Motor recovery via transcallosal and transpontine fibers in a patient with intracerebral hemorrhage.

Little is known about the motor recovery mechanisms via transcallosal or tranpontine fibers in stroke patients. In the current study, an attempt was made to demonstrate motor recovery via transcallosal and transpontine fibers in a patient with intracerebral hemorrhage using diffusion tensor tractography and transcranial magnetic stimulation. A 39-yr-old male patient presented with complete weakness of the right extremities at the onset of a left midbrain hemorrhage. His motor weakness had shown slow recovery for 4 mos to the point that he was able to grasp and release using the right hand. Diffusion tensor tractography and transcranial magnetic stimulation were performed at 2 wks and 4 mos after onset. Discontinuation of the left corticospinal tract below the left midbrain was observed on the 2-wk diffusion tensor tractography and no motor evoked potential was elicited in the right hand on the 2-wk transcranial magnetic stimulation study. Four-month diffusion tensor tractography showed that the discontinuation of the left corticospinal tract had not been restored; however, a new neural pathway was observed, which originated from the left primary motor cortex and descended to the left corticospinal tract at the pons through the transcallosal and transpontine fibers. In the 4-mo transcranial magnetic stimulation study, the latency of motor evoked potential obtained at the right hand by stimulation of the left motor cortex was delayed by 9 msecs, compared with the opposite motor evoked potential, which seems to be compatible with transcallosal and transpontine conduction time. The results suggest that the motor function of the affected extremities in this patient was recovered through the transcallosal and transpontine fibers from the left motor cortex.