What is the treatment approach for myoclonus?

Treatment Approach for Myoclonus

Levetiracetam, valproate sodium, or clonazepam should be used as first-line treatments for myoclonus, with levetiracetam being particularly effective for post-anoxic myoclonus. 1

Classification and Diagnosis

Before initiating treatment, it's essential to classify myoclonus based on its origin:

1. Diagnostic Evaluation:

   • EEG is crucial to determine if myoclonus has an epileptiform correlate 1
   • Distinguish between epileptic and non-epileptic (subcortical) myoclonus 1
   • Continuous EEG monitoring should be considered in patients with suspected status epilepticus 1

2. Types of Myoclonus by Origin:

   • Cortical myoclonus
   • Subcortical/cortico-subcortical myoclonus
   • Brainstem myoclonus
   • Spinal myoclonus
   • Propriospinal myoclonus

Treatment Algorithm

First-Line Treatments Based on Myoclonus Type:

1. Cortical Myoclonus:

   • Levetiracetam: Start with 1000 mg/day (500 mg BID), increase by 1000 mg/day every 2 weeks to maximum 3000 mg/day 2, 3
   • Valproate sodium: Effective but avoid in women of childbearing age 1, 3
   • Clonazepam: Useful as adjunct therapy 1, 3

2. Subcortical and Brainstem Myoclonus:

   • Clonazepam as first-line agent 3
   • Levetiracetam and valproic acid can also be tried 3
   • L-5-Hydroxytryptophan and sodium oxybate for refractory cases 3

3. Spinal Myoclonus:

   • Clonazepam as first-line agent 3
   • Botulinum toxin for focal cases 3
   • Note: Anti-epileptic drugs are typically ineffective 3

4. Post-anoxic Myoclonus:

   • Levetiracetam is particularly effective 1
   • Propofol can be used for suppression in intensive care settings 1
   • Immediate treatment if there is evidence of epileptic activity 1

Special Considerations:

1. Status Myoclonus:

   • Status myoclonus (continuous myoclonic jerks lasting >30 minutes) requires aggressive treatment 4
   • In post-cardiac arrest patients, status myoclonus within 72 hours is associated with poor outcomes but should still be treated 4
   • Combination with other diagnostic tests at 72+ hours after cardiac arrest can help predict neurological outcomes 4

2. Lance-Adams Syndrome:

   • Chronic action myoclonus following hypoxic brain injury 4, 1
   • Requires long-term treatment 1
   • May have better prognosis than acute post-anoxic myoclonus 4

3. Juvenile Myoclonic Epilepsy:

   • Levetiracetam starting at 1000 mg/day, increasing to 3000 mg/day 2
   • Valproate is also effective but has more side effects 1

Medication Dosing and Administration:

1. Levetiracetam:

   • Adults: Start with 1000 mg/day (500 mg BID), increase by 1000 mg/day every 2 weeks to maximum 3000 mg/day 2
   • Pediatric patients (4-16 years): 20 mg/kg/day initially, increase to 60 mg/kg/day 2
   • Adjust dose for renal impairment 2

2. Valproate Sodium:

   • Start at lower doses and titrate based on response and tolerability 3, 5
   • Monitor for hepatotoxicity and other side effects

3. Clonazepam:

   • Useful for all types of myoclonus 3, 5
   • Often used as adjunctive therapy
   • Monitor for sedation and tolerance development

Treatment Pitfalls and Caveats:

1. Avoid certain medications:

   • Phenytoin and carbamazepine may paradoxically worsen cortical myoclonus 3
   • Opiates can induce or worsen myoclonus 3

2. Combination therapy:

   • Single agents rarely provide complete control of myoclonus 5
   • Polytherapy with a combination of drugs is usually needed 5

3. Prognostic considerations:

   • Presence of myoclonus alone should not be used to predict poor neurologic outcomes (FPR 5-11%) 4
   • Status myoclonus within 72 hours of cardiac arrest has stronger prognostic value 4

4. Refractory cases:

   • Consider deep brain stimulation targeting the globus pallidus pars-interna bilaterally when pharmacological treatments have been exhausted 3
   • For functional myoclonus, multimodal treatment including psychotropic drugs and physical therapy may be needed 3

By following this structured approach to the diagnosis and treatment of myoclonus, clinicians can optimize patient outcomes and quality of life while minimizing adverse effects from medication.