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We describe EEG changes in three patients in whom the carotid sinus baroreflex was precipitated during carotid endarterectomy. In all instances, the EEG showed diffuse attenuation and slowing of the baseline anesthetic pattern in association with bradyvcardia. This can help alert the surgeon to the changes occurring as a result of the cardioinhibitory carotid sinus baroreflex and guide appropriate timely intervention. [ABSTRACT FROM AUTHOR]

Since the term periodic lateralized epileptiform discharges (PLEDs) was first coined by Chatrian et al. in 1964, there has been an evolution of terms used to describe variants of this EEG pattern. This article is an attempt to collect and define various terms used to describe these patterns. [ABSTRACT FROM AUTHOR]

Sevoflurane is a volatile anesthetic commonly used for the induction and maintenance of anesthesia. We present the case of a 34-year-old woman in whom generalized periodic epileptiform discharges developed during induction of anesthesia with sevoflurane. Although sevoflurane anesthesia can be associated with the development of epileptiform discharges, the clinical relevance of this is unclear. [ABSTRACT FROM AUTHOR]

Objectives: To determine the surgical outcome and prognostic factors in adult patients with intractable epilepsy and focal cortical dysplasia (FCD)., Materials and Methods: We retrospectively studied the operative outcome in 21 consecutive adult patients with FCD who underwent surgical treatment for intractable partial epilepsy., Results: The mean age at surgery was 32.7 years (range, 18-58 years). The median post-operative follow-up was 2.5 years. The FCD was extratemporal in 11 patients, involved the temporal lobe in 10 patients, and was multilobar in eight patients. Eleven patients (52%) were rendered seizure-free, four patients (19%) had >95% reduction in seizures, and two patients (10%) had an 80-94% reduction in seizures. A seizure-free outcome was associated with shorter duration of epilepsy (P = 0.02)., Conclusion: Adult patients with FCD may be candidates for surgical treatment of intractable partial epilepsy. Most individuals have neocortical, extrahippocampal seizures and approximately 50% of patients are rendered seizure-free.

Objective: To determine the surgical outcome and factors of predictive value in patients undergoing reoperation for intractable partial epilepsy., Methods: The authors retrospectively studied the operative outcome in 64 consecutive patients who underwent reoperation for intractable partial epilepsy. Demographic data, results of comprehensive preoperative evaluations, and the seizure and neurologic outcome after reoperation were determined. All patients were followed a minimum of 1 year subsequent to their last operative procedure., Results: Fifty-three patients had two surgeries, and 11 patients had three or more operations. The first surgery involved a lesionectomy (n = 33), "nonlesional" temporal lobe resection (n = 28), and a "nonlesional" extratemporal resection (n = 3). The mean duration between the first and second procedure was 5.5 years. Fifty-five patients underwent an intralobar reoperation, whereas nine had a resection of a different lobe. After reoperation, 25 patients (39%) were free of seizure, 6 patients (9%) had rare seizures, 12 patients (19%) had a worthwhile improvement, and 21 patients (33%) failed to respond to surgery. Predictors of seizure-free outcome were age at seizure onset >15 years (p = 0.01), duration of epilepsy < or =5 years at the time of initial surgery (p = 0.03), and focal interictal discharges in scalp EEG (p = 0.03). Using a logistic regression model, two significant predictors emerged: duration of epilepsy < or =5 years (odds ratio, 3.18; p = 0.04) and preoperative focal interictal discharge (odds ratio, 4.45; p = 0.02). Complications of reoperation included visual field deficits (n = 9), wound infection (n = 2), subdural hematoma (n = 1), and hemiparesis (n = 1)., Conclusion: Reoperation may be an appropriate alternative form of treatment for selected patients with intractable partial epilepsy who fail to respond to initial surgery.

Principal component analysis (PCA) can separate multichannel electroencephalographic (EEG) epochs into linearly independent (temporally and spatially noncorrelated) components. Results of PCA include component time-series waveforms and factors representing the contribution of each component to each electrode; these factors may be displayed as contour maps representing the topographic distribution of each component. However, PCA often does not achieve the most useful separation of components. PCA may be performed in the frequency domain to potentially improve results. After inspecting principal components of the frequency spectra, spectral values in a selected frequency range are multiplied by a chosen factor to emphasize (or de-emphasize) these frequencies and PCA is redone, promoting the separation of different frequencies into different components. Phase-encoded Fourier spectral analysis (PEFSA) uses multichannel complex Fourier spectra (amplitude and phase) to obtain positive or negative (phase-encoded) potentials at each electrode for any selected frequency. These may be displayed as a contour map representing the topographic distribution of the selected frequency. Applying both techniques, we found that EEG activities of differing frequency were readily separated by PEFSA, while standard PCA often mixed activities with different frequencies into a single component. However, frequency-domain PCA gave a component whose spatial distribution well matched PEFSA results. PCA is superior to PEFSA for separating activities with overlapping frequencies but differing spatial distributions. Preservation of phase information is an advantage of PEFSA and PCA over topographic maps that represent only amplitude (or power) at a given frequency. PCA or PEFSA maps can serve as a starting point for source localization.

Purpose: To determine the extent to which periictal subtraction single-photon emission computed tomography (SPECT) may improve detection and definition of the epileptogenic zone in patients with focal malformations of cortical development (MCDs)., Methods: Subtraction SPECT coregistered to magnetic resonance (MR) images (SISCOM) were constructed for 22 consecutive patients with focal MCDs who underwent periictal SPECT injection (18 ictal and four postictal). In the 17 patients who had epilepsy surgery, concordance between the site of SISCOM localization and site of surgical resection was determined by coregistration of SISCOM images with postoperative MRIs., Results: SISCOM images were localizing in 19 (86%) patients, including eight of the 10 with nonlocalizing MRI. Concordance of SISCOM localization was 91% with MRI localization, 93% with scalp ictal EEG localization, and 100% with intracranial EEG localization. Eight patients whose SISCOM localization was concordant with the surgical resection site had lower postoperative seizure frequency scores (SFSs; p = 0.04) and greater postoperative improvement in SFSs (p = 0.05) than the nine patients whose SISCOM was either nonconcordant or nonlocalizing. On multiple regression analysis, a model combining SISCOM concordance with surgical resection site and extent of MRI lesion resection was predictive of postoperative SFS (R2 = 0.47; p = 0.03)., Conclusions: Periictal subtraction SPECT using the SISCOM technique provides useful information for seizure localization in patients with focal MCDs, even when MRI is nonlocalizing.

