Evidence of tolerance to baclofen in treatment of severe spasticity with intrathecal baclofen

Non-medical use of baclofen: A case series and review of the literature

BACKGROUND

Baclofen is widely used for spastic disorders and, most recently, for addictive disorders. The first signals of baclofen abuse occurred in the last decade. This study aims to assess the motives, diversion sources, and routes of administration associated with the non-medical use of baclofen and examine health problems related to the non-medical use of baclofen.

METHODS

Spontaneous reports of baclofen abuse reported to the addictovigilance centre of East France were analysed. A literature search was conducted using PubMed®, Web of Sciences®, and Google Scholar® databases. Both investigations were performed in February 2021 without a time limit.

RESULTS

Forty-six cases were analysed (33 from the literature review and 13 from the addictovigilance base). Baclofen's non-medical use mainly affected male subjects with addictive history, but issues of primary abuse in subjects without any substance abuse history were also observed. Euphoria search was the most common reason for misuse. The route of administration included oral, snorting, and sublingual use. Some cases involving illegal sources were also observed. Most patients misusing baclofen presented severe complications, mainly represented by neurological and respiratory disturbances. Physical and psychological dependence on baclofen was observed in three persons.

CONCLUSIONS

Although baclofen abuse remains relatively infrequent or (most likely) underestimated, this study helped confirm baclofen's intrinsic abuse potential and make visible the baclofen-abuse-related health visible harms. Careful consideration and benefit-risk analysis should be employed when prescribing baclofen, and emergency departments should be aware of baclofen dangers in abuse situations.

Human spinal GABA neurons alleviate spasticity and improve locomotion in rats with spinal cord injury

Spinal cord injury (SCI) often results in spasticity. There is currently no effective therapy for spasticity. Here, we describe a method to efficiently differentiate human pluripotent stem cells from spinal GABA neurons. After transplantation into the injured rat spinal cord, the DREADD (designer receptors exclusively activated by designer drug)-expressing spinal progenitors differentiate into GABA neurons, mitigating spasticity-like response of the rat hindlimbs and locomotion deficits in 3 months. Administering clozapine-N-oxide, which activates the grafted GABA neurons, further alleviates spasticity-like response, suggesting an integration of grafted GABA neurons into the local neural circuit. These results highlight the therapeutic potential of the spinal GABA neurons for SCI.

Evaluation of Risk Factors for Cerebrospinal Leakage in Pediatric Patients With Cerebral Palsy Treated With Intrathecal Baclofen

BACKGROUND

Insertion of an intrathecal baclofen (ITB) pump can provide significant benefits in patients with cerebral palsy (CP). However, there are little data describing the risk of complications. Specifically, there is a lack of data describing the incidence of cerebrospinal fluid (CSF) leakage and risk factors following ITB placement. The purpose of our study was to describe risk factors for developing CSF leak in pediatric patients with CP treated with ITB and to report the treatment and outcome of CSF leaks.

METHODS

Following institutional review board approval, 720 ITB procedures in 341 children with CP were identified retrospectively over a 15-year study period. Patients' demographic characteristics, medical comorbidities, muscle tone patterns, feeding tube status, seizure history, inpatient events, ITB-related CSF leak and headache complaints and their management, and other complications were evaluated.

RESULTS

Eighty-five (24.9%) patients experienced 90 CSF leak episodes over a follow-up time of 6.3±3.9 years. There were 72 episodes of headache as a result of CSF leakage in 61 (71.7%) of these 85 patients. There was a positive correlation between the risk of CSF leak and preoperative comorbidities such as epilepsy/seizure history, feeding tube, mixed type CP, and dystonic type CP. The risk of CSF leak after primary ITB administration was 5.8% (20/341), and the risk after secondary ITB procedures due to complications was 24.2% (32/132). There was no significant relationship between CSF leak and primary ITB (P=0.21), but the risk of CSF leak was positively correlated to the secondary ITB due to complications (P<0.05).

CONCLUSIONS

CSF leak was fairly common (25% incidence), and it correlated with epilepsy/seizure history, feeding tube, mixed type CP, and dystonic type CP. Recurrent ITB procedures were a risk factor for CSF leak. Half of these patients had self-limited symptoms that improved with conservative medical treatment, and the epidural blood patch was successful in resistant cases. Successful treatment of CSF leakage complications allows patients to continue ITB.

LEVEL OF EVIDENCE

Level III.

Intrathecal Baclofen Dosage for Long-Term Treatment of Patients With Spasticity Due to Traumatic Spinal Cord Injuries or Multiple Sclerosis

OBJECTIVE

To investigate dosage changes in intrathecal baclofen during long-term treatment of patients with severe leg spasticity.

METHODS

We performed a retrospective chart review of 49 patients treated with an intrathecal baclofen pump (ITB) because of severe leg spasticity, for a minimum of 7 years. Eight patients were excluded due to catheter/pump failure or factors aggravating spasticity. Of the remaining 41 patients, 19 had spinal cord injury (SCI) and 22 were diagnosed with multiple sclerosis (MS). Among the SCI patients, 15 had cervical and 4 thoracic SCI, with 7 patients showing the American Spinal Injury Association impairment scale (AIS) A and 12 patients with AIS B-D. The dose was regulated by discussion among the patients and their physicians, usually 4-10 times annually, to reduce leg spasticity and also avoid leg/trunk weakness.

RESULTS

After 1 year patients on ITB needed a median dose of 168 mg/24 hr (range, 30-725 mg) for an optimal effect. After 7 to 10 years the dosage needed to reduce leg spasticity in the MS patients was significantly increased compared with the initial dose (mean 157%, n=22 and mean 194%, n=18). In contrast, the SCI patients needed only a modest increase (mean 113% and 121%). The difference between MS and SCI patients was significant (t-test p=0.006 and p=0.004).

