Issn Print: 0143-3636

Publication Date: 2001/03/01


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Comparison of structural and functional imaging in the diagnosis of Alzheimer's, frontotemporal and vascular dementia

A. R. Varma; W. Adams; J. J. Lloyd; J. S. Snowden; D. Neary; H. J. Testa

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Excerpt

Various studies have evaluated the diagnostic value of single photon emission computed tomography (SPECT) in the diagnosis of dementias. It is, however, not clear how SPECT (functional) compares with magnetic resonance imaging (MRI) techniques (sensitive structural).
We compared hexamethylpropylene amine oxime (HMPAO) SPECT with MRI in patients with Alzheimer's disease (AD) (n = 22), frontotemporal dementia (FTD) (n = 21) and vascular dementia (VaD) (n = 18). Regional cerebral blood flow (rCBF) on SPECT and regional atrophy on MRI were rated separately and blindly using a previously described scale. Severe frontal atrophy on MRI and severe frontal rCBF change on SPECT had a similar sensitivity in the diagnosis of FTD. However, severe frontal atrophy on MRI proved more specific (specificity of 0.93) than severe frontal rCBF change on SPECT (specificity of 0.6) in these patients.
Mild parietal atrophy on MRI was sensitive but poorly specific for the diagnosis of AD. In contrast, severe parietal rCBF change on SPECT was more specific for the diagnosis of AD. Although severe parietal rCBF change was common on SPECT, severe parietal atrophy was uncommon in AD.
The recognition of different patterns of atrophy and rCBF changes within a form of dementia and also across various causes of dementias helps in making a diagnosis. These findings also raise important questions regarding the relationship of anatomy (MRI) and dysfunction (SPECT) in patients with dementia.

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