The effect of baclofen on the transmission in spinal pathways in spastic multiple sclerosis patients

Localized muscle vibration in the treatment of motor impairment and spasticity in post-stroke patients: a systematic review

INTRODUCTION

During the last decades, many studies have been carried out to understand the possible positive effects of vibration therapy in post-stroke rehabilitation. In particular, the use of localized muscle vibration (LMV) seems to have promising results. The aim of this systematic review was to describe the use of LMV in post-stroke patients to improve motor recovery, reducing spasticity and disability in both upper and lower limb.

EVIDENCE ACQUISITION

A search was conducted on PubMed, Scopus, Pedro and REHABDATA electronic database. Only randomized controlled trials have been included, excluding no-localized vibratory treatments and other pathological conditions. Fourteen studies met the inclusion criteria and were included in this review.

EVIDENCE SYNTHESIS

Collectively, the studies involved 425 stroke patients. Most studies included chronic stroke patients (ten) and treated only the upper limb (eleven). There is evidence that LMV therapy is effective in reducing spasticity and improving motor recovery, especially when associated with conventional physical therapy.

CONCLUSIONS

LMV may be a feasible and safe tool to be integrated into traditional and conventional neurorehabilitation programs for post-stroke patients to reduce spasticity. Analysis of the available clinical trials do not allow us to indicate vibration therapy as effective in functional motor recovery, despite some studies showed encouraging results. Further studies, with larger size of homogeneous patients and with a shared methodology are needed to produce more reliable data, especially on the lower limb.

Cannabinoids in multiple sclerosis: A neurophysiological analysis

OBJECTIVES

To investigate the action of cannabinoids on spasticity and pain in secondary progressive multiple sclerosis, by means of neurophysiological indexes.

MATERIAL AND METHODS

We assessed 15 patients with progressive MS (11 females) using clinical scales for spasticity and pain, as well as neurophysiological variables (H/M ratio, cutaneous silent period or CSP). Testing occurred before (T0) and during (T1) a standard treatment with an oral spray containing delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Neurophysiological measures at T0 were compared with those of 14 healthy controls of similar age and sex (HC). We then compared the patient results at the two time points (T1 vs T0).

RESULTS

At T0, neurophysiological variables did not differ significantly between patients and controls. At T1, spasticity and pain scores improved, as detected by the Modified Ashworth Scale or MAS (P = .001), 9-Hole Peg Test or 9HPT (P = .018), numeric rating scale for spasticity or NRS (P = .001), and visual analogue scale for pain or VAS (P = .005). At the same time, the CSP was significantly prolonged (P = .001).

CONCLUSIONS

The THC-CBD spray improved spasticity and pain in secondary progressive MS patients. The spray prolonged CSP duration, which appears a promising tool for assessing and monitoring the analgesic effects of THC-CBD in MS.

Retraining Reflexes: Clinical Translation of Spinal Reflex Operant Conditioning

Neurological disorders, such as spinal cord injury, stroke, traumatic brain injury, cerebral palsy, and multiple sclerosis cause motor impairments that are a huge burden at the individual, family, and societal levels. Spinal reflex abnormalities contribute to these impairments. Spinal reflex measurements play important roles in characterizing and monitoring neurological disorders and their associated motor impairments, such as spasticity, which affects nearly half of those with neurological disorders. Spinal reflexes can also serve as therapeutic targets themselves. Operant conditioning protocols can target beneficial plasticity to key reflex pathways; they can thereby trigger wider plasticity that improves impaired motor skills, such as locomotion. These protocols may complement standard therapies such as locomotor training and enhance functional recovery. This paper reviews the value of spinal reflexes and the therapeutic promise of spinal reflex operant conditioning protocols; it also considers the complex process of translating this promise into clinical reality.

Is two better than one? Muscle vibration plus robotic rehabilitation to improve upper limb spasticity and function: A pilot randomized controlled trial

Even though robotic rehabilitation is very useful to improve motor function, there is no conclusive evidence on its role in reducing post-stroke spasticity. Focal muscle vibration (MV) is instead very useful to reduce segmental spasticity, with a consequent positive effect on motor function. Therefore, it could be possible to strengthen the effects of robotic rehabilitation by coupling MV. To this end, we designed a pilot randomized controlled trial (Clinical Trial NCT03110718) that included twenty patients suffering from unilateral post-stroke upper limb spasticity. Patients underwent 40 daily sessions of Armeo-Power training (1 hour/session, 5 sessions/week, for 8 weeks) with or without spastic antagonist MV. They were randomized into two groups of 10 individuals, which received (group-A) or not (group-B) MV. The intensity of MV, represented by the peak acceleration (a-peak), was calculated by the formula (2πf)2A, where f is the frequency of MV and A is the amplitude. Modified Ashworth Scale (MAS), short intracortical inhibition (SICI), and Hmax/Mmax ratio (HMR) were the primary outcomes measured before and after (immediately and 4 weeks later) the end of the treatment. In all patients of group-A, we observed a greater reduction of MAS (p = 0.007, d = 0.6) and HMR (p<0.001, d = 0.7), and a more evident increase of SICI (p<0.001, d = 0.7) up to 4 weeks after the end of the treatment, as compared to group-B. Likewise, group-A showed a greater function outcome of upper limb (Functional Independence Measure p = 0.1, d = 0.7; Fugl-Meyer Assessment of the Upper Extremity p = 0.007, d = 0.4) up to 4 weeks after the end of the treatment. A significant correlation was found between the degree of MAS reduction and SICI increase in the agonist spastic muscles (p = 0.004). Our data show that this combined rehabilitative approach could be a promising option in improving upper limb spasticity and motor function. We could hypothesize that the greater rehabilitative outcome improvement may depend on a reshape of corticospinal plasticity induced by a sort of associative plasticity between Armeo-Power and MV.

Upper motor neuron evaluation in multiple sclerosis patients treated with Sativex®

BACKGROUND

Spasticity in multiple sclerosis (MS) results from an imbalance of inputs from descending pathways to the spinal motor circuits, as well as from a damage of the corticospinal tract (CST).

OBJECTIVES

To assess CST impairment in MS patients with and without spasticity and to evaluate its evolution under Sativex^® treatment.