CONCLUSION

The increased dosage in MS patients compared with patients diagnosed with SCI probably reflects the progressive disease course. The need for a large dosage increase in patients with SCI suggests possible pump failure, triggering factors for spasticity or progressive spinal disease.

Intrathecal Baclofen Therapy-Practical Approach: Clinical Benefits and Complication Management

Intrathecal baclofen is an expanding accepted treatment for children with cerebral palsy and other causes of spasticity and dystonia. The aims of this review are therefore to (1) delineate the clinical benefits of intrathecal baclofen therapy in pediatric spasticity and dystonia and (2) increase awareness of the potential complications and emergency management measures of intrathecal baclofen therapy. A current literature review demonstrates the benefits and complications of this minimally invasive device. Practical guides for recognizing acute conditions and management recommendations are included. Intrathecal baclofen is increasingly being used to help individuals attain realistic functional goals. Therefore, families and health care professionals should be aware of potential complications, symptoms, and emergency management.

Intrathecal baclofen trials: complications and positive yield in a pediatric cohort

OBJECT Intrathecal baclofen (ITB) is an effective management option for childhood hypertonia. Given the potential complications of implanted ITB pumps, trials of ITB are usually performed as part of the workup for ITB pumps. Two methods are used for ITB trials, lumbar puncture (LP) and catheter insertion into the intrathecal space. Little has been written to date on the number of positive trials and complications in trials. This study aimed to report the outcomes and complications in ITB trials for childhood hypertonia (dystonia, spastic, or mixed). METHODS A retrospective case notes review was conducted of all patients who underwent ITB trials at the Evelina London Children's Hospital between 2005 and 2012 (inclusive). Positive trials were defined as a reduction in Modified Ashworth Scale by a minimum of 1 point in at least 2 muscle groups and improvement reported by the caregivers in the areas of goals agreed upon between professionals and the families. RESULTS Our patient group comprised children with dystonia (n = 7), mixed spasticity/dystonia (n = 29), spasticity (n = 4), and pain (n = 1). A total of 47 trials were attempted in 41 children. Forty trials were successfully completed, with 39 being positive. Thirty-three were catheter trials, and 14 were LPs. The overall complication rate in the 47 attempted trials was 53%: 61% in catheter trials, and 36% in LP trials. This difference was not statistically significant. The most common complications were vomiting (n = 9) and CSF leak (n = 4). The most serious complication was meningitis (n = 1) in a catheter trial. No patients experienced a permanent injury. CONCLUSIONS There is a high risk of minor self-limiting complications with ITB trials, which needs to be factored into the decision process of progression to trials. The rate of positive trials in this study was 98%, of which 21% did not progress to pump implantation. While the authors would still advocate for ITB trials prior to ITB pump insertion to aid parental decision-making, this figure suggests that with good patient selection, ITB pumps could be placed without a preceding trial.

Chronic baclofen desensitizes GABA(B)-mediated G-protein activation and stimulates phosphorylation of kinases in mesocorticolimbic rat brain

The GABAB receptor is a therapeutic target for CNS and neuropathic disorders; however, few preclinical studies have explored effects of chronic stimulation. This study evaluated acute and chronic baclofen treatments on GABAB-activated G-proteins and signaling protein phosphorylation as indicators of GABAB signaling capacity. Brain sections from rats acutely administered baclofen (5 mg/kg, i.p.) showed no significant differences from controls in GABAB-stimulated GTPγS binding in any brain region, but displayed significantly greater phosphorylation/activation of focal adhesion kinase (pFAK(Tyr397)) in mesocorticolimbic regions (caudate putamen, cortex, hippocampus, thalamus) and elevated phosphorylated/activated glycogen synthase kinase 3-β (pGSK3β(Tyr216)) in the prefrontal cortex, cerebral cortex, caudate putamen, nucleus accumbens, thalamus, septum, and globus pallidus. In rats administered chronic baclofen (5 mg/kg, t.i.d. for five days), GABAB-stimulated GTPγS binding was significantly diminished in the prefrontal cortex, septum, amygdala, and parabrachial nucleus compared to controls. This effect was specific to GABAB receptors: there was no effect of chronic baclofen treatment on adenosine A1-stimulated GTPγS binding in any region. Chronically-treated rats also exhibited increases in pFAK(Tyr397) and pGSK3β(Tyr216) compared to controls, and displayed wide-spread elevations in phosphorylated dopamine- and cAMP-regulated phosphoprotein-32 (pDARPP-32(Thr34)) compared to acutely-treated or control rats. We postulate that those neuroadaptive effects of GABAB stimulation mediated by G-proteins and their sequelae correlate with tolerance to several of baclofen's effects, whereas sustained signaling via kinase cascades points to cross-talk between GABAB receptors and alternative mechanisms that are resistant to desensitization. Both desensitized and sustained signaling pathways should be considered in the development of pharmacotherapies targeting the GABA system.

Baclofen or nNOS inhibitor affect molecular and behavioral alterations evoked by traumatic spinal cord injury in rat spinal cord

BACKGROUND CONTEXT

The loss of descending control after spinal cord injury (SCI) and incessant stimulation of Ia monosynaptic pathway, carrying proprioceptive impulses from the muscles and tendons into the spinal cord, evoke exaggerated α-motoneuron activity leading to increased reflex response. Previous results from our laboratory have shown that Ia monosynaptic pathway is nitrergic.

PURPOSE

The aim of this study was to find out whether nitric oxide produced by neuronal nitric oxide synthase (nNOS) plays a role in setting the excitability of α-motoneurons after thoracic spinal cord transection.

STUDY DESIGN

We tested the hypothesis that the inhibition of nNOS in α-motoneurons after SCI could have a neuroprotective effect on reflex response.

