Corticobasal Degeneration

Corticobasal degeneration (CBD) is a 4 repeat tauopathy causing asymmetric cortical and basal ganglia dysfunction.

• Corticobasal syndrome (CBS) is the clinical syndrome, and pathologically heterogeneous (CBD, PSP, Alzheimer disease, FTLD-TDP).

• Prevalence 5 per 100,000; onset 60 to 70 years; median survival 6 to 8 years.

• Features include apraxia, alien limb phenomenon, cortical sensory loss.

• Asymmetric rigidity, bradykinesia, dystonic posturing of one hand/limb, limb apraxia, myoclonus, tremor.

• Alien limb phenomenon, cortical sensory loss (agraphaesthesia), neglect.

• Speech: nonfluent aphasia, apraxia of speech; frontal executive dysfunction.

• Eye movement abnormalities (vertical saccade slowing), falls, dysphagia.

• Clinical criteria (Armstrong): probable CBS with asymmetric motor and cortical features.

• MRI: asymmetric frontoparietal atrophy; FDG PET: asymmetric hypometabolism; DaTscan reduced asymmetrically.

• CSF Alzheimer biomarkers and amyloid PET to identify Alzheimer pathology presenting as CBS.

• Exclude stroke, tumour, Creutzfeldt-Jakob disease, Parkinson disease, PSP, frontotemporal dementia.

• Genetic testing (MAPT, GRN, C9orf72) in family history.

• Symptomatic care, with no disease modifying therapy.

• Levodopa/carbidopa trial up to 600 to 1000 mg daily (poor response); amantadine.

• Myoclonus: clonazepam 0.5 to 2 mg, levetiracetam 500 to 1500 mg twice daily, valproate.

• Dystonia: botulinum toxin; baclofen.

• Cognitive and behavioural symptoms: SSRIs; cholinesterase inhibitors if Alzheimer pathology.

• Multidisciplinary rehabilitation: occupational therapy, speech therapy, falls prevention, swallowing assessment.

• Palliative care.