Reflex changes induced by clonidine in spinal cord injured patients

Latest approaches for the treatment of spasticity and autonomic dysreflexia in chronic spinal cord injury

Two of the most prevalent secondary complications following spinal cord injury (SCI), besides loss of function and/or sensation below the level of injury, are uncontrolled muscle spasticity and hypertensive autonomic dysreflexia. Despite the desires of the SCI community, there have been few advances in the treatment and/or management of these fundamental impediments to the quality of life associated with chronic SCI. Therefore, the purpose of this review is to focus on current drug treatment strategies that alleviate symptoms of spasticity and autonomic dysfunction. Subsequently, looking ahead, we discuss whether individuals suffering from autonomic dysreflexia and/or muscle spasms can take certain compounds that specifically and rapidly block the neurotransmission of pain into the injured spinal cord to get rapid relief for both aberrant reflexes for which painful stimuli below the level of SCI are common precipitants.

Pediatric safety of tizanidine: clinical adverse event database and retrospective chart assessment

BACKGROUND

Tizanidine is an imidazoline with central alpha(2)-adrenoceptor agonist activity at both spinal and supraspinal levels, which is indicated as a short-acting drug for the management of spasticity. Despite being used in pediatric populations, there is no adequate information or well controlled studies to document the safety and efficacy of tizanidine in this group.

OBJECTIVE

To evaluate the safety of tizanidine in the pediatric population. We compared spontaneous adverse event reports in the Acorda Therapeutics worldwide clinical adverse event database for children (< or = 16 years; n = 99) and adults (>16 years; n = 1153) who had received tizanidine and for whom at least one adverse event was reported, and performed a retrospective chart review of the safety of tizanidine in children (< or = 16 years; n = 76) at a large US pediatric neurology practice. Causality of adverse events in our worldwide clinical adverse event database were neither assessed nor assigned by the company.

RESULTS

When adverse events from the clinical adverse event database were collapsed into the 25 Medical Dictionary for Regulatory Activities (MedDRA; version 9.0) organ system classes, five classes were more frequent in adults (general disorders and administration site conditions [p = 0.0006], hepatobiliary disorders [p = 0.0031], nervous system disorders [p = 0.0108], skin and subcutaneous disorders [p = 0.0063], and vascular disorders [p = 0.0029]), while one class was more frequent in children (psychiatric disorders [p < 0.0001]). The most common adverse event classes in children were psychiatric disorders (52.5%) followed by nervous system disorders (29.3%), and gastrointestinal disorders (16.2%), whereas the most common adverse event classes in adults were nervous system disorders (42.4%), general disorders and administration site conditions (28.6%), and gastrointestinal disorders (21.3%). Serious adverse events were substantially less frequent in children than adults (19.2% vs 45.9%) in the clinical adverse event database. In the pediatric practice chart review, the incidence of adverse events in the MedDRA psychiatric disorders class was very similar (52.6%) to that for children in the clinical adverse event database, while the next most common classes were gastrointestinal disorders (14.5%), and nervous system disorders (13.2%). There were three deaths in children across the databases, including one from accidental exposure and two from cardiac events; the relationship of cardiac events in relation to tizanidine or other causes was difficult to assess with the limited available information.The major causes of death in adults were related to suicide or overdose. Minor, transient liver transaminase increases were occasionally reported; the effect of tizanidine could not be ruled out.

CONCLUSION

The overall safety of tizanidine in the pediatric group appeared good; however, the adverse event profile differed from that in adults. This difference most likely reflects the off-label use of tizanidine as adjunctive treatment for attention disorders and autism. The frequency and nature of adverse events in adults were consistent with the tizanidine prescribing information as reported for its approved indication, i.e. management of spasticity.

Modulatory effects of alpha1-,alpha2-, and beta -receptor agonists on feline spinal interneurons with monosynaptic input from group I muscle afferents

