Intrathecal baclofen: does tolerance occur?

Intrathecal morphine therapy in the management of status dystonicus in neurodegeneration brain iron accumulation type 1

Neurodegeneration with brain iron accumulation type 1 (NBIA-1) is a rare disorder characterized by progressive extrapyramidal dysfunction and dementia. NBIA-1 encompasses typical iron brain accumulation, mostly in the globus pallidus with secondary dementia, spasticity, rigidity, dystonia, and choreoathetosis. Treatment remains mostly symptomatic and is challenging. We present the case of a 14-year-old boy diagnosed with NBIA-1, presenting intractable progressive generalized dystonia leading to unresponsive status dystonicus (SD). The patient received a SynchroMed II (model 8637) programmable system pump (Medtronic®, Inc.) implant with an Ascenda intrathecal catheter for intrathecal morphine therapy (IMT). The initial dose of morphine was 1.0 mg/day. Overall, we observed no complications with IMT treatment and important improvement of the patient's motor function with stabilization of his incapacitating dystonia and his quality of life. On the Global Dystonia Severity Rating Scale, he presented 52% improvement, 30% improvement on the Unified Dystonia Rating Scale, and 38% improvement on the Fahn-Marsden Rating Scale after 10 months, when the dose was 1.7 mg/day. IMT should be considered as a potential palliative treatment in the management of intractable dystonia and SD secondary to NBIA-1.

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.

Major surgical procedures in children with cerebral palsy

There are 3 surgical procedures that patients with cerebral palsy (CP) undergo that may be considered major procedures: femoral osteotomies combined with pelvic osteotomies, spine fusion, and intrathecal baclofen pump implant for the treatment of spasticity. Many complications are known to occur at a higher rate in this population, and some may be avoided with prior awareness of the preoperative pathophysiology of the patient with CP.

Examining the effectiveness of intrathecal baclofen on spasticity in individuals with chronic spinal cord injury: a systematic review

OBJECTIVE

To review the available evidence on the effectiveness of intrathecal baclofen in the treatment of spasticity in individuals with spinal cord injuries (SCIs) at least 6 months post-injury or diagnosis.

DATA SOURCES

A literature search of multiple databases (Pub Med, CINAHL, EMBASE) was conducted to identify articles published in the English language.

STUDY SELECTION

Studies were included for review if: (1) more than 50% of the sample size had suffered a traumatic or non-traumatic SCI; (2) there were more than three subjects; (3) subjects received continuous intrathecal baclofen via an implantable pump aimed at improving spasticity; and (4) all subjects were ≥6 months post-SCI, at the time of the intervention.

DATA EXTRACTION

Data extracted from the studies included patient and treatment characteristics, study design, method of assessment, and outcomes of the intervention.

DATA SYNTHESIS

Methodological quality was assessed using the PEDro for randomized-controlled trials (RCTs) and the Downs and Black (D&B) tool for non-RCTs. A level of evidence was assigned to each intervention using a modified Sackett scale.

CONCLUSION

The literature search resulted in 677 articles. No RCTs and eight non-RCTs (D&B scores 13-24) met criteria for inclusion, providing a pooled sample size of 162 individuals. There was substantial level 4 evidence that intrathecal baclofen is effective in reducing spasticity. Mean Ashworth scores reduced from 3.1-4.5 at baseline to 1.0-2.0 (P < 0.005) at follow-up (range 2-41 months). Average dosing increased from 57-187 µg/day at baseline to 218.7-535.9 µg/day at follow-up. Several complications from the use of intrathecal baclofen or pump and catheter malfunction were reported.

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.

