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The relation between neuromechanical parameters and Ashworth score in stroke patients.

de Vlugt E, de Groot JH, Schenkeveld KE, Arendzen JH, van der Helm FC, Meskers CG - J Neuroeng Rehabil (2010)

Bottom Line: Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomechanical Engineering, Faculty of Mechanical Engineering, Delft University of Technology, Mekelweg 2, Delft, The Netherlands. e.devlugt@tudelft.nl

ABSTRACT

Background: Quantifying 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.

Methods: Ramp-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.

Results: Ankle 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).

Conclusion: Stroke 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.

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Imposed ramp-and-hold movement profiles, joint torque and IEMG. Rows from top to bottom: Ankle joint angle showing the imposed (dorsiflexion) ramp-and-hold (RaH) joint rotation profiles at four different movement durations (columns: 0.25, 0.5, 1.0, 2.0 s), corresponding joint torque responses and IEMG signals from all four muscles. Traces are shown over a five second time frame for an AS3 patient. Positive values indicate to dorsiflexion.
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Figure 3: Imposed ramp-and-hold movement profiles, joint torque and IEMG. Rows from top to bottom: Ankle joint angle showing the imposed (dorsiflexion) ramp-and-hold (RaH) joint rotation profiles at four different movement durations (columns: 0.25, 0.5, 1.0, 2.0 s), corresponding joint torque responses and IEMG signals from all four muscles. Traces are shown over a five second time frame for an AS3 patient. Positive values indicate to dorsiflexion.

Mentions: As an example, Figure 3 shows the imposed movement for all four durations and the corresponding torque and muscle activity (IEMG) of all muscles of a stroke patient (AS3). Torque typically increased exponentially during the ramp phase, reaching to a peak value near the end of the RaH movement. Peak torque increased with shorter duration (higher velocity) of movement. When the movement stopped at the dorsiflexion angle, the torque decayed to a value that was independent on duration.


The relation between neuromechanical parameters and Ashworth score in stroke patients.

de Vlugt E, de Groot JH, Schenkeveld KE, Arendzen JH, van der Helm FC, Meskers CG - J Neuroeng Rehabil (2010)

Imposed ramp-and-hold movement profiles, joint torque and IEMG. Rows from top to bottom: Ankle joint angle showing the imposed (dorsiflexion) ramp-and-hold (RaH) joint rotation profiles at four different movement durations (columns: 0.25, 0.5, 1.0, 2.0 s), corresponding joint torque responses and IEMG signals from all four muscles. Traces are shown over a five second time frame for an AS3 patient. Positive values indicate to dorsiflexion.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927906&req=5

Figure 3: Imposed ramp-and-hold movement profiles, joint torque and IEMG. Rows from top to bottom: Ankle joint angle showing the imposed (dorsiflexion) ramp-and-hold (RaH) joint rotation profiles at four different movement durations (columns: 0.25, 0.5, 1.0, 2.0 s), corresponding joint torque responses and IEMG signals from all four muscles. Traces are shown over a five second time frame for an AS3 patient. Positive values indicate to dorsiflexion.
Mentions: As an example, Figure 3 shows the imposed movement for all four durations and the corresponding torque and muscle activity (IEMG) of all muscles of a stroke patient (AS3). Torque typically increased exponentially during the ramp phase, reaching to a peak value near the end of the RaH movement. Peak torque increased with shorter duration (higher velocity) of movement. When the movement stopped at the dorsiflexion angle, the torque decayed to a value that was independent on duration.

Bottom Line: Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomechanical Engineering, Faculty of Mechanical Engineering, Delft University of Technology, Mekelweg 2, Delft, The Netherlands. e.devlugt@tudelft.nl

ABSTRACT

Background: Quantifying 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.

Methods: Ramp-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.

Results: Ankle 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).

Conclusion: Stroke 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.

Show MeSH
Related in: MedlinePlus