METHODS

Ten MS patients with spasticity ("cases") underwent clinical (EDSS, 9-hole Peg, Ashworth scale, Timed 25-Foot Walk, and NRS for spasticity), MRI (CST fractional anisotropy [FA]), and electrophysiological (central motor conduction time [CMCT] and H/M ratio) evaluations at baseline and after 12 months. We selected 20 MS patients without spasticity as control group at baseline.

RESULTS

At baseline, cases showed a lower CST FA (0.492±0.045 vs 0.543±0.047; P=.01) and a higher CMCT (P=.001) compared to the control group. No correlations were found between clinical, electrophysiological, and MRI features. After 12 months, cases showed a decrease in non-prevalent degree of impairment (PDI) side FA (0.502±0.023 vs 0.516±0.033; P=.01) without differences for electrophysiological features compared to baseline. Treatment with Sativex^® resulted in a reduction of NRS for spasticity (P=.01).

CONCLUSIONS

We confirm the presence of CST impairment in MS patients with spasticity. We did not identify structural/electrophysiological correlates that could explain Sativex^® clinical effect.

Synaptopathy connects inflammation and neurodegeneration in multiple sclerosis

Multiple sclerosis (MS) has long been regarded as a chronic inflammatory disease of the white matter that leads to demyelination and eventually to neurodegeneration. In the past decade, several aspects of MS pathogenesis have been challenged, and degenerative changes of the grey matter, which are independent of demyelination, have become a topic of interest. CNS inflammation in MS and experimental autoimmune encephalomyelitis (EAE; a disease model used to study MS in rodents) causes a marked imbalance between GABAergic and glutamatergic transmission, and a loss of synapses, all of which leads to a diffuse 'synaptopathy'. Altered synaptic transmission can occur early in MS and EAE, independently of demyelination and axonal loss, and subsequently causes excitotoxic damage. Inflammation-driven synaptic abnormalities are emerging as a prominent pathogenic mechanism in MS-importantly, they are potentially reversible and, therefore, represent attractive therapeutic targets. In this Review, we focus on the connection between inflammation and synaptopathy in MS and EAE, which sheds light not only on the pathophysiology of MS but also on that of primary neurodegenerative disorders in which inflammatory processes contribute to disease progression.

Sativex(®) and clinical-neurophysiological measures of spasticity in progressive multiple sclerosis

Despite the proven efficacy of Sativex(®) (9-delta-tetrahydrocannabinol plus cannabidiol) oromucosal spray in reducing spasticity symptoms in multiple sclerosis (MS), little is known about the neurophysiological correlates of such effects. The aim of the study was to investigate the effects of Sativex on neurophysiological measures of spasticity (H/M ratio) and corticospinal excitability in patients with progressive MS. This was a randomized, double-blind, placebo-controlled, crossover study. Consecutive subjects with progressive MS and lower limb spasticity referred to our center were randomized to 4 weeks' treatment (including 2 weeks' titration) with Sativex or placebo, with crossover after a 2-week washout. Clinical and neurophysiological measures (H/M ratio and cortical excitability) of spasticity were assessed. The H/M ratio was the primary outcome, with sample size calculation of 40 patients. Of 44 recruited patients, 34 were analyzed due to 6 drop-outs and 4 exclusions, which lowered the power of the study to show differences between treatments. Neurophysiological measures did not differ significantly according to treatment and did not correlate significantly with clinical response. Response on the modified Ashworth scale (at least 20 % improvement) was significantly more frequent after Sativex than placebo (50 vs 23.5 %; p = 0.041; McNemar). Side effects did not differ significantly according to treatment. Our findings confirm the clinical benefit of Sativex on MS spasticity. The lack of corresponding changes in corticospinal excitability and on the monosynaptic component, of the stretch reflex, although in a limited sample size, points to the involvement of other spinal and supraspinal mechanisms in the physiopathology of spasticity in progressive MS.

Characteristics of preceding Ia activity on postactivation depression in health and disease

Previous activation of the soleus Ia afferents causes a depression in the amplitude of the H-reflex. This mechanism is referred to as postactivation depression (PAD) and is suggested to be presynaptically mediated. With the use of a paired reflex depression paradigm (eliciting two H-reflexes with conditioning-test intervals from 80 ms to 300 ms), PAD was examined in a group of healthy individuals and a group of hemiplegic patients. Healthy individuals showed substantial depression of the test H-reflex at all intervals. Although the patient group showed substantially less depression at all intervals, increasing the interval between the two reflexes sharply reduced the depression. In a separate experiment, we varied the size of the conditioning H-reflex against a constant test H-reflex. In healthy individuals, by increasing the size of the conditioning H-reflex, the amplitude of the test H-reflex exponentially decreased. In the patient group, however, this pattern was dependent on the conditioning-test interval; increasing the size of the conditioning H-reflex caused an exponential decrease in the size of the test reflex at intervals shorter than 150 ms. This pattern was similar to that of healthy individuals. However, conducting the same protocol at a longer interval (300 ms) in these patients resulted in an abnormal pattern (instead of an exponential decrease in the size of the test reflex, exaggerated responses were observed). Fisher discriminant analysis suggested that these two patterns (which differed only in the timing between the two stimuli) were substantially different from each other. Therefore, it is suggested that the abnormal pattern of PAD in hemiplegic stroke patients could be a contributing factor for the pathophysiology of spasticity.

Selective effects of baclofen on use-dependent modulation of GABAB inhibition after tetraplegia

Baclofen is a GABAB receptor agonist commonly used to relief spasticity related to motor disorders. The effects of baclofen on voluntary motor output are limited and not yet understood. Using noninvasive transcranial magnetic and electrical stimulation techniques, we examined electrophysiological measures probably involving GABAB (long-interval intracortical inhibition and the cortical silent period) and GABAA (short-interval intracortical inhibition) receptors, which are inhibitory effects mediated by subcortical and cortical mechanisms. We demonstrate increased active long-interval intracortical inhibition and prolonged cortical silent period during voluntary activity of an intrinsic finger muscle in humans with chronic incomplete cervical spinal cord injury (SCI) compared with age-matched controls, whereas resting long-interval intracortical inhibition was unchanged. However, long-term (~6 years) use of baclofen decreased active long-interval intracortical inhibition to similar levels as controls but did not affect the duration of the cortical silent period. We found a correlation between signs of spasticity and long-interval intracortical inhibition in patients with SCI. Short-interval intracortical inhibition was decreased during voluntary contraction compared with rest but there was no effect of SCI or baclofen use. Together, these results demonstrate that baclofen selectively maintains use-dependent modulation of largely subcortical but not cortical GABAB neuronal pathways after human SCI. Thus, cortical GABA(B) circuits may be less sensitive to baclofen than spinal GABAB circuits. This may contribute to the limited effects of baclofen on voluntary motor output in subjects with motor disorders affected by spasticity.

