Accuracy of single-photon emission computed tomography in differentiating frontotemporal dementia from Alzheimer's disease

Abstract

Background: Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the commonest causes of presenile dementia. In the absence of a biological marker, diagnosis is reliant on clinical evaluation. Confirmation is often sought from neuroimaging, including single-photon emission computed tomography (SPECT). Most previous SPECT studies lack pathological validation. Aim: To examine the accuracy of SPECT in differentiating FTD from AD in patients with subsequent pathological confirmation. Methods: Technetium-99-labelled hexamethyl propylene amine oxime SPECT images obtained at initial evaluation in 25 pathologically confirmed cases of FTD were examined. These images were visually rated by an experienced blinded nuclear medicine consultant and compared with those of 31 patients with AD, also with pathological validation. Results: A reduction in frontal cerebral blood flow (CBF) was more common in FTD and was of diagnostic value (sensitivity 0.8, specificity 0.65 and likelihood ratio (LR) 2.25; 95% CI 1.35 to 3.77). A pattern of bilateral frontal CBF reduction without the presence of associated bilateral parietal CBF change is diagnostically more accurate (sensitivity 0.80, specificity 0.81 and +LR 4.13, 95% CI 1.96 to 8.71). Diagnostic categorisation (FTD or AD) on the basis of SPECT alone was less accurate than clinical diagnosis (based on neurology and detailed neuropsychological evaluation). One patient with FTD was initially clinically misdiagnosed as AD, owing to the lack of availability of full neuropsychological assessment. However, SPECT correctly diagnosed this patient, providing a diagnostic gain of 4%. Conclusion: Technetium-99-labelled hexamethyl propylene amine oxime SPECT CBF patterns provide valuable information in the diagnosis of FTD and AD. These data can be better used as an adjunct to clinical diagnosis if pathology is to be correctly predicted in life.

Early Diagnosis of Alzheimer's Disease and Parkinson's Disease Associated with Dementia Using Cerebral Perfusion SPECT

“…Thus, it is difficult to sharply distinguish between PDD and AD using neuropsychological tests, particularly at the early stages [2]. Mild PDD is often misdiagnosed and is commonly confused with mild AD [6]. …”

Frontotemporal Dementias

“…Patterns of frontal or anterior temporal hypoperfusion with preserved parietal signal on SPECT can distinguish FTD from AD with a sensitivity and specificity of approximately 80%. 13 Similar patterns of hypometabolism on FDG-PET imaging show approximately 90% diagnostic accuracy when distinguishing FTD from AD. 14 PET amyloid imaging shows a similarly high accuracy of…”

The Diagnostic Utility of ^99mTc-HMPAO SPECT Imaging: A Retrospective Case Series from a Tertiary Referral Early-Onset Cognitive Disorders Clinic

“…Recently, published guidelines have suggested that SPECT can be used to differentiate between AD, VaD, FTD, and DLB in cases where diagnostic uncertainty exists [27,28]. Individual studies evaluating the diagnostic utility of SPECT imaging, however, have differed in terms of sample size, patient characteristics, clinical diagnostic criteria employed, cognitive testing, and imaging acquisition [17,29]. Studies to date have also focused on the diagnostic utility of SPECT in older adults with AD compared, predominantly, to cognitively unimpaired controls [30].…”