Dystonia is a neurological movement disorder that causes muscles in the body to contract or spasm involuntarily. The involuntary muscle contractions cause twisting, repetitive and patterned movements as well as abnormal postures.
5-20% give a family history of this or a similar condition and it is highly likely that there is a genetic component in these cases.
Dystonia responds promptly to the anticholinergic benztropine 1-2 mg by slow intravenous injection. Most patients respond within 5 minutes and are symptom-free by 15 minutes. If there is no response the dose can be repeated after 10 minutes, but if that does not work then the diagnosis is probably wrong. After initial treatment, patients should be given oral medication for two or three days, usually benztropine 1-2 mg twice daily.
In general practice, most reactions will have been caused by antiemetics.Fortunately benztropine, diphenhydramine and promethazine all have antiemetic effects so the causative agent can be safely discontinued.