What is the treatment for positive myoclonus?

Treatment of Positive Myoclonus

The first-line treatment for positive myoclonus should be levetiracetam, sodium valproate, or clonazepam, with the specific choice depending on the neurophysiological classification of the myoclonus. 1, 2

Neurophysiological Classification and Treatment Approach

Cortical Myoclonus

• Levetiracetam is a first-line agent for cortical myoclonus, with proven efficacy in myoclonic seizures (60.4% responder rate compared to 23.7% with placebo) 3
• Sodium valproate is another effective first-line option for cortical myoclonus 2, 4
• Clonazepam can be used as an alternative or adjunctive therapy 2, 5
• Avoid phenytoin and carbamazepine as they may paradoxically worsen cortical myoclonus 2

Subcortical and Brainstem Myoclonus

• Clonazepam is the first-line agent for subcortical and brainstem myoclonus 2, 5
• Levetiracetam and valproic acid can be tried as alternative or adjunctive therapies 2
• For refractory cases, L-5-Hydroxytryptophan and sodium oxybate may be considered 2

Spinal Myoclonus

• Clonazepam is the first-line treatment for spinal myoclonus 2, 5
• Anti-epileptic drugs are generally ineffective for spinal myoclonus 2
• Botulinum toxin injections can be useful for focal cases of spinal myoclonus 2, 4

Special Considerations for Post-Anoxic Myoclonus

Status Myoclonus After Cardiac Arrest

• Status myoclonus (continuous, repetitive myoclonic jerks lasting more than 30 minutes) within 72 hours after cardiac arrest is associated with poor neurological outcomes 1
• Treatment options include:
  • Sodium valproate 1
  • Levetiracetam 1
  • Clonazepam 1
  • Propofol (particularly effective for post-anoxic myoclonus) 1
  • Benzodiazepines 1
  • Barbiturates (for refractory cases) 1

Lance-Adams Syndrome

• Some patients with early-onset and prolonged myoclonus may evolve into Lance-Adams syndrome with chronic action myoclonus 1
• These patients can have good neurological recovery despite initial presentation with myoclonus 1
• Treatment is similar to cortical myoclonus with levetiracetam, valproic acid, and clonazepam 2, 5

Diagnostic Evaluation Before Treatment

• EEG monitoring is recommended in patients with clinical seizure manifestations to detect epileptic activity 1
• Continuous EEG should be considered to monitor patients with diagnosed status epilepticus and to assess treatment effects 1
• In the presence of myoclonic jerks, EEG recording is suggested to detect any associated epileptiform activity 1
• Distinguish between epileptic and non-epileptic myoclonus, as treatment approaches differ 6, 7

Treatment Challenges and Considerations

• A single pharmacological agent rarely controls myoclonus completely; polytherapy with a combination of drugs is often needed 4
• Medications may need to be used in large dosages for effective control 4
• For focal and segmental myoclonus, botulinum toxin injections may be effective regardless of origin 4
• Routine seizure prophylaxis in post-cardiac arrest patients is not recommended due to the risk of adverse effects and poor response to anti-epileptic agents 1

Important Caveats

• Before initiating symptomatic treatment, identify and address any underlying causes:
  • Metabolic derangements 8
  • Medication side effects (e.g., opiates) 2
  • Renal or hepatic failure 2
• Treatment response varies significantly based on the underlying etiology and neurophysiological classification 5
• Pharmacological treatments are often limited by adverse effects and variable efficacy 5
• For refractory cases of myoclonus-dystonia, deep brain stimulation targeting the globus pallidus pars-interna bilaterally may be considered when pharmacological treatments have been exhausted 2