METHODS

Rats underwent spinal cord transection at Th10 level followed by 7, 10, and 14 days of survival. The animals were treated with Baclofen (a gamma aminobutyric acid B receptor agonist, 3 μg/two times per day/intrathecally) applied for 3 days from the seventh day after transection; N-nitro-l-arginine (NNLA) (nNOS blocator) applied for the first 3 days after injury (20 mg/kg per day, intramuscularly); NNLA and Baclofen; or NNLA (60 mg/kg/day, single dose) applied on the 10th day after transection. We detected the changes in the level of nNOS protein, nNOS messenger RNA, and nNOS immunoreactivity. To investigate the reflex response to heat-induced stimulus, tail-flick test was monitored in treated animals up to 16 days after SCI.

RESULTS

Our data indicate that Baclofen therapy is more effective than the combined treatment with NNLA and Baclofen therapy. The single dose of NNLA (60 mg/kg) applied on the 10th day after SCI or Baclofen therapy reduced nNOS expression in α-motoneurons and suppressed symptoms of increased reflex activity.

CONCLUSIONS

The results clearly show that increased nNOS expression in α-motoneurons after SCI may be pharmacologically modifiable with Baclofen or bolus dose of nNOS blocker.

A nationwide register-based survey of baclofen toxicity

To study the use and misuse (poisonings) of baclofen in the time period of 2007-2012 and to evaluate the severity and clinical symptoms of poisonings including ingested baclofen. The National Patient Register (NPR) was searched for admissions due to baclofen poisonings from 2007 to 2012. The search was conducted with ICD-10 codes for poisoning, self-harm and suicide, and coupled with the baclofen ATC code. All enquiries about baclofen to the Danish Poison Information Centre (DPIC) in the same period were evaluated. Demographic and clinical data were extracted, and the poisonings were classified according to the Poison Severity Score. The number of baclofen poisonings did not increase from 2007 to 2012. Thirty-eight admissions with baclofen poisoning were registered at the NPR; however, only one-third of the reviewed DPIC cases were registered at the NPR with the correct coding. In the group of severely poisoned patients (PSS 3), three patients had only ingested baclofen (mean 2000 mg; SD 500 mg) and eight patients had ingested baclofen together with alcohol or psychotropic drugs (mean 900 mg; SD 641 mg). All patients presented with deep coma and respiratory depression. Additionally, seizures and cardiovascular events (mild hypo- or hypertension and bradycardia) occurred. There is a substantial degree of underreporting of baclofen poisonings in Denmark. Symptoms of baclofen poisoning progress very fast, and toxicity was observed even with doses as low as 150 mg. We therefore recommend that observation and treatment of these patients should be carried out in an intermediate- or intensive care unit. The most important treatment is the maintenance of a protected airway and respiration.

Patient experiences with intrathecal baclofen as a treatment for spasticity - a pilot study

PURPOSE

This study describes how patients experience intrathecal baclofen (ITB) treatment.

METHODS

Data were collected from interviews with 14 patients (19-76 years old) who were diagnosed with spinal cord injury (SCI), multiple sclerosis (MS), or cerebral palsy (CP). Data were analyzed using conventional content analysis.

RESULT

The analysis resulted in 16 subcategories arranged into five main categories: procedures before treatment, the effect of ITB on daily life and activities, continuous follow-up, expected and unexpected consequences of ITB, and overall level of satisfaction with ITB. Together these categories described the patients' experiences with ITB treatment. When the patients were asked whether they would undergo ITB again, they all stated that they would.

CONCLUSION

Patients stated that they were highly satisfied with the ITB treatment. However, the patients identified several areas that could be improved. Specifically, the patients wanted more information about the different steps in the treatment process and what to expect from ITB treatment.

Analysis of complications in 430 consecutive pediatric patients treated with intrathecal baclofen therapy: 14-year experience

OBJECT

This single-center study investigated adverse events that occurred in children and adolescent patients treated with intrathecal baclofen (ITB) therapy for spasticity and/or dystonia.

METHODS

In a 14-year period, 430 consecutive patients with a mean age of 13.3 ± 5.9 years received ITB over a mean follow-up period of 8.6 ± 3.8 years (range 12 months to 14 years). Eighty-nine percent of these patients had cerebral palsy. Major complications, defined as those that required a surgical intervention, were infections, CSF leaks, and device problems related to the catheter or pump. Assessing infections, the authors compared the 2 groups of patients implanted with an ITB system by either the subcutaneous or subfascial technique. The temporal distribution of events related to the catheter was also considered.

RESULTS

At least 1 complication was present in 25% of the patients: 9.3% experienced an infection, 4.9% a CSF leak, 15.1% a problem with the catheter, and 1% a problem related to the pump. Five percent of the assessed patients suffered more than 1 complication. The rate of infections was significantly lower (p < 0.001) in patients with the pump placed subfascially compared with those with the pump placed subcutaneously. A higher rate of infection was found after pump replacement compared with the first pump implantation (10.6% vs 6%, respectively). Catheter problems were the most common complication and occurred more frequently during the 1st year after the implant.

CONCLUSIONS

While ITB is an effective treatment to manage spasticity of different origins, adverse events may occur and need to be managed. The surgical procedure should be meticulous and different techniques may have a diverse impact on the infection rate, which is the most critical complication. Despite the adverse events that occurred in this study, the majority of patients were satisfied with the treatment received.

Occurrence of adverse events in long-term intrathecal baclofen infusion: a 1-year follow-up study of 158 adults

OBJECTIVE

To assess the frequency and types of adverse events (AEs) related to intrathecal baclofen (ITB) therapy in adults, and associated risk factors.

