Spikeandwave

Spikeandwave, commonly written as spike-and-wave, refers to a pattern seen on electroencephalography (EEG) characterized by a sharp spike followed by a slower wave, repeated in a generalized, rhythmic pattern. The term is most often associated with generalized spike-and-wave discharges that occur during absence seizures, a brief form of epilepsy.

The underlying mechanism involves abnormal synchronization of thalamocortical networks. Ill-balanced interactions between the cortex and thalamic nuclei, including the thalamic reticular nucleus, generate rhythmic, generalized activity. This results in brief lapses of consciousness and responsiveness typical of absence seizures. The classic EEG signature is generalized spike-and-wave discharges, most commonly around 3 Hz, though frequencies can vary in different epileptic syndromes.

On EEG, spike-and-wave discharges are usually bilateral and generalized, with a characteristic sequence: a sharp spike followed by a slower wave, repeating at a rate near 3 cycles per second. Clinically, absence seizures accompanied by spike-and-wave discharges often last several seconds and are associated with abrupt onset of unresponsiveness, eye blinking, and modest motor symptoms. Hyperventilation can provoke these discharges in the clinic, aiding diagnosis. Some individuals exhibit polyspike-and-wave patterns or faster rhythms, especially in other generalized epilepsies.

Spike-and-wave is most commonly seen in childhood absence epilepsy but can occur in other genetic generalized epilepsy syndromes and, less commonly, in structural or symptomatic epilepsies. Treatment typically involves antiseizure medications such as ethosuximide or valproate, with regimens tailored to the patient’s age, comorbidities, and seizure type. While often reversible in children, the prognosis varies with the underlying syndrome.