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Metz K, Matos IC, Hari K, Bseis O, Afsharipour B, Lin S, Singla R, Fenrich KK, Li Y, Bennett DJ, Gorassini MA. Post-activation depression from primary afferent depolarization (PAD) produces extensor H-reflex suppression following flexor afferent conditioning. J Physiol 2023; 601:1925-1956. [PMID: 36928599 PMCID: PMC11064783 DOI: 10.1113/jp283706] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 03/09/2023] [Indexed: 03/18/2023] Open
Abstract
Suppression of the extensor H-reflex by flexor afferent conditioning is thought to be produced by a long-lasting inhibition of extensor Ia afferent terminals via GABAA receptor-activated primary afferent depolarization (PAD). Given the recent finding that PAD does not produce presynaptic inhibition of Ia afferent terminals, we examined in 28 participants if H-reflex suppression is instead mediated by post-activation depression of the extensor Ia afferents triggered by PAD-evoked spikes and/or by a long-lasting inhibition of the extensor motoneurons. A brief conditioning vibration of the flexor tendon suppressed both the extensor soleus H-reflex and the tonic discharge of soleus motor units out to 150 ms following the vibration, suggesting that part of the H-reflex suppression during this period was mediated by postsynaptic inhibition of the extensor motoneurons. When activating the flexor afferents electrically to produce conditioning, the soleus H-reflex was also suppressed but only when a short-latency reflex was evoked in the soleus muscle by the conditioning input itself. In mice, a similar short-latency reflex was evoked when optogenetic or afferent activation of GABAergic (GAD2+ ) neurons produced a large enough PAD to evoke orthodromic spikes in the test Ia afferents, causing post-activation depression of subsequent monosynaptic EPSPs. The long duration of this post-activation depression and related H-reflex suppression (seconds) was similar to rate-dependent depression that is also due to post-activation depression. We conclude that extensor H-reflex inhibition by brief flexor afferent conditioning is produced by both post-activation depression of extensor Ia afferents and long-lasting inhibition of extensor motoneurons, rather than from PAD inhibiting Ia afferent terminals. KEY POINTS: Suppression of extensor H-reflexes by flexor afferent conditioning was thought to be mediated by GABAA receptor-mediated primary afferent depolarization (PAD) shunting action potentials in the Ia afferent terminal. In line with recent findings that PAD has a facilitatory role in Ia afferent conduction, we show here that when large enough, PAD can evoke orthodromic spikes that travel to the Ia afferent terminal to evoke EPSPs in the motoneuron. These PAD-evoked spikes also produce post-activation depression of Ia afferent terminals and may mediate the short- and long-lasting suppression of extensor H-reflexes in response to flexor afferent conditioning. Our findings highlight that we must re-examine how changes in the activation of GABAergic interneurons and PAD following nervous system injury or disease affects the regulation of Ia afferent transmission to spinal neurons and ultimately motor dysfunction in these disorders.
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Affiliation(s)
- Krista Metz
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Isabel Concha Matos
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Krishnapriya Hari
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Omayma Bseis
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Babak Afsharipour
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Shihao Lin
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Monica A Gorassini
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
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Jinkarn N, Tisavipat N, Jitprapaikulsan J, Prayoonwiwat N, Rattanathamsakul N, Siritho S. A comparison between subjective and objective measurements of spasticity in neuromyelitis optica spectrum disorder patients. Mult Scler Relat Disord 2022; 58:103517. [PMID: 35032877 DOI: 10.1016/j.msard.2022.103517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 01/07/2022] [Accepted: 01/08/2022] [Indexed: 11/19/2022]
Abstract
BACKGROUND Spasticity is a common and disabling problem in multiple sclerosis (MS), but its effect in other CNS inflammatory demyelinating diseases (CNSIDDs), such as neuromyelitis optica spectrum disorder (NMOSD) is not widely studied. This study aims to compare subjective and objective measurements of spasticity in NMOSD patients and determine associated factors. METHODS A prospective cross-sectional study was performed on CNSIDD patients attending the Multiple Sclerosis and Related Disorders Clinic at Siriraj Hospital, a tertiary hospital in Thailand, from June to November 2020 was performed. MS, NMOSD, and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) patients were included. Patients' self-rated Numeric Rating Scale (NRS) for spasticity and clinician-evaluated Modified Ashworth Scale (MAS) scores on the same visit were compared and assessed for correlations. Data on characteristics of patients including demographics, number of transverse myelitis (TM) attacks, disease duration, and Expanded Disability Status Scale (EDSS) score were collected. RESULTS Seventy-nine CNSIDD patients were included with 25 MS, 53 NMOSD, and 1 MOGAD. There was a statistically significant correlation between NRS and MAS scores (r = 0.934, p < 0.001). Spasticity was more commonly observed in NMOSD patients compared to MS (34% vs 8%, p = 0.016). Clinical characteristics strongly associated with spasticity were higher number of TM attacks (p < 0.001), severe TM attacks (p < 0.001), longitudinally extensive transverse myelitis attacks (p < 0.001), longer disease duration (p = 0.025), higher EDSS (p < 0.001), and pyramidal Functional System Scale scores (p = 0.001). CONCLUSIONS Patients' self-reported NRS score had a good correlation with clinician-evaluated MAS score for spasticity assessment in NMOSD and CNSIDD patients overall. Number and severity of TM attacks were associated with spasticity. Spastic patients had more disability measured by EDSS.
