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Hippocampal high frequency oscillations in unilateral and bilateral mesial temporal lobe epilepsy

Pavel Řehulka1, Jan Cimbálník2, Martin Pail1

  • 1Brno Epilepsy Center, Department of Neurology, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic.

Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology
|May 18, 2019
PubMed
Abstract

Insights

Low occurrence of interictal high-frequency oscillations (HFOs) may indicate non-epileptic hippocampi in mesial temporal lobe epilepsy (MTLE). This finding helps differentiate epileptic from non-epileptic brain tissue in MTLE patients.

Area of Science:

  • Neuroscience
  • Epileptology
  • Clinical Neurophysiology

Background:

  • Mesial temporal lobe epilepsy (MTLE) is a common form of epilepsy often associated with hippocampal abnormalities.
  • High-frequency oscillations (HFOs) are neural signals recorded during interictal periods, potentially reflecting epileptogenicity.

Purpose of the Study:

  • To investigate differences in interictal HFOs between hippocampi in unilateral (U-MTLE) and bilateral (B-MTLE) mesial temporal lobe epilepsy.
  • To determine if HFO rates and distributions correlate with hippocampal sclerosis (HS) and seizure onset laterality.

Main Methods:

  • Bilateral hippocampal depth electrodes were implanted in 16 MTLE patients for epilepsy surgery evaluation.
  • Automatic detection of interictal HFOs, including ripples and fast ripples (FR).
  • Comparison of HFO rates and spatial distribution in hippocampi and amygdalae, considering HS presence.

Main Results:

  • In U-MTLE, hippocampi ipsilateral to seizure onset showed higher ripple and FR rates than contralateral hippocampi.
  • Non-epileptic hippocampi in U-MTLE had significantly lower ripple rates compared to other analyzed hippocampi.
  • In hippocampi with HS, FR rates were higher in ventral than dorsal regions.

Conclusions:

  • Non-epileptic hippocampi in U-MTLE are characterized by significantly lower ripple rates.
  • Low interictal HFO occurrence could serve as a biomarker for identifying non-epileptic hippocampi in MTLE.
Keywords:
Bitemporal epilepsyHigh frequency oscillationsHippocampal sclerosisHippocampusTemporal lobe epilepsy

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