[Progressive supranuclear palsy; an unusual form of parkinsonism].

Progressive supranuclear palsy is a neurodegenerative disorder accompanied by parkinsonism, disturbances of eye movements, pseudobulbar palsy and often cognitive decline. Onset of disease is usually between 50-70 years of age and mean survival is 5-8 years. The prevalence of PSP has been estimated at around 5 per 100,000, although exact figures for the population of the Netherlands are not yet available. International consensus criteria differentiate between possible, probable and definite PSP; the latter requiring neuropathological confirmation. An extensive differential diagnosis may be made early in the course of the disease, but at a later stage development of the characteristic symptoms will make diagnosis easier. Imaging techniques can lend support to the clinical diagnosis to a limited extent, although they lack sufficient specificity to confirm it. PSP is a 'tauopathy' characterized by aggregates of abnormal tau protein in the basal ganglia and brainstem. Some mutations in the tau gene can cause a clinical and pathological picture similar to that of PSP, although most patients with sporadic and familial PSP do not have tau mutations. Various studies have found a strong association between PSP and a specific tau haplotype (H1 haplotype), but its role in the pathophysiological mechanism of PSP is still unclear and needs further research.