Preeminence of extrahippocampal structures in the generation of mesial temporal seizures: evidence from human depth electrode recordings.

Full Abstract

PURPOSE:
To examine the intralimbic localization and morphology of mesial temporal seizure onsets and to correlate the findings with patterns of initial seizure spread and the presence or absence of clinical manifestations.

METHODS:
Eighteen patients with temporal lobe epilepsy were investigated with intracranial depth electrodes implanted in the amygdala (AM), anterior hippocampus (HP), and parahippocampal gyrus (PH). Focal and regional ictal-onset morphologies were classified as rhythmic limbic spiking <2 Hz (RLS), spike-and-wave activity >2 Hz (S/W), rhythmic polyspike activity >13 Hz (RPS), and rhythmic sharp activity <13 Hz (RS).

RESULTS:
Onset morphologies in 389 total seizures (260 regional + 129 focal) were 50% RPS, 35% RS, 11% RLS, and 4% S/W. Focal AM or HP onsets (30% and 58% of focal onsets, respectively) were more likely to show RLS, whereas RPS was more common in regional onsets. Most patients showed two or more different morphologies and focal onsets at more than one ipsilateral limbic site. Seizure propagation and clinical manifestations were significantly more common with AM or PH onsets (both 67% clinical seizures):
only 23% of focal HP onsets resulted in clinical seizures.

CONCLUSIONS:
(a) There is substantial inter- and intrapatient variability in the morphology and localization of mesial temporal seizure onsets, which suggests that the epileptogenic temporolimbic system may be conceptualized as a dynamic network containing a multiplicity of potential ictal generators; (b) Seizures beginning in the AM or PH are more likely to propagate and give rise to clinical manifestations than are focal-onset HP seizures, which suggests that inhibitory circuits within the HP may function to prevent seizure spread.

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Author information

Author/s: Wennberg, Richard (R); Arruda, Francisco (F); Quesney, Luis Felipe (LF); Olivier, André (A);

Affiliation: Montreal Neurological Institute and Hospital, Quebec, Canada.

Journal and publication information

Publication Type: Comparative Study; Journal Article

Journal: Epilepsia (Epilepsia), published in United States. (Language: eng)

Reference: 2002-Jul; vol 43 (issue 7) : pp 716-26

Dates: Created 2002/07/09; Completed 2002/08/01; Revised 2006/11/15;

PMID: 12102674, status: MEDLINE (last retrieval date: 12/26/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Amygdala - physiopathology
Electrodes, Implanted
Electroencephalography - methods; statistics & numerical data
Epilepsy, Temporal Lobe - diagnosis; physiopathology
Female
Hippocampus - physiopathology

Humans
Limbic System - physiopathology
Male
Neural Pathways - physiopathology
Parahippocampal Gyrus - physiopathology
Stereotaxic Techniques
Temporal Lobe - physiopathology

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