In Reply.—
We thank Dr Hershey for her interest and comments on our study and for presenting data from her own unpublished observations.As we indicated in our description of the patient population, the 93 patients in the study had been diagnosed and medically treated for Parkinson's disease at The Mount Sinai Parkinson's Disease Clinical Center, New York, by the usual conventional clinical criteria of this disease entity, and did not include known clinical cases of Alzheimer's disease, progressive supranuclear palsy, multi-infarct dementia, normal pressure hydrocephalus, or Creutzfeldt-Jakob disease with a predominantly extrapyramidal presentation. The arbitrary division between so-called typical and atypical cases, made regardless of the mental status evaluation and without previous knowledge of computed tomographic (CT) scan findings, focused on the neurologic motor signs other than those strictly referable to extrapyramidal dysfunction, so that, in effect, the "typical" case of parkinsonism had a "pure" extrapyramidal picture, and the "atypical" case