Stretch reflex regulation in healthy subjects and patients with spasticity

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.

The use of intrathecal baclofen in pain management

SUMMARY Intrathecal therapy involves the subarachnoid delivery of medications where the administered agents have enhanced potency and diminished systemic exposure compared with oral administration. Baclofen exerts its therapeutic action by enhancing the inhibition produced by the endogenous neurotransmitter GABA. While well-established within the armamentarium of tools for spasticity management, the role of intrathecal baclofen for the management of chronic pain is less certain. The purpose of this review is to describe the pharmacology of intrathecal baclofen, relate the role of intrathecal baclofen in neurologic and non-neurologic conditions, and report upon the potential utility of coadministering baclofen with other agents via the intrathecal route of delivery.

Changes in correlation between spontaneous activity of dorsal horn neurones lead to differential recruitment of inhibitory pathways in the cat spinal cord

Simultaneous recordings of cord dorsum potentials along the lumbo-sacral spinal cord of the anaesthetized cat revealed the occurrence of spontaneous synchronous negative (n) and negative-positive (np) cord dorsum potentials (CDPs). The npCDPs, unlike the nCDPs, appeared preferentially associated with spontaneous negative dorsal root potentials (DRPs) resulting from primary afferent depolarization. Spontaneous npCDPs recorded in preparations with intact neuroaxis or after spinalization often showed a higher correlation than the nCDPs recorded from the same pair of segments. The acute section of the sural and superficial peroneal nerves further increased the correlation between paired sets of npCDPs and reduced the correlation between the nCDPs recorded from the same pair of segments. It is concluded that the spontaneous nCDPs and npCDPs are produced by the activation of interconnected sets of dorsal horn neurones located in Rexed's laminae III–IV and bilaterally distributed along the lumbo-sacral spinal cord. Under conditions of low synchronization in the activity of this network of neurones there would be a preferential activation of the intermediate nucleus interneurones mediating Ib non-reciprocal postsynaptic inhibition. Increased synchronization in the spontaneous activity of this ensemble of dorsal horn neurones would recruit the interneurones mediating primary afferent depolarization and presynaptic inhibition and, at the same time, reduce the activation of pathways mediating Ib postsynaptic inhibition. Central control of the synchronization in the spontaneous activity of dorsal horn neurones and its modulation by cutaneous inputs is envisaged as an effective mechanism for the selection of alternative inhibitory pathways during the execution of specific motor or sensory tasks.

Soleus H-reflex gain, threshold, and amplitude as function of body posture and load in spinal cord intact and injured subjects

In this study, we established parameters of the soleus H-reflex excitability in response to changes of posture and load in 8 chronic spinal cord injured (SCI) and 10 spinal-intact subjects. The soleus H-reflex recruitment curve was established in all subjects while they were supine, seated, and standing on a stable treadmill. During standing, body weight support (BWS) was provided via an upper body harness and ranged in SCI subjects from 20%-50% and in spinal-intact subjects was set at 0% and 50%. Stimuli corresponding to the H-threshold (H(th)), maximal H-reflex amplitude (H(max)), and 50% of H(max) as well as the reflex gain were estimated based on a sigmoid function of the ascending limb of the soleus H-reflex recruitment curve. The soleus H-reflex gain, H(max) amplitude, and stimuli corresponding to H(th), 50% of H(max), and H(max) were increased in SCI subjects regardless of the body position and loading. Further, the reflex gain was not modulated appropriately during conditions of weight bearing in SCI subjects. Impaired spinal reflex excitability in SCI subjects is accompanied by changes of the H-reflex recruitment curve parameters regardless of presence or absence of body loading.

Consensus on the appropriate use of intrathecal baclofen (ITB) therapy in paediatric spasticity

Among features of motor disorders in children, spasticity is associated with considerable morbidity and problems in care, particularly in severely affected patients. Intrathecal baclofen (ITB) has been increasingly used as a relatively specific treatment modality for spasticity. To date, most of the evidence for its use in paediatric patients has come from retrospective and uncontrolled studies, although randomised, controlled trials of screening ITB and ITB therapy itself have recently been published. This consensus statement on the use of ITB in paediatric patients with spasticity was developed on the basis of currently available evidence, with the aim of providing information for clinicians, promoting an expert opinion and a consistent approach to the management of these patients and emphasising the need for further prospective, large-scale studies.

EFFECT OF ACUTE UNLOADED LEG CYCLING ON SPASTICITY IN INDIVIDUALS WITH MULTIPLE SCLEROSIS USING ANTI-SPASTIC MEDICATIONS

This article examines the effect of a bout of unloaded leg cycling on the soleus H-reflex and modified Ashworth scale (MAS) in 6 individuals with multiple sclerosis (MS) who had spasticity of the leg muscles and were currently taking anti-spastic medications. H-reflex and MAS data were collected before and 10, 30, and 60 min after 20 min of unloaded leg cycling and a control condition. The unloaded leg cycling resulted in concomitant reductions in soleus H-reflex and MAS scores compared with the control condition. This provides a basis for incorporating exercise along with anti-spastic medications into a multifaceted plan for spasticity management in individuals with MS.

Clinical and neurophysiologic assessment of strength and spasticity during intrathecal baclofen titration in incomplete spinal cord injury: single-subject design

BACKGROUND/OBJECTIVE

Spasticity after spinal cord injury (SCI) is commonly managed with oral and intrathecal baclofen (ITB), with less attention to the effects on voluntary motor control. Studies combining clinical and neurophysiologic assessments during dose optimization are rare. Study aims (a) systematically evaluate effects of varied doses of oral and ITB on clinical and neurophysiologic measures of strength and spasticity and (b) relate clinical and neurophysiologic findings.

