Absence seizures are characterized on EEG by:

Answer is A (3 Hz spike and wave): EEG in absence seizures shows bursts of bilaterally synchronous and symmetric 3 Hz spike and wave activity. Characteristic features of Absence seizures / Petitmal seizures: Clinical Hallmarks Almost always begin in childhood and cease by age of 20. Sudden brief lapses of consciousness without loss of postural control Seizure typically lasts only for seconds. Impairment is so brief that patient may be unaware of it. Consciousness returns as suddenly as it was lost i.e. Inset and termination of attack, both are abrupt. Usually accompanied by subtle bilateral motor signs such as - Rapid blinking of eye lids - Chewing movements - Small amplitude, clonic movements of hands There is no postictal confusion The seizure can occur hundreds of times per day. First clued to absence seizure is often unexplained 'day dreaming' and a decline in school performance recognized by a teacher. Electrophysiological hallmark Electrophysiological hallmark of typical absence seizure is a generalized symmetric, 3 Hz spike and wave discharge that begins and ends suddenly superimposed on a normal EEG background. Hyperventilation tends to provoke these electrographic discharges and even the seizures themselves.