AUTHOR=Chen Songmei , Zhang Xiaolin , Chen Xixi , Zhou Zhiqing , Cong Weiqin , Chong KaYee , Xu Qing , Wu Jiali , Li Zhaoyuan , Lin Wanlong , Shan Chunlei 

TITLE=The assessment of interhemispheric imbalance using functional near-infrared spectroscopic and transcranial magnetic stimulation for predicting motor outcome after stroke

JOURNAL=Frontiers in Neuroscience

VOLUME=17

YEAR=2023

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2023.1231693

DOI=10.3389/fnins.2023.1231693

ISSN=1662-453X

ABSTRACT=<sec id="sec1"><title>Objective</title><p>To investigate changes in interhemispheric imbalance of cortical excitability during motor recovery after stroke and to clarify the relationship between motor function recovery and alterations in interhemispheric imbalance, with the aim to establish more effective neuromodulation strategies.</p></sec><sec id="sec2"><title>Methods</title><p>Thirty-one patients underwent assessments of resting motor threshold (RMT) using transcranial magnetic stimulation (TMS); the cortical activity of the primary motor cortex (M1), premotor cortex (PMC), and supplementary motor area (SMA) using functional near-infrared spectroscopy (fNIRS); as well as motor function using upper extremity Fugl-Meyer (FMA-UE). The laterality index (LI) of RMT and fNIRS were also calculated. All indicators were measured at baseline(T<sub>1</sub>) and 1 month later(T<sub>2</sub>). Correlations between motor function outcome and TMS and fNIRS metrics at baseline were analyzed using bivariate correlation.</p></sec><sec id="sec3"><title>Results</title><p>All the motor function (FMA-UE<sub>1</sub>, FMA-UE<sub>2</sub>, FMA-d<sub>2</sub>) and LI-RMT (LI-RMT<sub>1</sub> and LI-RMT<sub>2</sub>) had a moderate negative correlation. The higher the corticospinal excitability of the affected hemisphere, the better the motor outcome of the upper extremity, especially in the distal upper extremity (<italic>r</italic> = −0.366, <italic>p</italic> = 0.043; <italic>r</italic> = −0.393, <italic>p</italic> = 0.029). The greater the activation of the SMA of the unaffected hemisphere, the better the motor outcome, especially in the distal upper extremity (<italic>r</italic> = −0.356, <italic>p</italic> = 0.049; <italic>r</italic> = −0.367, <italic>p</italic> = 0.042). There was a significant moderate positive correlation observed between LI-RMT<sub>2</sub> and LI-SMA<sub>1</sub> (<italic>r</italic> = 0.422, <italic>p</italic> = 0.018). The improvement in motor function was most significant when both LI-RMT<sub>1</sub> and LI-SMA<sub>1</sub> were lower. Besides, in patients dominated by unaffected hemisphere corticospinal excitability during motor recovery, LI-(M1 + SMA + PMC)<sub>2</sub> exhibited a significant moderate positive association with the proximal upper extremity function 1 month later (<italic>r</italic> = 0.642, <italic>p</italic> = 0.007).</p></sec><sec id="sec4"><title>Conclusion</title><p>The combination of both TMS and fNIRS can infer the prognosis of motor function to some extent. Which can infer the role of both hemispheres in recovery and may contribute to the development of effective individualized neuromodulation strategies.</p></sec>