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. 2013 Apr 13:1:56-61.
doi: 10.1016/j.ebcr.2013.03.003. eCollection 2013.

Hippocampal seizure-onset laterality can change over long timescales: A same-patient observation over 500 days

Otis Smart  1 , John D Rolston  2 , Charles M Epstein  3 , Robert E Gross  4
Affiliations

Hippocampal seizure-onset laterality can change over long timescales: A same-patient observation over 500 days

Otis Smart et al. Epilepsy Behav Case Rep. .

Abstract

This study describes seizure laterality and localization changes over 500 consecutive days in a patient with bilateral temporal lobe epilepsy (BTLE) and implanted NeuroPace RNS™ System. During a continuous two-year time period, the RNS™ device stored 54 hippocampal electrocorticography (ECoG) seizures, which we analyzed to determine their distribution and time variance across hippocampi. We report nonrandom long-term seizure laterality and localization variations, especially in the first 200 days postimplant, despite equivalent total seizure counts in both hippocampi. This case suggests that hippocampal seizures dynamically progress over extensive timescales.

Keywords: Electrocorticography; Epilepsy; Laterality; Neurostimulation; Seizure; Shifting.

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Figures

Fig. 1
Fig. 1
Image coregistration after device implantation. (A) The pulse generator is affixed within a ferrule in the skull and attached to the leads in the brain (not visible) by an insulated electrical conductor that is tunneled under the scalp. (B–I) Implanted electrodes in coronal view of coregistration where each aspect is orthogonal to the long axis of the hippocampus.
Fig. 1
Fig. 1
Image coregistration after device implantation. (A) The pulse generator is affixed within a ferrule in the skull and attached to the leads in the brain (not visible) by an insulated electrical conductor that is tunneled under the scalp. (B–I) Implanted electrodes in coronal view of coregistration where each aspect is orthogonal to the long axis of the hippocampus.
Fig. 2
Fig. 2
Intraoperative (A–E) and extraoperative (F–G) recordings from both hippocampi. (A) Left and (B) right hippocampal action potentials (APs). (C) Left side with interictal spikes and (D) right side without interictal spikes. (E) Left interictal spikes (red) coincided with multiunit AP bursts (black). (F) The 1st and (G) 54th ECoG seizures with L1 and R1 SOZs, respectively (arrow). The RNS™ delivers therapy upon seizure detection (vertical line).
Fig. 3
Fig. 3
Tracking (A, C), tallying (B, D), and clustering (E–F) the ECoG seizures. Tracking the SOZ laterality (A, B) and localization (C, D) shows shifts from the left (L1 and L2) to the right (R1 and R2) side over daily (A, C) and monthly (B, D) timescales for the seizures (black asterisk) unrelated to changes in RNS™ detection or stimulation parameters (solid vertical lines). Total seizure preponderance does not indicate lateralization (A) but may indicate localization (C). (E) Seizure clusters mostly occur within a week, where (F) time between consecutive seizures models a negative binomial distribution.
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