Intrathecal baclofen pump for spasticity: an evidence-based analysis

Abstract

Objective: To conduct an evidence-based analysis of the effectiveness and cost-effectiveness of intrathecal baclofen for spasticity.

The technology: Spasticity is a motor disorder characterized by tight or stiff muscles that may interfere with voluntary muscle movements and is a problem for many patients with multiple sclerosis (MS), spinal cord injury (SCI), cerebral palsy (CP), and acquired brain injury (ABI).(1). Increased tone and spasm reduces mobility and independence, and interferes with activities of daily living, continence and sleep patterns. Spasticity may also be associated with significant pain or discomfort (e.g., due to poor fit in braces, footwear, or wheelchairs), skin breakdown, contractures, sleep disorders and difficulty in transfer. Goals of treatment are to decrease spasticity in order to improve range of motion, facilitate movement, reduce energy expenditure and reduce risk of contractures. Existing treatments include physical therapy, oral medications, injections of phenol or botulinum toxin, or surgical intervention. Baclofen is the oral drug most frequently prescribed for spasticity in cases of SCI and MS.(1) Baclofen is a muscle relaxant and antispasticity drug. In the brain, baclofen delivered orally has some supraspinal activity that may contribute to clinical side effects. The main adverse effects of oral baclofen include sedation, excessive weakness, dizziness, mental confusion, and somnolence.(2) The incidence of adverse effects is reported to range from 10% to 75%.(2) Ochs et al. estimated that approximately 25-30% of SCI and MS patients fail to respond to oral baclofen.(3;4) Adverse effects appear to be dose-related and may be minimized by initiating treatment at a low dose and gradually titrating upwards.(2) Adverse effects usually appear at doses >60 mg/day.(2) The rate of treatment discontinuation due to intolerable adverse effects has generally been reported to range from 4% to 27%.(2) When baclofen is administered orally, only a small portion of the original dose crosses the blood brain barrier and enters the central nervous system (CNS) fluid, which is the site of drug action. In order to bypass the oral route, baclofen may be administered intrathecally by infusion directly to the CNS. Candidates for intrathecal baclofen infusion are patients with spasticity who have intractable spasticity uncontrolled by drug therapy, or who experience intolerable side effects from oral baclofen. Advantages of intrathecal baclofen infusion are: Direct drug administration to the cerebrospinal fluid (CSF)The central side effects of oral baclofen, such as drowsiness or confusion, appear to be minimized with intrathecal administration.The intrathecal delivery of baclofen concentrates the drug in the CSF at higher levels than those attainable via the oral route.Intrathecal administration can use concentrations of baclofen of less than one hundredth of those used orally.(5)Adjustable/programmable continuous infusion makes it possible to finely titrate patients' doses and to vary the doses over the hours of the day. For example, the dose can be relatively low to give the patients the extensor tone needed for ambulation during the day and increased at night, thereby improving quality of sleep.Reversible (in contrast to surgery).A patient who is a candidate for intrathecal baclofen infusion must have no contraindications to the insertion of an intrathecal catheter (e.g., anticoagulant therapy, coagulopathy, local or systemic infection, anatomical abnormality of the spine).

Review strategy: The Medical Advisory Secretariat reviewed the literature to assess the effectiveness, safety, and cost-effectiveness of intrathecal baclofen to treat patients who have intractable spasticity uncontrolled by drug therapy, or who experience intolerable side effects to oral baclofen. The Medical Advisory Secretariat used its standard search strategy to retrieve international health technology assessments and English-language journal articles from selected databases.

Summary of findings: Level 2 evidence supports the effectiveness of intrathecal baclofen infusion for the short-term reduction of severe spasticity in patients who are unresponsive or cannot tolerate oral baclofenLevel 3 evidence supports the effectiveness of intrathecal baclofen for the long-term reduction of severe spasticity in patients who are unresponsive or cannot tolerate oral baclofenLevel 4 qualitative evidence demonstrates functional improvement for patients who are unresponsive or cannot tolerate oral baclofenIntrathecal baclofen is cost-effective with costs which may or may not be avoided in the Ontario health systemTrue functional use remains to be determined.