The authors developed a general mathematic algorithm to convert any montage (referential, bipolar, or Laplacian) to any other by linear transformation. Input and output montages are described by matrices, and singular value decomposition is used to find the linear transformation. An error signal can be calculated from the input data to monitor remontaging validity. This algorithm also identifies output channels that cannot be obtained from the specified input. The authors tested this algorithm using an instrument that retrieves digitally encoded EEG data from videotape and produces signals in referential or bipolar form. They obtained good agreement when they compared referential and Laplacian data derived from bipolar output with the same montages calculated from referential output for the same EEG segment.

Temporal lobectomy is an effective treatment for medically intractable seizures. The change in seizure status with prolonged postoperative follow-up is unclear. The authors followed 37 patients who underwent first time temporal lobectomy during childhood for at least 15 years. This study is the longest follow-up of children who have had a temporal lobectomy for intractable seizures. It demonstrates that seizure recurrence can increase with longer duration of follow-up.

Ictal vomiting is considered a localizing sign indicating nondominant lateralization in patients with partial seizures of temporal lobe origin. We report a case of ictal vomiting associated with left temporal seizure activity in a left hemisphere language-dominant patient with a left mesial temporal glioma. Bilateral mesial temporal depth electrodes helped verify seizure lateralization. Surgery consisting of tumor resection and a left anterior temporal lobectomy and amygdalohippocampectomy resulted in freedom from seizures and episodes of vomiting. This case indicates that ictal vomiting can occur as a manifestation of left temporal onset seizures in left hemisphere-dominant patients.

Purpose: High-dose i.v. opioids (e.g., alfentanil, 50 microg/kg bolus) are known to increase the intraoperative reading of epileptiform activity during epilepsy surgery (ES), thereby facilitating localization of the epileptogenic zone (i.e., the site of ictal onset and initial seizure propagation). However, this phenomenon has not been studied with remifentanil (i.e., a novel ultra-short acting opioid). The purpose of the present study was to evaluate the effect of remifentanil on electrocorticography (ECoG) during ES., Methods: After Institutional Review Board approval, 25 adult patients undergoing elective ECoG-guided anterior temporal corticectomy were enrolled. At the time of ECoG, anesthesia consisted of inhaled isoflurane < or =0.1% (end-tidal) in 50% N2O, and i.v. fentanyl, 2 microg/kg/h and vecuronium. Patients were maintained at normocapnia and normoxia during ECoG. After acquisition of baseline ECoG, bolus remifentanil, 2.5 microg/kg i.v., was administered. The number of epileptiform spikes occurring 5 min before and after this bolus were compared by using a one-sided sign test; p values < or =0.05 were considered statistically significant., Results: When compared with baseline ECoG, bolus i.v. remifentanil significantly increased the frequency of single spikes or repetitive spike bursts in the epileptogenic zone while suppressing activity in surrounding normal brain., Conclusions: During ES, remifentanil enhanced epileptiform activity during intraoperative ECoG. Such observations facilitate localization of the epileptogenic zone while minimizing resection of nonepileptogenic eloquent brain tissue. Although not specifically evaluated in this study, we speculate that remifentanil's short elimination half-life will facilitate neurologic function testing immediately after ES. Should this be the case, we envision remifentanil has the potential to supplant other opioids (e.g., alfentanil) during ECoG-guided ES.

Purpose: We investigated the relationship between preoperative quantitative magnetic resonance imaging (MRI) T2 relaxometry and volumetry of the hippocampi and pre- and postoperative verbal memory in temporal lobectomy patients who had nonlesional temporal lobe epilepsy., Methods: Pre- and postoperative memory data based on the Logical Memory (LM) subtest of the Wechsler Memory Scale-Revised (WMS-R) and the 30-min delayed recall trial of the Rey Auditory Verbal Learning Test (AVLT) were obtained from 26 left and 15 right temporal lobectomy patients. Coronal MRI T2 maps were generated for these 41 temporal lobectomy patients as well as 61 control patients. Hippocampal T2 relaxation times and hippocampal volumes, converted to z scores using control group data, were correlated with neuropsychological performance in the patients., Results: In left temporal lobe-onset patients, high T2 in the left hippocampal body predicted higher LM performance after surgery. Asymmetrically high T2 in the left hippocampal body (i.e., the right-minus-left difference), compared with the right hippocampal body, also predicted higher LM performance after surgery. In right temporal lobe-onset patients, high T2 in the left hippocampal body predicted relatively lower AVLT performance after surgery. Multiple regression analysis in left temporal-onset patients revealed that high T2 in the left hippocampal body together with higher preoperative LM performance predict higher postoperative LM performance., Conclusions: Our findings suggest that elevated (i.e., abnormal) hippocampal T2 signal is associated with memory ability (or hippocampal functional capacity) independent of MRI-determined hippocampal atrophy. Therefore, our findings support the use of quantitative T2 relaxometry as an independent predictor of verbal memory outcome in both left and right TLE patients who are candidates for temporal lobectomy.

