Generalized‐onset seizures with secondary focal evolution

Abstract

SUMMARYThe international seizure classification recognizes that partial-onset seizures can become secondarily generalized, but generalized-onset seizures are expected to remain generalized. We report six patients who had recorded seizures with generalized onset, but subsequent evolution into a focal discharge. The clinical seizure onset was generalized absence or myoclonic, and the most common subsequent clinical pattern was prolonged behavioral arrest with mild automatisms, and then postictal confusion. The ictal discharge started with generalized spike-and-wave activity and then acquired a focal predominance.Interictal epileptiform activity was generalized. There were no focal magnetic resonance imaging abnormalities. Four patients were misdiagnosed with complex partial seizures. All patients were initially refractory, but three became seizure-free and three improved after treatment with antiepileptic medications appropriate for absence or myoclonic seizures. Generalizedonset seizures that acquire focal features are easily misdiagnosed as complex partial. These seizures have a more favorable response to medications effective against generalized absence and myoclonic seizures.

Evidence that temporal lobe is a default area in absence epilepsy

“…Absence seizures occurred independently from myoclonus and were present both with and without electroclinical temporal transformation to distinguish our cases. Similar to prior case reports [7,15], our patients demonstrated focal ictal transformation in the semiology that included prolonged staring and post-ictal state, as well as the EEG depicting 3-to 4-Hz GSW seizure onset. Only one patient in the series by Williamson (patient 5) with drug-resistant absence epilepsy and frontal-temporal ictal transformation following a 4.5-Hz GSW onset was similar to our patients.…”

“…Bilateral seizure onset on EEG may also occur due to a focal lesion [14]. Generalized seizures that have lateralizing clinical and electrographic features are at risk for misdiagnoses [7]. Absence seizures occurred independently from myoclonus and were present both with and without electroclinical temporal transformation to distinguish our cases.…”

“…Concomitant focal and generalized interictal epileptiform discharges (IEDs) on the EEG in patients with epilepsy are not uncommon [6]. Generalized seizures with focal ictal transformation from generalized spike-andwaves have rarely been reported in a heterogeneous group of patients with generalized epilepsy [7]. A misdiagnosis of focal seizures may prompt ineffective or aggravating antiepileptic drug (AED) treatment.…”

The adolescent or adult with generalized tonic-clonic seizures

“…In a small number of patients, focal evolution of both clinical and EEG patterns have been reported. [4243]…”

“…[40] A third scenario was described recently by Williamson et al . [43] identifying six patients in whom the beginning of the ictal discharge consisted of GSW activity but subsequent EEG activity had a focal predominance. Interictal epileptiform discharges were also generalized, but the semiology consisted of prolonged behavioral arrest with mild automatisms, simulating complex partial seizures.…”