Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 6, 2010, pp. 823-824

Neurology India, Vol. 58, No. 6, November-December, 2010, pp. 823-824

Editorial

The role of single photon emission computed tomography scan in the diagnosis of dementia

PS Mathuranath

Cognition and Behavioral Neurology Section, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
Correspondence Address: P S Mathuranath, Cognition and Behavioral Neurology Section, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum - 695 011, India, mathu@sctimst.ac.in

Code Number: ni10241

PMID: 21150043
DOI: 10.4103/0028-3886.73734

Accurate subtyping of the dementia in the initial couple of years after its onset is the most important initial step in the management of dementia, but is often a challenge. In most instances it requires the expertise of an experienced cognitive neurologist with supportive ancillary investigations, such as detailed neuropsychological tests, which may not be always easily available. Thus it often requires an established setup going beyond the purview of general neurology. Given this situation, any other valid investigation that would assist the clinician in the process of typing the dementia would be welcome. In this issue of the journal Tripathi and colleagues ^[1] report in a well-conducted study the role of visual analysis of Single Photon Emission Computed Tomography (SPECT) in the diagnosis of different types of dementia, at about two and a half years from the onset of the disease, and estimate its validity against the diagnosis made clinically. Although the clinical profile of frontotemporal dementia (FTD) can be more easily differentiated from that of Alzheimer's disease (AD), it is often difficult to clinically distinguish AD from dementia with Lewy bodies (DLB), in the early stages of the disease, when amnesia is the feature in the forefront in both the conditions, and visual hallucination or parkinsonism might not yet have set in, in DLB.

Although the authors have used the older terminology of diffuse Lewy body disease for DLB, they have used fairly well-characterized criteria for the SPECT diagnosis of AD, FTD, DLB and vascular dementia. In addition, the gender distribution, the duration of symptoms and the mini mental status examination scores of all the three groups of AD, FTD and DLB are well matched, suggesting that the validity is being established in a well-matched group of dementia subjects. The authors go on to demonstrate a fairly high sensitivity and specificity of SPECT in the diagnosis of AD and FTD. They also go on to show a high positive predictive value of SPECT thereby suggesting that there is a low false-positive rate. The study could have been further strengthened if the authors had demonstrated that the different groups of dementia were also matched on a measure of the severity of dementia such as Clinical dementia rating. One of the other limitations of the study is that the diagnostic accuracy is rated against the clinical diagnosis. However, it is interesting to note that their sensitivity figures for AD and FTD are somewhat comparable to the sensitivity of SPECT determined against the pathological diagnosis by Mc Neill et al. ^[2]

References

1.	Tripathi M, Tripathi M, Vibha D, Gowda N, Bal C, Malhotra A. Tc-99m ethylcysteinate dimer SPECT in the differential diagnosis of dementias. Neurol India 2010;58:857-62.  Back to cited text no. 1  [PUBMED]
2.	McNeill R, Sare GM, Manoharan M, Testa HJ, Mann DM, Neary D, et al. Accuracy of single-photon emission computed tomography in differentiating frontotemporal dementia from Alzheimer's disease. J Neurol Neurosurg Psychiatry 2007;78:350-5.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]

Copyright 2010 - Neurology India