Measurement Properties of the NeuroFlexor Device for Quantifying Neural and Non-neural Components of Wrist Hyper-Resistance in Chronic Stroke

Abstract

Introduction: Differentiating between the components of wrist hyper-resistance post stroke, i.e., pathological neuromuscular activation (“spasticity”) and non-neural biomechanical changes, is important for treatment decisions. This study aimed to assess the reliability and construct validity of an innovative measurement device that quantifies these neural and non-neural components by biomechanical modeling. Methods: Forty-six patients with chronic stroke and 30 healthy age-matched subjects were assessed with the NeuroFlexor, a motor-driven device that imposes isokinetic wrist extensions at two controlled velocities (5 and 236°/s). Test-retest reliability was evaluated using intraclass correlation coefficients (ICC) and smallest detectable changes (SDC), and construct validity by testing the difference between patients and healthy subjects and between subgroups of patients stratified by modified Ashworth scale (MAS), and the association with clinical scales. Results: Test-retest reliability was excellent for the neural (NC) and non-neural elastic (EC) components (ICC 0.93 and 0.95, respectively), and good for the viscous component (VC) (ICC 0.84), with SDCs of 10.3, 3.1, and 0.5 N, respectively. NC and EC were significantly higher in patients compared to healthy subjects ( p < 0.001). Components gradually increased with MAS category. NC and EC were positively associated with the MAS ( r s 0.60 and 0.52, respectively; p < 0.01), and NC with the Tardieu scale ( r s 0.36, p < 0.05). NC and EC were negatively associated with the Fugl-Meyer Assessment of the upper extremity and action research arm test ( r s ≤ −0.38, p < 0.05). Conclusions: The NeuroFlexor reliably quantifies neural and non-neural components of wrist hyper-resistance in chronic stroke, but is less suitable for clinical evaluation at individual level due to high SDC values. Although construct validity has been demonstrated, further investigation at component level is needed.

Feasibility and potential effects of using the electro-dress Mollii on spasticity and functioning in chronic stroke

“…These findings are in agreement with previous studies demonstrating that motor function on the ipsilesional side may also be affected due to an interhemispheric imbalance after stroke [38,42]. Taking the questioned validity of the MAS into consideration [41], the bilateral findings based on assessment with the modified Ashworth scale could also be a result of a higher resistance in the elastic component rather than a neural. Given the observed results on sensorimotor function and upper extremity performance, future studies should move on to evaluate the effect of combining treatment with the Mollii® suit with rehabilitation interventions targeting activity performance.…”

“…These results may reflect that the MAS has low accuracy for diagnosing reflex-mediated resistance to passive stretch [39,40]. A recent study assessing the validity of the NeuroFlexor™ and the MAS confirms that clinical assessment according to the modified Ashworth scale cannot differentiate the active NC from the passive elastic component [41]. A new NeuroFlexor™ foot module has been developed and is currently tested on a stroke population and in healthy subjects.…”

“…These findings are in agreement with previous studies demonstrating that motor function on the ipsilesional side may also be affected due to an interhemispheric imbalance after stroke [ 38 , 42 ]. Taking the questioned validity of the MAS into consideration [ 41 ], the bilateral findings based on assessment with the modified Ashworth scale could also be a result of a higher resistance in the elastic component rather than a neural.…”

Time Course of Wrist Hyper-Resistance in Relation to Upper Limb Motor Recovery Early Post Stroke

“…The developers of the NeuroFlexor have previously underpinned the validity of the NC based on 3 arguments: (1) the NC as measured by the device was reduced after an ischemic nerve block, (2) the NC correlated with the integrated electromyography (EMG) across subjects and in the same subject during the ischemic nerve block, and (3) the NC was found to be velocity dependent. 22 In a recent study, 23 the NeuroFlexor method was suggested to be construct-valid against clinical assessments using the modified Ashworth and Tardieu scales. In addition, good to excellent reliability was shown for the quantification of the different , and inertial forces of the limb and the moving parts of the device (F in ), described as:…”

High Dosage of Botulinum Toxin Type A in Adult Subjects with Spasticity Following Acquired Central Nervous System Damage: Where Are We at?

“…Accordingly, spasticity is a motor disorder characterised by a velocity-dependent increased resistance to passive limb movement with increased muscle tone and hyperactive reflexes [1]. On the other hand, a key role has been attributed to muscle tissue change, consequently, it is defined as pathological neuromuscular activation and hyper-resistance around joints due to modification of visco-elastic muscle components [2]. Regardless of the pathophysiological mechanisms underlying this motor and muscular tone condition, spasticity may be a disabling and challenging symptom in people during the rehabilitation process and recovery.…”