Myoclonic seizures are a type of generalized seizure. They are seen in patients with a history of myoclonic epilepsy, but also in patients with toxic or metabolic disorders or after global hypoxic or ischemic injury, such as cardiac arrest.
In patients with a history of myoclonic epilepsy, seizures consist of focal or generalized, rapid, uncontrolled muscle movements that are usually synchronous. Consciousness may or may not be impaired. When these patients present with uncontrolled seizures, the prognosis for full recovery is generally good with proper treatment.15 Usually, they are exquisitely sensitive to treatment with IV benzodiazepines, although the addition of IV valproate preparations is sometimes required.
About 17% of patients who experience hypoxic or ischemic injury that results in coma develop focal, multifocal, or generalized periodic myoclonic movements, often manifested by eye blinking, chewing movements, or multifocal twitching.16 When this type of seizure activity is seen after a global ischemic event, the prognosis for a meaningful recovery is poor. Most experts believe that, with rare exception, this clinical presentation probably represents an agonal neurologic event in an irreparably injured brain rather than an electrical dysfunction in salvageable tissue.
Postanoxic myoclonus is notoriously difficult to control and may be continuous, giving rise to myoclonic status epilepticus. Sometimes paralytic agents are used to eliminate myoclonic movements, but this is not recommended. If the likelihood of survival is poor, it may be done purely for cosmetic reasons, to make the patientís death easier for the family. In this case, nothing is done to treat the agonal discharges of the dying brain, and electrical status epilepticus persists. Benzodiazepines and other antiepileptic drugs have been used to treat postanoxic myoclonus, but the results are generally poor.
Reviewed and revised May 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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