Abnormal cutaneous flexor reflex activity during controlled isometric plantarflexion in human spinal cord injury spasticity syndrome

Abstract

Study design: Although abnormal cutaneous reflex (CR) activity has been identified during gait after incomplete spinal cord injury (SCI), this activity has not been directly compared in subjects with and without the spasticity syndrome. Objectives: Characterisation of CR activity during controlled rest and 'ramp and hold' phases of controlled plantarflexion in subjects with and without the SCI spasticity syndrome. Design: Transverse descriptive study with non-parametric group analysis. Setting: SCI rehabilitation hospital. Methods: Tibialis Anterior (TA) reflexes were evoked by innocuous cutaneous plantar sole stimulation during rest and ramp and hold phases of plantarflexion torque in non-injured subjects (n = 10) and after SCI with (n = 9) and without (n = 10) hypertonia and/or involuntary spasm activity. Integrated TA reflex responses were analysed as total (50-300 ms) or short (50-200 ms) and long-latency (200-300 ms) activity. Results: Total and long-latency TA activity was inhibited in non-injured subjects and the SCI group without the spasticity syndrome during plantarflexion torque but not in the SCI spasticity group. Furthermore, loss of TA reflex inhibition during plantarflexion correlated with time after SCI (ρ = 0.79, P = 0.009). Moreover, TA reflex activity inversely correlated with maximum plantarflexion torque in the spasticity group (ρ = − 0.75, P = 0.02), despite similar non-reflex TA electromyographic activity during plantarflexion after SCI in subjects with (0.11, 0.08-0.13 mV) or without the spasticity syndrome (0.09, 0.07-0.12 mV). Conclusions: This reflex testing procedure supports previously published evidence for abnormal CR activity after SCI and may characterise the progressive disinhibition of TA reflex activity during controlled plantarflexion in subjects diagnosed with the spasticity syndrome. Spinal Cord (2016) 54, 687-694; doi:10.1038/sc.2016.9; published online 23 February 2016 INTRODUCTION Spasticity was originally defined as an increase in velocity-dependent, tonic stretch reflexes to passive movement 1 and has been used to describe a number of signs and symptoms that together contribute to the syndrome. 2 Cutaneous reflex (CR) dysfunction has also been regarded as an additional sign of the spasticity syndrome following spinal cord injury (SCI), 3-9 especially when detected in subjects with hypertonia and increased tonic stretch reflexes. [10][11][12] In addition, abnormal flexor reflex excitability is present during subacute 4,13 and chronic SCI, 14,15 impacts on residual gait function after SCI 16 and interferes with daily activities. 17 Lower limb CR activity in humans is modulated by several segmental and descending control mechanisms, 18-21 and the loss of descending modulatory mechanisms may contribute to the SCI spasticity syndrome. Tibialis Anterior (TA) muscle reflex activity evoked following cutaneous stimulation of the plantar surface (Pl-TA CR) [22][23][24] has been used as a test to assess the integrity of segmental and descending motor control mechanisms in healthy...

Non‐invasive spinal direct current simulation for spasticity therapy following spinal cord injury: mechanistic insights contributing to long‐term treatment effects

“…A and B ) (Gomez‐Soriano et al . ). Although the functional impact of long‐latency cutaneous hyperreflexia on residual muscle strength needs to be further defined (Gomez‐Soriano et al .…”

“…Electrical stimulation of the plantar pad is recorded as tibialis anterior (TA) EMG activity (Gomez‐Soriano et al . ). B , representative lower limb cutaneous reflex activity recorded from the TA muscle during plantarflexion in subjects with subacute motor incomplete spinal cord injury (SCI) without (left) and with (right) the spasticity syndrome (Gomez‐Soriano et al .…”

“…B , representative lower limb cutaneous reflex activity recorded from the TA muscle during plantarflexion in subjects with subacute motor incomplete spinal cord injury (SCI) without (left) and with (right) the spasticity syndrome (Gomez‐Soriano et al . ). Note the long‐latency cutaneous hyperreflexia in the subject with SCI spasticity syndrome.…”

“…Although the functional impact of long‐latency cutaneous hyperreflexia on residual muscle strength needs to be further defined (Gomez‐Soriano et al . ), our group has shown that focal vibration or transcutaneous electrical nerve stimulation of the plantar pad reduces cutaneous reflex activity (Gomez‐Soriano et al . ).…”

Longitudinal estimation of intramuscular Tibialis Anterior coherence during subacute spinal cord injury: relationship with neurophysiological, functional and clinical outcome measures

“…Outcome measures related to the SCI spasticity syndrome [31] included muscle hypertonia with the modified Ashworth scale (MAS) [32], and the Penn scale [33]. SCI severity and neurological level was performed by a clinical consultant who had participated in the AIS training course with the European Multicenter Study about Spinal Cord Injury (EMSCI) network.…”