FNIRS As A Tool For Localization Of Sensorimotor Cortex And Neural Plasticity In Patients With Intracranial Mass Lesions

Functional near-infrared spectroscopy(fNIRS) is a noninvasive optical method for brain function imaging, measuring changes of oxygenated hemoglobin(Oxy-Hb) and deoxygenated hemoglobin(Deoxy-Hb) concentration in cerebral tissue. fNIRS presents several advantages, such as resistance to motion artifact, naturalistic environment without restraint or sedation and relatively high temporal resolution. Although the spatial resolution of fNIRS is poor, the precise identification of brain areas beneath the fNIRS optodes can be improved by the use of three-dimensional MRI. So far few studies on brain mass lesions examine consistency between localization of eloquent areasmeasured byfNIRS and BOLD fMRI. In addition, understanding the machanisms of activation in motor cortex and neural plasticity of sensorimotor cortex can be crucial in the therapy of these patients.To explore the consistency between fNIRS and fMRI in measuring motor cortex activity in patients with brain mass lesions in central region, we examined cerebral blood oxygenation response of bilateral frontal-parietal cortex in 11 these patients using fNIRS. Based on changes of Oxy-Hb and Deoxy-Hb, activation maps of sensorimotor cortex were made respectively and compared with fMRI results. During motor tasks contralateral to the lesion, the occurrence probability of activations in lesion-sideprimary sensorimotr cortex(PSMC) and lesion-contralateral PSMC by both methods were comparable.Better consistencywas found between fMRI results and Oxy-Hb than Deoxy-Hb. Only in two patients Oxy-Hb failed find activation in supplementary motor area(SMA).To study the activation and cotical reorganization in PSMC in patients with brain tumor in central region, we employed fNIRS to measure bilateral frontoparietal cortex in 17 brain tumor patients and 9 volenteers during tumor-contralateral motor task. We analysed changes of Oxy-Hb and calculated laterality index(LI) of tumor-side PSMC. We found the strongest activation was found in contralateral PSMC in control group. Although in group level, changes of Oxy-Hb in tumor-side PSMC was bigger than tumor-contralateral PSMC, the variability was obvious, ranging from a reduction of PSMC lateralization to even inversion of PSMC lateralization during contralesional movements. The patients’ LI of PSMC was lower than that of control group. A positive correlation was found between tumor-side PSMC LI and Fugl-Meyer index, indicating more deteriorating hand conditionmore shifting to tumor-contralateral PSMC.In conclusion, the results of Oxy-Hb showed high agreement in detecting activation in PSMC with fMRI. Oxy-Hb failed in detecting activation in SMA only in 2 patients, which might be related to the deep anatomical location of part of SMA. During tumor-contralateral motor tasks, ipsitumoral PSMC activations were decreased, PSMC laterality was shifted to contralateral side, and LI of PSMC was related to the contralesional hand function.