METHODS

A 41-year-old man with an incomplete T11-ASIA D SCI was studied during ITB titration. Spasticity and strength in the lower extremities were assessed clinically and neurophysiologically at 5 different daily dosages of baclofen: (a) 80 mg oral, (b) 80 mg oral/50 microg ITB, (c) 80 mg oral/125 microg ITB, (d) 30 mg oral/125 microg ITB, and (e) 125 microg ITB only.

RESULTS

A dose-dependent change in the Ashworth score and lower limb motor score was observed during titration of oral and ITB. Whereas the Hoffman (H)-reflex was abolished after the introduction of ITB, the flexion withdrawal reflex approximated a dose-dependent pattern. Changes in the motor score and EMG during voluntary muscle activation were proportionally smaller than the corresponding changes in clinical and neurophysiologic measures of spasticity. Neurophysiologic assessment largely paralleled clinical findings.

CONCLUSIONS

This single-subject study shows that the control of spasticity can be achieved without detrimental effects on strength in incomplete SCI and suggests the need for including strength testing in comprehensive clinical assessment of spasticity. The study shows convergent validity between clinical and neurophysiologic assessments during ITB dose titration. Adding neurophysiologic assessment to clinical assessment may provide objectivity and sensitivity and facilitate decision-making during ITB titration.

Presynaptic modulation by endocannabinoids

Modulation of neurotransmitter release by G-protein-coupled receptors (GPCRs) is a prominent presynaptic mechanism for regulation of synaptic transmission. Activation of GPCRs located at the presynaptic terminal can decrease the probability of neurotransmitter release. This presynaptic depression involves activation of Gi/o-type G-proteins that mediate different inhibitory mechanisms, including inhibition of voltage-gated calcium channels, activation of potassium channels, and direct inhibition of the vesicle fusion process. A variety of neurotransmitters and modulatory agents can activate GPCRs that produce presynaptic depression. Among these are lipid metabolites that serve as agonists for GPCRs. The discovery of endocannabinoids and their cognate receptors, including the CB1 receptor, has stimulated intense investigation into the neurophysiological roles of these lipid metabolites. It is now clear that presynaptic depression is the major physiological role for the CB1 receptor. Endocannabinoids activate this receptor mainly via a retrograde signaling process in which these compounds are synthesized in and released from postsynaptic neuronal elements, and travel back to the presynaptic terminal to act on the CB1 receptor. This retrograde endocannabinoid modulation has been implicated in short-term synaptic depression, including suppression of excitatory or inhibitory transmission induced by postsynaptic depolarization and transient synaptic depression induced by activation of postsynaptic GPCRs during agonist treatment or synaptic activation. Endocannabinoids and the CB1 receptor also play a key role in one form of long-term synaptic depression (LTD) that involves a longlasting decrease in neurotransmitter release.

G-protein-coupled GABAB receptors inhibit Ca2+ channels and modulate transmitter release in descending turtle spinal cord terminal synapsing motoneurons

Presynaptic gamma-aminobutyric acid type B receptors (GABA(B)Rs) regulate transmitter release at many central synapses by inhibiting Ca(2+) channels. However, the mechanisms by which GABA(B)Rs modulate neurotransmission at descending terminals synapsing on motoneurons in the spinal cord remain unexplored. To address this issue, we characterized the effects of baclofen, an agonist of GABA(B)Rs, on the monosynaptic excitatory postsynaptic potentials (EPSPs) evoked in motoneurons by stimulation of the dorsolateral funiculus (DLF) terminals in a slice preparation from the turtle spinal cord. We found that baclofen depressed neurotransmission in a dose-dependent manner (IC(50) of approximately 2 microM). The membrane time constant of the motoneurons did not change, whereas the amplitude ratio of the evoked EPSPs in response to a paired pulse was altered in the presence of the drug, suggesting a presynaptic mechanism. Likewise, the use of N- and P/Q-type Ca(2+) channel antagonists (omega-conotoxin GVIA and omega-agatoxin IVA, respectively) also depressed EPSPs significantly. Therefore, these channels are likely involved in the Ca(2+) influx that triggers transmitter release from DLF terminals. To determine whether the N and P/Q channels were regulated by GABA(B)R activation, we analyzed the action of the toxins in the presence of baclofen. Interestingly, baclofen occluded omega-conotoxin GVIA action by approximately 50% without affecting omega-agatoxin IVA inhibition, indicating that the N-type channels are the target of GABA(B)Rs. Lastly, the mechanism underlying this effect was further assessed by inhibiting G-proteins with N-ethylmaleimide (NEM). Our data show that EPSP depression caused by baclofen was prevented by NEM, suggesting that GABA(B)Rs inhibit N-type channels via G-protein activation.

Ethanol reduces motoneuronal excitability and increases presynaptic inhibition of Ia afferents in the human spinal cord

INTRODUCTION

Already low blood concentrations of ethanol acutely impair motor control and coordination. In vitro experiments have given evidence that spinal effects of ethanol contribute to this by reducing spinal excitability and enhancing presynaptic inhibition of Ia fibers. In this study, we investigated the influence of 0.7 g per kilogram of bodyweight ethanol on motoneuronal excitability and presynaptic inhibition in humans.

METHODS

The study was performed in 10 volunteers. Spinal excitability was measured by the maximal H-reflex of the soleus muscle normalized to the maximal muscular response (Hmax/Mmax). Presynaptic inhibition was measured by changes in heteronymous Ia-facilitation of the soleus H-reflex, which is achieved by stimulation of the femoral nerve. A decrease in facilitation can be ascribed to an increase in presynaptic inhibition. Changes of these parameters under the influence of 0.7 g per kilogram of bodyweight ethanol were assessed in comparison to control measurements before ethanol application.

RESULTS

Both parameters, Hmax/Mmax and Heteronymous facilitation, were significantly reduced under the influence of ethanol (Wilcoxon signed-rank test with Bonferroni correction for each, p<0.01).

