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Ictal spikes: a marker of specific hippocampal cell loss
S S Spencer1, J Kim, D D Spencer
1Department of Neurology, Yale University School of Medicine, New Haven, CT 06510.
Abstract:
Spontaneous seizures recorded from mesial temporal depth electrodes in the human are commonly manifested by one of two onset patterns: a high frequency discharge or a periodic spike discharge morphologically similar but clearly distinguished from ongoing interictal activity. We categorized medial temporal lobe seizure onset for the presence of periodic ictal spikes at a frequency of less than 2 Hz lasting for more than 5 sec to investigate the relationship of this ictal pattern to anatomical changes in the resected temporal lobe tissue. Fifty-one patients had hippocampal depth electrode recordings of spontaneous seizures, subsequent hippocampal resection, and quantitative cell counts of hippocampal subfields. Thirty-two of these patients had ictal spikes lasting at least 5 sec in more than 50% of their seizures. The presence of ictal spikes was significantly correlated with decreased cells in CA1 only (P = 0.015). The correlation of a common ictal pattern with focal cell loss in the hippocampus suggests that electrophysiological manifestations of seizures provide a clue to the underlying pathological substrate. Ictal spikes may be a cause or result of the cell loss. These observations should be correlated with independent investigations in humans and animal models that reflect the CA1 cell loss associated with temporal lobe epilepsy.
Insights
Periodic ictal spikes during seizures correlate with CA1 cell loss in temporal lobe epilepsy. This finding links seizure patterns to underlying brain pathology, aiding epilepsy research.
Area of Science:
- Neuroscience
- Epileptology
- Neuropathology
Background:
- Spontaneous seizures in mesial temporal lobe epilepsy often present with distinct onset patterns, including periodic ictal spikes.
- Understanding the relationship between seizure electrophysiology and underlying anatomical changes is crucial for epilepsy research.
Purpose of the Study:
- To investigate the association between periodic ictal spike patterns during seizures and specific anatomical changes in resected temporal lobe tissue.
- To determine if the presence of ictal spikes correlates with cell loss in hippocampal subfields.
Main Methods:
- Analysis of hippocampal depth electrode recordings from 51 patients with spontaneous mesial temporal lobe seizures.
- Categorization of seizure onset patterns based on periodic ictal spikes (< 2 Hz, > 5 sec).
- Quantitative cell counting in hippocampal subfields following surgical resection.
Main Results:
- Thirty-two patients exhibited periodic ictal spikes in over 50% of their seizures.
- The presence of ictal spikes significantly correlated with reduced cell counts specifically in the CA1 hippocampal subfield (P = 0.015).
- No significant correlation was found with other hippocampal subfields.
Conclusions:
- The observed correlation between periodic ictal spikes and CA1 cell loss suggests a link between seizure manifestation and neuropathology in temporal lobe epilepsy.
- Ictal spike patterns may serve as an electrophysiological marker for focal hippocampal pathology, potentially indicating cause or consequence of cell loss.
- Further research in human and animal models is warranted to elucidate the role of CA1 cell loss in temporal lobe epilepsy.