Abstract 2889: Neural Systems Injury Provides Insight Into Individual Behaviors While Global Injury Is Useful For Global Outcome In Chronic Stroke
Authors: Burke Erin , Der-Yeghiaian Lucy , Riley Jeff , See Jill , McKenzie Alison , Le Vu , Cramer Steven C 
Published: March 2022

INTRODUCTION:
A key challenge in the treatment of patients with chronic stroke is identifying which patients are most likely to benefit from therapy. An assessment of stroke-related injury can help, but it remains unclear which are the most useful measures. This issue was examined in the current study bearing in mind that restorative therapeutics in chronic stroke often target modality-specific behavioral measures such as arm motor function or aphasia. The hypothesis is that deficits in modality-specific behaviors are better understood by measuring injury to the neural system underlying the behavior, while deficits in global outcome assessments are better understood by measuring a global measure of injury such as infarct volume.

METHODS:
Data were collected from pre-treatment assessments for patients enrolled in a study of robotic therapy for arm weakness after stroke (clinicaltrials.gov #
NCT01244243
). Entry criteria include age >18 yr, arm motor deficits, and stroke 3-6 months prior. Pre-therapy measures included assessment of global impairment (total NIHSS score) as well as arm motor deficits (Fugl-Meyer scale (FM); Action Research Arm Test (ARAT), and Box and Blocks (B&B)). Pre-treatment MRI (3T) included high resolution T1-weighted images, from which infarct volume was determined, and diffusion tensor imaging (DTI, 32 directions). DTI was used to determine corticospinal tract integrity by measuring fractional anisotropy (FA) within this tract. FA reflects the degree to which proton movements are directional, and so is higher in white matter tracts for which the axons are directional and intact, such as normal corticospinal tract.

RESULTS:
Of the 28 enrollees, 25 were able to complete MRI scanning. These 25 had mild-moderate global impairment (NIHSS = 4.5 +− 2.3, mean +− SD) associated with arm motor deficits that were variable but overall moderate-severe (FM score = 34 +− 15, range 14-60). Arm motor deficits correlated more strongly with FA in the affected cerebral peduncle (r=0.70, p=0.0001 for FM score; similar for ARAT and B&B) than with infarct volume (r=-0.44; p=0.0546). Global impairment, however, correlated more strongly with infarct volume (r=0.66, p=0.002) than with FA in the affected cerebral peduncle (e.g, r=0-.57, p=.005 for FM). Note that in all cases, behavior/FA relationships were stronger with FA expressed as the ipsilesional/contralesional ratio, as compared to ipsilesional value alone.

CONCLUSIONS:
In patients with chronic stroke, measuring injury to a specific neural system provides insight into the behavior arising from that system, and does so better than a global measure of injury. On the other hand, a global measure of neural injury correlates better with global outcome. These findings are useful for understanding injury underlying the deficits targeted by restorative therapies and might be useful for matching the right patients with the right therapies.