Modulation of spinal inhibitory reflexes depends on the frequency of transcutaneous electrical nerve stimulation in spastic stroke survivors

Modulation of Primary Afferent Nerve Fiber (Ia) Reciprocal Inhibition Under Voluntary and Electrically Stimulated Muscle Conditions: Within-Subject Study Design

Background: Reciprocal inhibition (RI) is a spinal reflex that controls posture and movement. The modulation of spinal RI represented by the H-reflex has been studied, before and after voluntary contraction and electrical nerve stimulation but not during voluntary, electrically induced muscle contraction or a combination of voluntary and electrically induced muscle contractions. This study investigates the effects of the ongoing voluntary isometric contraction, the electrically induced isometric contraction, and the combination of voluntary with electrically induced isometric contraction of the Tibialis Anterior (TA) muscle on spinal RI represented by Soleus H-reflex. Methods: Eighteen healthy adults participated. Soleus H-reflex and M-response were measured during four different conditions as follows: (1) at rest, (2) electrically induced isometric contraction of the TA, (3) voluntary isometric contraction of the TA with a 1 kg force, and (4) combined voluntary and electrically induced isometric contraction of the TA with a 1 kg force. Results: The ANOVA clearly demonstrated significant differences in Soleus H-reflex amplitude across the four recording conditions (F3,16, 17.28, p < 0.001). The amplitude at rest was significantly higher than during electrically induced isometric contraction, voluntary isometric contraction, and the combined contraction conditions (p < 0.05). Furthermore, the amplitude recorded during the electrically induced isometric contraction condition significantly surpassed that of voluntary isometric contraction and the combined contraction conditions (p < 0.05). Moreover, there was no significant difference between Soleus H-reflex amplitude recorded during voluntary isometric contraction and the combined voluntary isometric contraction and electrically induced isometric contraction (p < 0.87). The combined voluntary isometric contraction and electrically induced isometric contraction condition had a higher inhibitory effect on the Soleus H-reflex with no significant differences from voluntary isometric contraction. Moreover, both were significantly better than electrically induced isometric contraction (p = 0.05). In terms of Soleus H-reflex latency, there was no significant difference among all four conditions (p > 0.05), meaning Soleus H-reflex latency was not influenced by the conditions. Conclusions: RI can be best modulated by combining voluntary with electrically induced isometric muscle contractions.

Pathophysiology and Management Strategies for Post-Stroke Spasticity: An Update Review

Post-stroke spasticity (PSS), characterized by a velocity-dependent increase in muscle tone and exaggerated reflexes, affects a significant portion of stroke patients and presents a substantial obstacle to post-stroke rehabilitation. Effective management and treatment for PSS remains a significant clinical challenge in the interdisciplinary aspect depending on the understanding of its etiologies and pathophysiology. We systematically review the relevant literature and provide the main pathogenic hypotheses: alterations in the balance of excitatory and inhibitory inputs to the descending pathway or the spinal circuit, which are secondary to cortical and subcortical ischemic or hemorrhagic injury, lead to disinhibition of the stretch reflex and increased muscle tone. Prolongation of motoneuron responses to synaptic excitation by persistent inward currents and secondary changes in muscle contribute to hypertonia. The guidelines for PSS treatment advocate for a variety of therapeutic approaches, yet they are hindered by constraints such as dose-dependent adverse effects, high cost, and limited therapeutic efficacy. Taken together, we highlight key processes of PSS pathophysiology and summarize many interventions, including neuroprotective agents, gene therapy, targeted therapy, physiotherapy, NexTGen therapy and complementary and alternative medicine. We aim to confer additional clinical benefits to patients and lay the foundation for the development of new potential therapies against PSS.

