Cognitive Markers in Prodromal MS

CMRO2 is the amount of O2 the brain consumes per unit of time (in μmol O2/100g tissue per minute). To quantify absolute CMRO2, both TRUST MRI for quantification of venous oxygenation (Yv) and phase contrast (PC) MRI for quantification of total blows are needed. The total scan time for CMRO2 MRI is approximately 4 minutes.

The core Cogstate Reaction Time (RT) tasks involve a deck of cards on a green background screen and the participant answers "yes" or "no" by hitting a keyboard key ("D" or "K") across repeated trials. Each task first includes instructions and practice period before the test begins and takes approximately 3-4 minutes to complete (for a total of ~7 minutes). The representative timed RT scores are provided by the Detection task (indicating when a card is revealed; DET/simple RT), Identification task ("is the card revealed black or red?"; IDN/choice RT), and One-Back ("Is this the card that you just saw?"). Performance is characterized by near complete accuracy (i.e. all, or almost all, items are answered correctly), and validity checks are built into the scoring. IIV is calculated as intraindividual standardized deviations (ISD) in RTs across both tasks, measured in milliseconds and with log10 transformation.

SDMT is 90-second cognitive task in which the participant is shown a sheet containing rows of symbols. Each symbol corresponds to a specific number. The participant's task is to say out loud the number associated with each symbol. SDMT is used as a general cognitive screen to detect severe cognitive impairment. The raw score is the correct number of substitutions in 90 seconds, scores range between 0 and 110. The lower the score, the more severe the cognitive impairment. The raw score is converted to a Z-score with a central value of 0. Standard deviations below the mean indicate a worse outcome; a Z-score of -1.5 or lower suggests a significant deviation from the average performance, potentially indicating cognitive impairment.

RAVLT is a well-recognized measure of a person's ability to encode, combine, store and recover verbal information in different stages of immediate memory. consists of presenting a list of 15 words across consecutive trials. The list is read aloud to the participant, and then the participant is immediately asked to recall as many words as one remembers. This procedure is repeated for 5 consecutive trials (Trials 1 to 5). The total score is the sum of trials 1-5 and ranges from 0-75. The lower the score, the more severe the cognitive impairment. The raw score is converted to a Z-score with a central value of 0. Standard deviations below the mean indicate a worse outcome; a Z-score of -1.5 or lower indicates impairment, meaning the individual's performance is significantly below the average of their peer group.

Visual/spatial memory is assessed in BICAMS using the BVMT-R. In this test, six abstract designs are presented for 10 sec. The display is removed from view and patients render the stimuli via pencil on paper manual responses. Each design receives from 0 to 2 points representing accuracy and location. There are three Learning Trials, and the score is reported as the total number of points earned over the trials. Thus, scores range from 0 to 12 per trial; total score range is 0 to 36 for all three trials. The lower the score, the more severe the cognitive impairment. The raw score is converted to a Z-score with a central value of 0. Standard deviations below the mean indicate a worse outcome; a Z-score of -1.5 or lower on the BVMT-R is generally considered indicative of cognitive impairment.