Objectives: To determine whether localization of extratemporal epilepsy with subtraction ictal SPECT coregistered with MRI (SISCOM) is predictive of outcome after resective epilepsy surgery, whether SISCOM images provide prognostically important information compared with standard tests, and whether blood flow change on SISCOM images is useful in determining site and extent of excision required., Background: The value of SISCOM in predicting surgical outcome for extratemporal epilepsy is unknown, especially if MRI findings are nonlocalizing., Methods: SISCOM images in 36 consecutive patients were classified by blinded reviewers as "localizing and concordant with site of surgery," "localizing but nonconcordant with site of surgery," or "nonlocalizing." SISCOM images were coregistered with postoperative MRI, and reviewers visually determined whether cerebral cortex underlying the SISCOM focus had been completely resected, partially resected, or not resected., Results: Twenty-four patients (66.7%) had localizing SISCOM, including 13 (76.5%) of those without a focal MRI lesion. Eleven of 19 patients (57.9%) with localizing SISCOM concordant with the surgical site, compared with 3 of 17 (17.6%) with nonlocalizing or nonconcordant SISCOM, had an excellent outcome (p < 0.05). With logistic regression analysis, SISCOM findings were predictive of postsurgical outcome, independently of MRI or scalp ictal EEG findings (p < 0.05). The extent of resection of the cortical region of the SISCOM focus was significantly associated with the rate of excellent outcome (100% with complete resection, 60% with partial resection, and 20% with nonresection, p < 0.05)., Conclusion: SISCOM images may be useful in guiding the location and extent of resection in extratemporal epilepsy surgery.

Objective: To analyze the clinical and EEG findings of patients with multifocal periodic lateralized epileptiform discharges (PLEDs)., Methods: EEGs containing multifocal PLEDs (3 or more foci of PLEDs) were reviewed. Thirty-five patients (15 males and 20 females), from 2.5 months to 91 years old, met the criteria for multifocal PLEDs., Results: The disease processes identified in the patients included vascular lesions in 9, central nervous system infections in 7, metabolic/toxic disorders in 6, exacerbation of a chronic seizure disorder in 6, hypoxic ischemic insults in 3, and fat embolism, paraneoplastic encephalitis, cerebral metastasis, and multiple sclerosis in one each. Twenty patients died. Detection of the spatiotemporal distribution of multifocal PLEDs was facilitated by the use of Laplacian montages., Conclusions: Multifocal PLEDs were recorded in 35 patients and were associated with processes resulting in diffuse or multifocal cerebral dysfunction. Multifocal PLEDs indicate a significant disturbance of cerebral function and are associated with a mortality rate of 57%.

Purpose: To identify factors that predict the outcome in seizure control after frontal lobe epilepsy surgery (FLES). FLES is the second most frequent type of epilepsy surgery, but the results are generally not as good as those after anterior temporal lobectomy., Methods: Our cohort consisted of 68 consecutive patients whose first epilepsy surgery involving the frontal lobe occurred between 1987 and 1994. Clinical history and results of imaging and electroencephalographic studies were reviewed in detail. Excellent outcome was defined as being seizure free or having only nondisabling seizures at last follow up., Results: Forty of the 68 patients (58.8%) had an excellent outcome; none of the patients with a history of childhood febrile seizures had an excellent outcome, whereas outcome was excellent in 63% of those without that history (p

Patients with medically intractable partial epilepsy and well-defined symptomatic MRI lesions were studied using phase-encoded frequency spectral analysis (PEFSA) combined with low-resolution electromagnetic tomography (LORETA). Ten patients admitted to the epilepsy monitoring unit with MRI-identified lesions and intractable partial epilepsy were studied using 31-electrode scalp EEG. The scalp electrodes were located in three-dimensional space using a magnetic digitizer and coregistered with the patient's MRI. PEFSA was used to obtain a phase-encoded scalp map for the ictal frequencies. The ictal generators were obtained from the scalp map using LORETA. In addition, the generators of interictal epileptogenic spikes were identified using time-domain LORETA. The LORETA generators were rostral to the MRI lesion in 87% (7/8) of patients with temporal lobe lesions, but all were located in the mesial temporal lobe in concordance with the patients' MRI lesions. In patients with frontal lobe epilepsy, the ictal generators at the time that the spectral power was maximal localized to the MRI lesions. Eight of 10 patients had interictal spikes, of which 4 were bilateral independent temporal lobe spikes. Only generators of the interictal spikes that were ipsilateral to seizure onset correlated with the ictal generators. LORETA combined with PEFSA of the ictal discharge can localize ictal EEG discharges accurately and improve correlation with brain anatomy by allowing coregistration of the ictal generator with the MRI. Analysis of interictal spikes was less useful than analysis of the ictal discharge.

Background: Activation of autonomic nervous system is common with seizures. No reliable biological markers of impending seizures have been found. Evaluation of autonomic changes might help elucidate the transition from interictal to ictal states., Methods: We studied twelve patients (eight females, four males), from 19 to 62 years old with temporal lobe complex partial seizures (CPS). Dynamics of autonomic functions from oscillations in R-R interval (RRI) using time-frequency mapping based upon a Wigner distribution during pre-ictal, ictal and post-ictal periods. Oscillations in RRI at respiratory frequencies (RF) (> 0.1 Hz) are parasympathetically mediated and at nonrespiratory frequencies (NONRF) (0.01-0.09 Hz) are under combined sympathetic and parasympathetic influence., Results: CPS evoked marked autonomic imbalance and tachycardia. Spectral powers at both RF&#95;RRI and NONRF&#95;RRI increased over the pre-ictal period. RF&#95;RRI power then fell rapidly over the 30 s before seizure onset and remained markedly reduced during seizure (P < 0.004). NONRF&#95;RRI power reached a maximum at seizure onset and declined to a minimum before the seizure cessation (P < 0.05)., Conclusion: Time-frequency analysis revealed that autonomic activation hallmarks clinical seizure onset for several minutes. After combined parasympathetic and sympathetic activation, rapid parasympathetic withdrawal occurred approximately 30 s before the seizure, and sympathetic activation peaks at seizure onset. Therefore, the transition from interictal to ictal states is relatively long and associated with subclinical autonomic changes.