Outcome measures for assessing the effectiveness of physiotherapy interventions on equinus foot deformity in post-stroke patients with triceps surae spasticity: A scoping review

OBJECTIVE

Equinus foot deformity (EFD) is the most common deviation after stroke. Several physiotherapy interventions have been suggested to treat it. However, studies evaluating the efficacy of these treatments vary widely in terms of assessment modalities, type of data analysis, and nomenclature. This scoping review aimed to map current available evidence on outcome measures and the modalities employed to assess the effectiveness of physiotherapy programs for the reduction of triceps surae (TS) spasticity and EFD in patients with stroke.

METHODS

Scoping review methodological frameworks have been used. Three databases were investigated. Primary literature addressing TS spasticity in adult patients with stroke using physiotherapy interventions was included. Findings were systematically summarized in tables according to the intervention used, intervention dosage, control group, clinical, and instrumental outcome measures.

RESULTS

Of the 642 retrieved studies, 53 papers were included. TS spasticity was assessed by manual maneuvers performed by clinicians (mainly using the Ashworth Scale), functional tests, mechanical evaluation through robotic devices, or instrumental analysis and imaging (such as the torque-angle ratio, the H-reflex, and ultrasound images). A thorough critical appraisal of the construct validity of the scales and of the statistics employed was provided, particularly focusing on the choice of parametric and non-parametric approaches when using ordinal scales. Finally, the complexity surrounding the concept of "spasticity" and the possibility of assessing the several underlying active and passive causes of EFD, with a consequent bespoke treatment for each of them, was discussed.

CONCLUSION

This scoping review provides a comprehensive description of all outcome measures and assessment modalities used in literature to assess the effectiveness of physiotherapy treatments, when used for the reduction of TS spasticity and EFD in patients with stroke. Clinicians and researchers can find an easy-to-consult summary that can support both their clinical and research activities.

Physical therapy interventions for the correction of equinus foot deformity in post-stroke patients with triceps spasticity: A scoping review

Objective

Equinus foot deformity (EFD) is the most common deformity following a stroke. Several approaches have been suggested for its correction, including pharmacological, surgical, and physical therapy (PT) interventions. This scoping review aims to map and synthesize the available evidence focusing on physical therapy treatments for EFD caused by triceps surae (TS) spasticity.

Methods

Scoping review methodological frameworks have been used. Pubmed, Cinahl, and Cochrane databases were searched for primary literature. Studies focusing on the treatment of EFD in adult stroke patients were included only when the intervention involved PT treatments and presented at least one outcome measure for the functional and/or structural condition of the TS. Data were systematically collected and reported in tables inclusive of type of intervention, sample characteristics, dosage, comparators, outcomes, follow-up timeline, and treatment efficacy. A narrative synthesis was also added.

Results

Of the 642 experimental or observational screened studies, 53 were included, focusing on stretching exercises, shock waves, electrical stimulation, dry needling, TENS, vibration therapy, ultrasounds, cryotherapy, and active physiotherapy. Patients with EFD benefited from specific physical therapy treatments. These usually resulted in Modified Ashworth Scale reduction, typically by 1 point, and an increase in ROM. Interventions consisting of shock waves, dry needling, and electrostimulation showed the best results in reducing EFD. Heterogeneous dosage and delivery mode generally limited conclusions.

Conclusions

This scoping review summarized available primary literature based on PT treatments for the correction of EFD. By highlighting the remaining gaps in knowledge, it provides a reference for future studies on this pathology. Further investigations are necessary to pinpoint the best dosage and delivery methods. Future studies should investigate whether early rehabilitation programs started during the acute phase might help prevent or limit the development of secondary deformities.

Effects of 60 Min Electrostimulation With the EXOPULSE Mollii Suit on Objective Signs of Spasticity

Background: The EXOPULSE Mollii method is an innovative full-body suit approach for non-invasive electrical stimulation, primarily designed to reduce disabling spasticity and improve motor function through the mechanism of reciprocal inhibition. This study aimed to evaluate the effectiveness of one session of stimulation with the EXOPULSE Mollii suit at different stimulation frequencies on objective signs of spasticity and clinical measures, and the subjective perceptions of the intervention.

