Purpose: The purpose of this study was to investigate the motor recovery mechanism following diffuse axonal injury (DAI) using transcranial magnetic stimulation (TMS) and functional MRI (fMRI).
Methods: Twenty-six hands of 13 control subjects and 14 affected hands of 8 patients (two hemiparetics and six quadriparetics) were evaluated. All the patients were initially diagnosed with DAI and were evaluated after they had reached their maximal motor recovery. fMRI was performed at 1.5 T using a hand grasp-release movement paradigm and TMS was applied with a round coil over the vertex.
Results: fMRI revealed that both normal subjects and patients with DAI showed increased contralateral primary sensori-motor cortex activation during affected hand movement. The motor evoked potentials (MEPs) of the patient group was slightly delayed in latency and significantly increased in duration and turns. The relative MEP amplitude, phase, and excitatory threshold were not significantly different between the groups.
Conclusions: These findings may indicate the heterogeneity of the axons in the recovery process of the corticospinal tract. It seems that the motor recovery in patients who had suffered DAI was attributable to the recovery of the corticospinal tract.