Effects of baclofen on motor units paralysed by chronic cervical spinal cord injury

Brain, 2010 · DOI: 10.1093/brain/awp285 · Published: January 1, 2010

Spinal Cord Injury Pharmacology Neurology

Simple Explanation

Baclofen, a drug used to treat muscle spasms, may have long-term effects on muscle properties in people with spinal cord injuries. This study aimed to determine if long-term baclofen use changes the properties of motor units in paralyzed muscles more than paralysis alone. The study compared the contractile properties of motor units in three groups: paralyzed individuals taking baclofen, paralyzed individuals not taking baclofen, and uninjured individuals. The researchers measured muscle force and electrical activity in response to nerve stimulation. The results indicated that paralyzed motor units from individuals taking baclofen were weaker and had slower relaxation times compared to those from uninjured individuals. Paralysis alone did not cause the same degree of weakness. This suggests that long-term baclofen use may contribute to muscle weakness in paralyzed individuals.

Study Duration

Not specified

Participants

12 spinal cord injured subjects and 12 uninjured control subjects

Evidence Level

Level 3, experimental study

Key Findings

1
Long-term baclofen use and paralysis resulted in significantly weaker motor unit tetanic forces compared to uninjured subjects.
2
Twitch half-relaxation times were longer in paralyzed motor units influenced by baclofen compared to those paralyzed alone or from uninjured subjects.
3
Axon conduction velocities were slowest in paralyzed units from subjects not taking baclofen and fastest in units from uninjured subjects; velocities were intermediate in baclofen users.

Research Summary

This study investigated the effects of long-term baclofen use on the contractile properties of paralyzed motor units in individuals with cervical spinal cord injury. The results indicated that baclofen use, in conjunction with paralysis, leads to weaker muscle forces and prolonged relaxation times. The study found that axon conduction velocities differed across groups, with the slowest velocities observed in paralyzed individuals not taking baclofen. These findings suggest that baclofen has differential effects on nerve and muscle properties. The authors concluded that greater motor unit weakness with long-term baclofen use and paralysis may make the whole muscle weaker and more fatigable, necessitating more extensive therapy to restore muscle strength and speed.

Practical Implications

Rehabilitation Strategies

Rehabilitation programs for individuals with spinal cord injury who use baclofen chronically may need to be tailored to address the potential for increased muscle weakness and fatigue.

Informed Treatment Decisions

Clinicians should carefully weigh the short-term benefits of baclofen for spasticity management against its potential long-term effects on muscle properties and rehabilitation outcomes.

Electrical Stimulation Parameters

Optimize stimulus parameters and training regimens when using electrical stimulation to improve muscle function in individuals with paralysis and chronic baclofen use.

Study Limitations

1
The study sample size was relatively small, particularly in the baclofen group.
2
The duration of baclofen use was estimated based on years post-injury, which may not be precise.
3
Other medications were balanced but not fully controlled, which could have influenced motor unit properties.

Your Feedback

Was this summary helpful?

Back to Spinal Cord Injury