Transcallosal Ipsilateral Motor Pathway from the Unaffected Hemisphere in a Patient with Traumatic Brain Injury

Purpose: We presented with a patient with traumatic brain injury who showed a transcallosal ipsilateral motor pathway from unaffected motor cortex to affected extremities, as evaluated by diffusion tensor tractography (DTT). Methods: One patient and six age-matched normal subjects were enrolled. A 42-year-old left hemiparetic male who suffered from brain injury by motor vehicle accident 9 years ago showed a leukomalactic lesion in the right corona radiata and parieto-temporal lobe. His left extremities were completely paralyzed initially, but recovered slowly over 2 years. At the time of the evaluation, he was able to grasp and release an object, and to walk with spastic gait pattern. DTT was performed using 1.5 T with a Synergy-L Sensitivity Encoding head coil. DTT was obtained with termination criteria of FA <0.2 and an angle change > $45^{\circ}c$. Results: The motor tracts of the unaffected (left) hemisphere of the patient and control subjects originated from the motor cortex and descended along the known corticospinal tract without any transcallosal tract. By contrast, the tract of the affected (right) hemisphere originated from the left premotor cortex, descended through the left corona radiata, and then crossed the mid-portion of the corpus callosum. The tract then descended through the known corticospinal tract pathway to the right medulla. Conclusion: We conclude that the transcallosal ipsilateral motor pathway from the unaffected hemisphere appeared to contribute to the motor recovery in this patient.