Changes in spinal reflex and locomotor activity after a complete spinal cord injury: a common mechanism?

Locomotor activity and spinal reflexes (SRs) show common features in different mammals, including humans. Here we report the time-course of the development of locomotor activity and SRs after a complete spinal cord injury in humans. SRs evoked by tibial nerve stimulation were studied, as was the leg muscle electromyography activity evoked by mechanically assisted locomotion (Lokomat) in biceps femoris, rectus femoris, tibialis anterior and gastrocenmius medialis. Around 8 weeks after the injury, an early SR component (latency 60-120 ms) appeared, as in healthy subjects, and a well-organized leg muscle activity was present during assisted locomotion. At around 6 months after injury an additional, late reflex component (latency 120-450 ms) appeared, which remained even 15 years after the spinal cord injury. In contrast, the early component had markedly decreased at 18 months after injury. These changes in SR were associated with a loss of electromyography activity and a successively stronger electromyography exhaustion (i.e. decline of electromyography amplitude), when comparing the level of electromyography activity at 2 and 10 min, respectively, during assisted locomotion. These changes in electromyography activity affected mainly the biceps femoris, gastrocenmius medialis and tibialis anterior but less so the rectus femoris. When the amplitude relationship of the early to late SR component was calculated, there was a temporal relationship between the decrease of the early component and an increase of the late component and the degree of exhaustion of locomotor activity. In chronic, severely affected but sensori-motor incomplete spinal cord injury subjects a late SR component, associated with an electromyography exhaustion, was present in subjects who did not regularly perform stepping movements. Our data are consistent with the proposal of a common mechanism underlying the changes in SR activity and locomotor activity after spinal cord injury. These findings should be taken into consideration in the development of novel rehabilitation schemes and programs to facilitate regeneration-inducing therapies in spinal cord injury subject

Are changes in nociceptive withdrawal reflex magnitude a viable central sensitization proxy? Implications of a replication attempt

Objective: The nociceptive withdrawal reflex (NWR) has been proposed to read-out central sensitization (CS). Replicating a published study, it was assessed if the NWR magnitude reflects sensitization by painful heat. Additionally, NWR response rates were compared for two stimulation, the sural nerve at the lateral malleolus (SU) and the medial plantar nerve on the foot sole (MP), and three recording sites, biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) muscles. Methods: 16 subjects underwent one experiment with six blocks of eight transcutaneous electrical stimulations to elicit the NWR while surface electromyography was collected. Tonic heat was concurrently applied in the same dermatome. Temperatures rose from 32 °C in the first to 46 °C in the last block following the previously published protocol. Results: Tonic heat did not influence NWR magnitude. The highest NWR response rate was obtained for MP-TA combination (79%). Regarding elicitation in all three muscles, SU stimulation outperformed MP (59% vs 57%). Conclusions: The replication failed. NWR magnitude as a CS proxy in healthy subjects needs continued investigation. With respect to response rates, MP-TA proved efficient, whereas SU stimulation seemed preferable for multiple muscle recordings. Significance: Unclear methodological descriptions in the original study affected CS and NWR replication. The NWR magnitude changes induced by CS may closely depend on the different stimulation methods used. Keywords: Central sensitization; Nociceptive withdrawal reflex; Reliability; Response rat

Legislative strengthening meets party support in international assistance: a closer relationship?

Recent reports recommend that international efforts to help strengthen legislatures in emerging democracies should work more closely with support for building stronger political parties and competitive party systems. This article locates the recommendations within international assistance more generally and reviews the arguments. It explores problems that must be addressed if the recommendations are to be implemented effectively. The article argues that an alternative, issue-based approach to strengthening legislatures and closer links with civil society could gain more traction. However, that is directed more centrally at promoting good governance for the purpose of furthering development than at democratisation goals sought by party aid and legislative strengtheners in the democracy assistance industry

Sensory phenotypes in complex regional pain syndrome and chronic low back pain-indication of common underlying pathomechanisms.