Background and Purpose: Presurgical sensorimotor mapping with functional MR imaging is gaining acceptance in clinical practice; however, to our knowledge, its therapeutic efficacy has not been assessed in a sizable group of patients. Our goal was to identify how preoperative sensorimotor functional studies were used to guide the treatment of neuro-oncologic and epilepsy surgery patients., Methods: We retrospectively reviewed the medical records of 46 patients who had undergone preoperative sensorimotor functional MR imaging to document how often and in what ways the imaging studies had influenced their management. Clinical management decisions were grouped into three categories: for assessing the feasibility of surgical resection, for surgical planning, and for selecting patients for invasive functional mapping procedures., Results: Functional MR imaging studies successfully identified the functional central sulcus ipsilateral to the abnormality in 32 of the 46 patients, and these 32 patients are the focus of this report. In epilepsy surgery candidates, the functional MR imaging results were used to determine in part the feasibility of a proposed surgical resection in 70% of patients, to aid in surgical planning in 43%, and to select patients for invasive surgical functional mapping in 52%. In tumor patients, the functional MR imaging results were used to determine in part the feasibility of surgical resection in 55%, to aid in surgical planning in 22%, and to select patients for invasive surgical functional mapping in 78%. Overall, functional MR imaging studies were used in one or more of the three clinical decision-making categories in 89% of tumor patients and 91% of epilepsy surgery patients., Conclusion: Preoperative functional MR imaging is useful to clinicians at three key stages in the preoperative clinical management paradigm of a substantial percentage of patients who are being considered for resective tumor or epilepsy surgery.

Purpose: To determine the factors associated with changes in seizure control during the postsurgical course of epilepsy surgery patients., Methods: Evaluation of patients after consecutive temporal and frontal resection whose seizure frequency was scored for each year of postsurgical follow-up. In each cohort, patients with a change in their seizure control after the first postsurgical year were compared with control subjects to determine factors that may be responsible for the change., Results: Thirty-three (15%) of 214 temporal lobectomy versus 12 (20%) of 59 frontal resection patients experienced a change in seizure control (p>0.05). Ten (5%) of 214 temporal lobectomy versus nine (15%) of 59 frontal resection patients experienced an improvement in seizure control (p = 0.009), but 23 (11%) of 214 temporal lobectomy versus three (5%) of 59 frontal resection patients had a worsening in seizure control (p>0.05). In temporal lobectomy patients, preoperative unilateral temporal epileptiform discharges were associated with improvement (p = 0.03), whereas older age at surgery was associated with worsening of seizure control (p = 0.007). In frontal resection patients, presence of a congenital central nervous system (CNS) anomaly was associated with late improvement in seizure control (p = 0.006)., Conclusion: During the postsurgical course, an improvement in seizure control is more common after frontal resection than after temporal lobectomy. Factors associated with improvement are the presence of a congenital CNS abnormality in frontal resection patients, and the occurrence of preoperative unilateral epileptiform discharges in temporal lobectomy patients. Older age at temporal lobectomy may be associated with greater risk of worsening seizure control.

Objective: To determine whether the detection of focal hypoperfusion by subtraction SPECT co-registered to MRI (SISCOM) improves the sensitivity and specificity of postictal SPECT in intractable partial epilepsy., Background: Postictal SPECT injections are easier to perform than are ictal injections, but the images are more difficult to interpret and have been reported to have lower sensitivity and specificity., Methods: Thirty-five consecutive intractable partial epilepsy patients who had postictal SPECT studies were evaluated. The following sets of SPECT images were separately interpreted by three blinded reviewers and classified as either localizing to 1 of 16 possible sites in the brain or as nonlocalizing: unsubtracted postictal and interictal images for conventional side-by-side comparison, SISCOM images of hyperperfusion, SISCOM images of hypoperfusion, and both sets of SISCOM hyperperfusion and hypoperfusion images (combined SISCOM evaluation)., Results: Significantly higher proportions of the hyperperfusion SISCOM images (65.7%), the hypoperfusion SISCOM images (74.3%), and the combined SISCOM evaluation (82.9%) were localizing than were the conventional method of side-by-side comparison of unsubtracted images (31.4%; p < 0.0001). Concordance with the discharge diagnosis was higher for the combined SISCOM evaluation than it was for either the hyperperfusion or the hypoperfusion SISCOM images alone (both p < 0.05). For the hypoperfusion SISCOM and the combined SISCOM evaluations, concordance of the localization with the site of epilepsy surgery was associated with a greater probability of an excellent outcome than were nonconcordant/nonlocalizing images (both p < 0.05)., Conclusion: The use of SISCOM to detect focal cerebral hypoperfusion, in addition to focal hyperperfusion, improves the sensitivity and specificity of postictal SPECT in intractable partial epilepsy.

Purpose: To evaluate the diagnostic yield and identify predictive factors of the surgical outcome in patients with intractable partial epilepsy undergoing chronic intracranial EEG monitoring (CIEM)., Methods: The clinical, magnetic resonance imaging (MRI) and electrophysiologic data of 108 patients that underwent CIEM were retrospectively reviewed. The discharge pattern and spatial extent of the initial ictal discharge were determined by blinded visual inspection and computerized analysis., Results: The main predictive indicator for epilepsy surgery outcome in patients that underwent CIEM was the presurgical MRI findings. Most patients with hippocampal atrophy or complete lesionectomy were rendered seizure free after epilepsy surgery (83 and 80%, respectively), whereas only a small minority of patients with partial lesionectomy or no detected MRI lesion had seizure-free operative outcomes (21 and 22%, respectively). Multifocal independent initiation of the initial ictal discharge was associated with a poor surgical outcome. In contrast, the pattern and local spatial extent of the initial ictal discharge observed with CIEM failed to predict the surgical outcome., Conclusions: The main predictor of the surgical outcome in patients that underwent CIEM was the MRI findings, whereas CIEM had only limited use in localizing the epileptogenic zone in the absence of an MRI lesion. The reported findings indicate a low specificity of CIEM in defining the site of seizure onset, which in turn significantly impairs the reliability of CIEM in delineating the epileptogenic zone for epilepsy surgery. Further studies are required to define the indications and patient subpopulations who can benefit from CIEM before epilepsy surgery.

