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View Count: 169 |  Publish Date: March 19, 2013
AAN: DaTscan Imaging May Improve Dementia Dx (CME/CE)
AAN: DaTscan Imaging May Improve Dementia DxByJohn Gever, Senior Editor, MedPage TodayPublished: March 19, 2013ReviewedbyRobert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San FranciscoAction PointsThis study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.Differential diagnosis of dementia in patients with equivocal clinical presentations may be sharpened with an imaging technique recently approved for differential diagnosis of Parkinsons disease versus essential tremor.Note that SPECT imaging with a radioactive iodine-based tracer distinguished patients with Lewy body dementia and non-amnestic mild cognitive impairment (MCI) from those with Alzheimers disease and amnestic MCI in a pilot study.
SAN DIEGO -- Differential diagnosis of dementia in patients with equivocal clinical presentations may be sharpened with an imaging technique recently approved for other purposes, a researcher said here.
SPECT imaging with a radioactive iodine-based tracer -- sold under the name DaTscan -- distinguished patients with Lewy body dementia and non-amnestic mild cognitive impairment (MCI) from those with Alzheimers disease and amnestic MCI in a pilot study, said Bradley Boeve, MD, of the Mayo Clinic in Rochester, Minn.
Boeve, who presented the findings at the American Academy of Neurologys annual meeting, told MedPage Today that the technique could be helpful in cases that are currently difficult to diagnose correctly.
Among them would be patients with cognitive impairments consistent with Alzheimers disease, but who dont show heavy burdens of beta-amyloid protein plaques on PET scans. Low DaTscan scores in such patients would point to Lewy body dementia or non-amnestic MCI, according to the Mayo study result,
By the same token, in patients with symptoms not like those normally seen in Alzheimers disease, but with PET scans showing substantial amyloid plaques, high DaTscan scores would support an Alzheimers disease diagnosis.
DaTscan involves an injection of an iodine-123 compound called ioflupane prior to SPECT imaging. The tracer binds selectively to dopamine transporter molecules in the striatum, and was approved last year for the differential diagnosis of Parkinsons disease versus essential tremor.
Boeve and colleagues hypothesized that DaTscan results would also differ among patients with various kinds of dementias, insofar as Lewy body dementia is also marked by dopamine deficiency whereas Alzheimers disease is not.
In the current study, they recruited 25 patients with four types of cognitive impairments diagnosed clinically: Lewy body dementia (12 patients), Alzheimers disease (five patients), and amnestic and non-amnestic MCI (three and five patients, respectively). All but two of the participants were men; the mean age was 71.
The clinical diagnoses were reached in part on the basis of REM sleep behavioral disorder, which is common with Lewy body disorder and non-amnestic MCI but uncommon in the other two conditions. Amnestic MCI is often a precursor to full-blown Alzheimers disease and, in such cases, shares the same underlying pathology.
DaTscan imaging in the study was performed with identical region-of-interest parameters for the left and right putamen and for the ipsilateral occipital cortical tissue. Scores were based on the means of the ratios of putamen to occipital tissue tracer uptake for the left and right sides (mPOR).
Mean mPOR scores for each diagnostic group were as follows: Alzheimers disease: 2.59 (standard deviation 0.57) Lewy body dementia: 1.27 (SD 0.27) Amnestic MCI: 2.33 (SD 0.24) Non-amnestic MCI: 1.80 (SD 0.57)
An mPOR cutoff of 2.1 separated the Lewy body dementia and non-amnestic MCI patients almost perfectly from those with Alzheimers disease and amnestic MCI. All patients in the latter two groups were above it and all the Lewy body dementia patients were below it. However, one non-amnestic MCI patient had a score of exactly 2.1 and one other was above the cutoff.
Boeve emphasized that the study was too small to determine conclusively that DaTscan imaging would be clinically valuable in the differential diagnosis of dementia. He told MedPage Today that it would take a study of hundreds of patients to validate the mPOR cutoff of 2.1 and to establish classification accuracy.
He also noted that few women were included in the pilot study which was a significant limitation.
The study was funded by GE Healthcare (maker of DaTscan), the National Institute on Aging, and charitable foundations.
Boeve reported relationships with GE Healthcare, Allon, and Cephalon.
Primary source: American Academy of Neurology Source reference: Boeve B, et al DaTscan findings in patients with mild cognitive impairment, Alzheimers Disease and dementia with Lewy bodies AAN 2013; Abstract IN3-1.008. This meeting news coverage is provided to AAN members and partners as a service. In some cases, links appearing in this newsletter may lead to the website of our Conference Reporter partner, MedPage Today, and are considered external resources. External Resources are not a part of the AAN.com website and are subject to the terms and conditions of the Conference Reporter partners website. AAN is not responsible for the content of sites that are external to the AAN. Linking to a website does not constitute an endorsement by AAN of the sponsors or advertisers of the site or the information presented on the site. In addition, please note that content appearing outside of AANs own website, AAN.com, is not subject to the same editorial review process and policies outlined on AAN.com. For clarification of ACCs official positions and policies, we refer you to AAN.com.
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