Differential development of tolerance to the functional and behavioral effects of repeated baclofen treatment in rats

Baclofen, a gamma-aminobutyric acid (GABA)B receptor agonist, has been used clinically to treat muscle spasticity, rigidity and pain. More recently, interest in the use of baclofen as an addiction medicine has grown, with promising preclinical cocaine and amphetamine data and demonstrated clinical benefit from alcohol and nicotine studies. Few preclinical investigations, however, have utilized chronic dosing of baclofen, which is important given that tolerance can occur to many of its effects. Thus the question of whether chronic treatment of baclofen maintains the efficacy of acute doses is imperative. The neural substrates that underlie the effects of baclofen, particularly those after chronic treatment, are also not known. In the present study, therefore, rats were treated with either a) vehicle, b) acute baclofen (5 mg/kg) or c) chronic baclofen (5 mg/kg, t.i.d. for 5 days). The effects of acute and chronic baclofen administration, compared to vehicle, were assessed using locomotor activity and changes in brain glucose metabolism (a measure of functional brain activity). Acute baclofen significantly reduced locomotor activity (horizontal and total distance traveled), while chronic baclofen failed to affect locomotor activity. Acute baclofen resulted in significantly lower rates of local cerebral glucose utilization throughout many areas of the brain, including the prefrontal cortex, caudate putamen, septum and hippocampus. The majority of these functional effects, with the exception of the caudate putamen and septum, were absent in animals chronically treated with baclofen. Despite the tolerance to the locomotor and functional effects of baclofen following repeated treatment, these persistent effects on functional activity in the caudate putamen and septum may provide insights into the way in which baclofen alters the reinforcing effects of abused substances such as cocaine, alcohol, and methamphetamine both in humans and animal models.

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.

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.

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.

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.

Managing severe lower limb spasticity in multiple sclerosis: does intrathecal phenol have a role?

OBJECTIVE

Established treatment options for managing severe lower limb spasticity and associated pain are of limited value in people with advanced multiple sclerosis (MS). This has resulted in a resurgence of the use of lumbar intrathecal phenol injection (IP). The aim of this study was to investigate the authors' experience with IP.

METHODS

This observational study collected cross sectional data from patients with progressive MS who received IP for severe lower limb spasticity. Data from 25 patients were collected prospectively before and after treatment. In 15 cases the data related to the first treatment and in 10 to serial injections. Outcome measures collected included the Ashworth scale, a spasm frequency scale, a pain rating score, and the percentage achievement of practical goals.

RESULTS

After injection, all patients demonstrated reduced lower limb tone bilaterally. After the initial injection there was significant improvement on the targeted as compared with the non-targeted side (Wilcoxon rank p=0.003), while no difference in the degree of improvement between the targeted and non-targeted side was seen after serial injections (Wilcoxon rank p=0.731). Twenty four patients were easier to position and 21 had a reduction in their spasm frequency and intensity. Eleven patients with pain reported benefit. Carers found washing and dressing easier in 16 patients and improved safety when using the hoist in 10. Six patients had recurrence of skin breakdown and five patients reported transient adverse changes in their bowel function.

CONCLUSIONS

IP can reduce lower limb tone bilaterally after both initial and serial injections. This is most noticeable on the targeted side after initial injection. IP can reduce spasms and pain, leading to improvements in care and overall comfort. IP is an effective treatment option in the management of severe spasticity. Documented selection criteria are essential.

Intrathecal baclofen therapy in children with cerebral palsy: efficacy and complications

OBJECTIVES

To describe the efficacy of intrathecal baclofen (ITB) therapy in the management of spasticity in young children with cerebral palsy (CP) and to identify risk factors for complications.

DESIGN

Consecutive case series of 25 implanted ITB delivery systems during a 48-month period.

SETTING

Pediatric specialty hospital and outpatient department.

PARTICIPANTS

Twenty-three children (age range, 4.5-17.4y) with CP (spastic diplegia in 22%; spastic quadriplegia in 61%; mixed-type diplegia in 4%; mixed-type quadriplegia in 13%).

INTERVENTION

Intrathecal baclofen therapy in children with cerebral palsy.

MAIN OUTCOME MEASURES

Ashworth Scale scores before treatment and at 6 and 12 months after ITB therapy; frequency and nature of complications; and relation between patient characteristics and outcomes.

