Author Brenda Higgins responds:
Dystonias are complex and classified according to the parts of the body affected, specific syndromes, and primary and secondary etiology. Many primary dystonias appear to be inherited in a dominant manner, but they are rare. Secondary dystonias more commonly result from drug reactions, poisoning, trauma, infection, or stroke.
The acute dystonic reaction described is a common one to neuroleptic agents. Features suggestive of a secondary etiology include acute onset of unilateral involvement following an exposure to a known risk factor (such as prochlorperazine). Further workup for a possible primary dystonia would have been indicated had the symptoms failed to resolve, been slowly progressive, or returned after discontinuation of the medication. However, removal of the offending drug and treatment with diphenhydramine are appropriate for secondary dystonia. For more information, visit www.dystonia-foundation.org.