Fig. 3.

²³Na-MRI signal intensity in the area of the skin is increased in patients with RRMS. The ²³Na-MRI signal intensity in the area of the skin was analyzed in MS patients and age-, weight-, and biological sex-matched HC (n = 29 per group). The lower leg was positioned inside a 3-T ²³Na-MRI with a specific sodium coil. Four tubes containing aqueous solutions with increasing sodium concentrations (10, 20, 30, and 40 mM) were placed inside the coil and were used for normalization of the ²³Na-MRI signal intensities. (A) Representative T2 images, anatomic images (T1-weighted), and sodium (²³Na) images of matched individuals. Arrows in the pictures on the right indicate the sodium content in the skin in pictures with sevenfold magnification. (B) Quantification of total sodium in the skin. (C) Age-matched analysis of total sodium in the skin. (D and E) Quantification of total sodium in (D) musculus triceps surae and (E) the tibial bone marrow in age-matched MS patients and HC. (F–H) ¹H fat–saturated inversion-recovery signal in the (F) skin, (G) musculus triceps, and (H) tibial bone marrow of MS patients compared to age-matched HC. (I) Bioimpedance spectroscopy measurements of extracellular water (overhydration) in age-matched MS patients and HC. (J) Correlation between the skin sodium signal in MS patients and the percentage of MRI activity during a follow-up period of 3.5 ± 2.1 y. All data are given as mean ± SEM and were analyzed by unpaired two-tailed Student’s t test.