[Progressive supranuclear palsy]

Progressive supranuclear palsy (PSP) is a parkinsonian syndrome 20 to 30 times less common than Parkinson's disease. PSP and Parkinson's disease share certain symptoms, but also present distinctive features. The histopathological features of PSP are highly specific and enable certain diagnosis. Since no biological marker has been identified, clinical signs must be recognized to establish the probability of the histopathological diagnosis. The NINDS program distinguishes two categories: probable PSP and possible PSP with distinctive characteristics. The sensitivity of probable PSP is only 50 p. 100, but the specificity and positive predictive value are 100 p. cent. For possible PSP, specificity is 83 p. cent (93 p. cent if diagnostic errors are included) and the positive predictive value is lower (83 p. cent). Although there number is smaller, patients with probable PSP are retained for research on new treatments. There have been few, non-controlled therapeutic trials in PSP. No drug and no surgical procedure has been demonstrated to be highly effective. Neuroprotection is a new avenue of research which requires knowledge of the natural course of clinical incapacity. A longitudinal study of 50 patients with probable PSP has provided mid-term results on symptom onset and on the development of three key signs, detected with the standard Unified Parkinson's Disease Rating Scale: incapacity to stand alone without help, incapacity to speak intelligently, incapacity to eat (tube feeding). The Kaplan-Meier curves show that the mean duration of the disease before development of one of these signs is 50 months. Research on protocols designed to stop disease progression should be centered on this period.