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Affiliation(s)
- Narudol Jinkarn
- Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand
| | - Nanthaya Tisavipat
- Siriraj Neuroimmunology Center, Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand
| | - Jiraporn Jitprapaikulsan
- Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand; Siriraj Neuroimmunology Center, Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand
| | - Naraporn Prayoonwiwat
- Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand; Siriraj Neuroimmunology Center, Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand
| | - Natthapon Rattanathamsakul
- Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand; Siriraj Neuroimmunology Center, Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand
| | - Sasitorn Siritho
- Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand; Siriraj Neuroimmunology Center, Division of Neurology, Department of Medicine, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, 10700, Thailand; Bumrungrad International Hospital, Bangkok, 10110, Thailand.
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Zelenin PV, Lyalka VF, Orlovsky GN, Deliagina TG. Changes in Activity of Spinal Postural Networks at Different Time Points After Spinalization. Front Cell Neurosci 2019; 13:387. [PMID: 31496938 PMCID: PMC6712497 DOI: 10.3389/fncel.2019.00387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 08/06/2019] [Indexed: 11/25/2022] Open
Abstract
Postural limb reflexes (PLRs) are an essential component of postural corrections. Spinalization leads to disappearance of postural functions (including PLRs). After spinalization, spastic, incorrectly phased motor responses to postural perturbations containing oscillatory EMG bursting gradually develop, suggesting plastic changes in the spinal postural networks. Here, to reveal these plastic changes, rabbits at 3, 7, and 30 days after spinalization at T12 were decerebrated, and responses of spinal interneurons from L5 along with hindlimb muscles EMG responses to postural sensory stimuli, causing PLRs in subjects with intact spinal cord (control), were characterized. Like in control and after acute spinalization, at each of three studied time points after spinalization, neurons responding to postural sensory stimuli were found. Proportion of such neurons during 1st month after spinalization did not reach the control level, and was similar to that observed after acute spinalization. In contrast, their activity (which was significantly decreased after acute spinalization) reached the control value at 3 days after spinalization and remained close to this level during the following month. However, the processing of postural sensory signals, which was severely distorted after acute spinalization, did not recover by 30 days after injury. In addition, we found a significant enhancement of the oscillatory activity in a proportion of the examined neurons, which could contribute to generation of oscillatory EMG bursting. Motor responses to postural stimuli (which were almost absent after acute spinalization) re-appeared at 3 days after spinalization, although they were very weak, irregular, and a half of them was incorrectly phased in relation to postural stimuli. Proportion of correct and incorrect motor responses remained almost the same during the following month, but their amplitude gradually increased. Thus, spinalization triggers two processes of plastic changes in the spinal postural networks: rapid (taking days) restoration of normal activity level in spinal interneurons, and slow (taking months) recovery of motoneuronal excitability. Most likely, recovery of interneuronal activity underlies re-appearance of motor responses to postural stimuli. However, absence of recovery of normal processing of postural sensory signals and enhancement of oscillatory activity of neurons result in abnormal PLRs and loss of postural functions.
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Acute and chronic neuromuscular adaptations to local vibration training. Eur J Appl Physiol 2017; 117:1939-1964. [PMID: 28766150 DOI: 10.1007/s00421-017-3688-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 07/22/2017] [Indexed: 12/19/2022]
Abstract
Vibratory stimuli are thought to have the potential to promote neural and/or muscular (re)conditioning. This has been well described for whole-body vibration (WBV), which is commonly used as a training method to improve strength and/or functional abilities. Yet, this technique may present some limitations, especially in clinical settings where patients are unable to maintain an active position during the vibration exposure. Thus, a local vibration (LV) technique, which consists of applying portable vibrators directly over the tendon or muscle belly without active contribution from the participant, may present an alternative to WBV. The purpose of this narrative review is (1) to provide a comprehensive overview of the literature related to the acute and chronic neuromuscular changes associated with LV, and (2) to show that LV training may be an innovative and efficient alternative method to the 'classic' training programs, including in the context of muscle deconditioning prevention or rehabilitation. An acute LV application (one bout of 20-60 min) may be considered as a significant neuromuscular workload, as demonstrated by an impairment of force generating capacity and LV-induced neural changes. Accordingly, it has been reported that a training period of LV is efficient in improving muscular performance over a wide range of training (duration, number of session) and vibration (frequency, amplitude, site of application) parameters. The functional improvements are principally triggered by adaptations within the central nervous system. A model illustrating the current research on LV-induced adaptations is provided.
