Characterization of Differences in the Time Course of Reflex and Voluntary Responses Following Botulinum Toxin Injections in Chronic Stroke Survivors

Hyperexcitability of spinal motoneurons may contribute to muscular hypertonia after hemispheric stroke. The origins of this hyperexcitability are not clear, but we hypothesized that prolongation of the Ia excitatory postsynaptic potential (EPSP) in spastic motoneurons may be one potential mechanism, by enabling more effective temporal summation of Ia EPSPs, making action potential initiation easier. Thus, the purpose of this study is to quantify the time course of putative EPSPs in spinal motoneurons of chronic stroke survivors. To estimate the EPSP time course, a pair of low-intensity electrical stimuli was delivered sequentially to the median nerve in seven hemispheric stroke survivors and in six intact individuals, to induce an H-reflex response from the flexor carpi radialis muscle. H-reflex response probability was then used to quantify the time course of the underlying EPSPs in the motoneuron pool. A population EPSP estimate was then derived, based on the probability of evoking an H-reflex from the second test stimulus in the absence of a reflex response to the first conditioning stimulus. Our experimental results showed that in six of seven hemispheric stroke survivors, the apparent rate of decay of the population EPSP was markedly slower in spastic compared with contralateral (stroke) and intact motoneuron pools. There was no significant difference in EPSP time course between the contralateral side of stroke survivors and control subject muscles. We propose that one potential mechanism for hyperexcitability of spastic motoneurons in chronic stroke survivors may be associated with this prolongation of the Ia EPSP time course. Our subthreshold double-stimulation approach could provide a noninvasive tool for quantifying the time course of EPSPs in both healthy and pathological conditions. NEW & NOTEWORTHY Spastic motoneurons in stroke survivors showed a prolonged Ia excitatory postsynaptic potential (EPSP) time course compared with contralateral and intact motoneurons, suggesting that one potential mechanism for hyperexcitability of spastic motoneurons in chronic stroke survivors may be associated with this prolongation of the Ia EPSP time course.

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Critically appraised paper: Additional rehabilitation following botulinum toxin-A does not improve goal attainment and upper limb activity in chronic stroke survivors [commentary]

Journal of Physiotherapy ◽

10.1016/j.jphys.2021.05.004 ◽

2021 ◽

Author(s):

Kelly Bower

Keyword(s):

Botulinum Toxin ◽

Upper Limb ◽

Goal Attainment ◽

Botulinum Toxin A ◽

Chronic Stroke ◽

Stroke Survivors ◽

Toxin A

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Variations of Tendon Tap Force Threshold needed to Evoke Surface Electromyogram Responses after Botulinum Toxin Injection in Chronic Stroke Survivors*

2019 9th International IEEE/EMBS Conference on Neural Engineering (NER) ◽

10.1109/ner.2019.8717098 ◽

2019 ◽

Author(s):

Babak Afsharipour ◽

Guijin Li ◽

Sourav Chandra ◽

William Z. Rymer ◽

Nina L. Suresh

Keyword(s):

Botulinum Toxin ◽

Botulinum Toxin Injection ◽

Chronic Stroke ◽

Stroke Survivors ◽

Surface Electromyogram ◽

Tendon Tap

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Can the positions of the spastic upper limb in stroke survivors help muscle choice for botulinum toxin injections?

Arquivos de Neuro-Psiquiatria ◽

10.1590/0004-282x20190087 ◽

2019 ◽

Vol 77 (8) ◽

pp. 568-573 ◽

Cited By ~ 2

Author(s):

André Luiz Salcedo Gomes ◽

Francisco Falleiros de Mello ◽

Jorge Cocicov Neto ◽

Marcelo Causin Benedeti ◽

Luis Felipe Miras Modolo ◽

...

Keyword(s):

Botulinum Toxin ◽

Upper Limb ◽

Botulinum Toxin A ◽

Neuromuscular Block ◽

Stroke Survivors ◽

Motor Impairments ◽

Brazilian Sample ◽

Pronator Teres ◽

Elbow Flexors And Extensors ◽

Botulinum Toxin Injections

ABSTRACT Motor impairments in stroke survivors are prevalent and contribute to dependence in daily activities, pain and overall disability, which can further upper-limb disability. Treatment with botulinum toxin A (BoNT-A) is indicated for focal spasticity and requires knowledge of biomechanics and anatomy to best select muscles to be injected in the limb. Objective: We aimed to describe the frequency of posture patterns in a Brazilian sample of stroke survivors and correlate them with recommendations of muscle selection for treatment with BoNT-A. Methods: Fifty stroke patients with spastic upper limbs scheduled for neuromuscular block were photographed and physically examined, to be classified by three independent evaluators according to Hefter's classification. Muscles that were injected with BoNT-A by their routine doctors were retrieved from medical charts. Results: Pattern III and IV were the most common (64.7%, 21.6%). We further subclassified pattern III according to the rotation of the shoulder, which effectively interfered in muscle choice. The muscles most frequently treated were shoulder adductors and internal rotators, elbow flexors and extensors, in forearm, the pronator teres and finger and wrist flexors, and, in the hand the adductor pollicis. Conclusion: Frequencies of upper-limb postures differed from previous reports. Other clinical features, besides spasticity, interfered with muscle choice for BoNT-A injection, which only partially followed the recommendations in the literature.

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