Previous studies have shown that monoamines may modulate operation of spinal neuronal networks by depressing or facilitating responses of the involved neurons. Recently, activation of interneurons mediating reciprocal inhibition from muscle spindle (Ia) afferents and nonreciprocal inhibition from muscle spindle and tendon organ (Ia/Ib) afferents in the cat was found to be facilitated by noradrenaline (NA). However, which subclass membrane receptors are involved in mediating this facilitation was not established; the aim of the present experiments was to investigate this. Individual Ia- and Ia/Ib-inhibitory interneurons were identified in the cat lumbar spinal cord, and NA agonists were applied close to these neurons by ionophoresis. The agonists included the alpha1-receptor agonist phenylephrine, the alpha2-receptor agonists clonidine and tizanidine, and the beta-receptor agonist isoproterenol. Effects were measured by comparing changes in the number of extracellularly recorded spike potentials evoked by electrical stimulation of muscle nerves and changes in the latency of these potentials before, during, and after application of the tested compounds. Results show that the facilitatory effect of phenylephrine is as strong as that of NA, whereas the facilitatory effect of isoproterenol is weaker. Clonidine depressed activity of both Ia- and Ia/Ib-inhibitory interneurons, whereas tizanidine had no effect. These findings lead to the conclusion that beneficial antispastic effects of clonidine and tizanidine in humans are unlikely to be associated with an enhancement of the actions of Ia- and Ia/Ib-inhibitory interneurons, and the findings also support previous proposals that these compounds exert their antispastic actions via effects on other neuronal populations.

Pain and spasticity after spinal cord injury: mechanisms and treatment

STUDY DESIGN

A comprehensive survey of literature on the proposed mechanisms and treatment of pain and spasticity after spinal cord injury (SCI) was completed.

OBJECTIVES

To define the current understanding of these entities and to review various treatment options.

SUMMARY OF BACKGROUND DATA

The neurophysiologic basis of spasticity after SCI is well established. The mechanism of neuropathic pain after SCI remains conjectural, although considerable new data, much of it from animal models, now add to our understanding of this condition.

METHODS

A comprehensive search and review of the published literature was undertaken.

RESULTS

Treatment options for spasticity are effective and include oral medication (baclofen, tizanidine), intrathecal baclofen, and rarely, surgical rhizotomy or myelotomy. Selected patients with post-SCI pain can respond to surgical myelotomy (DREZ lesions) or intrathecal agents (e.g., morphine + clonidine), but the majority continue to suffer.

CONCLUSIONS

Medical and surgical treatments for spasticity are established and highly successful. Management of post-SCI pain remains a clinical challenge, as there is no uniformly successful medical or surgical treatment.

Sensitivity of qualitative and quantitative spasticity measures to clinical treatment with cryotherapy

This study examined the extent to which a battery of tests could detect a reduction of plantarflexor spasticity resulting from cryotherapy. The tests included a traditional qualitative spasticity scale, three potential quantitative spasticity measures and a measure of voluntary ankle muscle function. Twenty-six adult traumatic-brain-injured subjects were examined; these included 22 males and 4 females. The mean age was 28.15 years (range: 18-57, SD 10.78). The five tests were performed in random sequence on both ankles of each subject, before and after a 20 minute cold pack application to the calf. Tests were: modified Ashworth scale (MAS) scoring; H-reflex testing with and without dorsiflexor contraction (Hdf/Hctrl ratio); H-reflex testing with and without Achilles tendon vibration (Hvib/Hctrl ratio); reflex threshold angle (RTA) and timed toe tapping (TIT). Cryotherapy resulted in lowered MAS scores consistent with a reduction in spasticity. Doubly multivariate repeated measures ANOVA revealed a significant difference (F = 24.16, P < 0.001) in test scores between the pre- and post-cryotherapy test batteries. Significant pre- and post-cryotherapy differences (P < or = 0.03) for all dependent measures contributed to the main effect for cryotherapy. However, among the potential quantitative measures of spasticity only the RTA test demonstrated appropriate sensitivity to the reduction in spasticity. In spite of spasticity reduction, TIT performance was impaired following muscle cooling. Failure of the H-reflex ratios to show a reduction consistent with reduced spasticity was attributed to competing alpha and gamma motoneuron effects resulting from peripheral cooling.

Gabapentin effect on spasticity in multiple sclerosis: a placebo-controlled, randomized trial

OBJECTIVE

To investigate the effect of gabapentin on subject self-report and physician-administered spasticity scales in individuals with multiple sclerosis.

DESIGN

Prospective, double-masked, placebo-controlled, crossover design.

SETTING

The Multiple Sclerosis Center at the Denver Veterans Affairs Medical Center.

INTERVENTION

Subjects were titrated to either 900 mg gabapentin orally three times a day or placebo over a 6-day period. Subjects underwent a 14-day washout and then were crossed over. No other changes were made to their medication regimen.

