How does baclofen help patients with stroke-related muscle spasticity?

Baclofen for Stroke-Related Muscle Spasticity

Baclofen helps patients with stroke-related muscle spasticity by acting as a GABA-B receptor agonist that reduces muscle tone and spasms, though it may be less effective for stroke spasticity compared to other conditions and carries risks of sedation and withdrawal complications. 1

Mechanism of Action

Baclofen works through several mechanisms to reduce spasticity:

• Acts primarily as a GABA-B receptor agonist, inhibiting excitatory neurotransmission in the spinal cord 1
• Normalizes altered interneurone activity in the spinal cord 2
• Decreases alpha motoneurone hyperactivity that contributes to spasticity 2
• Reduces muscle tone in a dose-dependent manner regardless of the cause of spasticity 3

Efficacy in Post-Stroke Spasticity

Baclofen's effectiveness for stroke-related spasticity shows mixed results:

• It may be less effective for stroke-related spasticity compared to other conditions 1
• Studies show variable response rates with oral baclofen, with some patients showing significant improvement while others show minimal response 4
• In one study, only 3 out of 29 stroke patients (10.3%) showed significant reduction in ankle clonus and velocity-dependent muscle tone with oral baclofen 4
• Baclofen can reduce spastically increased muscle tone and Babinski sign, but has limited effect on muscle force, tendon reflexes, and ankle clonus in some patients 2

Administration Options

Oral Baclofen

• Considered an alternative first-line oral medication for post-stroke spasticity 1
• Should be started at low doses and gradually titrated to minimize side effects
• May cause significant sedation, which limits its use in some patients 1

Intrathecal Baclofen (ITB)

• Reserved for severe spasticity unresponsive to oral medications 1
• Demonstrated to reduce spasticity in chronic stroke patients (>6 months post-stroke) 1
• Associated with significant improvements in pain and quality of life in post-stroke patients 5
• In the SISTERS study, ITB showed significant treatment effects over conventional medical management for:
  • Actual pain (p=0.0380)
  • Least pain (p=0.0136)
  • Quality of life measures (p=0.0197) 5

Important Considerations and Cautions

Functional Implications

• While baclofen reduces spasticity, it may cause functional deterioration in some patients 3
• 6 out of 8 patients in one study experienced functional deterioration with ITB as it weakened their paretic side, suppressing antigravity patterns used for ambulation 3
• Consider whether the patient uses spasticity for functional activities like standing or walking before initiating treatment 3

Pain Management

• Although not primarily antinociceptive, baclofen may alleviate pain if it arises from increased muscle tone 3
• ITB showed significant improvements in pain scores compared to conventional management in the SISTERS study 5

Withdrawal Risk

• Abrupt discontinuation of baclofen (especially intrathecal) can lead to potentially life-threatening withdrawal syndrome 1
• Always taper gradually when discontinuing 1

Patient Selection

• Best candidates for baclofen are those with:
  • Spasticity in multiple muscle groups
  • Spasticity that interferes with function, causes pain, or creates hygiene issues
  • No reliance on spasticity for functional activities 1, 3

Treatment Algorithm

1. Start with non-pharmacological interventions:

   • Positioning, passive stretching, range-of-motion exercises
   • Functional electrical stimulation, resistance training 1

2. If insufficient response, consider oral medications:

   • Tizanidine is often preferred as first-line for stroke patients (less sedation)
   • Baclofen as alternative first-line, starting at low doses 1

3. For focal spasticity, consider botulinum toxin injections 1

4. For severe, refractory spasticity:

   • Consider intrathecal baclofen, especially if pain is a significant component 1, 5
   • Carefully assess functional implications before proceeding 3

Monitoring and Follow-up

• Regularly assess skin integrity as spasticity can contribute to pressure ulcers 1
• Identify and treat factors that can worsen spasticity (pressure sores, infections) 1
• Monitor for side effects, particularly sedation and weakness
• Evaluate functional impact of treatment - improvement should be seen in pain, hygiene, and function, not just muscle tone 1