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ABSTRACT: Purpose: Neural tension technique (NTT) is a therapy believed to reduce spasticity and to increase range of motion (ROM). This study compared the ability of NTT and random passive movements (RPMs) to reduce spasticity in the knee flexors in 10 spastic patients with brain injury. Methods: An RCT study with crossover design evaluated muscle tone measured by: 1) hand-held dynamometer; 2) Modified Ashworth Scale (MAS); 3) and ROM by; 4) angles of resistance onset "catch" (R1) compensatory movement (R2); and 5) 'subjectively perceived reduction in muscle tone'. Outcome measures were recorded by three raters before and after a single treatment session. Results: Objective stiffness measured with the hand-held device showed no significant changes for the NTT or RPM (p ≥ 0.09-0.79). The subjective measures showed significant changes after the NTT for the non-blinded rater (MAS: p < 0.05: R1: p < 0.05; R2: p < 0.05), but for the blinded rater a significant reduction was found only for R1 (p < 0.05) and R2 (p < 0.05). For the non-blinded rater intervention effects were found for R1 (p < 0.01), R2 (p < 0.01) and subjectively perceived tone reduction (p < 0.01). For the blinded rater no intervention effect was found. Conclusions: An objective evaluation of NTT demonstrates that it does not reduce spasticity. However, it does increase ROM with the same effect as RPM. [Box: see text].
Disability and Rehabilitation 03/2012; 34(23):1978-85. · 1.50 Impact Factor
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ABSTRACT: Spasticity is a frequently used diagnosis, and anti-spastic medication is used widespread. In this systematic review article we highlight difficulties in diagnosing spasticity correctly and thus limit the value of the diagnosis in ensuring the best possible treatment. We review recent neuroscience research and conclude that it is necessary to develop better tools for clinical diagnosis of spasticity in order to avoid potential malpractice and to limit treatment with anti-spastic drugs for patients with documented increased reflex-mediated muscle tone as their main annoyance.
Ugeskrift for laeger 02/2012; 174(9):569-73.
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ABSTRACT: It has recently been demonstrated that soleus motor-evoked potentials (MEPs) are facilitated prior to the onset of dorsiflexion. The purpose of this study was to examine if this could be explained by removal of spinal inhibition of the descending command to soleus motoneurons. To test this, we investigated how afferent inputs from the tibialis anterior muscle modulate the corticospinal activation of soleus spinal motoneurons at rest, during static contraction and prior to movement. MEPs activated by transcranial magnetic stimulation (TMS) and Hoffmann reflexes (H-reflexes), activated by electrical stimulation of the posterior tibial nerve (PTN), were conditioned by prior stimulation of the common peroneal nerve (CPN) at a variety of conditioning-test (CT) intervals. MEPs in the precontracted soleus muscle were inhibited when the TMS pulse was preceded by CPN stimulation with a CT interval of 35 ms, and they were facilitated for CT intervals of 50-55 ms. A similar inhibition of the soleus H-reflex was not observed. To investigate which descending pathways might be responsible for the afferent-evoked inhibition and facilitation, we examined the effect of CPN stimulation on short-latency facilitation (SLF) and long-latency facilitation (LLF) of the soleus H-reflex induced by a subthreshold TMS pulse at different CT intervals. SLF is known to reflect the excitability of the fastest conducting, corticomotoneuronal cells whereas LLF is believed to be caused by more indirect descending pathways. At CT intervals of 40-45 ms, the LLF was significantly more inhibited compared to the SLF when taking the effect on the H-reflex into account. Finally, we investigated how the CPN-induced inhibition and facilitation of the soleus MEP were modulated prior to dorsiflexion. Whereas the late facilitation (CT interval: 55 ms) was similar prior to dorsiflexion and at rest, no inhibition could be evoked at the earlier latency (CT interval: 35 ms) prior to onset of dorsiflexion. The observation that the CPN-induced inhibition of soleus MEPs disappears prior to onset of dorsiflexion may explain why soleus MEPs are facilitated prior to onset of dorsiflexion contraction. A possible mechanism involves the removal of inhibition of the descending command to the motoneurons at a spinal interneuronal level because the inhibition was seen in LLF and not in SLF, and the MEP inhibition was not observed in the H-reflex. The data illustrate that spinal interneuronal pathways modify descending commands to human spinal motoneurons and influence the size of MEPs elicited by TMS.
