The most frequent neurological side effects of the muscle relaxants

1. Big picture

Muscle relaxants are drugs used to reduce excessive muscle tone, spasms, spasticity, dystonia, or painful muscle contraction. In neurology, they are used mainly for:

• spasticity after stroke;
• multiple sclerosis-related spasticity;
• spinal cord injury;
• cerebral palsy;
• painful muscle spasms;
• dystonia;
• trigeminal neuralgia as add-on treatment;
• severe rigidity/spasm syndromes.

The key exam sentence:

Muscle relaxants commonly cause neurological side effects such as drowsiness, dizziness, weakness, fatigue, ataxia, confusion, hypotonia, falls, respiratory depression, and withdrawal syndromes.

The most important clinical trap:

A muscle relaxant may improve spasticity but worsen walking, swallowing, breathing, alertness, and fall risk.

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2. Main muscle relaxant groups in neurology

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3. Why muscle relaxants cause neurological side effects

Muscle relaxants reduce muscle tone by acting at different levels:

1. Brain/spinal cord inhibition Examples: baclofen, tizanidine, benzodiazepines. Side effects: sedation, dizziness, confusion, ataxia.

2. Skeletal muscle contraction mechanism Example: dantrolene. Side effects: generalized weakness and fatigue.

3. Neuromuscular junction blockade Examples: botulinum toxin, anesthetic neuromuscular blockers. Side effects: focal or generalized weakness, dysphagia, respiratory risk.

4. Central psychoactive effects Example: cannabinoids. Side effects: dizziness, somnolence, cognitive slowing, psychiatric symptoms.

The clinical point:

The same mechanism that reduces pathological tone can also reduce useful muscle strength.

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4. Baclofen