Alexis N. Simpkins, MD, PhD
Many ischemic stroke patients will have residual disability from their stroke even if they receive thrombolysis or endovascular therapy. In fact, stroke is and is projected to continue to be one of the leading causes of long-term disability in adults. Identifying tools that can be used to accurately predict expected stroke recovery can change the way the patient is medically managed and can be used as an outcome measure in clinical trials. Changes in NIHSS, infarct volume, and stroke lesion have been shown to predict early neurologic outcome, but there are still limitations with each of these predictors. As a result, there are continued efforts to provide more sensitive and specific predictive models. Here, the authors assessed whether resting state-functional MRI (rs-fMRI) is associated with projected neurologic outcome at 90 days and can be combined with other frequently used predictors to improve accuracy. The selection of rs-fMRI was supported by previous studies that demonstrated an association between resting state and task-oriented functional connectivity and previous reports of the role of interhemispheric connectivity in stroke recovery.
To conduct the study, adult patients without prior stroke or additional neurologic disorder, treated with thrombolysis alone without parenchymal hemotoma-2 hemorrhagic transformation, and with persistent residual deficits 3 days after stroke onset were enrolled. Baseline demographic information was collected, and patients were followed for 90 days. The outcome measures included NIHSS at 3 days, modified Rankin Score at 90 days (good functional outcome = mRS ≤ 2), and MRI imaging (infarct volume assessment, annotation of stroke location, and the rs-fMRI). Of the 37 patients enrolled, those that had a good functional outcome were more likely to have more functional connectivity between the frontal and temporal lobes and less connectivity between the anterior inferior temporal gyrus and the caudate. Of the other predictors tested (age, NIHSS 3 days after stroke, infarct volume, and infarct territory), NIHSS at 3 days was most effective at discriminating between patients that had an mRS of 2 or less at 90 days. If rs-fMRI was also included in the model, the accuracy increased 10.5%. Resting brain connectivity has also been investigated in other facets of stroke recovery, including post-stroke fatigue, aphasia, post-stroke depression, and post-stroke cognitive deficits by other investigators. As rs-fMRI continues to be explored in the more acute setting, it will be interesting to see how the very early rs-fMRI findings predict these other symptoms which can frequently occur after stroke.