Temporal Onset Focal Seizures Induced by Intermittent Photic Stimulation.

Yue Niu,Zhixian Yang,Xianru Jiao,Haipo Yang,Pan Gong

doi:10.3389/fneur.2021.715236

Yue Niu, Zhixian Yang + Show 3 more

Open Access

https://doi.org/10.3389/fneur.2021.715236

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Abstract

The study aimed to review the clinical, radiological, and pathological findings and electroencephalogram (EEG) of pediatric epilepsy patients with temporal onset focal seizures induced by intermittent photic stimulation (IPS). Four patients with temporal onset photosensitivity focal seizures were analyzed. Three (75%) of the four patients were female. The average age of seizure-onset was 4.4 years. The interictal EEG showed both generalized and focal spike and waves in one patient and focal or multifocal spike and waves alone in three patients. Photoparoxysmal response (PPR) was evoked in all patients and showed generalized discharges (patients 2–4), both generalized and posterior discharges (patient 1). Both generalized and focal discharges could coexist in interictal discharges and PPR. The sensitive frequencies of PPR and photoconvulsive response (PCR) were 12–30 and 10–16 Hz, respectively, which were close to the occipital rhythm. In all patients, the onset of PCR was recorded, namely, the left anterior and mesial temporal lobe (TL), the left posterior TL, and the whole left TL, which showed two forms: the seizure of two patients was the onset of slow waves in the temporal area without spreading generalized discharges (patients 1 and 4), and the other one was fast rhythmic activities in the temporal area, spreading to the occipital area or gradually evolving into the generalized discharges (patients 2 and 3). During follow-up, except for patient 3 who had occasional seizures, the seizures of the remaining patients were under control. Temporal onset focal seizures could be induced by IPS. Temporal onset photosensitivity seizures were mostly easy to control with antiseizure drugs.

Highlights

Seizures triggered by photic stimulation are usually associated with a subtype of genetic generalized epilepsy, such as, childhood absence epilepsy, juvenile absence epilepsy, and juvenile myoclonic epilepsy [1]
We summarized the ictal EEG of the four cases and found that one was the onset of slow waves in the temporal area and the other was fast rhythmic activity in the temporal area, spreading to the occipital area or gradually evolving into the generalized discharges, which had not been previously associated
All the above suggested that the focal discharges originating from the temporal area or occipital area could coexist with generalized discharges in photosensitive seizures

Summary

Introduction

Seizures triggered by photic stimulation are usually associated with a subtype of genetic (idiopathic) generalized epilepsy, such as, childhood absence epilepsy, juvenile absence epilepsy, and juvenile myoclonic epilepsy [1]. In the electroencephalogram (EEG), the photoparoxysmal response (PPR) pattern induced by intermittent photic stimulation (IPS) is usually manifested as generalized polyspikes and slow waves. There are some reports of focal seizures induced by IPS, most of which are caused by the high excitability of the occipital cortex [2, 3]. In 1996, it was reported that a patient diagnosed with temporal lobe epilepsy was detected as having a photosensitive temporal seizure [4]. In 2021, a study reported a case of temporal lobe focal seizure induced by IPS, but no confirmed temporal lobe epilepsy [5].

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