Objective: MRI research in MS samples reveals pathology in both the cerebral cortex and deep gray matter. The classical subcortical dementia hypothesis has been ascribed to MS and is supported by studies highlighting the role of thalamic atrophy in neuropsychological outcomes. However, the importance of mesial temporal atrophy in MS is untested and poorly understood. New structural imaging techniques permit volumetric measures of multiple regions within the mesial temporal (MT) lobe and deep gray matter (DGM).
Objective: Determine the relative importance of MT and DGM structures in predicting MS performance on memory tests presented in the auditory/verbal and visual/spatial spheres.
Methods: Cross-sectional analysis of 50 MS patients undergoing structural brain MRI and neuropsychological testing. Using Freesurfer software, the volumes of MT [hippocampus, amygdala] and DGM [thalamus, caudate] structures were calculated. Neuropsychological testing contributed measures of new learning, delayed recall and recognition memory, in the auditory/verbal and visual/spatial memory modalities.
Results: Significant correlations between higher regional volume and better test performance were observed across all memory tests. For measures of free recall or new learning, DGM volumes were most strongly predictive of outcomes. In contrast, measures of recognition memory were predicted only by MT volumetric measures.
Conclusion: For the first time, the predictive validity of MT and DGM atrophy are simultaneously compared in MS using reliable and validated neuropsychological measures. We find that both compartments play significant but different roles in the amnesia of MS.