Altered nerve excitability properties after stroke are potentially associated with reduced neuromuscular activation

Klein, Cliff S.; Rymer, William Z.; Fisher, Morris A.

doi:10.1016/j.clinph.2020.02.009

Cited by 5 publications

(10 citation statements)

References 54 publications

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“…Reduced subexcitability was more obvious in patients with severely weak limbs. A flattened recovery cycle related to the reduction in both subexcitability and superexcitability was also reported in the chronic stage after stroke [ 15 ]. Subexcitability is one of the most sensitive parameters in membrane potential changes [ 26 ].…”

Section: Discussionmentioning

confidence: 82%

“…The results showed that paretic limb axons have a progressively reduced capacity to accommodate hyperpolarizing currents due to downregulation of I H. Reduced HCN channel expression was reported in corticospinal lesions [ 14 , 28 ]. Klein et al reported that reduced I H is correlated with a reduction in maximal voluntary muscle contraction in chronic stroke patients [ 15 ]. The significant difference of current-threshold relationship with reduced minimum I/V slope in the follow-up test supports the viewpoint of the evolution of internodal conductance.…”

Section: Discussionmentioning

confidence: 99%

“…Inward rectifier ( I H ) is one of the voltage-dependent ion conductance located on axons, which is activated by hyperpolarization. Changes in I H indicate higher axonal thresholds in the paretic limb (P) than in the non-paretic limb (NP) during 100 ms hyperpolarizing currents, and a tendency for the paretic limb axons to express less I H was found [ 13 – 15 ]. However, there is a difference in changes in nerve excitability between acute and chronic stages.…”

Section: Introductionmentioning

confidence: 99%

“…However, there is a difference in changes in nerve excitability between acute and chronic stages. First, in chronic stroke patients, more prominent changes in several different parameters of nerve excitability studies were noted [ 15 ], while Huynh et al reported no significant changes in nerve properties between the acute stage and the follow-up three months later [ 13 ]. Thus, additional data is needed to evaluate the axonal properties in the acute poststroke stage which have been less discussed in previous studies, and whether those properties change along the time.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, additional data is needed to evaluate the axonal properties in the acute poststroke stage which have been less discussed in previous studies, and whether those properties change along the time. Second, it was reported that reduced I H is correlated with a reduction in maximal voluntary muscle contraction in chronic stroke patients [ 15 ], but results of nerve excitability studies in acute stroke patients seem not correlated with the extent of muscular weakness or the clinical recovery. Huynh and colleagues demonstrated the accommodation changes in affected hands in a longitudinal stroke study; however, whether these changes were related to the mobility of affected hands was not mentioned [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

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Neuroplasticity of peripheral axonal properties after ischemic stroke

et al. 2022

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Objective This study investigated how peripheral axonal excitability changes in ischemic stroke patients with hemiparesis or hemiplegia, reflecting the plasticity of motor axons due to corticospinal tract alterations along the poststroke stage. Methods Each subject received a clinical evaluation, nerve conduction study, and nerve excitability test. Nerve excitability tests were performed on motor median nerves in paretic and non-paretic limbs in the acute stage of stroke. Control nerve excitability test data were obtained from age-matched control subjects. Some patients underwent excitability examinations several times in subacute or chronic stages. Results A total of thirty patients with acute ischemic stroke were enrolled. Eight patients were excluded due to severe entrapment neuropathy in the median nerve. The threshold current for 50% compound muscle action potential (CMAP) was higher in paretic limbs than in control subjects. Furthermore, in the cohort with severe patients (muscle power ≤ 3/5 in affected hands), increased threshold current for 50% CMAP and reduced subexcitability were noted in affected limbs than in unaffected limbs. In addition, in the subsequent study of those severe patients, threshold electrotonus increased in the hyperpolarization direction: TEh (100–109 ms), and the minimum I/V slope decreased. The above findings suggest the less excitable and less accommodation in lower motor axons in the paretic limb caused by ischemic stroke. Conclusion Upper motor neuron injury after stroke can alter nerve excitability in lower motor neurons, and the changes are more obvious in severely paretic limbs. The accommodative changes of axons progress from the subacute to the chronic stage after stroke. Further investigation is necessary to explore the downstream effects of an upper motor neuron insult in the peripheral nerve system.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neuroplasticity of peripheral axonal properties after ischemic stroke

et al. 2022

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Compound muscle action potential (CMAP) scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke

Chen¹,

Lu²,

et al. 2023

Sci. China Life Sci.

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This study presents a novel compound muscle action potential (CMAP) examination of motor unit changes in paretic muscle post stroke. CMAP scan of the first dorsal interosseous (FDI) muscle was performed bilaterally in 16 chronic stroke subjects. Various parameters were derived from the CMAP scan to examine paretic muscle changes, including CMAP amplitude, D50, step index (STEPIX) and amplitude index (AMPIX). A significant decrease in CMAP amplitude and STEPIX was observed in paretic muscles compared with contralateral muscles (CMAP amplitude: paretic (9.0±0.5) mV, contralateral (11.3±0.9) mV, P=0.024; STEPIX: paretic 101.2±7.6, contralateral 121.9±6.5, P=0.020). No significant difference in D50 and AMPIX was observed between the paretic and contralateral sides (P>0.05). The findings revealed complex paretic muscle changes including motor unit degeneration, muscle fiber denervation, reinnervation and atrophy, providing useful insights to help understand neuromuscular mechanisms associated with weakness and other functional deterioration post stroke. The CMAP scan experimental protocols and the applied processing methods are noninvasive, convenient, and automated, offering practical benefits for clinical application.

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Threshold tracking as a tool to study activity-dependent axonal plasticity

Moldovan

2020

Clinical Neurophysiology

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Altered nerve excitability properties after stroke are potentially associated with reduced neuromuscular activation

Cited by 5 publications

References 54 publications

Neuroplasticity of peripheral axonal properties after ischemic stroke

Neuroplasticity of peripheral axonal properties after ischemic stroke

Compound muscle action potential (CMAP) scan examination of paretic and contralateral muscles reveals motor unit alterations after stroke

Threshold tracking as a tool to study activity-dependent axonal plasticity

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