DESIGN

A prospective, observational cohort study of adults followed up from January 1 to December 31, 2010.

SETTING

A neurologic rehabilitation department in a university hospital.

PARTICIPANTS

All consecutive adult subjects (N=158) receiving ITB via a pump, either implanted or followed up during the study period.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

Frequency and type of AEs.

RESULTS

In 2010, 158 subjects were followed up for ITB therapy, of whom 128 were implanted before 2010 (nonsurgical subjects), and 30 underwent implantation in 2010 (surgical subjects). Of these 30 subjects, 20 were "newly implanted" and 10 were "replacements." The most frequent pathologic disorders were spinal cord injury (42%) and multiple sclerosis (28%). Twenty-eight subjects (18%) experienced a total of 38 AEs. The rate of AEs was .023 per month of ITB treatment. AEs were related to the surgical procedure in 53% of cases, to the device in 29% (predominantly catheter dysfunctions), and to adverse effects of baclofen in 18%. AEs related to the surgical incision (scar complications and collections) were more frequent in replacement than newly implanted subjects (P=.009). No significant association between occurrence of an AE and subject characteristics (age, gait capacity, spinal vs cerebral spasticity, duration of ITB therapy follow-up) was found. Nearly half of the AEs were serious, extending admission time by a mean of 16 days. No AE induced long-term morbidity or death.

CONCLUSIONS

The AE rate was relatively low in this cohort. This has to be balanced against the clinical, functional, and quality-of-life improvements, which are expected from ITB therapy.

Intrathecal baclofen in multiple sclerosis and spinal cord injury: complications and long-term dosage evolution

Objective:

To investigate the long-term dosage evolution and complication rate of intrathecal baclofen use in multiple sclerosis and spinal cord injury patients, based on a large population with a long follow-up.

Design:

Retrospective data analysis

Setting:

Academic hospital

Subjects:

Patients with multiple sclerosis ( n = 81) or spinal cord injury ( n = 49) having an intrathecal baclofen pump implanted at the University Hospitals Leuven between 1988 and 2009.

Intervention:

Medical records review of included patients in August 2010.

Main measures:

Complications linked to intrathecal baclofen therapy. Daily baclofen dosage after 3 and 6 months, and yearly thereafter. Data on dosage evolution were analysed using a mixed-effect linear model.

Results:

In 130 patients with a mean follow-up of 63 months, comprising 797 pump years, 104 complications were recorded. This corresponds to a complication rate of 0.011 per month, equally divided among both groups. Seventy-eight of these complications were catheter related. The mean dosage of baclofen stabilizes two years after implantation at 323 µg/day in the multiple sclerosis population. In spinal cord injury patients the daily dose only stabilizes after five years at a significantly higher dosage (504 µg/day). No significant increase in dosage is seen in the long term.

Conclusions:

In multiple sclerosis and spinal cord injury patients, intrathecal baclofen therapy has a complication rate of 1% per month. Complications are mainly due to catheter-related problems (74%). The intrathecal baclofen dosage stabilizes in the long term, indicating that long-term tolerance, defined as progressive diminution of the susceptibility to the effects of a drug, is not present.

Reduction of spinal sensory transmission by facilitation of 5-HT1B/D receptors in noninjured and spinal cord-injured humans

Activation of receptors by serotonin (5-HT1) and norepinephrine (α2) on primary afferent terminals and excitatory interneurons reduces transmission in spinal sensory pathways. Loss or reduction of descending sources of serotonin and norepinephrine after spinal cord injury (SCI) and the subsequent reduction of 5-HT1/α2 receptor activity contributes, in part, to the emergence of excessive motoneuron activation from sensory afferent pathways and the uncontrolled triggering of persistent inward currents that depolarize motoneurons during muscle spasms. We tested in a double-blind, placebo-controlled study whether facilitating 5-HT1B/D receptors with the agonist zolmitriptan reduces the sensory activation of motoneurons during an H-reflex in both noninjured control and spinal cord-injured participants. In both groups zolmitriptan, but not placebo, reduced the size of the maximum soleus H-reflex with a peak decrease to 59% (noninjured) and 62% (SCI) of predrug values. In SCI participants we also examined the effects of zolmitriptan on the cutaneomuscular reflex evoked in tibialis anterior from stimulation to the medial arch of the foot. Zolmitriptan, but not placebo, reduced the long-latency, polysynaptic component of the cutaneomuscular reflex (first 200 ms of reflex) by ∼50%. This ultimately reduced the triggering of the long-lasting component of the reflex (500 ms poststimulation to end of reflex) known to be mediated by persistent inward currents in the motoneuron. These results demonstrate that facilitation of 5-HT1B/D receptors reduces sensory transmission in both monosynaptic and polysynaptic reflex pathways to ultimately reduce long-lasting reflexes (spasms) after SCI.

Constitutively active 5-HT2/α1 receptors facilitate muscle spasms after human spinal cord injury

In animals, the recovery of motoneuron excitability in the months following a complete spinal cord injury is mediated, in part, by increases in constitutive serotonin (5-HT2) and norepinephrine (α1) receptor activity, which facilitates the reactivation of calcium-mediated persistent inward currents (CaPICs) without the ligands serotonin and norepinephrine below the injury. In this study we sought evidence for a similar role of constitutive monoamine receptor activity in the development of spasticity in human spinal cord injury. In chronically injured participants with partially preserved sensory and motor function, the serotonin reuptake inhibitor citalopram facilitated long-lasting reflex responses (spasms) previously shown to be mediated by CaPICs, suggesting that in incomplete spinal cord injury, functional descending sources of monoamines are present to activate monoamine receptors below the lesion. However, in participants with motor or motor/sensory complete injuries, the inverse agonist cyproheptadine, which blocks both ligand and constitutive 5-HT2/α1 receptor activity, decreased long-lasting reflexes, whereas the neutral antagonist chlorpromazine, which only blocks ligand activation of these receptors, had no effect. When tested in noninjured control participants having functional descending sources of monoamines, chlorpromazine was effective in reducing CaPIC-mediated motor unit activity. On the basis of these combined results, it appears that in severe spinal cord injury, facilitation of persistent inward currents and muscle spasms is mainly mediated by the activation of constitutive 5-HT2 and α1 receptor activity. Drugs that more selectively block these constitutively active monoamine receptors may provide better oral control of spasticity, especially in motor complete spinal cord injury where reducing motoneuron excitability is the primary goal.