MAIN OUTCOME MEASURES

The outcome measures were divided into two categories: subject self-report scales physician-administered scales. Subject self-report scales included the spasm frequency scale, spasm severity scale, interference with function scale, painful spasm scale, and global assessment scale. Physician-administered scales included the Modified Ashworth Scale, clonus scale, deep tendon reflexes, plantar stimulation response, and the Kurtzke Expanded Disability Status (EDSS) Scale. Digit Span and Digit Symbol subtests of the WAIS-R Intelligence Scale were administered to assess for possible impaired concentration. The Fatigue Impact Scale was administered to assess for changes in fatigue. The adjective generation technique was administered to assess for alterations in mood.

RESULTS

A statistically significant reduction in the impairment of spasticity was found in the gabapentin-treated subjects compared with placebo as measured by the self-report scales of the spasm severity scale, interference with function scale, painful spasm scale, and global assessment scale and by the physician-administered scales of the Modified Ashworth and plantar stimulation response. No significant difference was noted in the Digit Span, Digit Symbol, adjective generation technique, and EDSS.

CONCLUSION

Gabapentin reduces the impairment of spasticity, compared with placebo, without the side effects of worsening concentration and fatigue.

Pharmacological interventions for spasticity following spinal cord injury

BACKGROUND

Spasticity is a major health problem for patients with a spinal cord injury (SCI) that limits patients' mobility and affects independence in activities of daily living and work. Spasticity may also cause pain, loss of range of motion, contractures, sleep disorders and impair ambulation in patients with an incomplete lesion. The effectiveness of available drugs is still uncertain and they may cause adverse effects. Assessing what works in this area is complicated by the lack of valid and reliable measurement tools. The aim of this systematic review is to critically appraise and summarise existing information of the effectiveness of available treatments and to identify areas where further research is needed.

OBJECTIVES

To assess the effectiveness and safety of Baclofen, Dantrolene, Tizanidine and any other drugs for the treatment of long term spasticity in SCI patients as well as the effectiveness and safety of different routes of administration of Baclofen.

SEARCH STRATEGY

We searched the Injuries Group specialised register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE and CINHALH up to 1998. Drug companies and experts active in the area were also contacted.

SELECTION CRITERIA

All parallel and crossover RCTs including spinal cord injury patients complaining of "severe spasticity". Studies where less than 50% of patients had a spinal cord injury were excluded.

DATA COLLECTION AND ANALYSIS

Methodological quality of studies (allocation concealment, blinding, patients characteristics, inclusion and exclusion criteria; interventions; outcomes; lost to follow up) was independently assessed by two investigators. The heterogeneity among studies did not allow quantitative combination of results.

MAIN RESULTS

Nine out of 53 studies met the inclusion criteria. Study design was: 8 cross over, 1 parallel-group trial. Two studies (14 SCI patients), showed a significant effect of intrathecal baclofen in reducing spasticity (Ashworth Score and ADL performances), compared to placebo, without any side effect. The study comparing tizanidine to placebo (118 SCI patients) showed a significant effect of tizanidine in improving Ashworth Score but not in ADL performances. Tizanidine group reported significant rates of adverse effects (drowsiness, xerostomia). For the other drugs (Gabapentine, Clonidine, Diazepam, Amytal and oral Baclofen ) the results do not provide evidence for a clinical significant effectiveness.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to assist clinicians in a rational approach to antispastic treatment for SCI. Further research is urgently needed to improve the scientific basis of patient care.

Inhibitory casting decreases a vibratory inhibition index of the H-reflex in the spastic upper limb

OBJECTIVE

To test the hypothesis that application of an inhibitory cast to the spastic upper limb will decrease a vibratory inhibition index (VII) of the H-reflex in the spastic upper limb.

DESIGN

Prospective, nonrandomized, open-label trial.

SETTING

University tertiary care center.

PARTICIPANTS

Eight adults with upper limb spasticity.

INTERVENTION

Fiberglass cast application spanning the wrist to the upper arm.

MAIN OUTCOME MEASURE

The amplitude of the H-reflex with and without continuous 60Hz vibration to the tendon of the flexor carpi radialis was measured, and the VII was calculated using the formula: [H-reflex amplitude (vibrated)/H-reflex amplitude (control)] x 100%.

RESULTS

Mean VII decreased from baseline (70.7) on day 1 (67.6, p = .699), day 2 (55.9, p =.066), and day 3 (43.5, p = .033) of casting, and increased on day 4 (89.9, p = .146) after removal of the cast.

CONCLUSION

Findings lend support to the idea that during application of an inhibitory cast motor neuron excitability is decreased in the spastic upper limb.

Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold

PURPOSE

This study was conducted to test the hypothesis that clonidine produces a dose-dependent increase in the sweating threshold and dose-dependent decreases in vasoconstriction and shivering thresholds.

