From the Guidelines
Myoclonus in comatose survivors of cardiac arrest is a significant predictor of poor outcome, particularly when it presents as status myoclonus within 48 hours of return of spontaneous circulation (ROSC) 1.
Clinical Presentation and Prognosis
Myoclonus refers to brief, involuntary muscle jerks or twitches that occur suddenly, caused by rapid muscle contractions. In the context of cardiac arrest, myoclonus can be a symptom of various neurological disorders, including post-anoxic encephalopathy. The presence of myoclonic jerks in comatose survivors of cardiac arrest is not consistently associated with poor outcome, with a false positive rate (FPR) of 9% 1. However, status myoclonus, defined as a prolonged period of continuous and generalized myoclonic jerks, is highly predictive of poor outcome, with an FPR of 0% in both non-TTM-treated and TTM-treated patients 1.
Diagnosis and Treatment
Diagnosis of myoclonus and status myoclonus is primarily clinical, based on observation of the patient's motor activity. Electroencephalography (EEG) can be useful in identifying EEG signs of awareness and reactivity, as well as coexistent epileptiform activity 1. Treatment of myoclonus and status myoclonus is challenging, and may involve the use of antimyoclonic drugs such as clonazepam, sodium valproate, and levetiracetam 1. Propofol has also been shown to be effective in suppressing post-anoxic myoclonus 1.
Key Considerations
- Status myoclonus within 48 hours of ROSC is a significant predictor of poor outcome in comatose survivors of cardiac arrest 1.
- EEG can be useful in identifying EEG signs of awareness and reactivity, as well as coexistent epileptiform activity 1.
- Treatment of myoclonus and status myoclonus is challenging, and may involve the use of antimyoclonic drugs and propofol 1.
- Prolonged observation may be necessary after treatment of seizures to determine the patient's prognosis 1.
From the Research
Myoclytic Disorders
- Myoclonus is a sudden, brief, involuntary muscle jerk, caused by abrupt muscle contraction or sudden cessation of ongoing muscular activity 2
- It can be classified based on the underlying physiology, which is useful for therapeutic purposes 2
- The diagnosis of myoclonus involves taking a good history, clinically characterizing the myoclonus, and looking for additional findings on examination to limit the list of possible investigations 2
Causes and Related Conditions
- Rhabdomyolysis is a clinical syndrome of muscle injury associated with myoglobinuria, electrolyte abnormalities, and often acute kidney injury (AKI) 3
- Exertional rhabdomyolysis is characterized by muscle breakdown associated with strenuous exercise or normal exercise under extreme circumstances 4
- Myopathy can be reversible, as seen in cases of rhabdomyolysis caused by statins 5
Treatment and Management
- Treatment of rhabdomyolysis aims at discontinuation of further skeletal muscle damage, prevention of acute renal failure, and rapid identification of potentially life-threatening complications 3
- Early and aggressive fluid resuscitation is agreed on as the main intervention for preventing and treating AKI in rhabdomyolysis 3
- Myoclonus treatment often requires polytherapy with a combination of drugs, including antiepileptic drugs and clonazepam 2
- Focal and segmental myoclonus may be treated with botulinum toxin injections, with variable success 2