Digit Span Tests Are More Sensitive than SDMT for Detecting Working Memory Impairment and Correlate with Metabolic...

In this paper, we aimed to evaluate the efficacy and usefulness of three brief, easy-to-administer, and repeatable tests, namely SDMT, Digit Span Forward (DSF), and Digit Span Backward (DSB) in MS patients (MSp), and compared the results with those of healthy volunteers (CONs). We were hoping to identify the most sensitive test that could be used regularly in clinical practice. In addition, we tried to identify the metabolic background of the cognitive setting using the advanced radiological method, Mescher-Garwood (MEGA)-edited 1H Magnetic Resonance Spectroscopy (1H-MRS). A total of 22 relapsing MSp and 22 CONs were enrolled. The SDMT, DSF, and DSB tests were used on all participants. The patients also underwent a 1H-MRS brain examination. In addition to N-Acetyl-Aspartate (tNAA), Myoinositol (mIns), Choline (tCho), and Creatine (tCr) were also evaluated GABA and Glutamate-Glutamine (Glx) ratios. CONs were superior to MSp in the results of all neurocognitive tests. The DSB was found to be the most sensitive test for identifying MSp. The SDMT in MSp correlated with inflammatory and degenerative metabolites in the thalamus, hippocampus, and corpus callosum. A correlation between increased Glx- and GABA-ratios and SDMT was found. Unlike the SDMT, the DSF and DSB showed correlations with inflammatory metabolites in the caudate nucleus and hypothalamus. DSF correlated with GABA ratios in the hippocampus. Our study confirms the efficacy of DSF and DSB tests in evaluating working memory cognitive impairment in MSp, showing an association of the tests with specific brain metabolites.