DISCUSSION

The increase in presynaptic inhibition by ethanol is probably caused by an increase in GABAA receptor-mediated Cl-conductance, which has been shown in spinal cord cultures. The role of presynaptic inhibition in movement is assumed to be there to control the afferent input of muscle spindles and tendon organs as a mechanism of specific input-selection. This study demonstrated that ethanol reduces spinal excitability and increases GABAergic presynaptic inhibition on Ia afferent fibers in humans.

Intrathecal baclofen in the treatment of spasticity, dystonia and vegetative disorders

Baclofen (beta-p-chlorophenyl-GABA) binds to a number of spinal and cerebral sites and depresses the excitability of motor neurons. Intrathecal administration induces much higher CSF concentrations compared to the limited passage through the blood-brain barrier after oral administration. The development of reliable implanted pumps allows long-term intrathecal baclofen treatment (ITB). Baclofen is mainly an antispastic drug and the main indication of ITB is generalized lower limb spasticity in spinal cord injury and multiple sclerosis. The side-effects are due to either drug over-dose or withdrawal and to malfunctions of the implanted device (disconnections of the catheter, infections, etc.). Large numbers of patients have been treated over the past twenty years. More recently, baclofen has been used in the treatment of spasticity of cerebral origin, and in the treatment of other motor disorders, mainly dystonia. The results in cerebral palsy are promising and ITB's role will probably grow in the management of the movement disorders of these children. Further studies are required on the exact site of action, on the possible association with other drugs, especially clonidine and on the development of sustained release formulations.

Neurophysiological basis and clinical applications of the H-reflex as an adjunct for evaluating response to intrathecal baclofen for spasticity

Implanted programmable pumps that infuse intrathecal baclofen (ITB) markedly enhance the ability of clinicians to manage severe spasticity in appropriately selected patients. Studies addressing the efficacy of this treatment modality have primarily used clinical outcome measures of impairment, particularly reduction in stiffness as measured by the Ashworth scale. Several recent studies, however, highlight comparalively higher sensitivity of neurophysiologic techniques, especially the H-reflex, as an objective index of spinal cord response to ITB administration. We review the conceptual, physiological, and methodological hases for use of the H-reflex as an adjunct to clinical evaluation among patients receiving ITB infusion, including published reports and selected case studies that address the potential advantages and limitations of such techniques when applied to dose titration and system "troubleshooting" scenarios, We also address the implications of such findings in the context of reported complications such as "tolerance" to ITB administration and catheter "microfracture". The accumulated knowledge suggests that H-reflex is a sensitive method for documenting altered spinal cord responsiveness in the presence of ITB delivery. We therefore recommend using H-reflex as an adjunct to clinical evaluation when judging the overall effectiveness of ITB administration.

Baclofen and potential therapeutic use: Studies of neuronal survival

Up to now, baclofen (a GABA(B) receptor agonist) has been used for the treatment of severe spasticity unresponsive to oral antispasmodics. Although in humans it is usually administered at 2 mg/ml, the dosage to be used in the treatment of other diseases is unknown. For this reason, it is important to determine the safe maximum dosage and toxicity at the clinically used concentration. Primary cortical neurons represent a useful model to test the safety of baclofen. We performed a colorimetric assay (MTT test) as well as electron microscopy investigations, to determine neuronal survival after the treatment with baclofen at a concentration of 2 and 4 mg/ml. Our results demonstrated that, in our experimental model, neither concentration affected neuronal survival. Considering the above results, we can conclude that at the used concentrations, this drug is safe and its clinical use should be encouraged.

Effect of acute leg cycling on the soleus H-reflex and modified Ashworth scale scores in individuals with multiple sclerosis

This study examined the effect of a single bout of unloaded leg cycling on the soleus H-reflex and modified Ashworth scale (MAS) in 27 individuals with multiple sclerosis (MS) who had spasticity of the leg muscles, but were not currently taking anti-spastic medications. The soleus H-reflex and MAS data were collected before and 10, 30, and 60 min after 20 min of unloaded leg cycling and a control condition. The acute bout of unloaded leg cycling resulted in concomitant and prolonged reductions in the soleus H-reflex and MAS scores compared with the control condition. This provides converging evidence for the anti-spastic potential of acute unloaded leg cycling in individuals with MS.

Intrathecal baclofen therapy and multiple sclerosis: outcomes and patient satisfaction

OBJECT

In this study the authors provide an assessment of intrathecal baclofen (ITB) therapy and evaluate patient outcomes and satisfaction.

METHODS

Records for patients with multiple sclerosis who were selected as candidates for ITB therapy were reviewed for their response to test dose, surgical technique, surgery- and pump-related complications, and short- and long-term response to therapy. Family and caregiver assessments of the value of ITB therapy were also reviewed.

CONCLUSIONS

Intrathecal baclofen therapy is safe and effective. Most patients and caregivers express satisfaction with the therapy and would recommend it to other patients. Spasm frequency appears to be the single most common variable positively affected by therapy.

Placebo controlled utility and feasibility study of the H-reflex and flexor reflex in spastic children treated with intrathecal baclofen

OBJECTIVE

To evaluate feasibility and utility of the soleus H-reflex and tibialis anterior flexor reflex (FR) in identifying spinal cord neuronal response to intrathecal baclofen (ITB) in children with severe spastic cerebral palsy.

METHODS

During a randomized, double-blind, placebo-controlled dose-escalation test treatment, maximum H amplitude/maximum M amplitude (H/M ratio) and FR parameters were bilaterally recorded at baseline and 2-3 h after intrathecal bolus administration of placebo and increasing doses of baclofen until both an improvement in the individual treatment goal(s) and a one-point reduction on the Ashworth scale were observed.

RESULTS

Electrophysiological data of 14 children were studied. The H-reflex was feasible in 13 children, the FR threshold area in 9 and the FR, elicited with supramaximal stimulation, in only one child. After ITB, the H/M ratio significantly decreased (left: 0.67+/-0.47 to 0.15+/-0.18, P=0.005; right: 0.55+/-0.32 to 0.14+/-0.19, P=0.002) without placebo effect. FR threshold area after ITB, only decreased significantly in children not taking oral baclofen (left: 146+/-53 to 41+/-54 mV ms, P=0.000; right: 156+/-80 to 66+/-48 mV ms, P=0.002).