INTRODUCTION First-line pain treatment is unsatisfactory in more than 50% of chronic pain patients, likely because of the heterogeneity of mechanisms underlying pain chronification. OBJECTIVES This cross-sectional study aimed to better understand pathomechanisms across different chronic pain cohorts, regardless of their diagnoses, by identifying distinct sensory phenotypes through a cluster analysis. METHODS We recruited 81 chronic pain patients and 63 age-matched and sex-matched healthy controls (HC). Two distinct chronic pain cohorts were recruited, ie, complex regional pain syndrome (N = 20) and low back pain (N = 61). Quantitative sensory testing (QST) was performed in the most painful body area to investigate somatosensory changes related to clinical pain. Furthermore, QST was conducted in a pain-free area to identify remote sensory alterations, indicating more widespread changes in somatosensory processing. RESULTS Two clusters were identified based on the QST measures in the painful area, which did not represent the 2 distinct pain diagnoses but contained patients from both cohorts. Cluster 1 showed increased pain sensitivities in the painful and control area, indicating central sensitization as a potential pathomechanism. Cluster 2 showed a similar sensory profile as HC in both tested areas. Hence, either QST was not sensitive enough and more objective measures are needed to detect sensitization within the nociceptive neuraxis or cluster 2 may not have pain primarily because of sensitization, but other factors such as psychosocial ones are involved. CONCLUSION These findings support the notion of shared pathomechanisms irrespective of the pain diagnosis. Conversely, different mechanisms might contribute to the pain of patients with the same diagnosis

Influence of spinal reflexes on the locomotor pattern after spinal cord injury

In complete spinal cord injured (cSCI) subjects a shift from dominant early (60-120ms latency) to dominant late (120-450ms latency) spinal reflex (SR) components occurs over time after injury. This shift is assumed to reflect a spinal neuronal dysfunction below the level of a spinal lesion. The neuronal pathways of SR are suggested to be closely connected with spinal locomotor circuits. The aim of this study was to explore the influence of the two SR components on the electromyographic (EMG) pattern induced by assisted locomotion in cSCI subjects. Leg muscle EMG activity was analysed during assisted locomotion in both healthy and motor cSCI subjects. SR were evoked by non-noxious tibial nerve stimulation during mid-stance phase of the gait cycle. Early and late SR components had a differential influence on the locomotor pattern. In healthy and cSCI subjects with a dominant early SR component the locomotor EMG pattern was modulated in the form of a short increase in leg flexors activity in the stance phase (tibialis anterior, biceps femoris). In contrast, in chronic cSCI subjects with a dominant late SR component no activation in biceps femoris but a long-lasting activation of tibialis anterior and rectus femoris muscles during the stance phase was evoked. It is concluded that the same tibial nerve stimuli activated two different neuronal pathways, resulting in divergent interactions with spinal locomotor circuitries. It is proposed that the two SR components have different physiological roles during locomotion

Modulation of spinal neuronal excitability by spinal direct currents and locomotion after spinal cord injury

OBJECTIVE: Spinal neuronal function is impaired after a severe spinal cord injury (SCI) and can be assessed by the analysis of spinal reflex (SR) behavior. We applied transcutaneous spinal direct current stimulation (tsDCS) and locomotor activity, to determine whether the excitability of spinal neuronal circuitries underlying locomotion can be modulated after motor complete SCI. METHOD: SRs were evoked by non-noxious electrical stimulation of the tibial nerve. SR behavior was assessed before, immediately after, and 20min after four different interventions (anodal, cathodal, sham tsDCS, or locomotion) in subjects with motor complete SCI and healthy subjects. RESULTS: SR amplitudes in SCI subjects were increased after anodal tsDCS by 84% (p<0.05). Cathodal, sham tsDCS and locomotion had no influence on SR amplitudes. In addition, reflex threshold was lower after anodal tsDCS and locomotion in SCI subjects (p<0.05). CONCLUSION: Anodal tsDCS is able to modulate spinal neuronal circuitries after SCI. SIGNIFICANCE: This novel, noninvasive approach might be used as a tool to excite spinal neuronal circuitries. If applied repetitively within a training approach, anodal tsDCS might prevent adverse alterations in spinal reflex function in severely affected SCI subjects, i.e., a manifestation of a spinal neuronal dysfunction taking part below the level of a spinal lesion