Motor Cortex Activation During Treatment May Predict Therapeutic Gains in Paretic Hand Function After Stroke

 It is vastly more important to DELIVER HAND FUNCTION than predict it! When the hell will stroke leadership get a strategy going to DELIVER 100% RECOVERY? I'm guessing never since survivors are not in charge.

Motor Cortex Activation During Treatment May Predict Therapeutic Gains in Paretic Hand Function After Stroke

Yun Dong, MD, PhD, Bruce H. Dobkin, MD, Steven Y. Cen, PhD, Allan D. Wu, MD, and Carolee J. Winstein, PhDAuthor Info & Affiliations

Stroke

Volume 37, Number 6

https://doi.org/10.1161/01.STR.0000221281.69373.4e

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Abstract

Background and Purpose— Functional brain imaging after stroke offers insight into motor network adaptations. This exploratory study examined whether motor cortical activation captured during arm-focused therapy can predict paretic hand functional gains.

Methods— Eight hemiparetic patients had serial functional MRI (fMRI) while performing a pinch task before, midway, and after 2 weeks of constraint-induced therapy. The Wolf Motor Function Test (WMFT) was performed before and after intervention.

Results— There was a linear reduction in ipsilateral (contralesional) primary motor (M1) activation (voxel counts) across time. The midpoint M1 Laterality Index anticipated post-therapeutic change in time to perform the WMFT. The change in ipsilateral M1 voxel count (pre- to mid-) correlated with the change in mean WMFT time (pre- to post-).

Conclusions— The relationship between brain activation during treatment and functional gains suggests a use for serial fMRI in predicting the success and optimal duration for a focused therapeutic intervention.

Functional MRI (fMRI) has revealed reorganization in the primary and secondary motor cortices during poststroke recovery and after therapeutic interventions.¹ Few studies have explored the evolution of brain activation in relation to behavioral gains in a “one-to-one” correspondence during a specific rehabilitation intervention.² This exploratory study examined whether the brain activation midway through a 2-week arm-focused intervention might capture adaptations induced by the initial week of training and, in turn, could be used to anticipate post-therapeutic behavioral changes in paretic hand function. If so, this brain–behavior correspondence may offer guidance to determine an optimal duration for task-specific therapy.²

Subjects and Methods

Eight patients with hemiparetic stroke (Fugl-Meyer [FM] motor score 33 to 62) participated. Inclusion criteria were >3 months after stroke, ability to perform the fMRI task, and a minimum of 10° of voluntary wrist and finger extension. Lesions varied in location, but all spared the hand motor representation (M1). No alternative therapy group was studied. Seven healthy volunteers were scanned twice to test the reproducibility of fMRI activation.

Physical Therapy and Functional Measure

All patients received constraint-induced therapy for 2 weeks as defined for the EXCITE trial.³ The Wolf Motor Function Test (WMFT)⁴ was performed before and after intervention. The behavioral outcome measure consisted of 6 dexterity items from the full 15-item WMFT (Lift Can; Lift Pencil; Lift Paper Clip; Stack Checkers; Flip Cards; Turn Key in Lock) that most directly captured fine motor control. The change in mean WMFT (mWMFT) time for the 6-item subset was correlated with that for the 15-item test (r=0.98), indicating reliability and validity for the subset. The pre-mWFT–post-mWFMT (absolute time) difference was used as a proxy for functional change in motor skill.

fMRI Acquisition

fMRI acquisition parameters were described previously.⁵ fMRI sessions were performed before intervention, midintervention, and after intervention, each with 4 30-s bouts of repetitive pinch alternating with 5 30-s rest periods. The pinch apparatus included a vertical plastic tube connected to a pressure transducer. The task required tube compression with the index and middle fingers against the thumb, creating enough pressure to match 50% of maximum, viewed through goggles as a target line, and paced by auditory cues at 75% maximum rate. These parameters were maintained constant across the 3 sessions. Practice before each fMRI session minimized unwanted movements and deviations from consistent task performance.

Data Analysis

fMRI data were analyzed as described previously.^5,6 Volumes related to head motion (>2 mm), and associated movements (visually identified from videotape) were excluded. Z statistic images were thresholded at Z>3.1, and significant clusters were defined atP<0.01 (corrected for multiple comparisons). Regions of interest (ROIs) were set in bilateral M1 and dorsal premotor (PMd) areas. Percentage signal change (% SC) and voxel counts (VCs) within each ROI were measured and a Laterality Index [LI=(contralateral−ipsilateral)/(contralateral+ipsilateral)] (contralateral and ipsilateral activation to the hand movement. LI ranges from −1 [all ipsilateral activation] to 1 [all contralateral activation]) was calculated using VC for each ROI. Linear Mixed Model was used for intersession comparisons of fMRI variables (% SC, VC), pinch pressure, and rate, separately. Individual linear regression analyses were performed between LI, VC (M1 and PMd; independent variable) pre-, mid-, and post- and the post-pre–mWMFT time difference (dependent variable). Pearson correlation coefficient analysis was used to assess the relationship between changes in fMRI measures and changes in mWMFT time. Preintervention fMRI from patients 5 and 6 was technically unusable.

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