Assessment of the corona radiata sensory tract using awake surgery and tractography

Anatomical localization of brain function can be achieved by functional changes during awake surgery combined with tractography constructed by diffusion tensor imaging studies. We aimed to use these techniques to characterize the sensory tract in the corona radiata in patients with closely associated brain tumors. Of nine patients who had brain tumors in the primary sensory area (S1) and who underwent awake surgery between October 2004 and July 2007, two patients showed deterioration in deep sensation during and after awake surgery. Both of these patients also developed involuntary movements (for patient 1 this was myoclonus of the left hand, while patient 2 experienced unintentional lifting of the arm). In these two patients, tumors were located just beside the sensory tract in the corona radiata of the right hemisphere. In patient 2, Wallerian degeneration of the sensory tract and concomitant deterioration of superficial and deep sensation were observed at 6 months after awake surgery. These results suggest that damage to a closely associated sensory tract in the corona radiata is critical to the development of sensory deficits and involuntary movements. For patients who undergo surgical resection of S1 brain tumors, pre-operative tractography to detect the sensory tract in the corona radiata may allow protection of the sensory tract during awake surgery, thereby preventing post-operative sensory deficits.