Some researchers and physicians consider the differentiation between cortical and sub-cortical dementia important for patient diagnosis, but others remain skeptical that a significant difference exists. The major criticism of the studies that show variation between cortical and sub-cortical dementias is that there is pathological overlap between the sample groups that are used to model the two categories. These studies often assume that Alzheimer's patients mostly have cortical dementia and HD or Parkinson's patients preferentially exhibit subcortical dementia. Necropsies have shown, however, that the brains of both Alzheimer's and HD patients exhibit a certain degree of both categories of dementia.
If in fact both cortical and subcortical dementia occur in Alzheimer's, HD, and Parkinson's patients, then these studies may be problematic. As a result, physicians are still trying to learn more about the differences between the pathologies of the diseases in hopes of finding a more reliable way of differentiating dementias. The ability to differentiate dementias may lead researchers and physicians to better diagnose and treat neurodegenerative diseases.
- T. Wang, 5/17/09
Further reading
Langbehn, Douglas R. et al. "Predictors of diagnosis in Huntington disease." Neurology. 2007; 68: 1710-1717.
Researchers and The Huntington Study Group performed a longitudinal study to identify early clinical symptoms that arise in HD patients. Findings showed that psychological performance can be used in diagnosis along with motor impairment. There is a thorough discussion of clinical evaluation of neurological performance in HD patients and the types of tests administered to patients.
Rosser, Anne and John R. Hodges. "Initial letter and semantic category fluency in Alzheimer's disease, Huntington's disease and progressive supranuclear palsy." Journal of Neurology, Neurosurgery and Psychiatry 1994; 57: 1389-1394.
This study examined symptoms related to semantic and episodic memory in three different neurodegenerative diseases. Several neuropsychological tests were administered to patients and the results suggested that semantic memory is more heavily influenced in cortical dementias like Alzheimer's disease.
Sadek, Joseph R. et al. "Retrograde Amnesia in Dementia: Comparison of HIV-Associated Dementia, Alzheimer's Disease, and Huntington's Disease." Neuropsychology, 2004; 18.4: 692-699.
This study tested how three different types of dementia affect memory. The findings show that overall dementia is equally severe in all three types, but memory impairment differs. Time-dependent memory loss was not found in HD patients and HD patients were able to improve on memory tasks under "cued" conditions. The authors discuss their findings in the context of the debate on how cortical and subcortical dementias differ.
Wedderburn, C et al. "The utility of the Cambridge Behavioural Inventory in neurodegenerative disease." Journal of Neurology, Neurosurgery, and Psychiatry. 2008; 79: 500-503.
A review of a new test that is used to evaluate the mental condition of patients with neurodegenerative diseases. It includes helpful information about cognitive and psychological symptoms in HD, Parkinson's and Alzheimer's patients and how these symptoms differ between the diseases.
Additional Resources:
Ho AK, Sahakian BJ, Brown RG, Barker RA, Hodges JR, Ane MN, Snowden J, Thompson J, Esmonde T, Gentry R, Moore JW, Bodner T (2003) "Profile of cognitive progression in early Huntington's disease." Neurology 61:1702-1706.
Kirkwood SC, Siemers E, Hodes ME, Conneally PM, Christian JC, Foroud T (2000) "Subtle changes among presymptomatic carriers of the Huntington's disease gene." J Neurol Neurosurg Psychiatry 69:773-779.
Lawrence A, Hodges J, Rosser A, Kershaw A, French-Constant C, Rubinsztein D, Robbins T, BJ S (1998) "Evidence for specific cognitive deficits in preclinical Huntington's disease." Brain Pathol 121:1329-1341.
Lemiere J, Decruyenaere M, Evers-Kiebooms G, Vandenbussche E, Dom R (2004) "Cognitive changes in patients with Huntington's disease (HD) and asymptomatic carriers of the HD mutation—a longitudinal follow-up study." J Neurol 251:935-942.
Meade, Catherine E. "Diagnosing Dementia: mental status testing and beyond." Australian Prescriber, 2005 (28): 11-13.
Savla, Gauri Nayak and Barton W. Palmer. "Neuropsychology in Alzheimer's disease and other dementia research." Current Opinions in Psychiatry, 2005 (18): 621-627.
Last Modified: 05/22/2009
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