White matter tract involvement in alien hand syndrome following stroke: diffusion tensor imaging study

Alien Hand Syndrome (AHS) disrupts hand control, often attributed to corpus callosum (CC) damage, which connects the two brain hemispheres. AHS can also result from damage to the medial frontal cortex, parietal lobe, or thalamus, but its precise causes remain unclear. This study aimed to identify the white matter tracts associated with AHS development using the automated reconstruction of 42 tracts from diffusion tensor imaging (DTI). We included three female AHS patients with anterior cerebral arterial (ACA) infarctions. Additionally, we enrolled 20 age-matched control subjects and six patients with ACA infarctions but without AHS symptoms (N-AHS group) for comparison. DTI was conducted in AHS, N-AHS, and control groups. Fractional anisotropy (FA) and volume values were extracted from the DTI datasets of participants using TRActs Constrained by UnderLying Anatomy (TRACULA) technique. The AHS group showed lower FA values of the CC body (parietal and temporal section), right arcuate fasciculus, corticospinal tract, extreme capsule, inferior longitudinal fasciculus, and superior longitudinal fasciculus than the control group. However, these tracts exhibited no significant difference between N-AHS and control groups. Similarly, the volume value in the genu of CC in the AHS group was lower than controls, but not in other tracts. Our results suggest that the extensive CC lesion, especially in the posterior parietal and temporal section of CC body, is associated with the development of AHS. These results shed light on the neural mechanisms involved in AHS and underscore the significance of considering various white matter tracts beyond CC for understanding this syndrome.