gilles de la Tourette syndrome was a disorder of the basal ganglia has now been superseded by evidence of dysfunction within the cingulate and orbitofrontal cortex, perhaps related to excessive endorphin release.
The etiological differential diagnosis of tic includes:
- Idiopathic
- Gilles de la Tourette syndrome
- Tics related to structural brain damage
- Drug-induced tics.
Treatment of tics is most usually with dopamine antagonists (haloperidol, sulpiride) and opioid antagonists (naltrexone); clonidine (central α2 adrenergic receptor antagonist) and tetrabenazine (dopaminedepleting agent) have also been reported to be beneficial on occasion.
The word tic has also been used to describe the paroxysmal, lancinating pains of trigeminal neuralgia (tic douloureux).
References
Lees AJ. Tics and related disorders. Edinburgh: Churchill Livingstone, 1985
Weeks RA, Turjanski N, Brooks DJ. Tourette’s syndrome: a disorder of cingulate and orbitofrontal function? Quarterly Journal of Medicine1996; 89: 401-408
Cross References
