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Methohexital (Brevital) effect on electrocorticogram may be misleading
Abstract:
Intravenous (i.v.) methohexital (MTH, Brevital) was found to have an effect on the intraoperative electrocorticogram (ECOG) of 63 patients who had temporal lobectomies performed under general anesthesia for intractable complex partial seizures. In the preresection ECOG, MTH increased the frequency of spikes in 78%, the area of cortical spiking in 30% and induced seemingly "new" spike foci in 43%. Similar although less dramatic changes occurred in the final (i.e., postresection) ECOG. Whether these changes induced by MTH, specifically the new spike foci, are significant was assessed by correlating surgical results with the presence of "residual spikes" (i.e., after all resections, not spontaneously occurring but activated by MTH). Surprisingly, nine patients with residual "MTH-spikes" did not have any postoperative seizures whereas two had some. This raises the question of whether MTH effects are significant overall. Caution is advised in the use of MTH in intraoperative assessment of interictal spike fields, especially when new spike foci are activated. Further study of the possibility of false activation, with a larger series, is advised.
Insights
Intravenous methohexital (MTH) can alter electrocorticogram (ECOG) readings during epilepsy surgery. MTH-activated spikes did not reliably predict postoperative seizures in patients undergoing temporal lobectomy.
Area of Science:
- Neurosurgery
- Epileptology
- Neurophysiology
Background:
- Intractable complex partial seizures often necessitate surgical intervention like temporal lobectomy.
- Intraoperative electrocorticography (ECOG) is used to map seizure foci.
- Methohexital (MTH) is an anesthetic agent sometimes used during epilepsy surgery.
Purpose of the Study:
- To investigate the effect of intravenous methohexital (MTH) on intraoperative electrocorticogram (ECOG) during temporal lobectomies.
- To assess the significance of MTH-induced spike changes, particularly new spike foci, in predicting surgical outcomes for intractable complex partial seizures.
Main Methods:
- ECOG recordings were analyzed in 63 patients undergoing temporal lobectomy under general anesthesia.
- The impact of intravenous methohexital (MTH) on preresection and postresection ECOG was evaluated.
- Surgical outcomes were correlated with the presence of MTH-activated 'residual spikes'.
Main Results:
- Methohexital (MTH) increased spike frequency (78%), cortical spiking area (30%), and induced new spike foci (43%) in the preresection ECOG.
- Similar, though less pronounced, changes were observed in the postresection ECOG.
- Nine patients with residual MTH-activated spikes had no postoperative seizures, while two did, indicating a weak correlation with surgical success.
Conclusions:
- Methohexital (MTH) significantly alters intraoperative ECOG findings, potentially creating false-positive indicators of seizure activity.
- Caution is advised when interpreting MTH-induced spike foci during epilepsy surgery, as they may not accurately predict seizure recurrence.
- Further research with larger patient cohorts is recommended to understand the implications of MTH-induced false activations.