[Pharmacological treatment of spasticity in multiple sclerosis]

The medicinal treatment of spasticity includes use of oral treatments (baclofène and tizanidine), botulinum toxin, intrathecal baclofène and local application of alcohol or phenol. However, spasticity may not be uncomfortable and may even be useful. Therefore, all spastic diseases do not systematically require treatment. First-line treatments (oral treatments and botulinum toxin) can be considered depending on the local or diffuse nature of the spasticity and depending on the etiology.

Combinational spinal GAD65 gene delivery and systemic GABA-mimetic treatment for modulation of spasticity

Background

Loss of GABA-mediated pre-synaptic inhibition after spinal injury plays a key role in the progressive increase in spinal reflexes and the appearance of spasticity. Clinical studies show that the use of baclofen (GABA_B receptor agonist), while effective in modulating spasticity is associated with major side effects such as general sedation and progressive tolerance development. The goal of the present study was to assess if a combined therapy composed of spinal segment-specific upregulation of GAD65 (glutamate decarboxylase) gene once combined with systemic treatment with tiagabine (GABA uptake inhibitor) will lead to an antispasticity effect and whether such an effect will only be present in GAD65 gene over-expressing spinal segments.

Methods/Principal Findings

Adult Sprague-Dawley (SD) rats were exposed to transient spinal ischemia (10 min) to induce muscle spasticity. Animals then received lumbar injection of HIV1-CMV-GAD65 lentivirus (LVs) targeting ventral α-motoneuronal pools. At 2–3 weeks after lentivirus delivery animals were treated systemically with tiagabine (4, 10, 20 or 40 mg/kg or vehicle) and the degree of spasticity response measured. In a separate experiment the expression of GAD65 gene after spinal parenchymal delivery of GAD65-lentivirus in naive minipigs was studied. Spastic SD rats receiving spinal injections of the GAD65 gene and treated with systemic tiagabine showed potent and tiagabine-dose-dependent alleviation of spasticity. Neither treatment alone (i.e., GAD65-LVs injection only or tiagabine treatment only) had any significant antispasticity effect nor had any detectable side effect. Measured antispasticity effect correlated with increase in spinal parenchymal GABA synthesis and was restricted to spinal segments overexpressing GAD65 gene.

Conclusions/Significance

These data show that treatment with orally bioavailable GABA-mimetic drugs if combined with spinal-segment-specific GAD65 gene overexpression can represent a novel and highly effective anti-spasticity treatment which is associated with minimal side effects and is restricted to GAD65-gene over-expressing spinal segments.

Subchronic administration and combination metabotropic glutamate and GABAB receptor drug therapy in fragile X syndrome

The most common cause of inherited mental retardation, fragile X syndrome, results from a triplet repeat expansion in the FMR1 gene and loss of the mRNA binding protein, fragile X mental retardation protein (FMRP). In the absence of FMRP, signaling through group I metabotropic glutamate receptors (mGluRs) is enhanced. We previously proposed a mechanism whereby the audiogenic seizures exhibited by FMR1 null mice result from an imbalance in excitatory mGluR and inhibitory GABA(B) receptor (GABA(B)R) signaling (Mol Pharmacol 76:18-24, 2009). Here, we tested the mGluR5-positive allosteric modulator 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB), the mGluR5 inverse agonist 2-methyl-6-(phenylethynyl)pyridine (MPEP), and GABA(B) receptor agonists, alone and in combination on receptor protein expression and audiogenic seizures in FMR1 mice. Single doses of MPEP (30 mg/kg), the GABA(B)R orthosteric agonist R-baclofen (1 mg/kg), or the GABA(B)R-positive allosteric modulator N,N'-dicyclopentyl-2-(methylthio)-5-nitro-4,6-pyrimidine diamine (GS-39783) (30 mg/kg), reduced the incidence of seizures. However, when administered subchronically (daily injections for 6 days), MPEP retained its anticonvulsant activity, whereas R-baclofen and GS-39783 did not. When administered at lower doses that had no effect when given alone, a single injection of MPEP plus R-baclofen also reduced seizures, but the effect was lost after subchronic administration. We were surprised to find that subchronic treatment with R-baclofen also induced tolerance to a single high dose of MPEP. These data demonstrate that tolerance develops rapidly to the antiseizure properties of R-baclofen alone and R-baclofen coadministered with MPEP, but not with MPEP alone. Our findings suggest that cross-talk between the G-protein signaling pathways of these receptors affects drug efficacy after repeated treatment.

Suppression of stretch reflex activity after spinal or systemic treatment with AMPA receptor antagonist NGX424 in rats with developed baclofen tolerance

BACKGROUND AND PURPOSE

Baclofen (a GABA(B) receptor agonist) is the most commonly used anti-spasticity agent in clinical practice. While effective when administered spinally or systemically, the development of progressive tolerance represents a serious limitation for its long-term use. The goal of the present study was to characterize the treatment potency after intrathecal or systemic treatment with the selective AMPA receptor antagonist NGX424 on stretch reflex activity (SRA) and background muscle activity (BMA) in rats with developed baclofen tolerance.