Previous descriptions of the subclinical rhythmic electrographic discharges of adults (SREDA) have been based entirely on visual analysis of analog electroencephalographic (EEG) recordings. The introduction of digital electroencephalograms (EEGs) and advances in digital signal processing provide an opportunity to restudy in more depth the nature of SREDA. We identified nine patients who had SREDA diagnosed on a routine EEG recording since the introduction of digital EEG to our laboratory in August 1995. Following careful rereview using standard montages, six of these patients were determined to fulfill the traditional requirements for the diagnosis of SREDA, whereas three were believed to have other benign discharges. Review with Laplacian montages demonstrated that the site of the SREDA activity was maximal in the parietal region or parietocentrotemporal regions, whereas it was maximal in the temporal or frontotemporal regions in the non-SREDA discharges. Frequency analysis, using both the conventional fast Fourier transform (FFT) and time-frequency mapping with the Wigner FFT variant, demonstrated that the SREDA consisted of a complex mixture of multiple rapidly shifting frequencies which showed little spatial and temporal correlation. In contrast, the non-SREDA all consisted of a single dominant well-organized rhythmic frequency spectrum that remained stable throughout space and time.

Objective: To identify presurgical and postsurgical factors that are independently predictive of the outcome of anterior temporal lobectomy (ATL) for intractable epilepsy., Background: There have been reports of prognostic factors in epilepsy surgery, but little is known about factors that independently predict outcome of ATL., Methods: We studied 175 consecutive ATL patients who had at least 2 years of postsurgical follow-up. Significant factors on univariate analyses were subjected to stepwise logistic regression analysis., Results: On univariate analyses, two presurgical conditions were significantly associated with excellent seizure control at last follow-up: (1) unilateral hippocampal formation atrophy as detected on MRI and (2) all scalp interictal epileptiform discharges concordant with the location of ictal onset (p < 0.05). Three postsurgical factors that occurred during the first year were associated with excellent seizure outcome: the absence of interictal epileptiform discharges at 3 months, complete seizure control, and having only nondisabling seizures for those who did not become seizure free. Logistic regression analysis revealed the following to be independently predictive of excellent seizure control: MRI-detected unilateral hippocampal formation atrophy, concordant interictal epileptiform discharges, complete seizure control during the first postsurgical year, and having only nondisabling seizures during the first postsurgical year for those who did not become seizure free., Conclusions: Presurgical identification of unilateral hippocampal formation atrophy, or of interictal epileptiform discharges that are all concordant with the location of ictal onset, predict excellent outcome of ATL. However, the probability of excellent outcome is highest (94%) when both factors are present.

Scalp-recorded EEG is a noninvasive and widely available tool for studying normal and dysfunctional human neurophysiology with unsurpassed temporal resolution. However, scalp-recorded EEG data is difficult to correlate with anatomy, and most current display and neural source estimation algorithms are based on unrealistic spherical or elliptical models of the head. It is possible to measure the positions of electrodes on the patient's scalp, and to register those electrode positions into the space of a high-resolution MRI volume, and to then use the patient-specific anatomy as the basis for display and estimation of neural sources. We use a surface matching algorithm to register digitized electrode and scalp surface coordinates to a three-dimensional MRI volume. This study uses fiducial markers in phantom and volunteer studies to quantitatively estimate the accuracy of the electrode registration method. Our electrode registration procedure is accurate to 2.21 mm for a realistic head phantom and accurate to 4.16 mm on average for five volunteers. This level of accuracy is considered within acceptable limits for clinical applications.

Purpose: To compared the ictal discharge patterns between local onset and remote propagated electrographic seizures recorded with chronic intracranial electrodes., Methods: The electrophysiological data from 88 consecutive patients who underwent chronic intracranial EEG monitoring were retrospectively reviewed. The early and late discharge patterns of electrographic seizures at local onset and distant propagated sites were determined by blinded visual inspection and computerized analysis., Results: Four early and three late electrographic seizure patterns were observed at the local onset sites. The four early patterns consisted of a rhythmic discharge in the beta range ("beta buzz"), rhythmic alpha-theta activity, rhythmic sharp waves in the delta range, and an irregular spike discharge. The three distinct late-discharge patterns consisted of a late beta buzz, rhythmic sharp theta activity, and a rhythmic polyspike and wave discharge. At remote propagated sites, electrographic seizures could be divided into two different types according to their early discharge pattern. The first was unique to remote propagated electrographic seizures and consisted of a rhythmic theta-delta activity correlated with the concurrent activity at the local-onset site. The second remote initiation type consisted of patterns indistinguishable from the earlier discharge patterns recorded at the local onset site., Conclusions: The initial ictal discharge pattern recorded with intracranial electrodes can assist in differentiating local onset and remote propagated electrographic seizures, with rhythmic round theta-delta activity being unique to distant propagated sites. Nevertheless, the initial discharge of a subclass of remote propagated electrographic seizures consists of an independent pattern indistinguishable from that observed at local onset sites.