CONCLUSIONS

This is the first randomized, double-blind, placebo-controlled dose-escalation study in spastic children demonstrating the soleus H-reflex to be a feasible and objective measure to quantify the decreasing motoneuron excitability in response to ITB bolus administration. Only in children not taking oral baclofen, FR threshold area can also be used as an objective outcome measure, yet feasibility is limited.

SIGNIFICANCE

We suggest introducing the H-reflex as the electrophysiological gold standard for the evaluation of the effect of ITB in spastic children.

Dose-response relationship between the H-reflex and continuous intrathecal baclofen administration for management of spasticity

OBJECTIVE

To determine the relationship between the H-reflex (H/M ratio) and continuous intrathecal baclofen (CITB) dose after pump implantation for control of spastic hypertonia.

METHODS

Soleus H-reflexes were serially recorded in 34 subjects (19 men, mean age 32 years, mean follow-up 1.7 years) during simple continuous mode of CITB delivery. Different fitting methods were explored to determine which function best described changes in H/M ratio with increasing CITB dose. We then calculated effective CITB doses yielding H/M ratios equal to 75, 50, and 25% (ED75, ED50, ED25) of the baseline recorded before the implant in 22 subjects.

RESULTS

We found a significant dose-response relationship between the soleus H/M ratio and CITB dose. A two-decay exponential function was the best fit on each side for pooled data, but a general linear model when controlling for subject. The mean ED75, ED50, ED25 were 30, 70, and 110 mcg/day. Logistical regression predicted with high probability that the H/M ratio should be less than 30% at CITB doses above 150 mcg/day.

CONCLUSIONS

H/M ratio is strongly dependent on CITB dose. It sharply decreases up to 150 mcg/day of CITB followed by a plateau.

SIGNIFICANCE

Establishing the relationship between the H/M ratio and CITB dose may be useful for dose titration and early identification of an ITB system malfunction.

Temporal facilitation of spastic stretch reflexes following human spinal cord injury

Recent evidence suggests that alterations in ionic conductances in spinal motoneurones, specifically the manifestation of persistent inward currents, may be partly responsible for the appearance of hyperexcitable reflexes following spinal cord injury (SCI). We hypothesized that such alterations would manifest as temporal facilitation of stretch reflexes in human SCI. Controlled, triangular wave, ankle joint rotations applied at variable velocities (30-120 deg s(-1)) and intervals between stretches (0.25-5.0 s) were performed on 14 SCI subjects with velocity-dependent, hyperexcitable plantarflexors. Repeated stretch elicited significant increases in plantarflexion torques and electromyographic (EMG) activity from the soleus (SOL) and medial gastrocnemius (MG). At higher velocities (> or = 90 deg s(-1)), reflex torques declined initially, but subsequently increased to levels exceeding the initial response, while mean EMG responses increased throughout the joint perturbations. At lower velocities (< or = 60 deg s(-1)), both joint torques and EMGs increased gradually. Throughout a range of angular velocities, reflex responses increased significantly only at intervals < or = 1 s between stretches and following at least four rotations. Ramp-and-hold perturbations used to elicit tonic stretch reflexes revealed significantly prolonged EMG responses following one or two triangular stretches, as compared to single ramp-and-hold excursions. Post hoc analyses revealed reduced reflex facilitation in subjects using baclofen to control spastic behaviours. Evidence of stretch reflex facilitation post-SCI may reflect changes in underlying neuronal properties and provide insight into the mechanisms underlying spastic reflexes.

Effects of hip joint angle changes on intersegmental spinal coupling in human spinal cord injury

Pathological expression of movement and muscle tone in human upper motor neuron disorders has been partly associated with impaired modulation of spinal inhibitory mechanisms, such as reciprocal or presynaptic inhibition. In addition, input from specific afferent systems contributes significantly to spinal reflex circuits coupled with posture or locomotion. Accordingly, the objectives of this study were to identify the involved afferents and their relative contribution to soleus H-reflex modulation induced by changes in hip position, and to relate these effects with activity of spinal interneuronal circuits. Specifically, we investigated the actions of group I synergistic and antagonistic muscle afferents (e.g. common peroneal nerve, CPN; medial gastrocnemius, MG) and tactile plantar cutaneous afferents on the soleus H-reflex during controlled hip angle variations in 11 motor incomplete spinal cord injured (SCI) subjects. It has been postulated in healthy subjects that CPN stimulation evokes an inhibition on the soleus H-reflex at a conditioning test (C-T) interval of 2-4 ms. This short latency reflex depression is caused mainly by activation of the reciprocal Ia inhibitory pathway. At longer C-T intervals (beyond 30 ms) the soleus H-reflex is again depressed, and is generally accepted to be caused by presynaptic inhibition of soleus Ia afferents. Similarly, MG nerve stimulation depresses soleus H-reflex excitability at the C-T interval of 6 ms, involving the pathway of non-reciprocal group I inhibition, while excitation of plantar cutaneous afferents affects the activity of spinal reflex pathways in the extensors. In this study, soleus H-reflexes recorded alone or during CPN stimulation at either short (2, 3, 4 ms) or long (80, 100, 120 ms) C-T intervals, and MG nerve stimulation delivered at 6 ms were elicited via conventional methods and similar to those adopted in studies conducted in healthy subjects. Plantar skin conditioning stimulation was delivered through two surface electrodes placed on the metatarsals at different C-T intervals ranging from 3 to 90 ms. CPN stimulation at either short or long C-T intervals and MG nerve stimulation resulted in a significant facilitation of the soleus H-reflex, regardless of the hip angle tested. Plantar skin stimulation delivered with hip extended at 10 degrees induced a bimodal facilitation reflex pattern, while with hip flexed (10 degrees , 30 degrees ) the reflex facilitation increased with increments in the C-T interval. This study provides evidence that in human chronic SCI, classically key inhibitory reflex actions are switched to facilitatory, and that spinal processing of plantar cutaneous sensory input and actions of synergistic/antagonistic muscle afferents interact with hip proprioceptive input to facilitate soleus H-reflex excitability. These actions might be associated with the pathological expression of neural control of movement in individuals with SCI, and potentially could be considered in rehabilitation programs geared to restore sensorimotor function in these patients.

