On the Relationship between Spasticity and Gait ...

On the Relationship between Spasticity and Gait Variability Arnaud Gouelle, PhD Gait and Motion Analysis Unit Robert Debré University Hospital for Children Paris, France

Disclosure: No financial interest to disclose. nd Annualde 26ème la SOFMER, octobre - Nantes ACRM 92congrès Conference, 29th 14 October 20152011 – Dallas, TX, USA

Learning Objectives 

What is gait variability and How quantified it

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Different levels of influence of spasticity on variability

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“Bad” and “Good” variability

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Mid-term and long term effects

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Impact of therapy against spasticity

What is gait variability? 

Fluctuations in gait characteristics (kinematics, kinetics, spatiotemporal parameters) between strides or steps

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Natural variability in healthy persons due to:  Neuromuscular noise in the sensori-motor system  Errors or deficits in the motor control system

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Variability is affected in advanced age and various neurologically impaired populations (including CP, MS, Stroke, SCI….)

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Key parameter of dynamic instability during walking  Measure of motor ability  Tool for assessing progressive changes or the efficacy of therapeutic interventions

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Note: can arise too from external (e.g., environmental demands) and methodological (e.g., instrumentation) factors

How is gait variability quantified? 

No gold standard and different analysis techniques depending on:  Methods used to record data (accelerometers, gait mats, 3D mocap, etc.)  Nature of the main variables (STP, angles, CoP, CoM, etc.)  Pathological condition (treadmill, distance, etc.)

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Fluctuation magnitude  Distributional metrics such as standard deviation, coefficient of variation  Conglomerate measure: Gait Variability Index (Gouelle et al., 2013)  Most commonly used: more clinically applicable

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Fluctuation dynamics (For a review, see Hausdorff, 2007)  Temporal structuring of the signal  Non linear metrics (e.g. DFA, approximate entropy, Lyapunov exponent)

Presenter’s images Gouelle et al. (2013). The Gait Variability Index: A new way to quantify fluctuation magnitude of spatiotemporal parameters during gait. Gait and Posture, 38, 461-465. Hausdorff (2007). Gait dynamics, fractals and falls finding meaning in the stride-tostride fluctuations of human walking. Human Movement Science, 26, 555-589.

Influence of spasticity 

Direct noisy impact (“bad variability”)  Abnormal muscle tone and loss of selective control  Alteration in the outcome of descending motor command driving walking  More variability in movement trajectories Spasticity

Stimulus

Central Nervous system

Musculoskeletal system

Trajectory

Influence of spasticity 

Direct noisy impact (“bad variability”)

Bakir et al. (2013) Children (from 6 of age) with spastic bilateral CP compared to TD children Absence of contractures, Modified Ashworth Scale 1.5 ± 0.4  CV significantly higher in CP Prosser et al. (2010) Children (from 7 of age) with spastic bilateral CP Spasticity in hamstrings and hip adductors using modified Tardieu scale  CV significantly higher in CP  But not related to any Tardieu test value

WHY???

Bakir et al. (2013). Temporal but not spatial variability during gait Is reduced after selective dorsal rhizotomy in children with cerebral palsy. PLoS ONE, 8(7), e69500. Prosser et al. (2010). Variability and symmetry of gait in early walkers with and without bilateral cerebral palsy. Gait and Posture, 31, 522-526.

Influence of spasticity 

Immediate adaptation to the perturbation (“good variability”)  Required to preserve movement and prevent falling  Depending on physiological and physical capacities  

Difficult to clearly differentiate perturbation and regulation More visible in patients with a more affected/spastic side

Balasubramanian et al. (2009) Post-stroke with chronic hemiparesis, No control for spasticity  SD swing time greater on the paretic side  SD single phase time greater on the non-paretic side = more regulation

Balasubramanian et al. (2009). Variability in spatiotemporal step characteristics and its relationship to walking performance post-stroke. Gait and Posture, 29, 408-414.

Influence of spasticity 

Immediate adaptation to the perturbation (“good variability”)

Femery et al. (2001), Descatoire et al. (2009) Children (15±3 years) with Cerebral Palsy hemiplegia Spasticity (hamstrings, rectus femoris, triceps surae) using Ashworth Scale Low spasticity group (mean 1) versus High spasticity group (mean 3) Spatiotemporal parameters + Foot pressure   

Global variability is higher in the High spasticity group High spasticity: plegic limb more variable Low spasticity: non-plegic limb more variable

REGULATION STRATEGY

Femery et al. (2001). Spasticity and dynamic plantar pressure distribution measurements in hemiplegic spastic children. Annals of Physical and Rehabilitation Medicine, 44, 26-34.

Influence of spasticity 

Mid- and long-term impact  Primary effects of the original brain injury (spasticity) lead to…  … Secondary anomalies (e.g. bones torsional misalignment, muscular contractures)  … Tertiary compensation (e.g. vaulting in plantarflexor spasticity)

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Dynamic theories of self-organization (task, organism, environment) Gait variability depending on the possibilities, the quality of coping strategies… … and WHAT is optimized? (energy, velocity, or stability)

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High level of constraints  Very reproducible walk with low gait variability  Hide often inability to manage high perturbation

Changes in gait variability during spasticity therapy 

Few articles with follow-up of the outcomes  Gait variability is reduced after therapy

Bakir et al. (2013) Children (from 6 of age) with spastic bilateral CP, Dorsal Rhyzotomy  Modified Ashworth Scale from 1.5 (±0.4) to 0.6 (±0.5)  Temporal variability is reduced Gross et al. (2012) Case study on patient with Spinal Cord Injury, Motor nerve block in Rectus Femoris  ICC for knee flexion/extension curves of the different gait cycles  Reproducibility improved at 6 weeks after toxin 

How does patient re-organize his gait?  New degrees of freedom to manage  Immediate improvement of the functional aspect of gait  Increased gait variability that decreases with time

Bakir et al. (2013). Temporal but not spatial variability during gait Is reduced after selective dorsal rhizotomy in children with cerebral palsy. PLoS ONE, 8(7), e69500. Gross et al. (2012). Unstable gait due to spasticity of the rectus femoris: Gait analysis and motor nerve block. Annals of Physical Rehabilitation and Medicine, 55, 609622.

Conclusion 

Combination of deficits contribute to gait

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Not easy to assess which part is really due to spasticity

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Which proportion of “Bad” and “Good” variability

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Spasticity is commonly evaluated in a passive condition

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Need of electromyography during spasticity testing

Thank you!