Silent cerebrovascular lesions can cause various functional impairments and cognitive deficits. However, the distinct effects of different types of lesions on cognitive performance remain unclear. Using both neuro-psychological tests and multi-sequence MRI scans, we can assess whether various types of cerebrovascular lesions are differentially associated with deficits in specific cognitive domains.
Demonstrating the study procedures will be done by Junling Gao, my research officer, and Tracy Lam, my technical officer. To set up a symbol digit modalities test, pair one to nine digits in numeric order with nine unassociated symbols. A battery of structured neuro-psychological tests were administered, and two of them were chosen for demonstration.
Before starting the test, instruct the participant to fill in the blank with the correctly paired digit below each symbol. Allow the participant to fill in the first 10 blanks as practice, pointing out any errors during the practice stage, and encouraging the participant to be correct. When the participant is ready, start the test, encouraging the participant to fill in the blanks as quickly and accurately as possible in 90 seconds.
When the participant has finished or the time has run out, record the number of correct responses and restart the test, this time having the participant provide the correctly pair digits verbally. To assess verbal fluency, ask the participant to verbally provide a list of names belonging to each of two categories for one minute per category. Then record the total number of names listed for each category.
To perform visual ratings of the lesions, first import the data into an appropriate medical imaging software program, and use the Anonymize button to anonymize the participants'information. To rate visual silent cerebrovascular lesions, first locate the silent lacunes and T1 weighted horizontal images in which the lesions appear as hypointense two to 15 millimeter diameter foci. Search all of the brain regions in a pre-specified order from one side to the other to avoid any omission.
For example, search from the frontal lobe insula and basil ganglion, temporal lobe, parietal lobe, and occipital lobe, cerebellum, and brainstem. To confirm the presence of the silent lacunes, view the FLAIR NT1 weighted images in which the lacunes can be observed as hypointense foci of two to 15 millimeter diameters, often with a hyperintense rim and the T2 weighted images in which then the lacunes are hyperintense. To identify cerebral microbleeds as punctate, or two to 10 millimeter diameter round oval hypointense foci their locations, load susceptibility weighted images into the software, and use the Brain Observer micro bleed scale to divide the entire brain region into seven anatomical locations.
A participant is considered to have strictly low bar cerebral microbleeds when all of the lesions are confined to the cortex and the subcortical white matter. To identify white matter hyperintensities as bilateral, almost symmetrical hyperintense areas, view the T2 weighted and FLAIR images. Use the Fazekas scale to score periventricular hyperintensities appearing as caps or pencil thin lining as grade one foci, smooth halos as grade two, and irregular signals extending into the deep white matter as grade three.
Rate deep white matter hyperintensities appearing as punctate foci as grade one, small confluent areas as grade two, and large confluent areas as grade three. In this representative analysis, the mean age of the 398 participants was 72 years, and 213 of the participants were men. Here the neuropsychological assessment results for the participants are shown.
One or more types of silent cerebrovascular lesions were found in 169 participants, with 35 participants exhibiting two types, and 17 exhibiting three types. Only five participants had all four types of silent cerebrovascular lesions. The data confirmed an independent association between the burden of periventricular white matter hyperintensities, and a poorer performance in executive function and information processing speed.
An increasing load of cerebral microbleeds was associated with impaired language related performance, and additional adjustment for vascular risk factors and other types of silent cerebrovascular lesions did not affect the independent impact of cerebral microbleeds on language function. Although there was a significant association between the presence of silent lacunes and a poorer performance on executive function, this association was lost following additional correction for other types of silent cerebrovascular lesions. While it is not difficult to learn this neuro-psychological test, it could be challenging to follow the same standardized procedure on hundreds of patients over several years.
A unified standard should be adopted for both the neuropsychological assessments and rating of the MRI lesions for participants. These procedures should be reviewed periodically to ensure that uniformity. Some of the neuropsychological tests have overlaps in the evaluated domain.
In the future, computer-based assessment can be more precise and additional function on your imaging study can be applied to specific cognitive domain.