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Zelenin PV, Lyalka VF, Hsu LJ, Orlovsky GN, Deliagina TG. Effects of acute spinalization on neurons of postural networks. Sci Rep 2016; 6:27372. [PMID: 27302149 PMCID: PMC4908393 DOI: 10.1038/srep27372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 05/18/2016] [Indexed: 11/15/2022] Open
Abstract
Postural limb reflexes (PLRs) represent a substantial component of postural corrections. Spinalization results in loss of postural functions, including disappearance of PLRs. The aim of the present study was to characterize the effects of acute spinalization on two populations of spinal neurons (F and E) mediating PLRs, which we characterized previously. For this purpose, in decerebrate rabbits spinalized at T12, responses of interneurons from L5 to stimulation causing PLRs before spinalization, were recorded. The results were compared to control data obtained in our previous study. We found that spinalization affected the distribution of F- and E-neurons across the spinal grey matter, caused a significant decrease in their activity, as well as disturbances in processing of posture-related sensory inputs. A two-fold decrease in the proportion of F-neurons in the intermediate grey matter was observed. Location of populations of F- and E-neurons exhibiting significant decrease in their activity was determined. A dramatic decrease of the efficacy of sensory input from the ipsilateral limb to F-neurons, and from the contralateral limb to E-neurons was found. These changes in operation of postural networks underlie the loss of postural control after spinalization, and represent a starting point for the development of spasticity.
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Affiliation(s)
- Pavel V. Zelenin
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Vladimir F. Lyalka
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Li-Ju Hsu
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Grigori N. Orlovsky
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
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Abstract
Postural limb reflexes (PLRs) represent a substantial component of the postural system responsible for stabilization of dorsal-side-up trunk orientation in quadrupeds. Spinalization causes spinal shock, that is a dramatic reduction of extensor tone and spinal reflexes, including PLRs. The goal of our study was to determine changes in activity of spinal interneurons, in particular those mediating PLRs, that is caused by spinalization. For this purpose, in decerebrate rabbits, activity of individual interneurons from L5 was recorded during stimulation causing PLRs under two conditions: (1) when neurons received supraspinal influences and (2) when these influences were temporarily abolished by a cold block of spike propagation in spinal pathways at T12 ("reversible spinalization"; RS). The effect of RS, that is a dramatic reduction of PLRs, was similar to the effect of surgical spinalization. In the examined population of interneurons (n = 199), activity of 84% of them correlated with PLRs, suggesting that they contribute to PLR generation. RS affected differently individual neurons: the mean frequency decreased in 67% of neurons, increased in 15%, and did not change in 18%. Neurons with different RS effects were differently distributed across the spinal cord: 80% of inactivated neurons were located in the intermediate area and ventral horn, whereas 50% of nonaffected neurons were located in the dorsal horn. We found a group of neurons that were coactivated with extensors during PLRs before RS and exhibited a dramatic (>80%) decrease in their activity during RS. We suggest that these neurons are responsible for reduction of extensor tone and postural reflexes during spinal shock.
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Nielsen JB, Petersen NT, Crone C, Sinkjaer T. Stretch reflex regulation in healthy subjects and patients with spasticity. Neuromodulation 2013; 8:49-57. [PMID: 22151383 DOI: 10.1111/j.1094-7159.2005.05220.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In recent years, part of the muscle resistance in spastic patients has been explained by changes in the elastic properties of muscles. However, the adaptive spinal mechanisms responsible for the exaggeration of stretch reflex activity also contribute to muscle stiffness. The available data suggest that no single spinal mechanism is responsible for the development of spasticity but that failure of different spinal inhibitory mechanisms (reciprocal IA inhibition, presynaptic inhibition, IB inhibition, recurrent inhibition) are involved in different patients depending on the site of lesion and the etiology of the spastic symptoms. A recent finding also shows no sign of exaggerated stretch reflexes in muscles voluntarily activated by the spastic patient in general. This is easily explained by the control of stretch reflex activity in healthy subjects. In healthy subjects, the stretch reflex activity is increased during voluntary muscle contraction in part because of depression of the inhibitory mechanisms that are affected in spasticity. In spastic patients, these inhibitory mechanisms are already depressed at rest and cannot be depressed further in connection with a contraction. In relation to most normal movements, antagonist muscles should remain silent and maximally relaxed. This is ensured by increasing transmission in several spinal inhibitory pathways. In spastic patients, this control is inadequate, and therefore stretch reflexes in antagonist muscles are easily evoked at the beginning of voluntary movements or in the transition from flexor to extensor muscle activity. This problem is contradicted by the fact that antispastic therapy to improve voluntary movements should be directed.
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Affiliation(s)
- Jens Bo Nielsen
- Department of Medical Physiology, University of Copenhagen, Copenhagen; Department of Clinical Neurophysiology, Copenhagen University Hospital (Rigshospitalet), Copenhagen; Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark
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8
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Abstract
The term "spasticity" describes the velocity-dependent increase in tonic stretch reflexes. The symptom is commonly seen in patients with injury to the central nervous system. It is rarely isolated but, instead, part of a set of symptoms that is sometimes confusing. However, the pathophysiology of the symptom has evolved over the past three decades, and it is now considered part of a global process that includes not only spinal reflex loop modifications, but also changes in the biomechanical properties of muscle fibers. Finally, recent studies of changes in the membrane properties of motor neurons and the occurrence of plateau potential have opened new perspectives. This review aims to describe these new pathophysiological models.
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Affiliation(s)
- P Marque
- Unité 825 Inserm, Pavillon Baudot, CHU Purpan, 1 Place Baylac, 31059 Toulouse cedex 9, France.