METHODS

Six healthy subjects (two female) were studied on four days after taking clonidine in oral doses of either 0 (control), 3, 6 or 9 micrograms.kg-1. The order followed a balanced design in a double-blind fashion. Oesophageal temperature and mean skin temperature (from 12 sites) were measured. Subjects were seated in 37 degrees C water which was gradually warmed until sweating occurred (sweat rate increased above 50 g.m-2.h-1). The water was then cooled gradually until thresholds for vasoconstriction (onset of sustained decrease in fingertip blood flow) and shivering (sustained elevation in metabolism) were determined. Thresholds were then referred to as the core temperature, adjusted to a designated mean skin temperature of 33 degrees C.

RESULTS

High dose clonidine similarly decreased the adjusted core temperature thresholds for vasoconstriction by 1.16 +/- 0.30 degrees C and for shivering by 1.63 +/- 0.23 degrees C (P < 0.01). The dose response effects were linear for both cold responses with vasoconstriction and shivering thresholds decreasing by 0.13 +/- 0.05 and 0.19 +/- 0.09 degree C.microgram-1 respectively (P < 0.0001). The sweating threshold was unaffected by clonidine, however the interthreshold range between sweating and vasoconstriction thresholds increased from control (0.19 +/- 0.48 degree C) to high dose clonidine (1.31 +/- 0.54 degrees C).

CONCLUSION

The decreases in core temperature thresholds for cold responses and increased interthreshold range are consistent with the effects of several anaesthetic agents and opioids and is indicative of central thermoregulatory inhibition.

Gabapentin for relief of upper motor neuron symptoms in multiple sclerosis

OBJECTIVE

To examine the efficacy of gabapentin in the treatment of spasticity and painful muscle spasms in patients with multiple sclerosis.

DESIGN

Double-blind, placebo-controlled crossover study.

SETTING

Free-standing, 93-bed, university-affiliated rehabilitation hospital.

PARTICIPANTS

There were 15 patients between the ages of 18 and 50 who had laboratory-supported definite multiple sclerosis with spasticity and leg cramps severe enough to interfere with daily activities, including sleep.

INTERVENTION

The patients received the placebo or 400mg gabapentin orally three times a day for 48 hours with an 11-day washout period. If the patients were on currently accepted modes of therapy, including oral baclofen, their current medication was not changed.

MAIN OUTCOME MEASURES

The outcome measures were Visual Faces Scale rating, Kurtzke Disability Scale, quantitative surface electromyography, Ashworth Scale, presence or absence of clonus in response to rapid ankle dorsiflexion and wrist extension, presence or absence of reflex withdrawal in response to nailbed pressure to the first finger, and assessment of Babinski response.

RESULTS

Statistically significant improvements for the gabapentin treated patients were found in the Ashworth Scale, Visual Faces Scale, and Kurtzke Disability Scale.

CONCLUSIONS

At a dose of 400mg orally three times a day, gabapentin may be of value in the treatment of the spasticity and painful muscle cramping experienced by patients with multiple sclerosis.

The enhancement of muscimol-stimulated 36C1 influx by the antispastic 5-aryl-3-(alkylsulfonyl)-4H-1,2,4-triazole (MDL 27,531) in rat brain membrane vesicles

The antispastic triazole, 4-methyl-3-methylsulphonyl-5-phenyl-4H-1,2,4-triazole (MDL 27,531) was tested in glycine- and muscimol-stimulated 36Cl- influx into brain membrane preparations. MDL 27,531 (100 nM) had no effect on glycine- (100 nM-400 microM) stimulated 36Cl- influx in brain stem tissue; on the other hand, MDL 27,531 (10 nM-10 microM) enhanced muscimol- (1 microM) stimulated 36Cl- influx in cerebellar but not cortical membranes. In the presence of the benzodiazepine (BZD) antagonist, flumazenil (10 microM), MDL 27,531 inhibited muscimol-stimulated flux. These data suggest a novel interaction of this triazole with subtypes of the gamma-aminobutyric acid (GABA)A receptor complex and the BZD receptor.