RESULTS

Average Ashworth scores +/- standard deviation decreased from 3.26+/-.73 to 2.34+/-.83 (P<or=.01) in the lower extremities and from 2.69+/-.79 to 2.00+/-.55 (P<or=.05) in the upper extremities 6 months after ITB therapy and remained comparably decreased at 12 months. Explantation was required in 44% (11/25), with wound complications as the leading cause in 73% (8/11). Complications were associated with the diagnosis of mixed-type CP, as compared with pure spastic types (P<or=.01). Trends suggest that children of smaller size and younger age, as well as those with gastrostomy tubes and nonambulatory status, were more likely to encounter complications necessitating explantation.

CONCLUSION

ITB therapy effectively reduced spasticity in children with CP. However, complications necessitating explantation can occur. Further research is needed to identify criteria describing the ideal pediatric candidate for ITB.

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

In a retrospective study, changes in baclofen dose and complication frequency were recorded in 79 patients with intrathecal baclofen administration and the effect on nightly muscle spasms was measured over a mean observation period of 34 months, during which time an increase in the daily dose of baclofen during the first 1--1-1/2 years is notified. On subsequent pump fillings the daily dose of baclofen remained stable in the group of non-multiple sclerosis patients. In contrast, the group of multiple sclerosis patients showed a steady increase in their daily dose of baclofen. We found a frequency of complications of 0.014 monthly often due to catheter problems. There was a significant decrease in numbers of nightly muscle spasms in an 8 h recording period from 77+/-20 preoperatively and 9+/-3 (P=0.02) 3 months after surgery. The steady increase in the daily dose of baclofen in order to obtain adequate reduction in spasticity and nightly muscle spasms in the first 1--1-1/2 years cannot fully be explained by caution and difficulties in achieving the correct dose, but also indicates that tolerance to baclofen occurs. Complications are often due to infection or catheter problems.

Effects of repeated administration of baclofen on transient lower esophageal sphincter relaxation in the dog

The metabotropic gamma-aminobutyric acid (GABA) receptor (GABA(B) receptor) agonist baclofen inhibits transient lower esophageal sphincter relaxation in dogs, ferrets, and humans. Since transient lower esophageal sphincter relaxations are the major cause of gastroesophageal reflux, GABA(B) receptor agonists may have a therapeutic value in the treatment of gastroesophageal reflux disease. However, repeated stimulation of the GABA(B) receptor may induce receptor desensitization which, depending on the magnitude, would limit the therapeutic effect. The aim of the present study was to follow the effects of baclofen on transient lower esophageal sphincter relaxation in the dog after repeated administration. The effect of 7 micromol/kg baclofen b.i.d. (given intragastrically) on transient lower esophageal sphincter relaxation and related parameters was determined in four dogs. Transient lower esophageal sphincter relaxations stimulated by infusion of liquid nutrient and insufflation of air were quantified after placebo and then after the 1st, 13th, and 27th dose. Baclofen reduced the number of transient lower esophageal sphincter relaxations without affecting their duration, and the latency to the first transient lower esophageal sphincter relaxation was prolonged. Basal sphincter pressure was unaffected by baclofen, and the number of reflux episodes and esophageal acid exposure decreased. There was a statistically insignificant numerical decrease (approximately 30%) in the effect of baclofen on transient lower esophageal sphincter relaxation after the seventh dose but this was not further accentuated after the 27th dose. The effect on latency was also reduced with repeated dosing, but again, the effects after the 1st, 13th, and 27th doses were not statistically significant. The attenuation of acid exposure and reflux episodes was unaltered after repeated dosing. Three of the dogs greatly reduced their food intake within the first 2-3 days but this side effect was resolved subsequently. It is concluded that repeated dosing of baclofen leads to mild tolerance development in terms of the effects on transient lower esophageal sphincter relaxation, but that the tolerance is much less pronounced than that previously reported in other animal models.

