To the Editor: I thank Dr. Rasmussen and Dr. Francis and his colleagues for raising important issues in relation to our study. For the diagnosis of catatonia, we needed the presence of one of the following: mutism, extreme negativism, peculiarities of voluntary movement (posturing, waxy flexibility, and so forth) or echophenomena. Excessive and purposeless motor activity was in itself not sufficient for this purpose, since we considered establishing "purposelessness" to be an unreliable exercise and excessive motor activity to be a common feature of many psychiatric disorders. Such an approach would underdiagnose catatonic excitement, which we accepted as a limitation of a retrospective study. Catatonia was diagnosed in 11 subjects (44%) with neuroleptic malignant syndrome but in only two comparison subjects (4%) in our study. Catatonia was, however, present before the onset of neuroleptic malignant syndrome in only one subject from the neuroleptic malignant syndrome group.Our data, therefore, do not permit us to comment on catatonia as a possible risk factor for the development of neuroleptic malignant syndrome as has been suggested elsewhere R6415511CHDBAAAJ. We acknowledge that catatonia is an important manifestation of neuroleptic malignant syndrome, and lethal catatonia R6415511CHDBADAJ may be indistinguishable from a severe case of neuroleptic malignant syndrome. The overlap does suggest some common features in the pathophysiology, but until we understand the pathogenesis of catatonic withdrawal and how that may differ from excitement, this similarity will not yield new insights. That the presence of catatonia may be a risk factor for neuroleptic malignant syndrome is worth examining further, however, as it may urge us to use alternative treatments such as ECT.

The finding of previous ECT as a risk factor for neuroleptic malignant syndrome has excited comment from both groups. In our article, we resisted the temptation to speculate on this finding until it had been confirmed independently. We agree with Dr. Rasmussen that it is, at best, an association that possibly flags the characteristics of the primary psychiatric disorder that prompted treatment with ECT. A prominence of affective symptoms (manic or depressive) or catatonia in the histories of these individuals is distinctly possible, but we cannot present satisfactory data to examine either. Future studies should pay attention to these possibilities.