The Journal of Physiology 12/2011; 589(Pt 23):5819-31. · 4.72 Impact Factor
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ABSTRACT: Antispastic medication is often used in the clinic together with physiotherapy. However, some of the antispastic drugs, e.g., baclofen and diazepam, may influence the plastic mechanisms that are necessary for motor learning and hence efficient physiotherapy. In the present study, we consequently investigated the influence of baclofen and diazepam on acquisition of a visuomotor skill. The study was designed as a semi-randomized, double-blinded, placebo-controlled, crossover study in 16 healthy human subjects. The motor skill task required the subjects to match a given force trajectory by increasing or decreasing ankle dorsiflexor torque. Subjects trained for a total of 30 min. Transcranial magnetic stimulation of the primary motor cortex leg area was applied to elicit motor evoked potentials in the anterior tibial muscle (TA). Coupling between populations of TA motor units was calculated in the frequency (coherence) domain during isometric dorsiflexion. Subjects receiving placebo showed statistically significant improvement in motor performance (q = 34.1, P = 0.014) accompanied by a statistically significant reduction in intramuscular coherence. Subjects receiving baclofen and diazepam conversely showed no progression in motor performance (P > 0.05), and the training was not accompanied by a decrease in intramuscular coherence. TA motor evoked potentials had significantly lower threshold following the training in the placebo group, whereas this was not the case in the treatment groups. These data indicate that diazepam and baclofen interfere with the acquisition of a motor skill by disrupting some of the neuroplastic changes that are involved in improved motor performance. This suggests that antispastic treatment should be used with caution in subjects receiving concomitant physiotherapy.
Experimental Brain Research 09/2011; 213(4):465-74. · 2.39 Impact Factor
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ABSTRACT: Spasticity is a common manifestation of lesion of central motor pathways. It is essential for correct anti-spastic treatment that passive and active contributions to increased muscle stiffness are distinguished. Here, we combined biomechanical and electrophysiological evaluation to distinguish the contribution of active reflex mechanisms from passive muscle properties to ankle joint stiffness in 31 healthy, 10 stroke, 30 multiple sclerosis and 16 spinal cord injured participants. The results were compared to routine clinical evaluation of spasticity.
A computer-controlled robotic device applied stretches to the ankle plantar flexor muscles at different velocities (8-200deg/s; amplitude 6°). The reflex threshold was determined by soleus EMG. Torque and EMG data were normalized to the maximal torque and EMG evoked by supramaximal stimulation of the tibial nerve. Passive resistance (the torque response to stretches) was confirmed to be a good representation of the passive stiffness also at higher velocities when transmission in the tibial nerve was blocked by ischemia.
Passive torque tended to be larger in the neurological than in the healthy participants, but it did not reach statistical significance, except in the stroke group (p<0.05). Following normalization to the maximal stimulus-evoked torque, the passive torque was found to be significantly larger in neurological participants identified with spasticity than in non-spastic participants (p<0.01). There was no significant difference in the reflex threshold between the healthy and the neurological participants. The reflex evoked torque and EMG were significantly larger in all neurological groups than in the healthy group (p<0.001). Twenty three participants with evidence of hypertonia in the plantar flexors (Ashworth score⩾1) showed normal reflex torque without normalization. With normalization this was only the case in 11 participants. Increased reflex mediated stiffness was detected in only 64% participants during clinical examination.
The findings confirm that the clinical diagnosis of spasticity includes changes in both active and passive muscle properties and the two can hardly be distinguished based on routine clinical examination.
