Tonic Clonic and Myoclonic Seizures

Generalized tonic clonic and myoclonic seizures may occur in patients with generalized absence epilepsy. It is important to understand that the two seizures are not the same. However, some features of each can help distinguish them. In addition, the relative asymmetry of the seizures can aid in their diagnosis.

Tonic clonic and myoclonic syndrome is a form of epilepsy that occurs in children. The onset of seizures typically occurs in the early adolescent years. These seizures are characterized by the presence of sudden muscular contractions that produce an opisthotonic posture. They are also accompanied by a prolonged high-pitched moan or a respiratory stridor. Typically, these jerks last about one minute.

Generalized tonic-clonic and myoclonic seizures are often associated with extratemporal focal seizures. Electrographic features of these seizures include synchronous and asymmetrical spike waves, and bursts of GPFA, or diffuse repetitive spike discharges. Bursts are not pathognomonic for LGS, but may indicate spinal cord and cerebellar dysfunction.

EEG can be used to detect tonic clonic and myoclonic absence seizures. A 3-4 Hz spike complex is common during absences. If the occurrence of these EEG characteristics is frequent, the patient is likely to have generalized tonic-clonic seizures.

Video-EEG can be used to identify GTC and myoclonic seizures. Family members had a range of symptoms. One family member had myoclonic jerks that preceded GTC. Another family member experienced lifelong tonic-clonic convulsions.

Seizure Alarms There is a 50% risk of a sibling or an offspring expressing an EEG trait. Siblings are more likely to be affected than offspring.