Baclofen-loaded microspheres: preparation and efficacy testing in a new rabbit model

Intrathecal baclofen is the reference treatment for severe spasticity. This drug has to be injected chronically in the intrathecal space by implanted pumps which are very expensive, uncomfortable and sometimes lead to side effects. Previous work has been performed by our group to assess the feasibility of encapsulating baclofen into poly(lactide-co-glycolide) (PLGA) microspheres and injecting these preparations in the intrathecal space of rabbits. The aims of the present study were to improve the encapsulation process for industrial application (scale-up), and to set up an animal model to assess the duration of effect of the new formulations. Modifications included the replacement of methylene chloride by a less toxic solvent, ethyl acetate, and the use of high molecular weight polymers to extend the release rate of the drug. The temperature and organic solvent extraction rate were fully controlled during the whole manufacturing process. All these modifications resulted in high quality microsphere batches with a CV inferior to 5% for encapsulation efficiency and drug loading. Encapsulation efficiency and release patterns were dependent on the drug payload and the polymer used. A formulation displaying a sustained release of baclofen over 174 days and a moderate burst effect of 16% in the first day in vitro was evaluated in a new reliable model of baclofen activity based on electrophysiological measurement of H-reflex in the rabbit. The activity of a very low dose of baclofen microspheres in vivo was sustained over 35 days. Furthermore, the preparation was well tolerated. These newly developed preparations are a very promising approach for enhancing the efficacy and comfort of patients undergoing spasticity treatment.

Neurobiology of rehabilitation

Rehabilitation aims to lessen the physical and cognitive impairments and disabilities of patients with stroke, multiple sclerosis, spinal cord or brain injury, and other neurologic diseases. Conventional approaches beyond compensatory adjustments to disability may be augmented by applying some of the myriad experimental results about mechanisms of intrinsic biological changes after injury and the effects of extrinsic manipulations on spared neuronal assemblies. The organization and inherent adaptability of the anatomical nodes within distributed pathways of the central nervous system offer a flexible substrate for treatment strategies that drive activity-dependent plasticity. Opportunities for a new generation of approaches are manifested by rodent and non-human primate studies that reveal morphologic and physiologic adaptations induced by injury, by learning-associated practice, by the effects of pharmacologic neuromodulators, by the behavioral and molecular bases for enhancing activity-dependent synaptic plasticity, and by cell replacement, gene therapy, and regenerative biologic strategies. Techniques such as functional magnetic resonance imaging and transcranial magnetic stimulation will help determine the most optimal physiologic effects of interventions in patients as the cortical representations for skilled movements and cognitive processes are modified by the combination of conventional and biologic therapies. As clinicians digest the finer details of the neurobiology of rehabilitation, they will translate laboratory data into controlled clinical trials. By determining how much they can influence neural reorganization, clinicians will extend the opportunities for neurorestoration.

Neurophysiologic evaluation of spastic hypertonia: implications for management of the patient with the intrathecal baclofen pump

A number of techniques attempt to objectively quantify various clinical characteristics associated with spastic hypertonia and related motor disorders. These range in cost, complexity, physiologic basis of measured response, and invasiveness. With a greater range of treatment options for spasticity and an increase in the number of centers participating in studies of interventions for spasticity, published reports reflect increasing use of objective quantification techniques. We review studies that highlight the potential utility of neurophysiologic techniques, including the H-reflex, F-wave, and flexion withdrawal reflex, in the objective evaluation of response to intrathecal baclofen administration. The accumulated knowledge suggests that neurophysiologic evaluation is useful for assessing spinal cord responsiveness, and we recommend it as an adjunct to clinical evaluation when judging the overall effectiveness of intrathecal baclofen administration.

Comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions: a systematic review

Skeletal muscle relaxants are a heterogeneous group of medications used to treat two different types of underlying conditions: spasticity from upper motor neuron syndromes and muscular pain or spasms from peripheral musculoskeletal conditions. Although widely used for these indications, there appear to be gaps in our understanding of the comparative efficacy and safety of different skeletal muscle relaxants. This systematic review summarizes and assesses the evidence for the comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions. Randomized trials (for comparative efficacy and adverse events) and observational studies (for adverse events only) that included oral medications classified as skeletal muscle relaxants by the FDA were sought using electronic databases, reference lists, and pharmaceutical company submissions. Searches were performed through January 2003. The validity of each included study was assessed using a data abstraction form and predefined criteria. An overall grade was allocated for the body of evidence for each key question. A total of 101 randomized trials were included in this review. No randomized trial was rated good quality, and there was little evidence of rigorous adverse event assessment in included trials or observational studies. There is fair evidence that baclofen, tizanidine, and dantrolene are effective compared to placebo in patients with spasticity (primarily multiple sclerosis). There is fair evidence that baclofen and tizanidine are roughly equivalent for efficacy in patients with spasticity, but insufficient evidence to determine the efficacy of dantrolene compared to baclofen or tizanidine. There is fair evidence that although the overall rate of adverse effects between tizanidine and baclofen is similar, tizanidine is associated with more dry mouth and baclofen with more weakness. There is fair evidence that cyclobenzaprine, carisoprodol, orphenadrine, and tizanidine are effective compared to placebo in patients with musculoskeletal conditions (primarily acute back or neck pain). Cyclobenzaprine has been evaluated in the most clinical trials and has consistently been found to be effective. There is very limited or inconsistent data regarding the effectiveness of metaxalone, methocarbamol, chlorzoxazone, baclofen, or dantrolene compared to placebo in patients with musculoskeletal conditions. There is insufficient evidence to determine the relative efficacy or safety of cyclobenzaprine, carisoprodol, orphenadrine, tizanidine, metaxalone, methocarbamol, and chlorzoxazone. Dantrolene, and to a lesser degree chlorzoxazone, have been associated with rare serious hepatotoxicity.

Electrophysiological assessment of the effect of intrathecal baclofen in dystonic children

OBJECTIVE

To evaluate the effect of intrathecal baclofen in a group of dystonic children using electrophysiological procedures previously validated in spastic children.

