[A case with frontal lobe epilepsy presenting with absence seizures as cardinal manifestation: ictal EEG findings]

We report here a 9-year-old boy presenting with absence and complex partial seizures. Absence seizures occurred several times a day, with sudden arrest of speech and gesture, alteration of consciousness, myoclonus of unilateral or bilateral angles of the mouth, occasional simple automatism and brisk recovery of consciousness. Complex partial seizures occurred once to three times a month with loss of consciousness, salivation, deviation of the head and eyes toward the left, elevation of upper limbs and tonic convulsion of the left upper and lower limbs. Interictal EEG showed right frontal pole-dominant high-voltage slow waves or spike-and-waves. Ictal simultaneous video-EEG recordings of absence seizures revealed a frontal dominant 3-3.5 Hz spike-wave burst lasting several seconds. A partial seizure never preceded the absence seizure. Transverse topographical analysis revealed that the first spike component of the spike-wave burst of absence seizure always showed phase reversal on the right anterior temporal electrode. The following ones, however, showed phase reversal on the left anterior temporal electrode. Ictal EEG of the complex partial seizure could not be detected because it rarely occurred. There was no abnormal finding on brain MRI. Interictal single photon emission tomography (SPECT) indicated hypoperfusion of the dorsal and medial cortex of the right middle frontal lobe. Interictal positron emission tomography (PET) also indicated hypometabolic areas in the dorsal and medial cortex of the right frontal lobe, together with those in the right temporal and parietal cortex. EEG evolution and neuroimaging studies suggested that the epileptic focus of the absence seizure might have originated at the dorsal cortex of the right middle frontal lobe and immediately spread to the medial cortex. Both the seizures were well controlled by the combination of phenytoin and high dose sodium valproate.