The data suggest that evaluation techniques which are more efficient in distinguishing active and passive contributions to muscle stiffness than routine clinical examination should be considered before anti-spastic treatment is initiated.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 05/2010; 121(11):1939-51. · 3.12 Impact Factor
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ABSTRACT: At the onset of dorsiflexion disynaptic reciprocal inhibition (DRI) of soleus motoneurons is increased to prevent activation of the antagonistic plantar flexors. This is caused by descending facilitation of transmission in the DRI pathway. Because the risk of eliciting stretch reflexes in the ankle plantar flexors at the onset of dorsiflexion is larger the quicker the movement, it was hypothesized that DRI may be increased when subjects are trained to perform dorsiflexion movements as quickly as possible For this purpose, 14 healthy human subjects participated in explosive strength training of the ankle dorsiflexor muscles 3 times a week for 4 wk. Test sessions were conducted before, shortly after, and 2 wk after the training period. The rate of torque development measured at 30, 50, 100, and 200 ms after onset of voluntary explosive isometric dorsiflexion increased by 24-33% (P < 0.05). DRI was measured as the depression of the soleus H reflex following conditioning stimulation of the peroneal nerve (1.1 x motor threshold) at an interval of 2-3 ms. At the onset of dorsiflexion the amount of DRI measured relative to DRI at rest increased significantly from 6% before the training to 22% after the training (P < 0.05). We speculate that DRI at the onset of movement may be increased in healthy subjects following explosive strength training to ensure efficient suppression of the antagonist muscles as the dorsiflexion movement becomes faster.
Journal of Applied Physiology 06/2008; 105(3):915-22. · 3.75 Impact Factor
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ABSTRACT: Reduced depression of transmitter release from Ia afferents following previous activation (post-activation depression) has been suggested to be involved in the pathophysiology of spasticity. However, the effect of this mechanism on the myotatic reflex and its possible contribution to increased reflex excitability in spastic participants has not been tested. To investigate these effects, we examined post-activation depression in Soleus H-reflex responses and in mechanically evoked Soleus stretch reflex responses. Stretch reflex responses were evoked with consecutive dorsiflexion perturbations delivered at different intervals. The magnitude of the stretch reflex and ankle torque response was assessed as a function of the time between perturbations. Soleus stretch reflexes were evoked with constant velocity (175 degrees /s) and amplitude (6 degrees) plantar flexion perturbations. Soleus H-reflexes were evoked by electrical stimulation of the tibial nerve in the popliteal fossa. The stretch reflex and H-reflex responses of 30 spastic participants (with multiple sclerosis or spinal cord injury) were compared with those of 15 healthy participants. In the healthy participants, the magnitude of the soleus stretch reflex and H-reflex decreased as the interval between the stimulus/perturbation was decreased. Similarly, the stretch-evoked torque decreased. In the spastic participants, the post-activation depression of both reflexes and the stretch-evoked torque was significantly smaller than in healthy participants. These findings demonstrate that post-activation depression is an important factor in the evaluation of stretch reflex excitability and muscle stiffness in spasticity, and they strengthen the hypothesis that reduced post-activation depression plays a role in the pathophysiology of spasticity.
