Absence of a proximal to distal gradient of motor deficits in the upper extremity early after stroke

Abstract

Objective: Our first purpose was to determine whether there was a proximal to distal gradient in motor deficits in nine segments of the affected upper extremity (shoulder, elbow, forearm, wrist, and five fingers) post-stroke. Our second purpose was to determine which upper extremity segments made the greatest contributions to hand function.

Methods: Thirty-three subjects were tested on average 18.6 (+/-5.6) days after stroke. The ability to move each segment was measured by active range of motion (AROM). Hand function was measured by a battery of standardized clinical tests which were synthesized into a single, sensitive score for hand function using principal component analysis.

Results: AROM at all nine segments of the upper extremity was reduced and there was no evidence of a proximal to distal gradient in AROM values. Strength of each segment was reduced and there was also no evidence of a gradient in strength values. AROM at each segment was strongly correlated with hand function scores (range 0.76-0.94). General multiple regression analysis showed that AROM explained 82% of the variance in hand function, with most of the variance shared across proximal, middle, and distal segments. Hierarchical regression analysis showed that shoulder AROM alone could explain 88% of the variance in hand function.

Conclusions: Early after stroke a proximal to distal gradient of motor deficits was not present, and loss of hand function was due to a loss of ability to move many segments of the upper extremity and not just the distal ones.

Significance: These results suggest that a change in the clinical perception of motor deficits post-stroke is needed. Our finding that shoulder AROM predicted almost all the variance in hand function opens up the possibility that this quick, simple measure may be predictive of future hand function. This would be of high economic and clinical utility compared to other ongoing efforts attempting to predict outcomes post-stroke (e.g. fMRI, MEG).

Figure 1

A: Group means ± SDs for affected side AROM (●) values for each of the 9 segments. (Δ) represents normal AROM for each of the 9 segments. Normal AROM values were obtained from the unaffected side of comparable aged individuals with stroke performing the same task (Figure 5A, Lang & Beebe, 2007) and are shown only to appreciate how the percent of normal AROM was calculated. B: Bars represent mean percent of normal AROM ± SEs. C. Group means ± SEs for the percentage of affected to unaffected side strength. SH: shoulder, EL: elbow, FA: forearm, WR: wrist, LT: little finger, RG: ring finger, MD: middle finger, IX: index finger, TH: thumb, FLEX: flexion, EXT: extension

Figure 2

Figures A, B, and C show individual data for percent of normal AROM at each segment of the upper extremity. Values may be greater than 100% if a subject moved a particular segment much more than the average of the healthy sample. Subjects were stratified according to the percent strength in their unaffected arm. Figure A: mild ≥ 50% strength of unaffected side. Figure B: moderate < 50% strength of unaffected side. Figure C: severe = 0% strength of unaffected side. It is possible to have 0% strength, but still have some AROM because a person was given a score of 0 at a segment if they were unable to hold the test position against gravity. If distal segments were affected to a greater degree than proximal segments, we would have expected to see lines sloping downward from left to right. Abbreviations same as in figure 1.