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Interictal indices of temporal seizure origin
W T Blume1, J L Borghesi, J F Lemieux
1University Hospital, Epilepsy Unit, University of Western Ontario, London, Canada.
Annals of Neurology
|November 1, 1993
Summary
Interictal electroencephalography (EEG) spikes and delta activity in the temporal lobe strongly correlate with the side of seizure origin. This suggests awake scalp EEG is crucial for determining the laterality of temporal epileptogenesis.
Area of Science:
- Neurology
- Epilepsy Research
- Clinical Neurophysiology
Background:
- Determining the side of seizure origin in temporal lobe epilepsy is critical for surgical planning.
- Interictal electroencephalographic (EEG) findings, such as spikes and delta activity, are often used to lateralize epileptogenesis.
- The correlation between interictal EEG patterns and the actual seizure onset side requires further validation.
Purpose of the Study:
- To assess the value of temporal lobe interictal electroencephalographic (EEG) spikes and delta activity in indicating the side of temporal epileptogenesis.
- To investigate the correlation between the laterality of interictal EEG abnormalities and the origin of seizures.
- To determine if awake scalp EEG can reliably lateralize the epileptogenic zone in temporal lobe epilepsy.
Main Methods:
- Two studies were conducted involving patients with epilepsy.
- Study 1 analyzed laterality of spikes/delta in 56 patients with unilaterally originating seizures confirmed by EEG and >90% post-lobectomy improvement.
- Study 2 examined laterality of temporal seizures in 156 patients based on spike or delta ratios across 1 to >4 awake EEG recordings.
Main Results:
- In Study 1, 93% of patients showed ipsilateral spikes and 82% showed ipsilateral delta relative to seizure origin.
- In Study 2, 95% of patients with temporal spikes on four or more recordings had seizures ipsilateral to most spikes.
- High ratios of side-vs-side spikes (≥3) showed 98% of seizures originating ipsilateral to most spikes, correlating with lateralized delta activity.
Conclusions:
- There is a high correlation between the laterality of interictal EEG entities (spikes and delta) and the ictal onset zone in temporal lobe epilepsy.
- Awake interictal scalp EEG findings, particularly prominent temporal spikes and persistent unilateral delta activity over multiple recordings, are valuable for lateralizing epileptogenesis.
- The awake interictal scalp EEG should not be disregarded when assessing the laterality of temporal epileptogenesis.