Comorbid pathologies and their impact on progressive supranuclear palsy: current view

Progressive supranuclear palsy, a four-repeat tauopathy, is clinically characterized by early postural instability and falls, vertical supranuclear palsy, levodopa poorly-responsive parkinsonism, pseudobulbar palsy, and cognitive impairment. It is morphologically featured by accumulation of hyperphosphorylated tau protein in neurons and glia predominantly in the basal ganglia, brainstem tegmentum and frontal cortex, associated with degeneration of the extrapyramidal system and cortical atrophy. Isolated PSP neuropathology is uncommon, with nearly 70% showing co-neuropathologies including Alzheimer-type, Lewy body, TDP-43 pathologies, argyrophilic grains, and other tauopathies and neurodegenerative disorders (Parkinson disease, amyotrophic lateral sclerosis). The most common comorbid conditions are hypertension, cardiovascular and cerebrovascular diseases, diabetes mellitus, polyneuropathies, muscular and urological disorders. Due the increased prevalence of comorbidities and their eminent impact on the progress and outcome of the disease, clinical trials should account for them in their design and selection. However, currently little is known about co-pathologies in these patients. In view of the eminent burden of comorbidities and resulting therapeutic consequences, the frequency of the different co-pathologies in PSP and their clinical impact will be discussed. It should provide insight into their pathogenic backgrounds as a basis for adequate treatment procedures to improve the quality of life of patients with this fatal disease.