[Progressive supranuclear palsy: what's new?].

Progressive supranuclear palsy (PSP) has been described as a clinical syndrome characterized by an impairment of voluntary control of gaze (supranuclear palsy), postural and gait instability, and behavioral and cognitive deficits including a frontal syndrome and psychic retardation. However, in the recent years, at least four other clinical forms of PSP have been recognized: PSP-Parkinsonism, "pure akinesia with gait freezing", PSP with cortico-basal syndrome, and PSP with speech apraxia. PSP-Parkinsonism mimics the signs and symptoms of idiopathic Parkinson's disease, including a significant reactivity to levodopa. "Pure akinesia with gait freezing" is characterized by a difficulty of self-initiation of motor programs, usually walking program. PSP with cortico-basal syndrome mimics cortico-basal degeneration (CBD) in that unilateral or asymmetric limb dystonia and apraxia are prominent signs. PSP with speech apraxia is an isolated syndrome of progressive anarthria. All these clinical syndromes are due to brain accumulation of phosphorylated tau protein. The differences in clinical expression within the framework of PSP can be explained by the differences in the topographical distribution of the lesions. PSP is considered as a primary tau disease ("tauopathy") such as CBD and some forms of fronto-temporal lobar degeneration. At the level of neuropathology, the pattern of tau abnormal inclusions differentiates PSP from other tau diseases, but some overlaps are reported. Moreover, several of the clinical forms of PSP partially or fully overlap with the other tauopathies. As a whole, the emergence of new clinical forms of PSP challenges the nosology of tauopathies and our understanding of these diseases.