Localization of the Epileptic Focus During Methohexital‐Induced Anesthesia

Hufnagel, A.; Burr, W.; Elger, Christian E.; Nadstawek, J.; Hefner, Gerda

doi:10.1111/j.1528-1157.1992.tb02316.x

Cited by 52 publications

(11 citation statements)

References 29 publications

(45 reference statements)

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“…This has been shown in experimental cortical undercutting (3 l), functional hemispherectomy (1 8), and selective amygdalohippocampectomy (6). These spikes are not predictive of poor outcome (6,32) and are thought to arise from thalamic deafferentation, a similar mechanism to the inducement of spikes after the administration of methohexital (32,33).…”

Section: Discussionmentioning

confidence: 99%

Do Reactive Post‐Resection “Injury” Spikes Exist?

et al. 2000

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Summary:Purpose: New post-resection spikes on electrocorticography (ECoG) after lesionectomy in patients with seizures may represent residual epileptogenic tissue or presumed reactive injury spikes. We investigated the existence of postresection injury spikes by eliminating the possibility of residual epileptogenic tissue.Methods: Preresection and post-resection ECoG was performed on seven patients with an intra-axial neocortical tumor (glioblastoma multiforme or metastasis) and no history of seizures. All tumors were gross-totally resected.Results: The mean age of the patients was 59 years. The tumor location was frontal in four patients, parietal in two, and temporal in one. Two patients had preresection spikes with an average rate of 68 spikedmin that disappeared after surgery. Two different patients had new post-resection spikes, with an average firing rate of 4 spikedmin, despite normal preresection ECoG. In one of these patients, the new spikes were superimposed over a burst suppression pattern. Neither patient developed seizures after surgery.Conclusions: Surgical irritation of the neocortex is sufficient to produce reactive post-resection epileptogenic discharges surrounding an intra-axial neocortical tumor even in the absence of preoperative seizures and spikes. Injury spikes fire at a slow rate and are not predictive of clinical seizures.

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Section: Discussionmentioning

confidence: 99%

Do Reactive Post‐Resection “Injury” Spikes Exist?

et al. 2000

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“…To provide highly uniform test conditions and to facilitate the comparison with patients who did not undergo invasive investigation, memory evaluation was performed 3 months after AHE instead of immediately after IDE implantation. In the first 1-2 weeks after implantation, many clinical factors during invasive presurgical evaluation such as anesthesia, postoperative course, frequency of seizures, dose changes of anticonvulsant drugs, and focus-activation procedures did not allow comparable test conditions for all patients (23). In spite of this sensitive investigation set-up with highly uniform conditions, no alterations of verbal memory performance induced by IDEs were found.…”

Section: No Impairment Of Verbal Memory and Learningmentioning

confidence: 97%

Safety of Intrahippocampal Depth Electrodes for Presurgical Evaluation of Patients with Intractable Epilepsy

et al. 1997

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Summary:Purpose: Intracerebral depth electrodes are used in preoperative evaluation of selected patients with intractable epilepsies. In spite of their usefulness, safety of depth electrodes is disputed, and the number of insertions is decreasing. This study examined retrospectively possible deleterious effects such as perioperative complications, induction of epileptogenesis, and neuropsychologic deficits.Methods: Clinical course and neuroradiologic findings of 1 15 patients with bilaterally inserted longitudinal intrahippocampal depth electrodes (IDEs) were analyzed. Hippocampal resection specimens were examined histopathologically. To detect newly developed epileptogenic areas, EEG recordings, seizure control, and semiology after standardized resection procedures were compared between patients who received IDEs and those who did not. To demonstrate functional deficits caused by IDE insertion into an unaffected hippocampus of the speech-dominant hemisphere, changes of verbal learning and memory performances before and after right amygdalohippocampectomy were compared between patients evaluated with and without IDEs.Results: Five significant complications without any permanent neurologic deficit were noted, and only one was specifically linked to IDE insertion. The tissue damage associated with the insertion was minimal and sharply circumscribed. No differences of seizure outcome after standardized resections were identified between patients with and without IDEs. In postoperative EEG recordings, there was no evidence of new epileptogenic areas. No verbal memory deficit caused by IDE implantation into the hippocampus of the speech-dominant hemisphere was detectable.Conclusions: Results indicate that it is safe to implant these IDEs in selected patients. Key Words: Epilepsy surgerySafety-Depth electrodes-Memory-Hippocampus.Two thirds to three quarters of presurgical evaluation protocols use intracerebral depth electrodes (IDES) (1,2).The usefulness of depth electrodes has been well documented (3-10). Specifically, the aim of tailored resections with better neuropsychologic outcome demonstrates their increasing necessity (1 1,12). However, because of current budget cuts and the presumed risks, the number of depth-electrode insertions is decreasing. The main safety considerations are concerned with a higher rate of complications or with the possible induction of new epileptogenic zones. Furthermore, functional deficits may result from structural damage, especially if electrodes are inserted into a brain area that will not be resected (8,lO). All reports on safety profiles of depth electrodes have been limited to the assessment of neurologic complications and imaging findings (3,8,10,(13)(14)(15) in our series, all patients received depth electrodes inserted longitudinally into each hippocampus (Fig. 1).The hippocampus is one of the most vulnerable brain areas with respect to epileptogenesis, and its role in processing of declarative memory can be adequately measured by neuropsychological testing (1 l, 16-1 8). The...

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“…Therefore, methohexital is used as an induction agent during electroconvulsive therapy because the therapeutic benefit of this procedure is related to the quality of the seizure activity it induces (Avramov et al 1995). Low-dose methohexital is also used during cortical mapping studies to help identify seizure foci (Hufnagel et al 1992). …”

Section: Sedation and Unconsciousness: Gabaa Receptor Agonistsmentioning

confidence: 99%

General Anesthesia and Altered States of Arousal: A Systems Neuroscience Analysis

Brown

Purdon

Dort

2011

Annu. Rev. Neurosci.

449

403

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Placing a patient in a state of general anesthesia is crucial for safely and humanely performing most surgical and many nonsurgical procedures. How anesthetic drugs create the state of general anesthesia is considered a major mystery of modern medicine. Unconsciousness, induced by altered arousal and/or cognition, is perhaps the most fascinating behavioral state of general anesthesia. We perform a systems neuroscience analysis of the altered arousal states induced by five classes of intravenous anesthetics by relating their behavioral and physiological features to the molecular targets and neural circuits at which these drugs are purported to act. The altered states of arousal are sedation-unconsciousness, sedation-analgesia, dissociative anesthesia, pharmaco-logic non-REM sleep, and neuroleptic anesthesia. Each altered arousal state results from the anesthetic drugs acting at multiple targets in the central nervous system. Our analysis shows that general anesthesia is less mysterious than currently believed.

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Localization of the Epileptic Focus During Methohexital‐Induced Anesthesia

Cited by 52 publications

References 29 publications

Do Reactive Post‐Resection “Injury” Spikes Exist?

Do Reactive Post‐Resection “Injury” Spikes Exist?

Safety of Intrahippocampal Depth Electrodes for Presurgical Evaluation of Patients with Intractable Epilepsy

General Anesthesia and Altered States of Arousal: A Systems Neuroscience Analysis

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