Temporoparietal hypometabolism in frontotemporal lobar degeneration and associated imaging diagnostic errors.

Abstract

OBJECTIVE:

To evaluate the cause of diagnostic errors in the visual interpretation of positron emission tomographic scans with fludeoxyglucose F 18 (FDG-PET) in patients with frontotemporal lobar degeneration (FTLD) and patients with Alzheimer disease (AD).

DESIGN:

Twelve trained raters unaware of clinical and autopsy information independently reviewed FDG-PET scans and provided their diagnostic impression and confidence of either FTLD or AD. Six of these raters also recorded whether metabolism appeared normal or abnormal in 5 predefined brain regions in each hemisphere-frontal cortex, anterior cingulate cortex, anterior temporal cortex, temporoparietal cortex, and posterior cingulate cortex. Results were compared with neuropathological diagnoses.

SETTING:

Academic medical centers.

PATIENTS:

Forty-five patients with pathologically confirmed FTLD (n=14) or AD (n=31).

RESULTS:

Raters had a high degree of diagnostic accuracy in the interpretation of FDG-PET scans; however, raters consistently found some scans more difficult to interpret than others. Unanimity of diagnosis among the raters was more frequent in patients with AD (27 of 31 patients [87%]) than in patients with FTLD (7 of 14 patients [50%]) (P=.02). Disagreements in interpretation of scans in patients with FTLD largely occurred when there was temporoparietal hypometabolism, which was present in 7 of the 14 FTLD scans and 6 of the 7 scans lacking unanimity. Hypometabolism of anterior cingulate and anterior temporal regions had higher specificities and positive likelihood ratios for FTLD than temporoparietal hypometabolism had for AD.

CONCLUSIONS:

Temporoparietal hypometabolism in FTLD is common and may cause inaccurate interpretation of FDG-PET scans. An interpretation paradigm that focuses on the absence of hypometabolism in regions typically affected in AD before considering FTLD is likely to misclassify a significant portion of FTLD scans. Anterior cingulate and/or anterior temporal hypometabolism indicates a high likelihood of FTLD, even when temporoparietal hypometabolism is present. Ultimately, the accurate interpretation of FDG-PET scans in patients with dementia cannot rest on the presence or absence of a single region of hypometabolism but rather must take into account the relative hypometabolism of all brain regions.

• Authors: Kyle B Womack, Ramon Diaz-Arrastia, Howard J Aizenstein, Steven E Arnold, Nancy R Barbas, Bradley F Boeve, Christopher M Clark, Charles S DeCarli, William J Jagust, James B Leverenz, Elaine R Peskind, R Scott Turner, Edward Y Zamrini, Judith L Heidebrink, James R Burke, Steven T DeKosky, Martin R Farlow, Matthew J Gabel, Roger Higdon, Claudia H Kawas, Robert A Koeppe, Anne M Lipton, Norman L Foster
• Journal: Archives of neurology (Arch Neurol) Vol. 68 Issue 3 Pg. 329-37 (Mar 2011) ISSN: 1538-3687 [Electronic] United States
• PMID: 21059987 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Radiopharmaceuticals
• Fluorodeoxyglucose F18

Topics

• Adult
• Age of Onset
• Aged
• Alzheimer Disease (diagnostic imaging, metabolism, pathology)
• Brain (pathology)
• Diagnosis, Differential
• Diagnostic Errors
• Female
• Fluorodeoxyglucose F18
• Frontotemporal Lobar Degeneration (diagnostic imaging, metabolism, pathology)
• Humans
• Image Processing, Computer-Assisted
• Male
• Middle Aged
• Neuropsychological Tests
• Observer Variation
• Parietal Lobe (diagnostic imaging, metabolism, pathology)
• Positron-Emission Tomography
• Radiopharmaceuticals
• Reproducibility of Results
• Temporal Lobe (diagnostic imaging, metabolism, pathology)