Somatosensory area 3b is selectively unaffected in corticobasal syndrome: combining MRI and histology.

An increasing number of neuroimaging studies addressing patients with corticobasal syndrome use macroscopic definitions of brain regions. As a closer link to functionally relevant units, we aimed at identifying magnetic resonance-based atrophy patterns in regions defined by probability maps of cortical microstructure. For this purpose, three analyses were conducted: (1) Whole-brain cortical thickness was compared between 36 patients with corticobasal syndrome and 24 controls. A pattern of pericentral atrophy was found, covering primary motor area 4, premotor area 6, and primary somatosensory areas 1, 2, and 3a. Within the central region, only area 3b was without atrophy. (2) In 18 patients, longitudinal measures with follow-ups of up to 59 months (mean 21.3 ± 15.4) were analyzed. Areas 1, 2, and 6 showed significantly faster atrophy rates than primary somatosensory area 3b. (3) In an individual autopsy case, longitudinal in vivo morphometry and postmortem pathohistology were conducted. The rate of magnetic resonance-based atrophy was significantly correlated with tufted-astrocyte load in those cytoarchitectonically defined regions also seen in the group study, with area 3b being selectively unaffected.