Experimental Brain Research 03/2008; 185(2):189-97. · 2.39 Impact Factor
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ABSTRACT: Ballet dancers have small soleus (SOL) H-reflex amplitudes, which may be related to frequent use of cocontraction of antagonistic ankle muscles. Indeed, SOL H-reflexes are depressed during cocontraction compared with plantarflexion at matched background EMG level. We investigated the effect of 30-min training of simultaneous activation of ankle dorsi- and plantarflexor muscles (cocontraction task) on the SOL H-reflex in 10 healthy volunteers. Measurements were taken during cocontraction. After training, there was a significant improvement in the ability of the subjects to perform a stable cocontraction. SOL H-reflex recruitment curves and H-max/M-max ratios were decreased after cocontraction training but not after 30 min of static dorsi or plantarflexion. The decreased H-reflex size correlated with improved motor performance. No changes in SOL and tibialis anterior (TA) EMG activity or EMG power were observed, suggesting that increased presynaptic inhibition of Ia afferents is a likely mechanism for H-reflex depression. In different sessions we measured SOL and TA motor-evoked potentials (MEPs) by using transcranial magnetic stimulation (TMS), TMS-elicited suppression of SOL EMG, and coherence between electroencephalographic (EEG) activity (Cz) and TA and SOL EMG. SOL and TA MEPs were depressed, whereas TMS-elicited suppression of SOL EMG and coherence were increased after training. Decreased excitability of corticospinal neurons due to increased intracortical inhibition seems a likely explanation of these observations. Our results indicate that the depression in H-reflex observed during a cocontraction task can be trained and that repeated performance of tasks involving cocontraction may lead to prolonged changes in reflex and corticospinal excitability.
Journal of Neurophysiology 01/2008; 98(6):3677-87. · 3.32 Impact Factor
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ABSTRACT: We have previously demonstrated an increase in the excitability of the leg motor cortical area in relation to acquisition of a visuo-motor task in healthy humans. It remains unknown whether the interaction between corticospinal drive and spinal motoneurones is also modulated following motor skill learning. Here we investigated the effect of visuo-motor skill training involving the ankle muscles on the coupling between electroencephalographic (EEG) activity recorded from the motor cortex (Cz) and electromyographic (EMG) activity recorded from the left tibialis anterior (TA) muscle in 11 volunteers. Coupling in the time (cumulant density function) and frequency domains (coherence) between EEG-EMG and EMG-EMG activity were calculated during tonic isometric dorsiflexion before and after 32 min of training a visuo-motor tracking task involving the ankle muscles or performing alternating dorsi- and plantarflexion movements without visual feedback. A significant increase in EEG-EMG coherence around 15-35 Hz was observed following the visuo-motor skill session in nine subjects and in only one subject after the control task. Changes in coherence were specific to the trained muscle as coherence for the untrained contralateral TA muscle was unchanged. EEG and EMG power were unchanged following the training. Our results suggest that visuo-motor skill training is associated with changes in the corticospinal drive to spinal motorneurones. Possibly these changes reflect sensorimotor integration processes between cortex and muscle as part of the motor learning process.
The Journal of Physiology 07/2006; 573(Pt 3):843-55. · 4.72 Impact Factor
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ABSTRACT: Sensory information continuously converges on the spinal cord during a variety of motor behaviours. Here, we examined presynaptic control of group Ia afferents in relation to acquisition of a novel motor skill. We tested whether repetition of two motor tasks with different degrees of difficulty, a novel visuo-motor task involving the ankle muscles, and a control task involving simple voluntary ankle movements, would induce changes in the size of the soleus H-reflex. The slope of the H-reflex recruitment curve and the H-max/M-max ratio were depressed after repetition of the visuo-motor skill task and returned to baseline after 10 min. No changes were observed after the control task. To elucidate the mechanisms contributing to the H-reflex depression, we measured the size of the long-latency depression of the soleus H-reflex evoked by peroneal nerve stimulation (D1 inhibition) and the size of the monosynaptic Ia facilitation of the soleus H-reflex evoked by femoral nerve stimulation. The D1 inhibition was increased and the femoral nerve facilitation was decreased following the visuo-motor skill task, suggesting an increase in presynaptic inhibition of Ia afferents. No changes were observed in the disynaptic reciprocal Ia inhibition. Somatosensory evoked potentials (SEPs) evoked by stimulation of the tibial nerve (TN) were also unchanged, suggesting that transmission in ascending pathways was unaltered following the visuo-motor skill task. Together these observations suggest that a selective presynaptic control of Ia afferents contributes to the modulation of sensory inputs during acquisition of a novel visuo-motor skill in healthy humans.