EXPERIMENTAL APPROACH

Animals were exposed to 10 min of spinal ischaemia to induce an increase in BMA and SRA. Selected animals were implanted with an intrathecal PE-5 catheter and infused intrathecally with baclofen (1 µg·h⁻¹ ) for 14 days. Before and after baclofen infusion, changes in BMA and SRA were measured at 2 day intervals. After development of baclofen tolerance, the animals were injected intrathecally (1 µg) or subcutaneously (3, 6 or 12 mg·kg⁻¹) with NGX424, and changes in BMA and SRA were measured.

KEY RESULTS

Intrathecal or systemic delivery of NGX424 significantly suppressed the BMA and SRA in baclofen-tolerant animals. This effect was dose dependent. The magnitude of BMA and SRA suppression seen after 1 µg (intrathecal) or 12 mg·kg ⁻¹ (s.c.) of NGX424 injection was similar to that seen during the first 5 days of baclofen infusion. CONCLUSIONS AND IMPLICATIONS These data demonstrate that the use of NGX424 can represent an effective therapy to modulate chronic spasticity in patients who are refractory or tolerant to baclofen treatment.

Review: Procedure- and Device-Related Complications of Intrathecal Baclofen Administration for Management of Adult Muscle Hypertonia: A Review

Background. Intrathecal baclofen (ITB) effectively reduces muscle hypertonia; however, associated complications influence its utility and acceptance. Objective. To systematically review the literature on procedure- and device-related complications associated with ITB infusion therapy for adult muscle hypertonia of spinal or cerebral origin. Methods. The authors searched the PubMed database for full-length articles published in English that reported ITB-associated complications in adults. Of 147 articles retrieved, 32 full-length manuscripts and 10 case reports were reviewed in detail. Results. Overall, 558 complications were reported after 1362 pump implants (0.41 per implant). Methods for characterizing complications varied greatly between studies, as did complication rates, ranging from 0 to 2.24 per implant. Of the 558 complications, 148 (27%) were related to surgical procedures, 39 (7%) to pump problems, and 369 (66%) to catheter malfunctions. The overall complication rate was higher for studies that followed patients for more than 18 months on average (mean 0.56/implant) versus studies with shorter follow-up (0.23/implant, P < .05). Although correlation between the number of implants and the number of complications was significant ( r = .58), the goodness of linear fit was poor because of clusters with varied complication rates. Conclusions. Catheter problems are relatively common and more frequent than pump or surgical procedure complications after ITB pump implantation. Higher complication rates should be expected in centers that follow patients for a longer period of time. Standardized data collection and complication-reporting procedures along with appropriate training should be implemented in centers offering ITB treatment for management of muscle hypertonia.

Intrathecal baclofen for spasticity management: a comparative analysis of spasticity of spinal vs cortical origin

BACKGROUND/OBJECTIVE

To examine the differences in intrathecal baclofen management of individuals with spasticity of cortical vs spinal etiologies.

DESIGN

Retrospective chart review of 57 individuals with the diagnoses of severe cortical and spinal spasticity requiring an intrathecal baclofen pump.

METHODS

Parameters evaluated included daily dosage of medication required, flex vs simple continuous delivery modes, dosing changes, need for other local spasticity treatment, and catheter complications.

RESULTS

There were no statistically significant differences between individuals with cortical spasticity and spinal spasticity when comparing daily dosage, number of contacts, and mode of delivery. At 6 months, there was a statistically significant difference in dosing between individuals with multiple sclerosis and those without. Within groups, there was a significant difference in average daily dosing over 3 years. A significant difference was found comparing the use of botulinum toxin type A for upper extremity spasticity within the cortical group. Nine individuals had catheter complications.

CONCLUSIONS

Cortical and spinal spasticity appear to parallel each other with no significant differences in daily dosing, dosing changes, and mode of delivery of intrathecal baclofen. This did not hold true at all time points for the multiple sclerosis subgroup. The significant difference noted within groups for daily dosing over the first 3 years challenges the notion of stable dosing over time. Focal injections of Botox/phenol in the upper extremities are an important adjunct therapy for patients with cortical spasticity, even after the placement of an intrathecal baclofen pump. Our complication rate was slightly lower than that reported in the literature.

Motor neuron inhibition-based gene therapy for spasticity

Spasticity is a condition resulting from excess motor neuron excitation, leading to involuntary muscle contraction in response to increased velocity of movement, for which there is currently no cure. Existing symptomatic therapies face a variety of limitations. The extent of relief that can be delivered by ablative techniques such as rhizotomy is limited by the potential for sensory denervation. Pharmacological approaches, including intrathecal baclofen, can be undermined by tolerance. One potential new approach to the treatment of spasticity is the control of neuromuscular overactivity through the delivery of genes capable of inducing synaptic inhibition. A variety of experiments in cell culture and animal models have demonstrated the ability of neural gene transfer to inhibit neuronal activity and suppress transmission. Similarly, enthusiasm for the application of gene therapy to neurodegenerative diseases of motor neurons has led to the development of a variety of strategies for motor neuron gene delivery. In this review, we discuss the limitations of existing spasticity therapies, the feasibility of motor neuron inhibition as a gene-based treatment for spasticity, potential inhibitory transgene candidates, strategies for control of transgene expression, and applicable motor neuron gene targeting strategies. Finally, we discuss future directions and the potential for gene-based motor neuron inhibition in therapeutic clinical trials to serve as an effective treatment modality for spasticity, either in conjunction with or as a replacement for presently available therapies.

