Spatial orientation - a stable marker for vascular cognitive impairment?

Abstract

Vascular cognitive impairment (VCI) is the second most prevalent form of dementia, but little is known about the early cognitive and neuroimaging markers. Spatial navigation deficits are an emerging marker for Alzheimer's disease (AD), yet less is known about spatial orientation deficits sensitive to VCI. This case report follows up on the first VCI patient identified to have an egocentric orientation deficit. The study aimed to examine the patient's spatial deficits three years on and gain insights from the addition of the patient's MRI brain scan. A battery of spatial navigation tasks were administered following neuropsychological assessment. Results continue to show spatial orientation deficits. Critically, these changes appear stable and are sensitive to novel spatial tests. Whereas conventional screening tools demonstrate patient recovery. MRI DTI analysis indicates a non-significant trend towards loss of structural integrity to the posterior tracts of the longitudinal superior fasciculus (SLF), while the medial temporal lobe, typically implicated in spatial navigation, is unaffected. This finding potentially reflects reduced network connectivity in posterior to anterior white matter tracts co-existing with spatial orientation deficits. Findings have clinical utility and show spatial orientation as a potential sensitive cognitive marker for VCI.

Keywords: COT, Clock Orientation Test; Egocentric orientation; SHQ, Sea Hero Quest; Spatial navigation; VST, Virtual Supermarket Test; Vascular cognitive impairment; Vascular dementia; Vascular dementia case report; WMH, white matter hyperintensities.

Fig. 1

Virtual Supermarket Test. Videos were presented in a first-person perspective and participants are provided with optic flow cues from the moving shopping trolley and changing scenery as it followed different routes to reach a different end point in each trial (1A-C). Once the video clip stops, participants indicate in real-life the direction of their starting point (egocentric orientation; 1D). In a second step, participants indicate their finishing location on a birds-eye view map of the supermarket (allocentric orientation; 1E). Lastly, participants are asked to indicate which direction they were facing at the finishing location (heading direction; 1F). Participants indicate their responses by taping their response location on the screen.

Fig. 2

SHQ Wayfinding (allocentric) and Flare Accuracy (egocentric) levels.

Fig. 3

Visual rating of RK's FLAIR imaging. A. White matter hyperintensities on FLAIR MRI (in MNI space) predominately in the right frontal lobe of the cerebral cortex and cerebral white matter. Periventricular white matter lesions are present near the left and right ventricles and close to the white matter colossal body and the lateral occipital cortex, superior division. B. While matter hyperintensity in the occipital lobe. C. Signs of punctuate deep white matter lesions beginning confluence.

Fig. 4

SLF parietal division RK and controls FA mean score.