Neuroleptic malignant syndrome: long-term follow-up of 20 cases.

The authors obtained long-term follow-up data on 20 (91%) of the 22 patients who had experienced index episodes of neuroleptic malignant syndrome (NMS) at McLean Hospital between 1983 and 1990. Eleven of the 20 patients resumed neuroleptic treatment after the index episode and have now collectively received more than 16 years of neuroleptic exposure with no recurrences of the syndrome. Furthermore, 14 of the 20 patients had already collectively accumulated more than 71 additional years of neuroleptic exposure before their index episodes; only 1 had experienced a possible episode of NMS in the past. These findings suggest that NMS may not predictably develop even in predisposed individuals upon neuroleptic exposure and that additional cofactors must be present for the full syndrome to evolve.