Consensus panel guidelines for the use of intrathecal baclofen therapy in poststroke spastic hypertonia

Intrathecal baclofen (ITB) therapy has been increasingly employed for the management of poststroke spastic hypertonia, a complication that can lead to deformity, discomfort, and exacerbation of motor impairments. Because its use in stroke is not as established as other indications, ITB therapy has not been subjected to rigorous investigation. There is limited evidence to guide clinicians regarding application of this therapy in this patient population. This article aims to review the available scientific literature and the opinion of several experts on the topic. It will also describe the recommendations of these experts with regard to addressing common clinical situations that may influence treatment decisions in the stroke population.

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.

Development of baclofen tolerance in a rat model of chronic spasticity and rigidity

Systemic or spinal treatment with baclofen has been associated with the development of tolerance in patients with chronic spasticity. In the present study, we used a rat model of spinal ischemia-induced spasticity to characterize the development of baclofen tolerance after chronic intrathecal (i.t.) baclofen infusion. Following the induction of spinal ischemia and the development of behavioral spasticity, animals were implanted with i.t. catheters connected to osmotic pumps to continuously infuse baclofen (1.0 microg/0.5 microl/h). Hindleg peripheral muscle resistance (PMR) was measured periodically after initiation of chronic infusion and after bolus i.t. baclofen injection (1.0 microg). Peripheral muscle resistance was significantly decreased at the onset of baclofen infusion, however, after 5-7 days of infusion a progressive return of spasticity was noted, where baseline PMR values returned to preinfusion levels. At the same time, the efficacy of bolus i.t. baclofen treatment also decreased, where after 5 days of baclofen infusion 1.0 microg (i.t.) baclofen only reduced PMR by 10% (compared to 40-50% preinfusion). Baclofen efficacy progressively returned once continuous infusion was stopped. These data demonstrate that transient spinal ischemia leads to the development of spasticity which is sensitive to spinal baclofen. Chronic i.t. infusion leads to a progressive development of tolerance. This model offers potential to study tolerance mechanisms after spinal injury, and aid in drug discovery for use in baclofen-tolerant patients.

An Unusual Cause of Overdose after Baclofen Pump Implantation: Case Report

OBJECTIVE AND IMPORTANCE:

Intrathecal baclofen delivery for the treatment of spasticity has been used for almost 20 years with a great deal of success. A wide variety of complications and pitfalls have been described. This report details a novel complication involving inadvertent and initially unrecognized canalization of the subdural space with the spinal catheter, which ultimately resulted in an overdose.

CLINICAL PRESENTATION:

An intrathecal pump system was implanted in a 15-year-old girl with spasticity. This initially resulted in a lack of therapeutic effect. The diagnostic workup ultimately led to contrast administration through the pump system, which precipitated a baclofen overdose when sequestered medication in the subdural compartment was released into the intrathecal space.

INTERVENTION:

The spinal catheter was subsequently revised, and the patient made a full recovery.

CONCLUSION:

The possibility of a subdural catheter should be included in the differential diagnosis in patients who experience a lack of drug effect after pump implantation, despite increases in dosage. Close monitoring is required because of the risk of spontaneous or induced overdose, which may occur when a communication develops between the subdural and intrathecal compartments.

COMPLETE AND PROLONGED SUPPRESSION OF SYMPTOMS AND CONSEQUENCES OF ALCOHOL-DEPENDENCE USING HIGH-DOSE BACLOFEN: A SELF-CASE REPORT OF A PHYSICIAN

AIMS

To test whether the dose-dependent motivation-suppressing effect of baclofen in animals could be transposed to humans, and suppress craving and sustain abstinence.

METHODS

Neurologists safely use up to 300 mg/day (10 times the dosage currently used for alcohol dependence) of high-dose oral baclofen, to control spasticity, in order to avoid invasive therapy. I am a physician with alcohol dependence and comorbid anxiety. I self-prescribed high-dose baclofen, starting at 30 mg/day, with 20 mg increments every third day and an (optional) additional 20-40 mg/day for cravings.

RESULTS

Cravings became easier to combat. After reaching the craving-suppression dose of 270 mg/day (3.6 mg/kg) after 5 weeks, I became and have remained free of alcohol dependence symptoms effortlessly for the ninth consecutive month. Anxiety is well controlled. Somnolence disappeared with a dosage reduction to 120 mg/day, now used for the eighth consecutive month.

CONCLUSIONS

High-dose baclofen induced complete and prolonged suppression of symptoms and consequences of alcohol dependence, and relieved anxiety. This model, integrating cure and well-being, should be tested in randomized trials, under medical surveillance. It offers a new concept: medication-induced, dose-dependent, complete and prolonged suppression of substance-dependence symptoms with alleviation of comorbid anxiety.

A benefit-risk assessment of baclofen in severe spinal spasticity

Baclofen is used for treatment of the spasticity of spinal origin that is a common sequela of spinal cord injury and multiple sclerosis; spasticity occurs in about 50% of patients affected by these disorders. In open-label studies of oral baclofen, the drug improved spasticity in 70-87% of patients; additionally, improvement in spasms was reported in 75-96% of patients. In double-blind, crossover, placebo-controlled trials, baclofen was reported to be effective, producing statistically significant improvements in spasticity. Tizanidine is the antispasticity drug that has been most widely compared with oral baclofen; studies have generally found the two drugs to have equivalent efficacy. However, tizanidine has better tolerability, in particular weakness was reported to be occur less frequently with tizanidine than with baclofen. The main adverse effects of oral baclofen include: sedation or somnolence, excessive weakness, vertigo and psychological disturbances. The incidence of adverse effects is reported to range from 10% to 75%. The majority of adverse effects are not severe; most are dose related, transient and/or reversible. The main risks of oral baclofen administration are related to withdrawal: seizures, psychic symptoms and hyperthermia can occur. These symptoms improve after the reintroduction of baclofen, usually without sequelae. When not related to withdrawal; these symptoms mainly present in patients with brain damage and in the elderly. The limited data on baclofen toxicity in patients with renal disease suggest that administration of the drug in these persons may carry an unnecessarily high risk. Intrathecal baclofen is indicated for use in patients with spasticity of spinal origin unresponsive to treatment with maximum doses of oral baclofen, tizanidine and/or dantrolene. The benefits of continuous intrathecal baclofen infusion have been demonstrated: >80% and >65% of patients have improvement in tone and spasms, respectively. The main risks of intrathecal baclofen infusion are symptoms related to overdose or withdrawal; the latter is more important because of the associated severe effects on clinical status and the possibility of death, but it is responsive to rapid treatment. Overdose primarily arises from drug test doses or human error during refill and programming of the pump, and withdrawal most commonly occurs as a result of a problem with the delivery system. Since the adverse consequences do not exceed the benefits of oral and intrathecal baclofen for patients with spinal spasticity, the benefit/risk assessment is favourable.

