Myoclonic Seizures

Myoclonic seizures are characterized by brief, jerking spasms of a muscle or muscle group. They often occur with atonic seizures, which cause sudden muscle limpness.

What You Need to Know

  • The word “myoclonic” combines the Greek prefix for muscle — “myo” — with “clonus,” which means twitching.
  • Myoclonic seizures do not cause any loss of awareness — the person is awake and conscious during the seizure.
  • Infantile spasms and Lennox-Gastaut syndrome are two of the epilepsy syndromes characterized by myoclonic seizures, among other symptoms.

Symptoms of Myoclonic Seizures

A person having a myoclonic seizure experiences a sudden increases in muscle tone as if they have been jolted with electricity.

The mechanism is similar to a myoclonic jerk, the sudden spasm occasionally experienced by people as they are falling asleep. However, unlike myoclonic jerks, the “jolts” of myoclonic seizures occur in bouts.

Infantile Spasms

This type of myoclonic epilepsy typically begins between the ages of 3 and 12 months and may persist for several years. Infantile spasms typically consist of a sudden jerk followed by stiffening.

During the characteristic seizures (spasms), the child’s arms fling outward as the knees pull up and the body bends forward. Each seizure lasts only a second or two but multiple episodes can occur close together in a series — or cluster. Sometimes the spasms are mistaken for colic, but colic cramps do not typically occur in a series.

Infantile spasms are most common just after waking up and rarely occur during sleep. This particularly severe form of epilepsy can have lasting effects on the child and should be treated without delay.

Lennox-Gastaut Syndrome

This rare epilepsy syndrome affects young children and includes myoclonic seizures of the neck, shoulders, upper arms and face, along with other types of seizures.

Progressive Myoclonic Epilepsy

Another rare seizure disorder, progressive myoclonic epilepsy, is characterized by a combination of myoclonic and tonic-clonic (grand mal) seizures. Treatment may provide relief for a while, but the patient’s condition worsens over time.

Treatment for Myoclonic Seizures

Like other forms of seizures and epilepsy, myoclonic seizures are best addressed through an individualized approach. The doctor may recommend treatment with anti-seizure medication, nerve stimulation, dietary therapy or surgery.

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