Assessment of Inter-Hemispheric Imbalance Using Imaging and Noninvasive Brain Stimulation in Patients With Chronic Stroke

Abstract

OBJECTIVE To determine how inter-hemispheric balance in stroke, measured using transcranial magnetic stimulation (TMS), relates to balance defined using neuroimaging (functional magnetic resonance (fMRI) and diffusion tensor imaging (DTI)), and how these metrics of balance are associated with clinical measures of upper limb function and disability. DESIGN Cross-Sectional SETTING Clinical Research Laboratory PARTICIPANTS Ten chronic stroke patients (63±9 years) in a population based sample with unilateral upper-limb paresis. INTERVENTION Not applicable MAIN OUTCOME MEASURES Inter-hemispheric balance was measured with TMS, fMRI and DTI. TMS defined inter-hemispheric differences in recruitment of corticospinal output, the size of the corticomotor output maps and the degree of mutual transcallosal inhibition they exerted upon one another. fMRI studied whether cortical activation during the movement of the paretic hand was lateralized to the ipsilesional or to the contralesional primary motor (M1), premotor (PMC) and supplementary motor cortices (SMA). DTI was used to define inter-hemispheric differences in the integrity of the corticospinal tracts projecting from M1. Clinical outcomes tested function (upper-extremity Fugl-Meyer (UEFM) and the perceived disability in the use of the paretic hand [Motor Activity Log (MAL)]. RESULTS Inter-hemispheric balance assessed with TMS relates differently to fMRI and DTI. Patients with high fMRI lateralization to the ipsilesional hemisphere possessed stronger ipsilesional corticomotor output maps [M1 (r=.831, p=.006), PMC (r=.797, p=.01)], and better balance of mutual transcallosal inhibition (r=.810, p=.015). Conversely, we have found that patients with less integrity of the corticospinal tracts in the ipsilesional hemisphere show greater corticospinal output of homologous tracts in the contralesional hemisphere (r=.850, p=.004). However, neither an imbalance in their integrity nor an imbalance of their output relates to transcallosal inhibition. Clinically, while patients with less integrity of corticospinal tracts from the ipsilesional hemisphere showed worse impairments (UEFM) (r = −.768, p=.016), those with low fMRI lateralization to the ipsilesional hemisphere had greater perception of disability (MAL) [M1 (r=.883, p=.006), PMC (r=.817, p=.007) and SMA (r=.633, p=.062). CONCLUSIONS In patients with chronic motor deficits of the upper limb, fMRI may serve to mark perceived disability as well as transcallosal influence between hemispheres. DTI-based integrity of corticospinal tracts, however, may be useful in categorizing the range of functional impairments of the upper-limb. Further, in patients with extensive corticospinal damage, DTI may help infer the role of the contralesional hemisphere in recovery.

Inhibition versus facilitation of contralesional motor cortices in stroke: Deriving a model to tailor brain stimulation

“…Total scan time was 12 minutes. (Cunningham et al, 2015a). Acquisition provided whole-brain coverage using 2-mm isotropic voxels (field of view: 256 × 256 mm, image matrix: 128 × 128 and 52 2-mm-thick slices).…”

“…Functional MRI (fMRI) activation was used for stereotactic guidance of TMS (Brainsight, Rogue Research Inc., Montreal, QC, Canada) (Cunningham et al, 2015a). FMRI guidance is helpful because patients with chronic stroke undergo cortical reorganization (Lotze et al, 2003, Ward et al, 2003a, Ward et al, 2006).…”

Ipsilesional High Frequency Repetitive Transcranial Magnetic Stimulation Add-On Therapy Improved Diffusion Parameters of Stroke Patients with Motor Dysfunction: A Preliminary DTI Study

“…There is evidence that PLIC and CR were mainly comprised of CST which project from the motor cortex to the PLIC [34, 36, 37] and to brain stem [33]. Previous diffusion microstructural studies have showed significantly decreased FA values in ipsilesional [5, 38, 39] and contralesional [24, 40] PLIC and CST after stroke.…”

It Takes Two: Noninvasive Brain Stimulation Combined With Neurorehabilitation

“…Still, to open these lines of discussion so a more strategic investigation of these factors can be conducted in various populations, we present the this supplement which provides data based papers and reviews discussing state of the art clinical and research application and considerations for non-invasive brain stimulation targeting a variety of neurorehabilitative diagnoses and impairments. Featured articles include the following: Cunningham et al 40 discuss the potential utility of neuro-navigated TMS in revealing mechanisms of functional motor recovery in chronic stroke. In comparing its use to state-of-the-art imaging- functional MRI and Diffusion Tensor Imaging (DTI)- they discuss how its neurophysiologic measurements relate to inter-hemispheric balance, and reveal adaptations to damaged output from stroke hemisphere.…”

“…Cunningham et al 40 discuss the potential utility of neuro-navigated TMS in revealing mechanisms of functional motor recovery in chronic stroke. In comparing its use to state-of-the-art imaging- functional MRI and Diffusion Tensor Imaging (DTI)- they discuss how its neurophysiologic measurements relate to inter-hemispheric balance, and reveal adaptations to damaged output from stroke hemisphere.…”