METHODS

Seven children (aged 2-16 years) with dystonia of various aetiologies (dyskinetic cerebral palsy, pantothenate kinase-associated neurodegeneration and Aicardi-Goutières syndrome) underwent transcranial magnetic stimulation, H-reflex and flexor reflex studies before and after intrathecal injection of baclofen. The Barry-Albright Dystonia Scale (BADS) was used for clinical evaluation of dystonia.

RESULTS

Motor-evoked potentials, present in 2 of 5 patients before baclofen, were preserved after injection. Before baclofen, H reflex was present in 6 of 7 patients (mean H(max)/M(max:) 0.45+/-0.21). It was markedly reduced after the injection (mean H(max)/M(max:) 0.09+/-0.11) (P<0.001). Area of flexor reflex significantly decreased after baclofen (P=0.047), while threshold significantly increased (P=0.01). No significant clinical improvement of the BADS scores was observed (P=0.058).

CONCLUSIONS

These electrophysiological procedures, previously demonstrated to quantify the action of intrathecal baclofen in spastic adults and children, also appear sensitive in dystonic children. The electrophysiological changes are consistent with primarily spinal sites of action of baclofen. They appear more sensitive than clinical evaluation.

Changes in voluntary torque and electromyographic activity following oral baclofen

The consequences of baclofen intake on voluntary motor behaviors remain unclear. We studied the effects of single oral doses of baclofen on voluntary, isometric knee extension torques and surface and single motor unit (MU) electromyographic (EMG) activity from the vastus lateralis in 11 individuals without neurological injury. Examination of submaximal to maximal contractions of varying duration performed pre- and post-baclofen ingestion revealed significant decreases in maximal knee torques and EMG magnitude, accompanied by an increase in slope of the torque-EMG relation. A decreased slope of the torque-MU firing rate relation was also demonstrated post-baclofen, but without changes in minimal firing rates or recruitment forces. During sustained contractions at < or =25% of maximal voluntary torque elicited after baclofen ingestion, increased EMG activity was observed without significant differences in MU firing rates. Our results demonstrate a clear reduction in the maximal torque-generating ability following baclofen. Specific changes in MU firing patterns indicate that weakness may be due partly to reduced motoneuronal excitability, although use of MU discharge patterns to assess these effects is limited in its sensitivity.

Effects of cycling exercise on the soleus H-reflex and state anxiety among men with low or high trait anxiety

The present study examined the effects of low- and high-intensity cycling exercise on the H-reflex and state anxiety among men having low (n=20) or high (n=20) trait anxiety. Participants completed measures of state anxiety and underwent elicitation and recording of the H-reflex in the soleus muscle before and 10 min after three 20-min conditions: (1) quiet rest, (2) cycling at 40% VO2peak, and (3) cycling at 70% VO2peak. We found that (1) exercise, but not quiet rest, resulted in a reduction of the H-reflex; the magnitude of the reduction did not differ between men having low or high trait anxiety; (2) exercise and quiet rest resulted in similar reductions of state anxiety, and the magnitude of the reductions was larger for men having high trait anxiety than low trait anxiety; and (3) reductions of the H-reflex were unrelated to reductions of self-reported state anxiety across all three conditions. Contrary to prior opinion, the postexercise reduction in the H-reflex reported by previous researchers and in the present study appears to be unrelated to self-reported anxiety after exercise.

Electrophysiological assessment of the effect of intrathecal baclofen in spastic children

OBJECTIVES

To evaluate the effect of intrathecal baclofen in a group of spastic children using electrophysiological procedures described in adults.

METHODS

Six children (aged 1-14 years) with severe spasticity of various aetiologies underwent transcranial magnetic stimulation, H reflex and flexor reflex studies before and after intrathecal injection of baclofen. Ashworth scale was used for clinical evaluation of spasticity.

RESULTS

Motor evoked potentials, present in two patients before baclofen, were preserved after injection. Before baclofen, H reflex was present in 5 patients (H(max)/M(max) from 0.23 to 0.84) and absent in one who had infantile neuroaxonal dystrophy. After baclofen, it was absent in 4 patients and markedly reduced in one. Surface of flexor reflex significantly decreased after baclofen (P=0.01), while threshold significantly increased (P=0.003).

CONCLUSIONS

In spastic children, the action of baclofen on spinal pathways may be quantified by the same electrophysiological procedures as in adults. This approach may contribute to select optimal dosage.

Anti-spasticity agents for multiple sclerosis

BACKGROUND

Spasticity is a common problem in MS patients causing pain, spasms, loss of function and difficulties in nursing care. A variety of oral and parenteral medications are available.

OBJECTIVES

To assess the absolute and comparative efficacy and tolerability of anti-spasticity agents in multiple sclerosis (MS) patients.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of anti-spasticity agents were identified using MEDLINE, EMBASE, bibliographies of relevant articles, personal communication, manual searches of relevant journals and information from drug companies.

SELECTION CRITERIA

Double-blind, randomised controlled trials (either placebo-controlled or comparative studies) of at least seven days duration.

DATA COLLECTION AND ANALYSIS

Two independent reviewers extracted data and the findings of the trials were summarised. Missing data were collected by correspondence with principal investigators. A meta-analysis was not performed due to the inadequacy of outcome measures and methodological problems with the studies reviewed.

MAIN RESULTS

Twenty-three placebo-controlled studies (using baclofen, dantrolene, tizanidine, botulinum toxin, vigabatrin, prazepam and threonine) and thirteen comparative studies met the selection criteria. Only thirteen of these studies used the Ashworth scale, of which only three of the six placebo-controlled trials and none of the seven comparative studies showed a statistically significant difference between test drugs. Spasms, other symptoms and overall impressions were only assessed using unvalidated scores and results of functional assessments were inconclusive.

REVIEWER'S CONCLUSIONS

The absolute and comparative efficacy and tolerability of anti-spasticity agents in multiple sclerosis is poorly documented and no recommendations can be made to guide prescribing. The rationale for treating features of the upper motor neurone syndrome must be better understood and sensitive, validated spasticity measures need to be developed.