Background: Carotid endarterectomy necessitates temporary unilateral carotid artery occlusion. Critical regional cerebral blood flow (rCBF) has been defined as the rCBF below which electroencephalographic (EEG) changes of ischemia occur. This study determined the rCBF50, the rCBF value at which 50% of patients will not demonstrate EEG evidence of cerebral ischemia with carotid cross-clamping., Methods: Fifty-two patients undergoing elective carotid endarterectomy were administered 0.6-1.2% (0.3-0.6 minimum alveolar concentration) sevoflurane in 50% nitrous oxide (N2O). A 16-channel EEG was used for monitoring. The washout curves from intracarotid 133Xenon injections were used to calculate rCBF before and at the time of carotid occlusion by the half-time (t(1/2)) technique. The quality of the EEG with respect to ischemia detection was assessed by an experienced electroencephalographer., Results: Ischemic EEG changes developed in 5 of 52 patients within 3 min of carotid occlusion at rCBFs of 7, 8, 11, 11, and 13 ml x 100 g(-1) x min(-1). Logistic regression analysis was used to calculate an rCBF50 of 11.5 +/- 1.4 ml x 100 g(-1) x min(-1) for sevoflurane. The EEG signal demonstrated the necessary amplitude, frequency, and stability for the accurate detection of cerebral ischemia in all patients within the range of 0.6-1.2% sevoflurane in 50% N2O., Conclusions: The rCBF50 of 0.6-1.2% sevoflurane in 50% N2O, as determined using logistic regression analysis, is 11.5 +/- 1.4 ml 100 g(-1) x min(-1). Further, in patients anesthetized in this manner, ischemic EEG changes due to carotid occlusion were accurately and rapidly detected.

Traditional side-by-side visual interpretation of ictal and interictal single-photon emission computed tomography (SPECT) scans can be difficult in identifying the surgical focus, particularly in patients with extratemporal or otherwise unlocalized intractable epilepsy. Computer-aided subtraction ictal SPECT co-registered to MRI (SISCOM) may improve the clinical usefulness of SPECT in localizing the surgical seizure focus. We studied 51 consecutive intractable partial epilepsy patients who had interictal and ictal scans. The SPECT studies were blindly reviewed and classified as either localizing to 1 of 16 sites in the brain or as nonlocalizing. SISCOM images were localizing in 45 of 51 (88.2%) compared with 20 of 51 (39.2%) for traditional side-by-side inspection of ictal and interictal SPECT images (p < 0.0001). Inter-rater agreement for two independent reviewers was better for SISCOM (84.3% versus 41.2%, kappa = 0.83 versus 0.26; p < 0.0001). Concordance of seizure localization with the more established tests was also higher for SISCOM. Late injection of the radiotracer (> 45 seconds), but not secondary generalization of the seizure, was associated with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with the surgical site were more likely to have excellent outcome than patients with nonconcordant or nonlocalizing findings (62.5% [10/16] versus 20% [2/10]; p < 0.05). On the other hand, seizure localization by the traditional method of SPECT inspection had no significant association with postsurgical outcome. We conclude that SISCOM improves the sensitivity and the specificity of SPECT in localizing the seizure focus for epilepsy surgery. Concordance between SISCOM localization and site of surgery is predictive of postsurgical improvement in seizure outcome.

Medical records were reviewed for 94 consecutive inpatients diagnosed with nonepileptic seizures. A 122-item follow-up questionnaire was returned by 71 patients (76%). The majority of the subjects reported fewer seizures (73%), their general health as "very good" (20%) or "good" (37), and "improved" quality of life (55%). Many patients had either discontinued (50%) or reduced (17%) use of anticonvulsant medications. The patients most often sought care from primary care providers (46%), followed by psychiatrists/psychologists (41%) and neurologists (31%). Of the 57 patients (80%) advised to seek psychiatric care, 27 individuals (47%) followed this recommendation.

Purpose: Because focal encephalomalacia is an important cause of medically intractable partial epilepsy and few studies have evaluated the efficacy and the safety of resecting focal-encephalomalacias to improve seizure control, we studied a cohort of 17 consecutive patients who underwent resection of encephalomalacias in the frontal lobes as a treatment of their intractable epilepsy., Methods: We evaluated several factors for their value in predicting postsurgical seizure control. Pre- and postsurgical magnetic resonance imaging (MRI) scans were reviewed independently by 2 blinded investigators., Results: At a median of 3 years of follow-up (range 0.6-7.5 years), 12 patients (70%) were seizure-free or had only rare seizures. The presence of a focal fast frequency discharge (focal ictal beta pattern) at the beginning of seizures on scalp EEG was predictive of seizure-free outcome (p = 0.017), even among patients who had complete resection of their encephalomalacias (p = 0.016). There was no significant differences in outcome with regard to age at the time of the injury that caused encephalomalacia, interval between injury and onset of seizures, duration of presurgical seizure history, presurgical seizure frequency, age at surgery, or the completeness of encephalomalacia resection. The analysis regarding completeness of encephalomalacia resection almost reached significance, suggesting that it may also be an important predictive factor (p = 0.051)., Conclusions: We conclude that surgery is a very effective treatment for intractable frontal lobe epilepsy (FLE) secondary to encephalomalacias. Patients are more likely to become seizure-free if they have a focal ictal beta discharge on their scalp EEG. Complete resection of the encephalomalacia should be attempted, since our results suggest that this may be a favorable predictive factor. Moreover, the operative strategy for our patients entailed, whenever possible, complete resection of the encephalomalacias and of the adjacent electrophysiologically abnormal tissues.

Purpose: Whereas the effect of anterior temporal lobectomy on seizure frequency is well recognized, less is known about its impact on work status., Methods: One hundred thirty-four of 190 consecutive patients with temporal lobectomy participated in this study. Eligibility criteria were developed to ensure that only patients with the potential of achieving specific outcomes were included in the corresponding analyses., Results: After surgery, significantly more patients were independent in activities of daily living (p < 0.001) or able to drive (p < 0.001). Income from work also increased (p < 0.01). Nearly one fifth of the patients who were eligible for analysis had either a gain (8%) or a loss (11%) of full- or of part-time work. Univariate analyses revealed the following factors to be associated with full-time work after surgery: student or full-time work within a year before surgery, full-time work experience before surgery, full- or part-time employment experience before surgery, no disability benefits before surgery, low postsurgical seizure frequency, improved postsurgical seizure control, excellent postsurgical seizure control, driving after surgery, and further education after surgery (p < 0.05). Significant factors on multivariate analysis were being a student or having full-time work within a year before surgery [odds ratio, 16.2 (95% CI, 4.3-60.5)], driving after surgery [15.2 (3.2-72.0)], and obtaining further education after surgery [9.2 (2.2-53.0)]., Conclusions: Anterior temporal lobectomy for intractable epilepsy improves activities of daily living and the ability to drive. Work outcome of this surgery is influenced by presurgical work experience, successful postsurgical seizure control especially to allow driving, and obtaining further education after surgery.