The Journal of Physiology 11/2005; 568(Pt 1):343-54. · 4.72 Impact Factor
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ABSTRACT: Changes in corticospinal excitability induced by 4 wk of heavy strength training or visuomotor skill learning were investigated in 24 healthy human subjects. Measurements of the input-output relation for biceps brachii motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation were obtained at rest and during voluntary contraction in the course of the training. The training paradigms induced specific changes in the motor performance capacity of the subjects. The strength training group increased maximal dynamic and isometric muscle strength by 31% (P < 0.001) and 12.5% (P = 0.045), respectively. The skill learning group improved skill performance significantly (P < 0.001). With one training bout, the only significant change in transcranial magnetic stimulation parameters was an increase in skill learning group maximal MEP level (MEP(max)) at rest (P = 0.02) for subjects performing skill training. With repeated skill training three times per week for 4 wk, MEP(max) increased and the minimal stimulation intensity required to elicit MEPs decreased significantly at rest and during contraction (P < 0.05). In contrast, MEP(max) and the slope of the input-output relation both decreased significantly at rest but not during contraction in the strength-trained subjects (P < or = 0.01). No significant changes were observed in a control group. A significant correlation between changes in neurophysiological parameters and motor performance was observed for skill learning but not strength training. The data show that increased corticospinal excitability may develop over several weeks of skill training and indicate that these changes may be of importance for task acquisition. Because strength training was not accompanied by similar changes, the data suggest that different adaptive changes are involved in neural adaptation to strength training.
Journal of Applied Physiology 11/2005; 99(4):1558-68. · 3.75 Impact Factor
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ABSTRACT: Repetitive transcranial magnetic stimulation (rTMS) has been shown to induce adaptations in cortical neuronal circuitries. In the present study we investigated whether rTMS, through its effect on corticospinal pathways, also produces adaptations at the spinal level, and what the neuronal mechanisms involved in such changes are. rTMS (15 trains of 20 pulses at 5 Hz) was applied over the leg motor cortical area in ten healthy human subjects. At rest motor evoked potentials (MEPs) in the soleus and tibialis anterior muscles were facilitated by rTMS (at 1.2xMEP threshold). In contrast, the soleus H-reflex was depressed for 1 s at stimulus intensities from 0.92 to 1.2xMEP threshold. rTMS increased the size of the long-latency depression of the soleus H-reflex evoked by common peroneal nerve stimulation and decreased the femoral nerve facilitation of the soleus H-reflex. These observations suggest that the depression of the H-reflex by rTMS can be explained, at least partly, by an increased presynaptic inhibition of soleus Ia afferents. In contrast, rTMS had no effect on disynaptic reciprocal Ia inhibition from ankle dorsiflexors to plantarflexors. We conclude that a train of rTMS may modulate transmission in specific spinal circuitries through changes in corticospinal drive. This may be of relevance for future therapeutic strategies in patients with spasticity.
Experimental Brain Research 05/2005; 162(2):202-12. · 2.39 Impact Factor
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ABSTRACT: Training-induced changes in cortical excitability may play an important role in rehabilitation of gait ability in patients with neurological disorders. In this study, we investigated the effect of a 32-min period of motor skill, non-skill and passive training involving the ankle muscles on leg motor cortical excitability in healthy humans. Transcranial magnetic stimulation (TMS) at a range of intensities was applied to obtain a recruitment curve of the motor evoked potentials (MEPs) in the tibialis anterior (TA) muscle before and after training. We also explored the effect of training on inhibitory and facilitatory cortical circuits by using a paired-pulse TMS technique at intervals of 2.5 ms (short-interval intracortical inhibition, SICI) and 8 ms (intracortical facilitation, ICF). During motor skill training, subjects were instructed to make a cursor follow a series of target lines on a computer screen by performing voluntary ankle dorsi- and plantarflexion movements. Non-skill and passive training consisted of repeated voluntary and assisted dorsi- and plantarflexion movements, respectively. Recruitment curves increased significantly after 32 min of motor skill training but not after non-skill and passive training, suggesting that only skill motor training increases motor cortical excitability. Motor skill training was not accompanied by any changes in the recruitment curves of TA MEPs evoked by transcranial electrical stimulation, suggesting that the increased MEPs to TMS was likely caused by changes in excitability at a cortical site. SICI was decreased after 32 min of motor skill training but no changes were observed in ICF. We conclude that similar plastic changes as have previously been reported for the hand motor following motor skill training may also be observed for the leg motor area. The observed plastic changes appeared to be related to the degree of difficulty in the motor task, and may be of relevance for rehabilitation of gait disorders.
