Loss of Swallow Tail Sign on Susceptibility-Weighted Imaging in Dementia with Lewy Bodies.

We assessed nigral dorsolateral hyperintensity (swallow tail sign) at susceptibility-weighted imaging using 3T-MRI in 15 dementia with Lewy bodies (DLB), 11 Alzheimer's disease (AD), and 8 frontotemporal dementia (FTD) patients and 10 subjects with subjective memory complaint (SMC). More DLB patients lacked nigral hyperintesity (p < 0.05). Sensitivity, specificity, and accuracy of DLB diagnosis were, respectively: 80%, 64%, and 73% versus AD; 80%, 75%, and 78% versus FTD; and 80%, 90%, and 84% versus SMC. Considering bilateral loss, sensitivity decreased (53%) but specificity increased (82-100%). Swallow tail sign loss, especially if bilateral, can be useful for DLB diagnosis.