🧠 Corticobasal Degeneration (CBD) is a rare adult-onset neurodegenerative disorder, classed within atypical parkinsonism and the spectrum of frontotemporal lobar degeneration (FTLD).
It often begins with asymmetrical motor symptoms and progresses to include cognitive, behavioural, and language decline.
A hallmark sign is the alien limb phenomenon – where a limb seems to act independently.
📌 About
- Also called Corticobasal Ganglionic Degeneration (CBGD).
- A tauopathy — abnormal accumulation of tau protein in neurons and glia.
- Shares pathology with progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD).
- Combines parkinsonism, dystonia, myoclonus, cognitive impairment, and language dysfunction.
⚠️ Aetiology & Pathology
- Tauopathy: abnormal tau protein deposits disrupt neuronal function.
- Key regions affected:
- Nigrostriatal pathways
- Thalamus, subthalamic nucleus, globus pallidus
- Red nucleus and dentate nucleus
- Histology: ballooned neurons and tau-positive inclusions in cortex and basal ganglia.
🩺 Clinical Features
- Asymmetrical parkinsonism: rigidity, bradykinesia (tremor less common than in Parkinson’s disease).
- Alien limb phenomenon: limb moves involuntarily, sometimes interfering with tasks.
- Dystonia: abnormal postures, especially hand clenched with flexed thumb.
- Myoclonus: jerky limb movements.
- Supranuclear gaze palsy: impaired voluntary vertical/horizontal gaze (overlaps with PSP).
- Cognitive & Speech: progressive non-fluent aphasia, apraxia, dementia, behavioural change (disinhibition, depression, emotional blunting).
- Other: postural instability, dysphagia, sensory deficits.
🔬 Investigations
- Bloods: FBC, U&E, ESR/CRP, LFT, TFT, B12, folate – exclude secondary causes.
- MRI: asymmetric frontoparietal cortical atrophy (contralateral to affected side).
- PET/FDG-PET: parietal hypometabolism, reduced fluorodopa uptake in basal ganglia.
- DaTscan (SPECT): abnormal uptake, helps distinguish from idiopathic Parkinson’s disease.
- Neuropsychological tests: memory, executive function, and language deficits.
💊 Management
- Supportive care: MDT approach (neurologist, physiotherapy, speech therapy, OT).
- L-Dopa: trial often ineffective or only transient benefit.
- Behavioural symptoms: quetiapine or other atypical antipsychotics (used cautiously).
- Dystonia/myoclonus: clonazepam, baclofen, valproate, or botulinum toxin.
- Mood disorders: SSRIs for depression or anxiety.
- Speech therapy: vital for dysphasia and swallowing; PEG feeding may be required in advanced stages.
- End-of-life care: focus on comfort, aspiration prevention, and mobility support.
📉 Prognosis
- Steadily progressive neurodegenerative course.
- Median survival: ~6–8 years after onset.
- Mortality often from pneumonia, aspiration, or immobility-related complications.
