Visuoperceptual Ability Test Effectively Determines Dementia with Lewy Bodies, Alzheimer Disease

The use of the Fragmented Letters Test, a widely-used clinical test that measures visual perception, is an effective way to distinguish between patients with Alzheimer disease (AD) and those with dementia with Lewy bodies, according to a recent study.

Currently, there is no way to determine whether someone with mild or moderate dementia has cognitive impairment due only to AD pathology or to a combination of AD and Lewy body pathology.  Dementia with Lewy bodies is the second most common form of progressive dementia after AD. The researchers aimed to discover whether the Fragmented Letters Test effectively differentiated patients with autopsy-confirmed Lewy bodies or AD, and correlated with the severity of Lewy bodies.

For their study, the researchers had patients with mild-to-moderate dementia (n = 42) and people who were not diagnosed with dementia (n = 22) perform a Fragmented Letter Test. Participants were asked to identify letters of the alphabet that were randomly visually degraded by 70%, along with additional visuospatial and episodic memory tests. Further, at autopsy, participants were confirmed to either have dementia cases of Lewy bodies (n = 19), all with concomitant AD, or only AD (n = 23).

Participants diagnosed with Lewy bodies performed worse on the Fragmented Letter Test when compared with participants with AD and those not diagnosed with dementia.

“Fragmented Letters Test performance can effectively differentiate patients with Lewy bodies pathology from those with only AD pathology at a mild to moderate stage of dementia, even when Lewy bodies occurs with significant concomitant AD pathology, and may also be useful for gauging severity of cortical α-synuclein pathology in those with LBD,” the researchers concluded.

While these results are promising, the authors noted that the study is small and further investigation with a clinic-based population is needed to determine how other comorbidities may impact the efficacy of the visual test.


—Jessica Ganga


Salmon DP, Smirnov DS, Coughlin DG, et al. Perception of fragmented letters by patients with pathologically confirmed dementia with Lewy bodies or Alzheimer disease. Neurology. Published online August 26, 2022. doi:10.1212/WNL.0000000000201068