June 2019 By PsychDB.com

Corticobasal Degeneration (CBD)

Corticobasal Degeneration (CBD) is an neurodegenerative disorder, classified as an atypical parkinsonian syndrome (also known as one of the Parkinson's-plus syndromes). CBD was previously classified as a progressive asymmetric movement disorder characterized by akinesia, rigidity, dystonia, focal myoclonus, ideomotor apraxia, and/or alien-limb phenomena. However, it is increasingly seen as a disorder with cognitive and behavioural disturbances as well. The diagnosis of CBD remain challenging because there is considerable overlap between CBD pathology and other neurodegenerative disorders including progressive supranuclear palsy (PSP), Alzheimer's Disease (AD), and frontotemporal dementia.

Corticobasal Syndrome (CBS)

Since CBD pathology overlaps with other neurodegenerative disorders, it is helpful to first think of CBD on spectrum of neurodegenerative syndromes. The term Corticobasal Syndrome (not Corticobasal Degeneration), includes other neurodegenerative disorders such as progressive supranuclear palsy (PSP), Alzheimer's Disease (AD), and frontotemporal dementia (FTD) pathology.

Proposed clinical phenotypes (syndromes) associated with the pathology of corticobasal degeneration

Armstrong, Melissa J., et al. Criteria for the diagnosis of corticobasal degeneration. Neurology 80.5 (2013): 496-503.
Syndrome Features
Probable corticobasal syndrome Asymmetric presentation of 2 of: a) limb rigidity or akinesia, b) limb dystonia, c) limb myoclonus plus 2 of: d) orobuccal or limb apraxia, e) cortical sensory deficit, f) alien limb phenomena (more than simple levitation)
Possible corticobasal syndrome May be symmetric: 1 of: a) limb rigidity or akinesia, b) limb dystonia, c) limb myoclonus plus 1 of: d) orobuccal or limb apraxia, e) cortical sensory deficit, f) alien limb phenomena (more than simple levitation)
Frontal behavioral-spatial syndrome Two of: a) executive dysfunction, b) behavioral or personality changes, c) visuospatial deficits
Nonfluent/agrammatic variant of primary progressive aphasia Effortful, agrammatic speech plus at least one of: a) impaired grammar/sentence comprehension with relatively preserved single word comprehension, or b) groping, distorted speech production (apraxia of speech)
Progressive supranuclear palsy (PSP) syndrome Three of: a) axial or symmetric limb rigidity or akinesia, b) postural instability or falls, c) urinary incontinence, d) behavioral changes, e) supranuclear vertical gaze palsy or decreased velocity of vertical saccades

Corticobasal Degeneration (CBD)

After thinking about the spectrum of symptoms that a patient may have, and ruling out other diagnoses on the differential, the following criteria can be used, as proposed by the 1st International CBD Investigators Meeting in 2013.[1]

Diagnostic Criteria for Corticobasal Degeneration

Armstrong, Melissa J., et al. Criteria for the diagnosis of corticobasal degeneration. Neurology 80.5 (2013): 496-503.
Clinical research criteria for probable sporadic CBD Clinical criteria for possible CBD
Presentation Insidious onset and gradual progression Insidious onset and gradual progression
Minimum duration of symptoms (year) 1 1
Age at onset (year) ≥ 50 No minimum
Family history (2 or more relatives) Exclusion Permitted
Permitted phenotypes (see previous table for criteria) 1) Probable CBS or 2) FBS or NAV plus at least one CBS feature (a–f) 1) Possible CBS or 2) FBS or NAV or 3) PSPS plus at least one CBS feature b–f
Genetic mutation affecting tau (e.g. - MAPT) Exclusion Permitted

Pathological findings in CBD patients have shown astrocytic abnormalities in the brain as well as accumulation of tau protein. Thus, CBD is considered a tauopathy.

There is a broad differential diagnosis for CBD, because there is considerable overlap between CBD pathology and progressive supranuclear palsy (PSP), Alzheimer's Disease (AD), and frontotemporal dementia (FTD) pathology.

    • Subsequent emergence of asymmetric motor/sensory signs, hyperreflexia, gait abnormalities, parkinsonism, falls, urinary incontinence, and extraocular movement abnormalities may suggest a CBD over AD, especially if ther are more than three of these signs and symptoms[2]