Methods: Twenty patients in the chronic phase after stroke were enrolled in a cross-over, double-blind controlled study. Electrical stimulation delivered through EXOPULSE Mollii was applied for 60 min at two active frequencies (20 and 30 Hz) and in OFF-settings (placebo) in a randomized order, every second day. Spasticity was assessed with controlled-velocity passive muscle stretches using the NeuroFlexor hand and foot modules. Surface electromyography (EMG) for characterizing flexor carpi radialis, medial gastrocnemius, and soleus muscles activation, Modified Ashworth Scale and range of motion were used as complementary tests. Finally, a questionnaire was used to assess the participants' perceptions of using the EXOPULSE Mollii suit.

Results: At group level, analyses showed no significant effect of stimulation at any frequency on NeuroFlexor neural component (NC) and EMG amplitude in the upper or lower extremities (p > 0.35). Nevertheless, the effect was highly variable at the individual level, with eight patients exhibiting reduced NC (>1 N) in the upper extremity after stimulation at 30 Hz, 5 at 20 Hz and 3 in OFF settings. All these patients presented severe spasticity at baseline, i.e., NC > 8 N. Modified Ashworth ratings of spasticity and range of motion did not change significantly after stimulation at any frequency. Finally, 75% of participants reported an overall feeling of well-being during stimulation, with 25% patients describing a muscle-relaxing effect on the affected hand and/or foot at both 20 and 30 Hz.

Conclusions: The 60 min of electrical stimulation with EXOPULSE Mollii suit did not reduce spasticity consistently in the upper and lower extremities in the chronic phase after stroke. Findings suggest a need for further studies in patients with severe spasticity after stroke including repeated stimulation sessions.

Clinical Trial Registration:https://clinicaltrials.gov/ct2/show/NCT04076878, identifier: NCT04076878.

Differential Changed Excitability of Spinal Motor Neurons Innervating Tibialis Anterior and Peroneus Muscles Cause Foot Inversion After Stroke

Objective: To study differential post-stroke changes of excitability of spinal motor neurons innervating a group of antagonist muscles of ankle and their effects on foot inversion.

Methods: F waves in tibialis anterior (TA) and peroneus muscles (PN) were recorded. The condition of spasticity and foot inversion in stroke patients were also evaluated. The differences of F wave parameters between patients and healthy controls (HC), as well as TA and PN, were investigated.

Results: There were natural differences in the persistence of the F waves (Fp) and F/M amplitude ratio (F/M) between TA and PN in HC. Stroke patients showed significantly higher F/M in TA and PN, while there was no difference in Fp comparing to HC. The natural differences in F wave parameters between TA and PN were differentially retained after stroke. The natural difference of the two muscles in Fp remained unchanged and the F/M difference disappeared in those without spasticity or foot inversion, while the Fp difference disappeared and the F/M difference remained in those with spasticity or foot inversion.

Conclusion: Based on the natural difference of the number and size of spinal motor neurons innervating TA and PN, their excitability may change differently according to the severity of the stroke, which may be the reason of foot inversion.

Effectiveness of Physiotherapy Interventions on Spasticity in People With Multiple Sclerosis: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of the study was to examine the effectiveness of physiotherapy (PT) interventions on spasticity in people with multiple sclerosis.

DESIGN

A systematic search was performed using PRISMA guidance. Studies evaluate the effect of PT interventions on spasticity were included. People with multiple sclerosis, spasticity, disability and PT interventions characteristics were extracted in included studies. Level of evidence was synthesized by the Grade of Recommendation, Assessment, Development and Evaluation approach. Meta-analyses were performed by calculating Hedges g at 95% confidence interval.

