The relation between neuromechanical parameters and Ashworth score in stroke patients

Abstract

BackgroundQuantifying increased joint resistance into its contributing factors i.e. stiffness and viscosity ("hypertonia") and stretch reflexes ("hyperreflexia") is important in stroke rehabilitation. Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties. We propose an instrumented identification paradigm for early and tailor made interventions.MethodsRamp-and-Hold ankle dorsiflexion rotations of various durations were imposed using a manipulator. A one second rotation over the Range of Motion similar to the Ashworth condition was included. Tissue stiffness and viscosity and reflexive torque were estimated using a nonlinear model and compared to the Ashworth Score of nineteen stroke patients and seven controls.ResultsAnkle viscosity moderately increased, stiffness was indifferent and reflexive torque decreased with movement duration. Compared to controls, patients with an Ashworth Score of 1 and 2+ were significantly stiffer and had higher viscosity and patients with an Ashworth Score of 2+ showed higher reflexive torque. For the one second movement, stiffness correlated to Ashworth Score (r2 = 0.51, F = 32.7, p < 0.001) with minor uncorrelated reflexive torque. Reflexive torque correlated to Ashworth Score at shorter movement durations (r2 = 0.25, F = 11, p = 0.002).ConclusionStroke patients were distinguished from controls by tissue stiffness and viscosity and to a lesser extent by reflexive torque from the soleus muscle. These parameters were also sensitive to discriminate patients, clinically graded by the Ashworth Score. Movement duration affected viscosity and reflexive torque which are clinically relevant parameters. Full evaluation of pathological joint resistance therefore requires instrumented tests at various movement conditions.

Arm Stiffness During Assisted Movement After Stroke: The Influence of Visual Feedback and Training

“…As a consequence, we suggest that the Ashworth score is more reflective of the rigidity of the connective and muscular (active) tissue [64] than it is of the reflexive component of spasticity [63]. This seems to be confirmed by the stiffness measurements taken toward the end of the training, when reflexes are more easily controlled.…”

An ultrasound based non-invasive method for quantifying soft tissue movement artefact during analysis of intrinsic foot motion

“…[1] Introduction and aim: The intrinsic kinematics of the foot are of interest for a number of clinical conditions, and this is reflected in the large number of multi-segment foot models for gait analysis reported in the literature [1]. These models tend to be based on skin mounted motion capture marker sets, however studies using bone pins have demonstrated significant differences between the true motion of the foot bones and the motion measured using skin mounted markers [2]. This is primarily due to movement of the underlying bony landmarks relative to the surrounding soft tissue.…”

Myotonometric Measurement of Muscular Properties of Hemiparetic Arms in Stroke Patients

“…Muscular atrophy and muscle phenotype shift to fast-twitch fiber proportions in the hemiparetic leg muscle after a stroke and relate to muscle fatigue, poor fitness, poor physical performance, and neurologic gait deficit (HaferMacko et al, 2008). Spasticity (hyperactivity of stretch reflexes) and hypertonia (i.e., increased stiffness and viscosity) are common impairments after stroke (de Vlugt et al, 2010;Katz & Rymer, 1989). Spasticity is attributed to increased muscle tone related to hyperreflexia according to Lance (1980) who defined spasticity as a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from reflex hyperexcitability (Lance, 1980).…”

“… not standardizing stretch velocity in manual testing (de Vlugt et al, 2010),  not quantifying resistance in absolute units (Pandyan et al, 1999),  not providing an assessment of activated muscle tone (Sommerfeld et al, 2004),  subjectively grading and clustering of scores (Katz & Rymer, 1989;Pandyan et al, 1999),  only being applicable for the extremities (Leonard et al, 2001),  lacking sensitivity for detecting smaller degrees of changes in spasticity (Lance, 1980),  poor discrimination between increased muscle tone and soft-tissue stiffness (de Vlugt et al, 2010;Sheean & McGuire, 2009), and  lacking correlation with functional changes after treatment (Ward, 2000).…”