Implantable Baclofen Pump as an Adjuvant in Treatment of Pressure Sores

Currently, the success of ulcer treatment is limited by the high recurrence and complication rates. Spasticity is an important contributing factor to ulcer recurrence, and intrathecal baclofen is an effective method to reduce spasticity. Spasticity creates friction, shear, and mobility impairment resulting in wound dehiscence, flap loss, infection, and hematoma. Spasticity can be managed pharmacologically and surgically; baclofen is the drug of choice. Baclofen inhibits spasticity by blocking excitatory neurotransmitters in the spinal dorsal horn. Intrathecal baclofen maximizes the dose delivered to spinal receptors and minimizes the side effects associated with oral baclofen. Case reports of intrathecal baclofen used in patients with pressure sores demonstrate the use of intrathecal baclofen to improve reconstructive outcomes in spastic patients.

Bladder stones - red herring for resurgence of spasticity in a spinal cord injury patient with implantation of Medtronic Synchromed pump for intrathecal delivery of baclofen - a case report

BACKGROUND

Increased spasms in spinal cord injury (SCI) patients, whose spasticity was previously well controlled with intrathecal baclofen therapy, are due to (in order of frequency) drug tolerance, increased stimulus, low reservoir volume, catheter malfunction, disease progression, human error, and pump mechanical failure. We present a SCI patient, in whom bladder calculi acted as red herring for increased spasticity whereas the real cause was spontaneous extrusion of catheter from intrathecal space.

CASE PRESENTATION

A 44-year-old male sustained a fracture of C5/6 and incomplete tetraplegia at C-8 level. Medtronic Synchromed pump for intrathecal baclofen therapy was implanted 13 months later to control severe spasticity. The tip of catheter was placed at T-10 level. The initial dose of baclofen was 300 micrograms/day of baclofen, administered by a simple continuous infusion. During a nine-month period, he required increasing doses of baclofen (875 micrograms/day) to control spasticity. X-ray of abdomen showed multiple radio opaque shadows in the region of urinary bladder. No malfunction of the pump was detected. Therefore, increased spasticity was attributed to bladder stones. Electrohydraulic lithotripsy of bladder stones was carried out successfully. Even after removal of bladder stones, this patient required further increases in the dose of intrathecal baclofen (950, 1050, 1200 and then 1300 micrograms/day). Careful evaluation of pump-catheter system revealed that the catheter had extruded spontaneously and was lying in the paraspinal space at L-4, where the catheter had been anchored before it entered the subarachnoid space. A new catheter was passed into the subarachnoid space and the tip of catheter was located at T-8 level. The dose of intrathecal baclofen was decreased to 300 micrograms/day.

CONCLUSION

Vesical calculi acted as red herring for resurgence of spasticity. The real cause for increased spasms was spontaneous extrusion of whole length of catheter from subarachnoid space. Repeated bending forwards and straightening of torso for pressure relief and during transfers from wheel chair probably contributed to spontaneous extrusion of catheter from spinal canal in this patient.

GABA(B) receptor activation desensitizes postsynaptic GABA(B) and A(1) adenosine responses in rat hippocampal neurones

Whole-cell recordings of EPSCs and G-protein-activated inwardly rectifying (GIRK) currents were made from cultured hippocampal neurones to determine the effect of long-term agonist treatment on the presynaptic and postsynaptic responses mediated by GABA(B) receptors (GABA(B)Rs). GABA(B)R-mediated presynaptic inhibition was unaffected by agonist (baclofen) treatment for up to 48 h, and was desensitized by about one-half after 96 h. In contrast, GABA(B)R-mediated GIRK currents were desensitized by a similar amount after only 2 h of agonist treatment. In addition, presynaptic inhibition mediated by A(1) adenosine receptors (A(1)Rs) was unaffected by prolonged GABA(B)R activation, whereas A(1)R-mediated GIRK currents were desensitized. Desensitization of postsynaptic GABA(B)R and A(1)R responses was blocked by the GABA(B)R antagonist (1-(S)-3,4-dichlorophenylethyl)amino-2-(S) hydroxypropyl-p-benzyl-phosphonic acid (CGP 55845A), but not by the A(1)R antagonist cyclopentyldipropylxanthine (DPCPX). GIRK current amplitude could be partially restored after baclofen treatment by either coapplication of baclofen and adenosine, or intracellular infusion of the non-hydrolysable GTP analog 5'-guanylylimidodiphosphate (Gpp(NH)p). Short-term (4-24 h) baclofen treatment also significantly desensitized the inhibition of postsynaptic voltage-gated calcium channels by activation of GABA(B)Rs or A(1)Rs. These results show that responses mediated by GABA(B)Rs and A(1)Rs desensitize differently in presynaptic and postsynaptic compartments, and demonstrate the heterologous desensitization of postsynaptic A1R responses.