Limb-kinetic apraxia due to injury of corticofugal tracts from secondary motor area in patients with corona radiata infarct

Limb-kinetic apraxia (LKA) is defined as an execution disorder of movements, resulting from injury of the corticofugal tract (CFT) from the secondary motor area. Diagnosis of LKA is difficult because it is made by clinical observation of movements. In this study, using diffusion tensor tractography (DTT), we attempted to investigate injury of the CFT from the secondary motor area in patients with corona radiata infarct. Twenty patients with corona radiata infarct were recruited. A probabilistic tractography method was used in fiber tracking for reconstruction of the corticospinal tract (CST) and CFT. Fractional anisotropy (FA), mean diffusivity, and tract volume of the CSTs and CFTs from the dorsal premotor cortex (dPMC) and supplementary motor area (SMA) were measured. In the affected hemisphere, FA values of the CST from the precentral hand knob and the CFT from the dPMC were significantly decreased compared with those of the unaffected hemisphere (p < 0.05). The tract volumes of the CST from the precentral hand knob and the CFTs from the dPMC and SMA in the affected hemisphere were also significantly decreased compared with those of the unaffected hemisphere (p < 0.05). We demonstrated concurrent injury of the CFTs from the secondary motor area along with injury of the CST in patients with corona radiata infarct, using DTT. Our results suggest that LKA ascribed to injury of the CFTs from the secondary motor area could be accompanied by injury of the CST ascribed to the corona radiata infarct.