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9
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Mukherjee A, Chakravarty A. Spasticity mechanisms - for the clinician. Front Neurol 2010; 1:149. [PMID: 21206767 PMCID: PMC3009478 DOI: 10.3389/fneur.2010.00149] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 11/13/2010] [Indexed: 11/13/2022] Open
Abstract
Spasticity, a classical clinical manifestation of an upper motor neuron lesion, has been traditionally and physiologically defined as a velocity dependent increase in muscle tone caused by the increased excitability of the muscle stretch reflex. Clinically spasticity manifests as an increased resistance offered by muscles to passive stretching (lengthening) and is often associated with other commonly observed phenomenon like clasp-knife phenomenon, increased tendon reflexes, clonus, and flexor and extensor spasms. The key to the increased excitability of the muscle stretch reflex (muscle tone) is the abnormal activity of muscle spindles which have an intricate relation with the innervations of the extrafusal muscle fibers at the spinal level (feed-back and feed-forward circuits) which are under influence of the supraspinal pathways (inhibitory and facilitatory). The reflex hyperexcitability develops over variable period of time following the primary lesion (brain or spinal cord) and involves adaptation in spinal neuronal circuitries caudal to the lesion. It is highly likely that in humans, reduction of spinal inhibitory mechanisms (in particular that of disynaptic reciprocal inhibition) is involved. While simply speaking the increased muscle stretch reflex may be assumed to be due to an altered balance between the innervations of intra and extrafusal fibers in a muscle caused by loss of inhibitory supraspinal control, the delayed onset after lesion and the frequent reduction in reflex excitability over time, suggest plastic changes in the central nervous system following brain or spinal lesion. It seems highly likely that multiple mechanisms are operative in causation of human spasticity, many of which still remain to be fully elucidated. This will be apparent from the variable mechanisms of actions of anti-spasticity agents used in clinical practice.
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Affiliation(s)
- Angshuman Mukherjee
- Department of Neurology, Vivekananda Institute of Medical Sciences Kolkata, India
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10
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Grey MJ, Klinge K, Crone C, Lorentzen J, Biering-Sørensen F, Ravnborg M, Nielsen JB. Post-activation depression of Soleus stretch reflexes in healthy and spastic humans. Exp Brain Res 2007; 185:189-97. [PMID: 17932663 DOI: 10.1007/s00221-007-1142-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 09/14/2007] [Indexed: 11/26/2022]
Affiliation(s)
- Michael J Grey
- Department of Exercise and Sport Science & Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
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Nielsen JB, Crone C, Hultborn H. The spinal pathophysiology of spasticity--from a basic science point of view. Acta Physiol (Oxf) 2007; 189:171-80. [PMID: 17250567 DOI: 10.1111/j.1748-1716.2006.01652.x] [Citation(s) in RCA: 258] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Spasticity is a term, which was introduced to describe the velocity-sensitive increased resistance of a limb to manipulation in subjects with lesions of descending motor pathways. This distinguishes spasticity from the changes in passive muscle properties, which are often seen in these patients, but are not velocity-sensitive. Increased excitability of the stretch reflex is thus a central component of the definition of spasticity. This review describes changes in cellular properties and transmission in a number of spinal reflex pathways, which may explain the increased stretch reflex excitability. The review focuses mainly on results derived from the use of non-invasive electrophysiological techniques, which have been developed during the past 20-30 years to investigate spinal neuronal networks in human subjects, but work from animal models is also considered. The reflex hyperexcitability develops over several months following the primary lesion and involves adaptation in the spinal neuronal circuitries caudal to the lesion. In animal models, changes in cellular properties (such as 'plateau potentials') have been reported, but the relevance of these changes to human spasticity has not been clarified. In humans, numerous studies have suggested that reduction of spinal inhibitory mechanisms (in particular that of disynaptic reciprocal inhibition) is involved. The inter-subject variability of these mechanisms and the lack of objective quantitative measures of spasticity have impeded disclosure of a clear causal relationship between the alterations in the inhibitory mechanisms and the stretch reflex hyperexcitability. Techniques which make such a quantitative measure possible as well as longitudinal studies where development of reflex excitability and changes in the inhibitory mechanisms are followed over time are in great demand.
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Affiliation(s)
- J B Nielsen
- Department of Exercise and Sport Science, University of Copenhagen, Copenhagen N, Denmark.
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Frigon A, Rossignol S. Functional plasticity following spinal cord lesions. PROGRESS IN BRAIN RESEARCH 2006; 157:231-260. [PMID: 17167915 DOI: 10.1016/s0079-6123(06)57016-5] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Spinal cord injury results in marked modification and reorganization of several reflex pathways caudal to the injury. The sudden loss or disruption of descending input engenders substantial changes at the level of primary afferents, interneurons, and motoneurons thus dramatically influencing sensorimotor interactions in the spinal cord. As a general rule reflexes are initially depressed following spinal cord injury due to severe reductions in motoneuron excitability but recover and in some instances become exaggerated. It is thought that modified inhibitory connections and/or altered transmission in some of these reflex pathways after spinal injury as well as the recovery and enhancement of membrane properties in motoneurons underlie several symptoms such as spasticity and may explain some characteristics of spinal locomotion observed in spinally transected animals. Indeed, after partial or complete spinal lesions at the last thoracic vertebra cats recover locomotion when the hindlimbs are placed on a treadmill. Although some deficits in spinal locomotion are related to lesion of specific descending motor pathways, other characteristics can also be explained by changes in the excitability of reflex pathways mentioned above. Consequently it may be the case that to reestablish a stable walking pattern that modified afferent inflow to the spinal cord incurred after injury must be normalized to enable a more normal re-expression of locomotor rhythm generating networks. Indeed, recent evidence demonstrates that step training, which has extensively been shown to facilitate and ameliorate locomotor recovery in spinal animals, directly influences transmission in simple reflex pathways after complete spinal lesions.
