The vast majority of cases are sporadic, although a number of familial cases have been described 2. Patients are usually in the fifth to seventh decades of life5, with the youngest reported case being 40 years of age 3.
Due to its myriad presentations which often crossover with other neurodegenerative condtions, corticobasal degeneration is challenging to diagnose5. The classical "corticobasal syndrome" is a progressive disorder with various asymmetric movement abnormalities, myoclonus, as well as cortical signs including ideomotor apraxia and alien limb phenomenon5. In the broader spectrum of corticobasilar syndrome, patients often present with slowly progressive symptoms and signs including 1,2:
- postural instability
- akinetic-rigid syndrome
- myoclonic jerks
- cognitive impairment, often with pronounced frontal lobe signs 2
- Alien limb phenomenon (believed to be due to supplementary motor area involvement) 1,2,4.
Unlike Parkinson disease, these symptoms are not ameliorated by levodopa 1.
The characteristic histopathological findings are neuronal loss and numerous swollen achromatic neurons 1. Although these features are seen throughout the brain, certain regions are more severely affected. They include:
- frontoparietal cortex
- subcortical structures
- substantia nigra
MRI is the modality of choice for assessing corticobasal degeneration, although similar findings can, only to a certain degree, be seen on CT.
Typical findings include 1-2:
- asymmetric cortical atrophy
- bilateral atrophy of the basal ganglia
- atrophy of the corpus callosum 2
- T2 hyperintensity
- subcortical white matter of affected gyri
- posterolateral putamen
The pattern of atrophy in corticobasilar degeneration may be distinguishable from that of progressive supranuclear palsy. Patients with CBD tend to have atrophy in posteriolateral and medial frontal cortical regions, but relatively preserved brainstem anatomy5.
Research is ongoing regarding the use of techniques such as 3D volumetric MRI and diffusion tensor imaging in the evaluation of CBD5.
SPECT and PET studies tend to demonstrate hypometabolism in the superior parietal and superior frontal areas, as well as (but less frequently) in the basal ganglia and thalamus 2,5.
Treatment and prognosis
There are no current drug therapies available to modify the course of CBD. Treatment is often focused on symptomatic relief, and supportive services such as speech and occupational therapy should not be overlooked5.
Unfortunately, the overall prognosis is poor, with patients demonstrating gradual neurological decline. Death occurs typically 5 to 10 years after the diagnosis is first made 3.
Clinically there is overlap with 1:
- 1. Tokumaru AM, O'uchi T, Kuru Y et-al. Corticobasal degeneration: MR with histopathologic comparison. AJNR Am J Neuroradiol. 17 (10): 1849-52. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 2. Esiri MM, Trojanowski JQ. The neuropathology of dementia. Cambridge Univ Pr. (2004) ISBN:0521819156. Read it at Google Books - Find it at Amazon
- 3. Moretti R. Corticobasal ganglionic degeneration, cognitive and functional aspects. Nova Science Pub Inc. (2005) ISBN:1594543887. Read it at Google Books - Find it at Amazon
- 4. Tiwari D, Amar K. A case of corticobasal degeneration presenting with alien limb syndrome. Age Ageing. 2008;37 (5): 600-1. doi:10.1093/ageing/afn103 - Pubmed citation
- 5. Grijalvo-Perez AM and I Litvan. Corticobasal Degeneration. Semin Neurol. 2014;34 (02): 160–73. . doi:10.1055/s-0034-1381734.
Neurodegenerative diseases are legion and their classification just as protean. A useful approach is to divide them according to underlying pathological process, although even using this schema, there is much overlap and thus resulting confusion.
neurodegenerative MRI brain (an approach)
- measurements and ratios
- midbrain to pons area ratio (for PSP)
- Magnetic Resonance Parkinsonism Index (MRPI) (for PSP)
- frontal horn width to intercaudate distance ratio (FH/CC) (for Huntington disease)
- intercaudate distance to inner table width ratio (CC/IT) (for Huntington disease)
- scoring systems
- measurements and ratios
- typical/classical Alzheimer disease
- variant (e.g. posterior cortical atrophy)
- chronic traumatic encephalopathy (CTE)
- corticobasal degeneration
- frontotemporal lobar degeneration (FTLD) (not all are tau)
- Pick disease
- progressive supranuclear palsy (PSP)
- Alzheimer disease
- cerebral amyloidosis
- spinocerebellar ataxias
- Huntington disease
- hereditary spastic paraplegia
- amyotrophic lateral sclerosis (ALS)
- clinically unclassifiable parkinsonism (CUP)
- Unverricht-Lundborg disease
- prion diseases (not always included as neurodegenerative)