RESULTS

A total of 29 studies were included in the review, and 25 were included in the meta-analyses. The included PT interventions were exercise therapy, electrical stimulation, radial shock wave therapy, vibration, and standing. The review and meta-analyses showed different evidences of benefits and nonbenefits for PT interventions on some spasticity outcomes. The best quality evidences were for beneficial effects of exercise therapy especially robot gait training and outpatient exercise programs on self-perceived spasticity and muscle tone respectively. The review results were positive regarding the acute effects, follow-up measurements, safety, progressive MS, and nonambulatory people with multiple sclerosis. The included articles were heterogeneous and badly reported in PT interventions and people with multiple sclerosis characteristics.

CONCLUSIONS

Physiotherapy interventions can be a safe and beneficial option for spasticity in people with multiple sclerosis. No firm conclusion can be drawn on overall spasticity. Further researches in different spasticity aspects are needed.

Bilateral Transcutaneous Electrical Nerve Stimulation Improves Lower-Limb Motor Function in Subjects With Chronic Stroke: A Randomized Controlled Trial

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) has been used to augment the efficacy of task-oriented training (TOT) after stroke. Bilateral intervention approaches have also been shown to be effective in augmenting motor function after stroke. The purpose of this study was to compare the efficacy of bilateral TENS combined with TOT versus unilateral TENS combined with TOT in improving lower-limb motor function in subjects with chronic stroke.

METHODS AND RESULTS

Eighty subjects were randomly assigned to bilateral TENS+TOT or to unilateral TENS+TOT and underwent 20 sessions of training over a 10-week period. The outcome measures included the maximal strength of the lower-limb muscles and the results of the Lower Extremity Motor Coordination Test, Berg Balance Scale, Step Test, and Timed Up and Go test. Each participant was assessed at baseline, after 10 and 20 sessions of training and 3 months after the cessation of training. The subjects in the bilateral TENS+TOT group showed greater improvement in paretic ankle dorsiflexion strength (β=1.32; P=0.032) and in the completion time for the Timed Up and Go test (β=-1.54; P=0.004) than those in the unilateral TENS+TOT group. However, there were no significant between-group differences for other outcome measures.

CONCLUSIONS

The application of bilateral TENS over the common peroneal nerve combined with TOT was superior to the application of unilateral TENS combined with TOT in improving paretic ankle dorsiflexion strength after 10 sessions of training and in improving the completion time for the Timed Up and Go test after 20 sessions of training.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02152813.

Transcutaneous electrical nerve stimulation improves walking capacity and reduces spasticity in stroke survivors: a systematic review and meta-analysis

OBJECTIVE

To evaluate (1) the effectiveness of transcutaneous electrical nerve stimulation (TENS) at improving lower extremity motor recovery in stroke survivors and (2) the optimal stimulation parameters for TENS.

REVIEW METHODS

A systematic search was conducted for studies published up to October 2017 using eight electronic databases (CINAHL, ClinicalTrials.gov, the Cochrane Central Register of Controlled Trials, EMBASE, MEDLINE, PEDro, PubMed and Web of Science). Randomized controlled trials that evaluated the effectiveness of the application of TENS at improving lower extremity motor recovery in stroke survivors were assessed for inclusion. Outcomes of interest included plantar flexor spasticity, muscle strength, walking capacity and balance.

RESULTS

In all, 11 studies met the inclusion criteria which involved 439 stroke survivors. The meta-analysis showed that TENS improved walking capacity, as measured by either gait speed or the Timed Up and Go Test (Hedges' g = 0.392; 95% confidence interval (CI) = 0.178 to 0.606) compared to the placebo or no-treatment control groups. TENS also reduced paretic plantar flexor spasticity, as measured using the Modified Ashworth Scale and Composite Spasticity Scale (Hedges' g = -0.884; 95% CI = -1.140 to -0.625). The effect of TENS on walking capacity in studies involving 60 minutes per sessions was significant (Hedges' g = 0.468; 95% CI = 0.201-0.734) but not in study with shorter sessions (20 or 30 minutes) (Hedges' g = 0.254; 95% CI = -0.106-0.614).

CONCLUSION

The results support the use of repeated applications of TENS as an adjunct therapy for improving walking capacity and reducing spasticity in stroke survivors.