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Affiliation(s)
- Alain Frigon
- Center and Group for Neurological Sciences, CIHR Group in Neurological Sciences, CIHR Regenerative Medicine and Nanomedicine Team, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
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Sjölund BH. Pain and rehabilitation after spinal cord injury: the case of sensory spasticity? BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2002; 40:250-6. [PMID: 12589923 DOI: 10.1016/s0165-0173(02)00207-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Sixty percent of patients with posttraumatic para- or tetraplegia suffer from severe, continuous burning and/or lancinating pain. Multiple sclerosis produces pain in more than 30%. This pain can be as important as the absent mobility or sexual function as a cause of lowered quality of life. Two unique types of longstanding neuropathic pain can be recognized in persons with spinal cord injury: (1). segmentally distributed pain at the lesion; and (2). pain in the body below the lesion, often with late onset. The first type could be produced by nerve root entrapment or by direct segmental deafferentation. The second type probably contains several forms of central pain, evoked either by the original spinal lesion, by an expanding syrinx in the spinal cord or by secondary changes at higher levels of the somatosensory systems. Patients with central pain almost always have stimulus-independent pain. Its intensity may vary independently, be related to the presence of visceral activity/inflammation or be constant. In addition, stimulus-dependent pain is sometimes present, usually because skin areas or viscera below the lesion are allodynic. Partial spinal lesions, especially centrally in the cervical spinal cord, may be more prone to produce pain than are complete lesions. There is limited analgesic effectiveness in controlled studies of serotonin reuptake inhibitors, of sodium channel blockers (lidocaine, tetracaine), of the GABA receptor agonist baclofen (one study) and of the NMDA-receptor antagonist ketamine (one study). There are anecdotal reports on oral carbamazepine, on gabapentin, on intrathecal opiates and also on the alpha(2)-agonist clonidine, being effective in central neuropathic pain. Neurostimulation is effective only if it evokes paraesthesia in the painful area; hence TENS may give relief of segmental pain. Neurodestructive procedures and central neurostimulation have been largely unsuccessful. As in other longstanding pain, improved coping through cognitive-behavioural rehabilitation may be helpful for the clinical outcome.
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Affiliation(s)
- Bengt H Sjölund
- Department of Rehabilitation Medicine, Umeå University, Building 9A, NUS, S-901 85, Umeå, Sweden.
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Chen XY, Chen L, Wolpaw JR, Jakeman LB. Corticospinal tract transection reduces H-reflex circadian rhythm in rats. Brain Res 2002; 942:101-8. [PMID: 12031858 DOI: 10.1016/s0006-8993(02)02702-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In freely moving rats and monkeys, H-reflex amplitude displays a marked circadian variation without change in background motoneuron tone. In rats, the H-reflex is largest around noon and smallest around midnight. The present study evaluated in rats the effects on this rhythm of calibrated contusions of mid-thoracic spinal cord and mid-thoracic transection of specific spinal cord pathways. In 33 control rats, rhythm amplitude averaged 29.0(+/-2.6 S.E.)% of H-reflex amplitude. Contusion injuries at T8-9 that destroyed 53-88% of the white matter significantly reduced the rhythm to 18.9(+/-2.4)% of H-reflex amplitude. Transection of the ipsilateral lateral column, which contains the rubrospinal, vestibulospinal, and reticulospinal tracts, or bilateral transection of the dorsal column ascending tract did not affect rhythm amplitude or phase. In contrast, bilateral transection of the main corticospinal tract significantly reduced the rhythm to 14.7(+/-6.6)%. These results indicate that the H-reflex circadian rhythm depends in part on descending influence from the brain and that this influence is conveyed by the main corticospinal tract.
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Affiliation(s)
- Xiang Yang Chen
- Wadsworth Center, New York State Department of Health and State University of New York, P.O. Box 509, Albany, NY 12201-0509, USA.
