Network localization of alien limb in patients with corticobasal syndrome

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OBJECTIVE

Perirolandic atrophy occurs in corticobasal syndrome (CBS) but is not specific vs. progressive supranuclear palsy (PSP). There is heterogeneity in the locations of atrophy outside perirolandic cortex and it remains unknown why atrophy in different locations would cause the same CBS‐specific symptoms. In prior work, we used a wiring diagram of the brain called the human connectome to localize lesion‐induced disorders to symptom‐specific brain networks. Here, we use a similar technique termed atrophy network mapping to localize single‐subject atrophy maps to symptom‐specific brain networks.

METHODS

Single‐subject atrophy maps were generated by comparing cortical thickness in CBS patients vs. controls. Next, we performed seed‐based functional connectivity using a large normative connectome to determine brain regions functionally connected to each patient’s atrophied locations.

RESULTS

CBS patients had perirolandic atrophy vs. controls at the group level, but locations of atrophy in CBS were heterogeneous outside of perirolandic cortex at the single‐subject level (mean spatial correlation = 0.04). In contrast, atrophy occurred in locations functionally connected to the perirolandic cortex in all CBS patients (spatial correlation = 0.66). Compared with PSP, CBS patients had atrophy connected to a network of higher‐order sensorimotor regions beyond perirolandic cortex, matching a CBS atrophy network from a recent meta‐analysis. Finally, atrophy network mapping identified a symptom‐specific network for alien limb, matching a lesion‐induced alien limb network and a network associated with agency in normal subjects.

INTERPRETATION

We identified a syndrome‐specific network for CBS and symptom‐specific network for alien limb using single‐subject atrophy maps and the human connectome.

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