How is physiological myoclonus treated?

Treatment of Physiological Myoclonus

Physiological myoclonus typically does not require pharmacological treatment unless it interferes with quality of life or mechanical ventilation. 1

Types of Physiological Myoclonus and Approach to Treatment

Physiological myoclonus must first be distinguished from pathological forms, as treatment approaches differ significantly based on the underlying mechanism:

Diagnostic Classification

• Determine the neurophysiological origin using EEG and clinical presentation:
  • Cortical
  • Subcortical/brainstem
  • Spinal
  • Peripheral

First-Line Treatments Based on Myoclonus Type

1. Cortical Myoclonus:

   • Levetiracetam (500-1000 mg IV or oral) 1, 2
   • Valproic acid 1, 2
   • Clonazepam 1, 2

2. Subcortical/Brainstem Myoclonus:

   • Clonazepam (first-line) 1, 2
   • Levetiracetam and valproic acid as alternatives 2

3. Spinal Myoclonus:

   • Clonazepam (first-line) 2
   • Botulinum toxin for focal cases 2

4. Post-anoxic Myoclonus:

   • Benzodiazepines (IV clonazepam) as first-line 1
   • Levetiracetam (500-1000 mg IV) 1

Treatment Algorithm

1. Initial Assessment:

   • Rule out medication-induced myoclonus (especially opiates) 1, 2
   • Check for metabolic causes (renal/hepatic failure) 2
   • Determine if epileptiform correlates exist using EEG 3, 1

2. Treatment Selection:

   • If subcortical myoclonus not interfering with mechanical ventilation → observation may be appropriate 3
   • If interfering with function → pharmacological treatment based on type

3. Medication Selection Hierarchy:

   • First-line: Benzodiazepines (clonazepam) 1, 2
   • Second-line: Levetiracetam or valproic acid 1, 2
   • Refractory cases: L-5-Hydroxytryptophan, sodium oxybate 2

Special Considerations

Lance-Adams Syndrome

For action or intention myoclonus occurring after hypoxic events:

• Combination therapy often needed 1
• Better prognosis than other post-anoxic myoclonus forms 1
• 85% show improvement over time 1

Important Cautions

• Avoid phenytoin and carbamazepine as they may paradoxically worsen myoclonus 1, 2
• Valproate should be avoided in women of childbearing age 1
• Routine anticonvulsant prophylaxis is not recommended in post-cardiac arrest patients 1

Refractory Cases

• Deep brain stimulation targeting the globus pallidus pars-interna may be considered when pharmacological treatments fail 1, 2
• Propofol may be considered for severe, persistent myoclonus requiring immediate suppression 1

Monitoring

• EEG monitoring is recommended to differentiate epileptic from non-epileptic myoclonus 3, 1
• Continuous monitoring for the first 24 hours is advised if status myoclonus is present 1

The American Heart Association notes that status myoclonus (continuous jerking >30 minutes) within 72 hours post-arrest has high specificity for poor neurological outcome, which should be considered in treatment decisions 1.