Progressive Supranuclear Palsy and Corticobasal Degeneration

Abstract

Abstract Progressive supranuclear palsy (PSP) is the second most common form of neurodegenerative parkinsonism after idiopathic Parkinson’s disease. Patients most often present with an insidious change in balance, personality, or cognitive function that characteristically leads to severe postural instability, vertical supranuclear gaze palsy, and death within seven or eight years; this classic clinical presentation is now know as Richardson syndrome (also Steele–Richardson–Olszewski syndrome). Less commonly, patients present with bradykinesia and rigidity (PSP–parkinsonism) which is only later followed by the emergence of falls, eye movement abnormalities, and cognitive impairment; others may present with pure akinesia and gait freezing (PSP–PAGF), corticobasal syndrome (PSP–CBS), or progressive non-fluent aphasia (PSP–PNFA). The characteristic neuropathological findings of abnormal accumulations of neurofibrillary tau protein in the subthalamic nucleus and other brainstem regions define the disease, and because of these findings PSP is included amongst the primary ‘tauopathies’. Corticobasal degeneration (CBD) is another rarer tauopathy characterized by the accumulation of neurofibrillary and oligodendroglial tau in the cortex and basal ganglia. The classic ‘motor’ presentation of CBD is known as ‘corticobasal syndrome’: a combination of limb apraxia, cortical sensory loss, alien limb, focal myoclonus, and limb dystonia, as well as rigidity and bradykinesia that do not respond to dopaminergic medications. Corticobasal syndrome is not specific to CBD and is also known to occur in other diseases such as PSP, Alzheimer’s diseas,e and the frontotemporal dementias. The ‘cognitive’ presentation of CBD typically includes behavioural disturbance, including personality change and executive dysfunction, and progressive non-fluent aphasia. There is some clinical and pathological overlap between these two conditions, and progressive decline over six to twelve years is usual in both. There are no disease-modifying therapies for PSP or CBD, and treatment is focused on optimizing independence, minimizing the complications of the advancing parkinsonism, and supporting care-givers.