Neuroleptic malignant syndrome in parkinsonian patients: risk factors.

A syndrome resembling the neuroleptic malignant syndrome (NMS) is known to develop occasionally following interruption of dopaminergic medications in patients with Parkinson's disease. However, NMS can develop even without withdrawal of antiparkinsonian drugs. In parkinsonian patients who continually received dopaminergic medications, the development of NMS occurred exclusively in warm seasons, May to August. The development of NMS could occur at any season in association with the cessation of dopaminergic drugs. A female parkinsonian patient showed two episodes of NMS during the premenstrual period. It is suggested that hot weather or dehydration and aggravation of parkinsonism premenstrually constitute risk factors for the development of NMS, in addition to withdrawal of antiparkinsonian drugs.