Voxel‐wise associations of grey matter deficits with higher NfL levels. (A) Widespread regions including ventral and dorsomedial prefrontal cortex, ventral and dorsal insula, anterior cingulate, caudate, and medial thalamus showed lower grey matter volume (voxel‐wise analysis) associated with higher NfL levels. Significant clusters were defined at a t‐threshold of P < 0.001 uncorrected (blue‐green colored) and p
fwe < 0.05 (red colored). Color bars represent t‐scores, and statistical maps are superimposed on the Montreal Neurological Institute template brain. The left side of the axial and coronal images corresponds to the left (L) side of the brain. (B) Mean grey matter intensity versus log‐transformed NfL levels within the P < 0.001 map in (A), for 24 presymptomatic C9orf72 expansion carriers (grey dots), 4 mild impairment (orange dots), 17 bvFTD (pink dots), 4 bvFTD‐MND (green dots), and 1 PPA (purple dot) plotted for visualization purposes only. Both presymptomatic (C) and symptomatic carriers (D) show associations of NfL with grey matter atrophy in bilateral dorsolateral prefrontal cortex, parietal regions, and caudate. Symptomatic carriers (D) additionally show grey matter atrophy associated with NfL in key hubs targeted in bvFTD, including anterior and mid cingulate cortex and insula.