In 1964 Steele et al. An estimated 4 percent of patients seen at a center for Parkinson's disease had progressive supranuclear palsy rather than Parkinson's disease. Several sets of criteria have been proposed for the clinical diagnosis of progressive supranuclear palsy. The finding of axial dystonia on extension strongly supports the diagnosis. Most patients with progressive supranuclear palsy have little or no tremor and a poor response to levodopa.
Opinions vary as to whether certain features are required for or only support the diagnosis.
Bradykinesia is considered an important diagnostic criterion. Supranuclear gaze palsy is required by all authorities, even though occasional cases in which it was not detected have been diagnosed on the basis of pathological findings. Since the upward gaze is commonly impaired in older patients, the impaired downward gaze in this patient is the important feature. Although cervical dystonia on extension is also considered an important diagnostic feature, it is generally absent early in the course of the disease, and in one study it was seen in only 5 percent of the cases. Several cases have met all the clinical criteria for progressive supranuclear palsy, but the pathological findings led to a different diagnosis.