Botulinum toxin in a case of hemimasticatory spasm with severe worsening during pregnancy.

Hemimasticatory spasm (HMS) is a rather uncommon movement disorder with a pathophysiology that is still unclear, although temporomasseter entrapment at the temporal fossa has been advanced. The authors present a case of HMS in a woman who experienced marked worsening in episode frequency and severity during pregnancy. Treatment with botulinum toxin led to marked improvement.