Symptoms of recurrent intrathecal baclofen withdrawal resulting from drug delivery failure: a case report

A 24-yr-old, completely (T8) paraplegic male patient presenting with severe spasticity had a drug administration device implanted in April 1991 for continuous intrathecal administration of baclofen. After a period of remarkable improvement in both the spasticity level and his quality of life, the patient experienced several short-lasting episodes of increased spasticity, with severe spasms. Among the possible causes of these deleterious episodes were microcrystalluria, obstipation, a decubitus ulcer, a foreign body in the buttocks, drug tolerance to baclofen, electromagnetic interference, and erroneous filling and programing of the pump. The catheter was the most common source of intrathecal baclofen withdrawal symptoms and had to be changed four times in 5 yr. Intrathecal baclofen administered through an implantable drug administration device is a highly effective but complex and expensive procedure that requires careful patient selection and close monitoring by highly qualified and well-trained health professional. Withdrawal symptoms may be related to noncompliance on the part of the patient, erroneous filling or programing of the pump, depletion of the battery, random component failure, concomitant illness, drug tolerance, or advancement of the disease itself. When failure of the device is suspected, substitution with oral baclofen is recommended until a full work-up is performed to determine the defect.

Long-term continuously infused intrathecal baclofen for spastic-dystonic hypertonia in traumatic brain injury: 1-year experience

OBJECTIVE

To determine if the long-term use of continuously infused intrathecal baclofen (ITB) over a 1-year period will control spastic-dystonic hypertonia in patients with traumatic brain injury (TBI).

SETTING

Tertiary care outpatient and inpatient rehabilitation center directly attached to a university hospital.

SUBJECTS

Persons with TBI and intractable spasticity and dystonia for more than 6 months' duration recruited in a consecutive manner.

DESIGN

TBI patients were admitted to the study after screening via a bolus injection of either intrathecal normal saline or 50 microg of baclofen. Data for Ashworth rigidity scores, spasm scores, and deep tendon reflex scores were collected for both the upper extremities (UE) and lower extremities (LE). Patients whose LE Ashworth scores decreased an average of 2 points were then offered implantation of a computer-controlled pump for continuous ITB. Changes over time were assessed statistically via Friedman's analysis for ordinal data and ANOVA for linear data. Differences between set points in time were also assessed via Wilcoxon signed rank.

DATA SET

Seventeen patients (average age 29+/-11 yrs) with spasticity and/or dystonia treated over 1 year via a computer-controllable intrathecal delivery system for the delivery of ITB.

RESULTS

After 1 year of continuous ITB treatment the average LE Ashworth score decreased from 3.5+/-1.3 (SD) to 1.7+/-0.9 (p < .0001), spasm score from 1.8+/-1.3 to 0.2+/-0.5 (p< .0001), and reflex score from 2.5+/-1.1 to 0.1+/-0.3 (p < .0001). The average UE Ashworth score decreased from 2.9+/-1.5 to 1.6+/-1.0 (p < .0001), spasm score from 1.2+/-1.5 to 0.2+/-0.6 (p < 0.0001), and reflex score from 2.2+/-0.5 to 1.0+/-0.8 (p < .0001). The average ITB dose required to attain these effects at 1 year was 302 microg continuously infused per day.

CONCLUSION

Continuous intrathecal infusion of baclofen is capable of maintaining a reduction in spasticity and dystonia in both the upper and lower extremities of TBI patients.

Intrathecally administered baclofen for treatment of children with spasticity of cerebral origin

