Abstract
PurposeSeizure originates from different pathological substrate; however, the same pathologies may have distinct mechanisms underlying seizure generation. We aimed to improve the understanding of such mechanisms in patients with temporal lobe epilepsy (TLE) by investigating the stereoelectroencephalography (SEEG) ictal onset patterns (IOPs).MethodsWe analyzed data from a cohort of 19 consecutive patients explored by SEEG and had 1–3-year seizure-freedom following temporal lobe resection.ResultsSix IOPs were identified. They were low voltage fast activity (LVFA) (36.5%), rhythmic spikes or spike-waves at low frequency and with high amplitude (34.1%), runs of spikes (10.6%), rhythmic sharp waves (8.2%), low frequency high amplitude repetitive spiking (LFRS) (7.1%), and delta activity (3.5%). All six patterns were found in patients with mesial temporal onset and only two patterns were found in patients with temporal neocortical onset. The most prevalent patterns for patients with mesial temporal onset were rhythmic spikes or spike-waves, followed by LVFA with a mean discharge rate 74 Hz. For patients with temporal neocortical onset, the most prevalent IOP pattern was LVFA with a mean discharge rate 35 Hz, followed by runs of spikes. Compared with Lateral TLE (LTLE), the duration between the onset of the IOPs to the onset of the symptom was longer for patients with MTLE (Mesial TLE) (MTLE:55.7 ± 50.6 s vs LTLE:19.5 ± 16.4 s).ConclusionMultiple IOPs underlie seizure generation in patients with TLE. However, the mesial and lateral temporal lobes share distinct IOPs.
Highlights
Temporal lobe epilepsy (TLE) is the most common refractory partial epilepsy, and it is suited for surgical treatment
According to the international classification of epileptic syndromes, TLE can be distinguished to two subtypes: mesial TLE (MTLE) and lateral TLE (LTLE) [12]
About twothirds of patients are MTLE and they have the features of hippocampal sclerosis (HS) on MRI and characteristic ictal EEG rhythm (4- to 7-Hz frequency)
Summary
Temporal lobe epilepsy (TLE) is the most common refractory partial epilepsy, and it is suited for surgical treatment. According to the international classification of epileptic syndromes, TLE can be distinguished to two subtypes: mesial TLE (MTLE) and lateral TLE (LTLE) [12]. About twothirds of patients are MTLE and they have the features of hippocampal sclerosis (HS) on MRI and characteristic ictal EEG rhythm (4- to 7-Hz frequency). One-third of patients are LTLE and they have the features of no HS and < 4 Hz ictal EEG rhythm. Diagnosing TLE is difficult in view of the lack of the EEG feature, seizure semiology, and HS on MRI. Intracranial electroencephalography (iEEG) is indispensable for identifying the epileptogenic zone (EZ). The ictal iEEG showed that the fast activity (20–30 Hz) and low-frequency high-amplitude periodic spikes (LFRS) are
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