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Chen XY, Feng-Chen KC, Chen L, Stark DM, Wolpaw JR. Short-Term and medium-term effects of spinal cord tract transections on soleus H-reflex in freely moving rats. J Neurotrauma 2001; 18:313-27. [PMID: 11284551 DOI: 10.1089/08977150151070973] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spinal cord function is normally influenced by descending activity from supraspinal structures. When injury removes or distorts this influence, function changes and spasticity and other disabling problems eventually appear. Understanding how descending activity affects spinal cord function could lead to new means for inducing, guiding, and assessing recovery after injury. In this study, we investigated the short-term and medium-term effects of spinal cord bilateral dorsal column (DC), unilateral (ipsilateral) lateral column (LC), bilateral dorsal column ascending tract (DA), or bilateral dorsal column corticospinal tract (CST) transection at vertebral level T8-T9 on the soleus H-reflex in freely moving rats. Data were collected continuously for 10-20 days before and for 20-155 days after bilateral DC (13 rats), DA (10 rats), CST (eight rats), or ipsilateral LC (seven rats) transection. Histological examination showed that transections were 98(+/- 3 SD)% complete for DC rats, 80(+/- 20)% complete for LC rats, 91(+/- 13 SD)% complete for DA rats, and 95(+/-13)% complete for CST rats. LC, CST, and DA transections produced an immediate (i.e., first-day) increase in H-reflex amplitude. LC transection also produced a small decrease in background activity in the first few posttransection days. Other than this small decrease, none of the transections produced evidence for the phenomenon of spinal shock. For all transections, all measures returned to or neared pretransection values within 2 weeks. DA and LC transections were associated with modest increase in H-reflex amplitude 1-3 months after transection. These medium-term effects must be taken into account when assessing transection effects on operant conditioning of the H-reflex. At the same time, the results are consistent with other evidence that, while H-reflex rate dependence and H-reflex operant conditioning are sensitive measures of spinal cord injury, the H-reflex itself is not.
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Affiliation(s)
- X Y Chen
- Wadsworth Center, New York State Department of Health and State University of New York, Albany 12201-0509, USA.
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Chen XY, Wolpaw JR, Jakeman LB, Stokes BT. Operant conditioning of H-reflex increase in spinal cord--injured rats. J Neurotrauma 1999; 16:175-86. [PMID: 10098962 DOI: 10.1089/neu.1999.16.175] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of long-term supraspinal control over spinal cord function. Primates and rats can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) the H-reflex when reward is based on H-reflex amplitude. An earlier study indicated that HRdown conditioning of the soleus H-reflex in rats is impaired following contusion injury to thoracic spinal cord. The extent of impairment was correlated with the percent of white matter lost at the injury site. The present study investigated the effects of spinal cord injury on HRup conditioning. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from 14 rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. At the lesion epicenter, 12-39% of the white matter remained. After control-mode data were collected, each rat was exposed to the HRup conditioning mode for 50 days. Final H-reflex amplitudes after HRup conditioning averaged 112% (+/-22% SD) of control. This value was significantly smaller than that for 13 normal rats exposed to HRup conditioning, in which final amplitude averaged 153% (+/-51%) SD of control. As previously reported for HRdown conditioning after spinal cord injury, success was inversely correlated with the severity of the injury as assessed by white matter preservation and by time to return of bladder function. HRup and HRdown conditioning are similarly sensitive to injury. These results further demonstrate that H-reflex conditioning is a sensitive measure of the long-term effects of injury on supraspinal control over spinal cord functions and could prove a valuable measure of therapeutic efficacy.
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Affiliation(s)
- X Y Chen
- Wadsworth Center, New York State Department of Health and State University of New York, Albany, USA.
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Sehgal N, McGuire JR. Beyond Ashworth: Electrophysiologic Quantification of Spasticity. Phys Med Rehabil Clin N Am 1998. [DOI: 10.1016/s1047-9651(18)30243-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chen XY, Wolpaw JR, Jakeman LB, Stokes BT. Operant conditioning of H-reflex in spinal cord-injured rats. J Neurotrauma 1996; 13:755-66. [PMID: 9002061 DOI: 10.1089/neu.1996.13.755] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of supraspinal control over spinal cord function. Both rats and primates can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) soleus H-reflex magnitude when exposed to an operant conditioning task. This study used H-reflex operant conditioning to assess and modify spinal cord function after injury. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. From 18 to 140 days after injury, background EMG, M response amplitude, and initial H-reflex amplitude were not significantly different from those of normal rats. HRdown conditioning was successful in some, but not all, spinal cord-injured rats. The H-reflex decrease achieved by conditioning was inversely correlated with the severity of the injury as assessed histologically or by time to return of bladder function. It was not correlated with the length of time between injury and the beginning of conditioning. The results confirm the importance of descending control from supraspinal structures in mediating operantly conditioned change in H-reflex amplitude. In conjunction with recent human studies, they suggest that H-reflex conditioning could provide a sensitive new means for assessing spinal cord function after injury, and might also provide a method for initiating and guiding functional rehabilitation.
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Affiliation(s)
- X Y Chen
- Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany, USA
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Burke JR, Schutten MC, Koceja DM, Kamen G. Age-dependent effects of muscle vibration and the Jendrassik maneuver on the patellar tendon reflex response. Arch Phys Med Rehabil 1996; 77:600-4. [PMID: 8831479 DOI: 10.1016/s0003-9993(96)90302-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To explore possible effects of aging on the excitability of spinal reflexes. DESIGN Using a cross-sectional design, the influences of muscle vibration and the Jendrassik maneuver on patellar tendon reflex function were compared between 30 young adults and 15 older adults. SETTING Motor control research laboratory. SUBJECTS The young adults were volunteers of college age. The older adults (74.5 +/- 4.14 yr) were volunteers from the local community. All subjects were free of medications and neurological conditions that would affect normal neuromuscular responses. MAIN OUTCOME MEASURES A force-time curve analysis of the patellar tendon reflex response was used to assess the inhibition and facilitation of spinal reflexes. In the experimental protocol to assess spinal reflex inhibition, 100 Hz vibration was applied to the right quadriceps muscle. In another experimental protocol, spinal reflex facilitation was assessed using the Jendrassik maneuver. To perform the Jendrassik maneuver, subjects were instructed to grasp their hands together and to pull as hard as possible while breathing normally. After a 2-second count, the tendon tap was delivered to the right leg and the subject was instructed to relax. In both experimental protocols, control patellar tendon reflexes were collected. RESULTS Analysis of variance for reflex peak force revealed a significant 30% reduction in the amount of vibration-induced reflex inhibition with increasing age, and a similar 33% reduction in the amount of Jendrassik maneuver facilitation observed for the older adults as compared with the younger adults. CONCLUSION These results support the hypothesis that inhibitory and excitatory influences acting on the alpha motoneuron pool are different in young and older adults.