Epileptiform abnormalities are uncommon in patients with hepatic encephalopathy. A review of EEGs in patients with hepatic encephalopathy over a 10-year period identified 18 (15%) with epileptiform abnormalities. Thirteen patients had interictal discharges consisting of focal spike and sharp wave discharges, bilateral independent discharges, and generalized spike and wave discharges. A total of 10 patients had electrographic seizure discharges, focal in 6 and generalized in 5 (some patients had more than one abnormality). Twelve patients had clinical seizures, partial in four and generalized in eight. Neuroimaging failed to provide an etiology for the generation of epileptiform discharges in most patients, including those with focal abnormalities. Most patients with epileptiform discharges died or deteriorated. We conclude that epileptiform can be seen in patients with hepatic encephalopathy, and when present imply a poor prognosis.

Current methods of evaluating seizure outcome after anterior temporal lobectomy (ATL) have major limitations. We evaluated the usefulness of a recently proposed system in our study of the stability of seizure frequency after ATL in 184 patients with intractable epilepsy. Data collection by chart review was supplemented by an intensive program of follow-up by our survey research center through correspondence or phone calls according to a protocol approved by our Institutional Review Board. Seizure frequency during each 12-month period after ATL was scored for each patient. The only statistically significant change in seizure frequency scores during follow-up was between the third and the fourth years (means of 2.61 and 2.11; P < 0.045). Further assessment showed that the change was most likely due to an increase in the proportion of patients who achieved a score of 0 when they successfully stopped taking antiepileptic medications (9.1% in the third year and 22.5% in the fourth year; P < 0.05). There was no statistically significant difference between follow-up years in the proportion of patients achieving excellent outcome (i.e. scores of 0-4). Outcome remained unchanged when follow-up at each year was confined to the same patients throughout their postsurgical course. By using the Seizure Frequency Scoring System, we have demonstrated that seizure outcome remains stable after ATL. The scoring system facilitates the detection of subtle changes in the postoperative course. The advantages and the limitations of the system are discussed.

Principal component analysis (PCA) by singular value decomposition (SVD) may be used to analyze an epoch of a multichannel electroencephalogram (EEG) into multiple linearly independent (temporally and spatially noncorrelated) components, or features; the original epoch of the EEG may be reconstructed as a linear combination of the components. The result of SVD includes the components, expressible as time series waveforms, and the factors that determine how much each component waveform contributes to each EEG channel. By omission of some component waveforms from the linear combination, a new EEG can be reconstructed, differing from the original in useful ways. For example, artifacts can be removed and features such as ictal or interictal discharges can be enhanced by suppressing the remainder of the EEG. We developed a variation of this technique in which the factors that reconstruct the modified EEG from the original are stored as a matrix. This matrix is applied to multichannel EEG at successive times to create a new EEG continuously in real time, without redoing the time-consuming SVD. This matrix acts as a spatial filter with useful properties. We successfully applied this method to remove artifacts, including ocular movement and electrocardiographic artifacts. Removal of myogenic artifacts was much less complete, but there was significant improvement in the ability to visualize underlying activity in the presence of myogenic artifacts. The major limitations of the method are its inability to completely separate some artifacts from cerebral activity, especially when both have similar amplitudes, and the possibility that a spatial filter may distort the distribution of activities that overlap with the artifacts being removed.

To assess the long-term outcome in patients who underwent surgical treatment of intractable epilepsy, we retrospectively reviewed the medical records of 291 consecutive Mayo patients treated between July 1972 and March 1985. We also evaluated the responses to a follow-up mailed questionnaire or telephone interview completed in 1992. Of the 291 patients, 245 (94% of the 261 patients known to be alive at the time of the survey) responded to the follow-up questioning. Information on the patients' neurologic status (including frequency of seizures, use of antiepileptic drugs, and self-reported assessment of functional capacity) and their overall satisfaction with the operative procedure and postoperative outcome were evaluated. Two hundred ninety patients survived the operation and were dismissed from the hospital. Of the 245 patients who responded to the follow-up survey, 41% and 58% had been free of seizures since surgical treatment and for 3 years preceding the follow-up survey, respectively. In addition, of the respondent cohort, 36% were successfully weaned off all antiepileptic drugs. Patients reported improvement in their daily functional capacity and quality of life after surgical treatment. For example, in comparison with the preoperative assessment, the patients' ability to obtain a driver's license was significantly increased, and seizure-related driving accidents, falls, and bodily injury significantly decreased. Furthermore, on the basis of current knowledge of the operation and its outcome, 85% reported that they would repeat the operative procedure. Thus, surgical treatment of intractable epilepsy is an effective option that is met with patient satisfaction.

Purpose: Episodic loss of consciousness presents a diagnostic challenge to the neurologist. A perhaps underrecognized cause of episodic loss of consciousness, which we call the ictal bradycardia syndrome, occurs when epileptic discharges profoundly disrupt normal cardiac rhythm, resulting in cardiogenic syncope during the ictal event. We attempt to determine whether the presence of the ictal bradycardia syndrome provides localizing information regarding the site of seizure onset and to describe the demographics of patients with this syndrome. We also discuss difficulties in diagnosis and treatment., Methods: We review 23 cases of the ictal bradycardia syndrome from the literature and present four additional cases. Brief histories are provided for the four previously unreported cases. Where data are available, cases are analyzed with respect to age, sex, and site of seizure onset., Results: Patients with the ictal bradycardia syndrome ranged from 4 months to 72 years (mean 39 years). There was an approximately 5:1 ratio of males to females. Twenty of the 23 patients (87%) whose site of ictal onset could be localized had temporal lobe epilepsy, although no clear lateralizing predominance was apparent., Conclusions: The ictal bradycardia syndrome should be considered in patients with unusual or refractory episodes of syncope, or in patients with a history suggestive of both epilepsy and syncope. It suggests seizure onset in temporal lobe, and is more commonly diagnosed in males. Diagnosis may be aided by ambulatory EEG/ECG monitoring. Cardiac pacemaker implantation along with antiepileptic drug therapy may be necessary to minimize the possibility of death.

