Corticobasal Syndrome (Clinical Subtypes)

Corticobasal syndrome (CBS) is the umbrella clinical term for an asymmetric akinetic-rigid syndrome with cortical features. The classic motor presentation includes asymmetric limb rigidity, bradykinesia, dystonia, focal myoclonus, postural instability, and ideomotor or limb-kinetic apraxia. Cortical features are alien limb phenomenon, cortical sensory loss, and visuospatial dysfunction.

Underlying pathology is heterogeneous: corticobasal degeneration (CBD) tauopathy in 50 percent, but also progressive supranuclear palsy, Alzheimer's disease, frontotemporal lobar degeneration with TDP-43, Pick's disease, and rarely Creutzfeldt-Jakob disease. Subtype phenotypes include CBS-CBD (classic motor), CBS-PSP (early postural instability and vertical gaze palsy), CBS-AD (early amnestic features), CBS-bvFTD (behavioral variant frontotemporal), and CBS-PNFA (progressive nonfluent aphasia).

Diagnosis is clinical (MDS criteria 2013) supported by brain MRI showing asymmetric perirolandic atrophy, FDG-PET showing asymmetric hypometabolism, amyloid and tau PET to differentiate underlying proteinopathy, and CSF biomarkers. Management is symptomatic with levodopa (limited response), botulinum toxin for dystonia, anticholinergics for sialorrhea, speech therapy, occupational therapy, and disease-specific approaches for AD or PSP variants.