Fig. 4

T2*-weighted images and QSM images of the primary motor cortex in a healthy subject (a–c) and an ALS patient (d–f). a In healthy subjects, two strips are recognisable in the primary motor cortex: a thin superficial hyperintense strip (arrow) and a thicker and slightly hypointense deep band (*). In many ALS patients, the deep strip is abnormally hypointense in T2*-weighted images (arrows in d and e), and the hypointensity corresponds to higher values of magnetic susceptibility (arrow in f)