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Affiliation(s)
- J R Burke
- Motor Control Laboratory, Indiana University, IN, USA
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Claus D, Mills KR, Murray NM. The influence of vibration on the excitability of alpha motoneurones. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1988; 69:431-6. [PMID: 2451590 DOI: 10.1016/0013-4694(88)90065-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Transcranial magnetic brain stimuli were delivered to 6 healthy subjects at different time intervals after the beginning of muscle vibration. Vibration of 6 sec duration in 4 subjects and of 100 msec duration in 6 subjects was applied to the right abductor digiti minimi muscle using an electromagnetic mechanical stimulator. The responses to brain stimuli were enhanced in this muscle when vibration began 9 msec before the transcranial stimulus, i.e., when the descending volley and the monosynaptic afferent Ia volley arrived simultaneously at the anterior horn cell. With long lasting vibration an enhancement of responses to brain stimuli was seen, which began after 120 msec and continued for up to 5 sec after the onset of vibration. This is consistent with a tonic, probably polysynaptic, excitatory Ia influence on homonymous alpha motoneurones, as well as the well known monosynaptic effect.
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Affiliation(s)
- D Claus
- Department of Clinical Neurophysiology, National Hospital, Queen Square, London, U.K
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Abstract
No single clinical electrophysiological test can evaluate disorders of muscle tone. These disorders, symptomatic of a variety of diseases have a multifactorial physiological basis. The several tests used are complimentary each aiming to study different aspects of spinal and supraspinal reflexes which become deranged. The H reflex and F wave (H max/M max and F max/M max ratios) measure motoneuron pool excitability in general. The tendon reflex includes spindle mechanisms bypassed by the H reflex and, with limitations, comparison of H max/M max and T max/M max yields information about the gamma system. Tonic vibration of a tendon inhibits the H reflex from the same muscle. The TVR measures autogenous presynaptic inhibition exerted by the Ia afferents of the muscle. Recurrent inhibition via Renshaw cells is evaluated by studying the effect of collision on the H reflex. Reciprocal inhibition of the Ia afferents can be assessed by measuring H reflex change induced by stimulating Ia afferents from antagonists. Changes in the H reflex recovery cycle measure polysynaptic influences on spinal motoneuron excitability. Cutaneo-muscular (flexor) reflexes measure poly- and oligosynaptic excitatory drive to spinal motoneurons and the blink reflex evaluates the excitatory drive to brainstem motoneurons. Long loop (segmental) responses can be evaluated by limb pertubation using a torque motor or electrical stimulation applied during voluntary muscle contraction. Finally needle electromyography is a more relevant test in several disorders of muscle tone such as the stiff-man syndrome and Isaacs' syndrome.
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Affiliation(s)
- A Eisen
- Neuromuscular Diseases Unit (EMG), Vancouver General Hospital, B.C., Canada
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Iles JF, Roberts RC. Presynaptic inhibition of monosynaptic reflexes in the lower limbs of subjects with upper motoneuron disease. J Neurol Neurosurg Psychiatry 1986; 49:937-44. [PMID: 2943875 PMCID: PMC1028957 DOI: 10.1136/jnnp.49.8.937] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Presynaptic inhibition of muscle spindle Ia afferents by group I afferents from the same and other muscles has been studied in the lower limbs of subjects with upper motoneuron lesions. The experiments utilised conditioning of soleus test monosynaptic reflexes during controlled voluntary contraction. The protocol was designed to isolate presynaptic inhibition from postsynaptic components. The relation between estimate of inhibition and test reflex amplitude was examined. The subjects showed less inhibition than controls at all levels of voluntary torque investigated (less than or equal 15 Nm). Two thirds had weak inhibition which did not show the decrease during muscle contraction characteristic of controls. The degree of difference from the normal situation correlated with severity of the clinical sign (weakness of voluntary ankle flexion).
