Peak width of skeletonized mean diffusivity (PSMD) is a new MRI marker, which has shown clinical relevance in some neurological conditions and, in preliminary data, in multiple sclerosis (MS). We aimed here to investigate, in a group of relapsing-remitting MS (RRMS) patients, the relationship between PSMD and cognitive performances, in comparison with other MRI measures. RRMS patients (n = 60) and normal controls (n = 15) underwent a 3 T MRI examination. MRI-based white matter (WM) lesion volume, microstructural integrity (assessed with Tract-Based Spatial Statistics of diffusion tensor imaging [DTI] images) and brain volumes (i.e., total brain, grey matter [GM] and WM) were computed. In addition, PSMD was calculated through “skeletonization” of WM tracts and diffusion histograms. Cognition was evaluated with Rao’s Brief Repeatable Battery (BRB), which incorporated tests of verbal and visual memory, attention, concentration, information processing speed and verbal fluency. PSMD closely correlated with symbol digit modalities test (SDMT) (r = −0.70, p < 0.001) and, to a lesser extent, with verbal and visual memory tests. Multiple regression analysis showed that PSMD explained SDMT variance (R² = 0.54, p < 0.001) more than other MRI measures. Results point out the relevance of microstructural damage, as assessed by PSMD, as a reliable marker of cognition in MS, especially in explaining dysfunction in information processing speed.

骨架化平均弥散率( PSMD) 的峰宽是一种新的 MRI 标志物，已在某些神经系统疾病中显示出临床相关性，并在初步数据中显示在多发性硬化症 (MS) 中。我们的目的是在一组复发缓解型 MS (RRMS) 患者中研究 PSMD 与认知表现之间的关系，并与其他 MRI 测量进行比较。RRMS 患者 ( n  = 60) 和正常对照 ( n = 15) 接受了 3 T MRI 检查。计算了基于 MRI 的白质 (WM) 病变体积、微观结构完整性（使用基于束的扩散张量成像 [DTI] 图像的空间统计评估）和脑体积（即，全脑、灰质 [GM] 和 WM）。此外，PSMD 是通过 WM 束和扩散直方图的“骨架化”计算的。使用 Rao 的简短可重复电池 (BRB) 评估认知，其中包括对语言和视觉记忆、注意力、注意力、信息处理速度和语言流畅性的测试。PSMD 与符号数字模态测试 (SDMT) (r = -0.70, p  < 0.001)密切相关，并且在较小程度上与语言和视觉记忆测试相关。多元回归分析表明，PSMD 解释了 SDMT 方差（R ² = 0.54, p  < 0.001) 比其他 MRI 测量值更多。结果指出，PSMD 评估的微观结构损伤的相关性是 MS 认知的可靠标志，尤其是在解释信息处理速度的功能障碍方面。