Management of severe spasticity in children is often a difficult problem. Orally administered medications generally offer limited benefits. This study examines the value of intrathecally administered baclofen in the treatment of 19 children with severe spasticity of cerebral origin: eight of whom sustained brain injury associated with trauma, near drowning, or cardiac arrest; 10 with cerebral palsy (spastic quadriplegia); and one child with Leigh's disease. At the time of entry into the study, patients ranged from 4 to 19 years of age, and all were completely dependent on caretakers for activities of daily living. Children who responded positively to a trial dose of intrathecal baclofen underwent insertion of a drug delivery system for continuous infusion. This was followed by a double-blind trial of baclofen or placebo and follow-up review at 3 and 6 months, and yearly thereafter. Seven children did not undergo pump implantation because of excess sedation or poor response. The 12 remaining children have been followed for a period of 1 to 5 years. Favorable responses were present in all 12 children as determined by the Ashworth Scale, with the greatest benefit being reduction of lower limb tone. Except in the case of one child who had reduction in lower limb tone that resulted in difficulty with transfers, the caretakers all reported significant benefits from intrathecal baclofen, with improvement in muscle tone, behavior, sitting, and general ease of care being most commonly noted. Central side effects were seen in some children who received continuous intrathecal baclofen infusion and included hypotension (two patients), bradycardia (two), apnea or respiratory depression (two), and sedation (one). During a total of 568 months of pump operation there were 10 mechanical complications, including two related to pump or side port failure and eight related to catheter kinks, extrusions, or dislodgment. Pump pocket effusion occurred in five children and a cerebrospinal fluid fistula was seen in one child. Local infection occurred in three children and meningitis in two children. The results demonstrate the potential value of continuous intrathecal baclofen infusion for treatment of severe spasticity of cerebral origin. However, this treatment can result in significant complications and more experience is required before the long-term benefits can be determined.

Baclofen in the treatment of cerebral palsy

Baclofen, a gamma-aminobutyric acid agonist, acts at the spinal cord level to impede the release of excitatory neurotransmitters that cause spasticity. Oral baclofen improves cerebral spasticity mildly, but its activity is limited because of its poor lipid solubility. Cerebrospinal fluid baclofen levels after intrathecal administration are many times higher than those achieved after oral administration. Continuous intrathecal baclofen infusion has been used to treat cerebral spasticity in two patient groups: in older ambulatory children with inadequate underlying leg strength, and in patients with severe spasticity in both the upper and lower extremities. Responsiveness to intrathecal baclofen is confirmed by test injections before insertion of a programmable subcutaneous pump. Continuous intrathecal baclofen infusion dosages vary from 27 to 800 micrograms/day. Continuous intrathecal baclofen infusion reduces spasticity in the upper and lower extremities, and improves upper extremity function and activities of daily living but has no effect on athetosis in the dosages used to treat spasticity. Complications related to the intrathecal catheter occur in approximately 20% of patients, and infection requiring pump removal occurs in approximately 5%. Preliminary studies indicate that continuous intrathecal baclofen infusion alleviates some forms of generalized dystonia associated with cerebral palsy.

Intrathecal baclofen administration for control of severe spinal spasticity: functional improvement and long-term follow-up

OBJECTIVES

To assess long-term efficacy and functional benefits of intrathecal baclofen for severe spinal spasticity.

DESIGN

A prospective before-after trial.

SETTING

A neurological rehabilitation department of a university hospital. Pump implantation was realized in neurosurgery; follow-up was carried out mostly on an outpatient basis.

PATIENTS

Eighteen patients with severe and disabling spinal spasticity received intrathecal baclofen by an implantable pump; average follow-up was 37.4 months (range, 9 to 72).

MAIN OUTCOME MEASURES

Spasticity (Ashworth and spasms frequency scores); disability (Functional Independence Measure [FIM]).

RESULTS

A significant decrease in tone and spasms was observed in all patients. Tolerance appeared during the first 6 to 9 months. Later on, efficacy remained stable, except in cases of mechanical problems of the pump or catheter. Functional assessment found a highly significant (p < .001) increase of FIM score (particularly for bathing, dressing lower body, transfers, and in some cases, locomotion). This was particularly marked in patients with thoracic spinal cord lesion. In cases of severe upper limb dysfunction, FIM was only improved for wheelchair displacements, due to a better sitting position, but nursing became easier and life comfort was enhanced. Severe side effects (overdose) were observed in two cases.

CONCLUSION

Efficacy remained stable after 6 to 9 months. Marked improvement of functional independence was observed in paraplegic patients. Improvement was less spectacular in patients with severe upper limb dysfunction, but nevertheless appreciable in terms of life comfort and use of attendants.