A neurodegenerative disease is a blanket term encompassing a wide variety of disorders, typically slowly progressive, with variable gradual neurologic dysfunction.
Over the years numerous classifications schemas have been described, each adding a layer of confusion for students. The main distinction to be aware of is classifications according to clinical presentation and those relying on underlying pathological processes. As expected earlier descriptions were primarily of the former, whereas as more and more neurodegenerative disease are understood at a biochemical level, classifications have shifted towards focusing on these changes.
As such a useful approach is to divide them according to underlying pathological process, although even so there is much overlap and confusion with many clinical patterns being caused by different pathological process and each pathology possibly manifesting in a number of clinical patterns 1,5. What is worse is that as definitive diagnosis currently necessitates histological diagnosis of brain tissue (either antemortum biopsy or postmortum assessment) the actual diagnosis in most cases is never established, further polluting the published data.
Dividing neurodegenerative disease by the main pathological process involved results in the classification below (under "related articles").
It should be noted that any such classification is by the very nature of the heterogeneity of the included conditions, not always felt to be complete. For the purpose of this section diseases that are primarily metabolic in origin, are excluded. See primary metabolic encephalopathies.
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)
- 1. Kornienko VN, Pronin IN. Diagnostic Neuroradiology. Springer Verlag. (2008) ISBN:3540756523. Read it at Google Books - Find it at Amazon
- 2. Duff K, Suleman F. Transgenic mouse models of Alzheimer's disease: how useful have they been for therapeutic development? Brief Funct Genomic Proteomic. 2004;3 (1): 47-59. doi:10.1093/bfgp/3.1.47 - Pubmed citation
- 3. Lindberg O, Ostberg P, Zandbelt BB et-al. Cortical morphometric subclassification of frontotemporal lobar degeneration. AJNR Am J Neuroradiol. 2009;30 (6): 1233-9. doi:10.3174/ajnr.A1545 - Pubmed citation
- 4. Adlam AL, Patterson K, Rogers TT et-al. Semantic dementia and fluent primary progressive aphasia: two sides of the same coin? Brain. 2006;129 (Pt): 3066-80. doi:10.1093/brain/awl285 - Pubmed citation
- 5. Galton CJ, Patterson K, Xuereb JH et-al. Atypical and typical presentations of Alzheimer's disease: a clinical, neuropsychological, neuroimaging and pathological study of 13 cases. Brain. 2000;123 Pt 3 : 484-98. doi:10.1093/brain/123.3.484 - Pubmed citation
- 6. Gorno-Tempini ML, Hillis AE, Weintraub S et-al. Classification of primary progressive aphasia and its variants. Neurology. 2011;76 (11): 1006-14. Neurology (full text) - doi:10.1212/WNL.0b013e31821103e6 - Free text at pubmed - Pubmed citation