alpha 2-Adrenergic receptors in human spinal cord: specific localized expression of mRNA encoding alpha 2-adrenergic receptor subtypes at four distinct levels

alpha 2-Adrenergic receptor (AR) subtype mRNA (alpha 2a, alpha 2b, alpha 2c) neuronal localization in human spinal cord has not been described. We therefore performed in situ hybridization to identify cell bodies at four levels of human spinal cord (cervical, thoracic, lumbar, sacral) containing alpha 2AR subtype specific mRNA. alpha 2AR mRNA is present in gray matter only (ventral > dorsal; sacral > cervical > thoracic = lumbar). In addition to alpha 2AR mRNA in cell bodies in thoracic and lumbar intermediolateral (sympathetic) and sacral intermediate (parasympathetic) cell columns (lamina VII), all levels in dorsal horn laminae I, II, V, and ventral horn lamina IX, we demonstrate alpha 2AR mRNA in dorsal horn laminae III and IV, and dorsal nucleus of Clarke, where alpha 2ARs have not been described. Previously unreported heterogeneity in alpha 2AR subtype distribution (alpha 2a and alpha 2bAR mRNA present, alpha 2cAR mRNA virtually absent) is found at all sites of alpha 2AR mRNA expression in human spinal cord, including locations known to mediate effects of alpha 2AR agonist drugs on nociception, autonomic function and motor tone. Cervical spinal cord demonstrates a predominance of alpha 2a mRNA signal, while thoracic, lumbar, and sacral spinal cord demonstrate an increasing predominance of alpha 2bAR mRNA. If confirmed at a protein level, these findings have profound implications for therapeutic strategies in managing human pain.

A comparison of clonidine, cyproheptadine and baclofen in spastic spinal cord injured patients

In twenty-five SCI subjects, antispasticity effects of three putative antispasticity agents [clonidine (an alpha-2 noradrenergic agonist), cyproheptadine (a 5-HT2 antagonist) and baclofen (a GABA-B agonist)] were tested in terms of changes in leg tone as graded by the Ashworth scale (AS), in terms of the vibratory inhibition of the H-reflex (VII) and in terms of the ability of the knee to swing passively in the pendulum test as quantified by video motion analysis. When compared to the no drug period, all three drug treatments showed an antispasticity effect on the AS, the VII and the amplitude of the first swing and the relaxation index of the pendulum test, p. < 0001. Surprisingly, cyproheptadine and baclofen produced a greater reduction in the VII than clonidine, p. < 01. The amplitude of the first swing in the pendulum test correlated well with the AS, r = .88, and the antispasticity effects of the drugs produced improvements in both measures, a reduced AS and increased amplitude of knee swing in the pendulum test. Therefore, video motion analysis of the pendulum test is as valid a measure of spasticity as the Ashworth scale and is not limited by subjectivity of the examiner.

MDL 27,531 reduces spontaneous hindlimb contractions in rats with chronic transections of the spinal cord

Disrupted glycinergic inhibition in the brainstem and spinal cord may contribute to some of the alterations in reflex control seen in patients with spastic disorders. MDL 27,531, which acts functionally like a glycine agonist in its capacity to selectively reverse seizures produced by the glycine antagonist strychnine, was evaluated in a model of spinal injury-induced reflex dysfunction. Rats recovering chronically from complete spinal cord transections exhibited intermittent contractions of the paralyzed hindlimbs, as measured with an automated apparatus. MDL 27,531 selectively decreased these hindlimb contractions, as did the clinically demonstrated antispastic agent clonidine. In its therapeutic dose range, clonidine, but not MDL 27,531, produced ataxia in non-transected rats. These data suggest that MDL 27,531 may be a useful therapeutic agent for the treatment of dysfunctions of reflex control seen in spastic disorders of spinal origin, with potentially fewer side effects than are seen with existing drug therapies.

The combined effects of clonidine and cyproheptadine with interactive training on the modulation of locomotion in spinal cord injured subjects

The combined effects of a noradrenergic agonist, clonidine, and a serotonergic antagonist, cyproheptadine, together with an interactive locomotor training program incorporating progressive body weight support and treadmill walking exercise, were investigated in two chronic spinal cord injured subjects. Both subjects had no independent locomotor ability due to severe spasticity. Kinematic, temporal distance and electromyographic (EMG) data were collected during treadmill walking. The EMG activity of the lower limb muscles, initially characterized by tonic discharge and abnormal timing, became more phasic with less clonus following medication, which was related to a change in the kinematic pattern. Further kinematic and functional improvement were gained by training. Previously wheelchair-bound, both patients became functionally ambulatory overground with the aid of Canadian crutches. Thus, a potentially effective strategy for facilitating the expression of the locomotor pattern following spinal cord injury is proposed. This preliminary study showed that such a treatment strategy could possibly lead to a recovery of locomotor function in some chronic, wheelchair-bound spinal cord injured patients who had previously been stabilized on conventional therapies.