Experimental Brain Research 12/2004; 159(2):197-205. · 2.39 Impact Factor
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ABSTRACT: In this review we discuss the contribution of transcranial magnetic stimulation (TMS) to the understanding of human motor control. Compound motor-evoked potentials (MEPs) may provide valuable information about corticospinal transmission, especially in patients with neurological disorders, but generally do not allow conclusions regarding the details of corticospinal function to be made. Techniques such as poststimulus time histograms (PSTHs) of the discharge of single, voluntarily activated motor units and conditioning of H reflexes provide a more optimal way of evaluating transmission in specific excitatory and inhibitory pathways. Through application of such techniques, several important issues have been clarified. TMS has provided the first real evidence that direct monosynaptic connections from the motor cortex to spinal motoneurons exist in man, and it has been revealed that the distribution of these projections roughly follows the same proximal-distal gradient as in other primates. However, pronounced differences also exist. In particular, the tibialis anterior muscle appears to receive as significant a monosynaptic corticospinal drive as muscles in the hand. The reason for this may be the importance of this muscle in controlling the foot trajectory in the swing phase of walking. Conditioning of H reflexes by TMS has provided evidence of changes in cortical excitability prior to and during various movements. These experiments have generally confirmed information obtained from chronic recording of the activity of corticospinal cells in primates, but information about the corticospinal contribution to movements for which information from other primates is sparse or lacking has also been obtained. One example is walking, where TMS experiments have revealed that the corticospinal tract makes an important contribution to the ongoing EMG activity during treadmill walking. TMS experiments have also documented the convergence of descending corticospinal projections and peripheral afferents on spinal interneurons. Current investigations of the functional significance of this convergence also rely on TMS experiments. The general conclusion from this review is that TMS is a powerful technique in the analysis of motor control, but that care is necessary when interpreting the data. Combining TMS with other techniques such as PSTH and H reflex testing amplifies greatly the power of the technique.
Experimental Brain Research 10/2003; 152(1):1-16. · 2.39 Impact Factor
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ABSTRACT: The involvement of the motor cortex during human walking was evaluated using transcranial magnetic stimulation (TMS) of the motor cortex at a variety of intensities. Recordings of EMG activity in tibialis anterior (TA) and soleus muscles during walking were rectified and averaged.TMS of low intensity (below threshold for a motor-evoked potential, MEP) produced a suppression of ongoing EMG activity during walking. The average latency for this suppression was 40.0 ± 1.0 ms. At slightly higher intensities of stimulation there was a facilitation of the EMG activity with an average latency of 29.5 ± 1.0 ms. As the intensity of the stimulation was increased the facilitation increased in size and eventually a MEP was clear in individual sweeps.In three subjects TMS was replaced by electrical stimulation over the motor cortex. Just below MEP threshold there was a clear facilitation at short latency (≈28 ms). As the intensity of the electrical stimulation was reduced the size of the facilitation decreased until it eventually disappeared. We did not observe a suppression of the EMG activity similar to that produced by TMS in any of the subjects.The present study demonstrates that motoneuronal activity during walking can be suppressed by activation of intracortical inhibitory circuits. This illustrates for the first time that activity in the motor cortex is directly involved in the control of the muscles during human walking.
