Article

OBJECTIVE: To determine how interhemispheric balance in stroke, measured using
transcranial magnetic stimulation (TMS), relates to balance defined using
neuroimaging (functional magnetic resonance [fMRI], 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: Laboratory.
PARTICIPANTS: Patients with chronic stroke (N = 10; age, 63 +/- 9 y) in a
population-based sample with unilateral upper-limb paresis. INTERVENTIONS: Not
applicable. MAIN OUTCOME MEASURES: Interhemispheric balance was measured with
TMS, fMRI, and DTI. TMS defined interhemispheric differences in the recruitment
of corticospinal output, size of the corticomotor output maps, and degree of
mutual transcallosal inhibition that they exerted on 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 cortex
(M1), premotor cortex (PMC), and supplementary motor cortex (SMA). DTI was used
to define interhemispheric differences in the integrity of the corticospinal
tracts projecting from the M1. Clinical outcomes tested function (upper extremity
Fugl-Meyer [UEFM]) and perceived disability in the use of the paretic hand (Motor
Activity Log [MAL] amount score). RESULTS: Interhemispheric 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 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, an imbalance in
integrity and output do not relate to transcallosal inhibition. Clinically,
although 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 amount score) (M1: r = .883, P = .006; PMC: r =
.817, P = .007; SMA: r = .633, P = .062). CONCLUSIONS: In patients with chronic
motor deficits of the upper limb, fMRI may serve to mark perceived disability and
transcallosal influence between hemispheres. DTI-based integrity of the
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.
CI - Copyright (c) 2015 American Congress of Rehabilitation Medicine. Published by
Elsevier Inc. All rights reserved.

Langue : ANGLAIS