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Taylor S, Ashby P, Verrier M. Neurophysiological changes following traumatic spinal lesions in man. J Neurol Neurosurg Psychiatry 1984; 47:1102-8. [PMID: 6502167 PMCID: PMC1028041 DOI: 10.1136/jnnp.47.10.1102] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Neurophysiological observations were made on normal subjects and on 57 patients who had had injuries to the spinal cord. The amplitude of the muscle compound action potential (M response) recorded from triceps surae in response to supramaximal stimulation of the tibial nerve was reduced in the patients indicating that there are changes in motor units below the level of a spinal lesion in man. In the patients who were clinically spastic it was found that: (1) The proportion of the triceps surae motoneuron pool reflexly activated either by tapping the Achilles tendon or by stimulating the tibial nerve just below the threshold of the alpha motoneuron axons (H reflex) was greater than in normal subjects. This can be explained by an increase in the excitability of central reflex pathways. (2) Vibration of the tendo Achilles depressed the H reflex less effectively than in normal subjects. This may indicate altered transmission in the premotoneuronal portion of the H reflex pathway. (3) The H reflex elicited 50 and 100 ms after a standardised conditioning stimulus to the tibial nerve and expressed as percentage of the unconditioned reflex was greater than in normal subjects. This could reflect a change in the excitability of motoneurons or of interneurons.
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Hultborn H, Malmsten J. Changes in segmental reflexes following chronic spinal cord hemisection in the cat. II. Conditioned monosynaptic test reflexes. ACTA PHYSIOLOGICA SCANDINAVICA 1983; 119:423-33. [PMID: 6666623 DOI: 10.1111/j.1748-1716.1983.tb07358.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In a companion paper (Hultborn & Malmsten 1983) it was described that ventral root discharges to stimulation of peripheral nerves became larger on the side of a chronic spinal hemisection (left) than on the other side. In the present paper, based on the same experiments, conditioning of monosynaptic test reflexes was used to study changes of both excitatory and inhibitory effects on specified motoneuronal pools. Conditioning stimulation was given to IA afferents (reciprocal Ia inhibition, presynaptic inhibition of Ia fibers), high threshold muscle afferents, low and high threshold cutaneous afferents and motor axons (recurrent inhibition). A comparison of the efficacy of conditioning stimuli on the two sides showed that facilitatory effects were larger on the side of hemisection in a clear majority of cases. Inhibition was almost always either more efficient on the side of hemisection or equally efficient on the two sides. In control cats, facilitatory effects tended to be larger on the right side, while the results for inhibitory conditioning generally showed no clear side-bias. The increase in facilitatory effects after lesions may contribute to symptoms of spasticity.
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Ashby P, Verrier M. Human motoneuron responses to group 1 volleys blocked presynaptically by vibration. Brain Res 1980; 184:511-6. [PMID: 7353166 DOI: 10.1016/0006-8993(80)90819-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Moddel G, Best B, Ashby P. Effect of differential nerve block on inhibition of the monosynaptic reflex by vibration in man. J Neurol Neurosurg Psychiatry 1977; 40:1066-71. [PMID: 599354 PMCID: PMC492904 DOI: 10.1136/jnnp.40.11.1066] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The differential nerve block produced by ischaemia has been used in an attempt to identify the afferent nerve fibres responsible for vibratory inhibition of the monosynaptic reflex in man. It is concluded that the inhibition arises mainly from receptors in the lower leg and is carried by myelinated afferent fibres larger than A-delta.
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Rezaian SM, Rezvani M, Movlavi M, Daneshbod A. The effect of medical sympathetic blockage (using reserpine) in the management of spinal cord injury in rats. PARAPLEGIA 1977; 15:172-5. [PMID: 909721 DOI: 10.1038/sc.1977.23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of medical sympathetic blockage with reserpine was studied in 48 rats following crushing of the cord. Control experiments were carried out with reserpined and unreserpined groups. Marked sensory-motor improvement was found in the reserpined group.
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Ashby P, Verrier M, Warsh JJ, Price KS. Spinal reflexes and the concentrations of 5-HIAA, MHPG, and HVA in lumbar cereborspinal fluid after spinal lesions in man. J Neurol Neurosurg Psychiatry 1976; 39:1191-200. [PMID: 1011029 PMCID: PMC492564 DOI: 10.1136/jnnp.39.12.1191] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Descending bulbospinal pathways that employ specific neurotransmitter substances are known to be capable of modulating segmental reflex activity in the experimental animal. To determine whether this might also occur in man correlations have been sought between the activity in spinal reflex pathways and the lumbar cerebrospinal fluid (CSF) concentrations of 5-hydroxyindolacetic acid (5-HIAA), 3 methoxy-4-hydroxyphenylglycol (MHPG), and homovanillic acid (HVA) in 12 patients with complete or virtually complete spinal lesions. The concentrations of 5-HIAA and MHPG in lumbar CSF ARE REDUCED AFTER COMPLETE OR VIRTUALLY COMPLETE SPINAL LESIONS IN MAN. This may occur within 18 days of the lesion. MHPG concentrations appear to be inversely related to the level of the lesion. The HVA concentration in lumbar CSF is reduced when there is obstruction of the CSF pathways. No relationship could be demonstrated between the concentrations of 5-HIAA or MHPG in lumbar CSF and the activity in the spinal monosynaptic pathway (estimated from the proportion of the motoneurone pool activated by the Achilles tendon reflex or H reflex) or the activity of a spinal inhibitory mechanism (estimated by the degree of vibratory inhibition of the monosynaptic reflex). Patients with a tonic vibration reflex (TVR) tended to have higher MHPG levels. There appeared to be an association between low CSF HVA and enhanced vibratory inhibition of the monosynaptic reflex in the nine patients whose spinal lesions were complete.
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