Purpose: We report two cases of unusual movement disorders associated with the use of gabapentin (GBP) in patients being treated for epilepsy who were otherwise neurologically intact., Methods: We describe two cases of unusual movement disorders associated with the use of GBP., Results: There were significant differences in the clinical findings between the two cases. In the first case, movements were very pronounced and the patient was in oculogyric crisis. Movements in the second case were quite subtle but nonetheless problematic for the patient. In each case, discontinuation of GBP led to rapid resolution of the movements, although a single dose of lorazepam was used in the first case., Conclusions: Although formal electrophysiologic studies have not been performed, the movements associated with GBP use appear to be dystonic or myoclonic. Discontinuation of GBP led to rapid resolution of the movements. In severe cases, as in patients with oculogyric crisis, small doses of a benzodiazepine (BZD) appear to be efficacious and safe.

Long-term electroencephalographic (EEG) monitoring is the process of recording an EEG for a prolonged period in order to document epileptic seizures or other episodic disturbances of neurologic function. Indications for long-term EEG monitoring include diagnosis of a seizure disorder (epilepsy), classification of seizure types in patients with epilepsy, and localization of the epileptogenic region of the brain. Methods used for long-term EEG monitoring include prolonged analog or digital EEG, prolonged analog or digital ambulatory EEG, and prolonged analog or digital video-EEG monitoring with telemetry. Each of these methods has distinct advantages and disadvantages, particularly relative to storage, retrieval, and manipulation of data. Long-term EEG monitoring is useful in the management of patients with epilepsy and in the diagnosis of a seizure disorder. For most patients, inpatient long-term EEG monitoring is best performed in a specialized epilepsy-monitoring unit, which can provide a safe environment and both educational and psychosocial support. The choice of the most appropriate method of long-term monitoring for a specific clinical situation is best made by an epileptologist or a neurologist at an epilepsy center.

Purpose: To investigate the relation among routine EEG, long-term EEG monitoring (LTM), quantitative magnetic resonance imaging (MRI), and surgical outcome in temporal lobe epilepsy (TLE)., Methods: We evaluated 159 patients with intractable TLE who underwent an anterior temporal lobectomy between 1988 and 1993. The epileptogenic temporal lobe was determined by ictal LTM. A single awake-sleep outpatient EEG with standard activating procedures was performed before LTM. EEGs were analyzed by a blinded investigator., Results: MRI scans showed unilateral medial temporal atrophy (109 patients) or symmetrical hippocampal volumes (50 patients). The surgically excised epileptogenic brain tissue revealed mesial temporal sclerosis, gliosis, or no histopathologic alteration. Routine EEG revealed temporal lobe epileptiform discharges in 123 patients. Routine EEG findings correlated with the temporal lobe of seizure origin (p < 0.0001) and the results of MRI volumetric studies (p < 0.0001). Interictal epileptiform discharges were seen only during LTM in 24 patients. Routine EEG was disconcordant with interictal LTM in another 20 patients. MRI-identified unilateral medial temporal lobe atrophy was a strong predictor of operative success (p < 0.0001). There was no significant relation between the routine EEG findings and operative outcome (p > 0.20)., Conclusions: Results of this study modified our approach in patients with TLE. Interictal epileptiform discharges localized to one temporal lobe on serial routine EEGs or during LTM may be adequate to identify the epileptogenic zone in patients with MRI-identified unilateral medial temporal lobe atrophy.

We investigated pre- and postoperative verbal memory in temporal lobectomy patients who had volumetrically symmetric hippocampi. Pre- and postoperative verbal memory data based on the Logical Memory subtest of the Wechsler Memory Scale-Revised (WMS-R) were obtained from 15 left and 18 right temporal lobectomy patients. The difference between hippocampal volumes (R/L) was between -0.1 and 0.3 cm3, which is indeterminate for lateralizing hippocampal atrophy. Patients were divided into four groups based on side of operation and combined hippocampal volume expressed as a function of total intracranial volume (R + L volume/total intracranial volume). Patients with a combined hippocampal volume that was smaller than any combined hippocampal value of a normal control group were defined as bilaterally atrophic. Left temporal lobectomy patients demonstrated the expected decrease in verbal memory postoperatively regardless of whether the volumetrically symmetric hippocampi were nonatrophic or atrophic. Left temporal lobectomy patients with bilaterally atrophic hippocampi, however, had the poorest verbal memory before and after operation. Right temporal lobectomy patients tended to have improved verbal memory after operation whether or not the volumetrically symmetric hippocampi were atrophic. We conclude that side of operation is a more potent predictor of verbal memory outcome than is hippocampal atrophy when hippocampi are bilaterally symmetric and that left temporal lobectomy patients with bilateral atrophy may be at risk for greater functional deficits after operation.

We have identified a previously unreported subtype of periodic lateralized epileptiform discharge (PLED) characterized by periodic discharges arising from ipsilateral independent foci. All 4 patients had acute cerebral lesions, and 3 of them had focal motor seizures with secondary generalization. The site of localization of the PLEDs corresponded to the boundaries of the underlying structural lesion or lesions, and this, together with the variable temporal relationship between them, supports a cortical origin for PLEDs associated with underlying lesions. the spatial and temporal independence of these periodic discharges in combination with their association with (1) acute cerebral lesions. (2) altered consciousness and seizures, and (3) resolution with time leads us to propose the term "IpsiIPs" to describe this subtype of PLEDs.

Seizure surgery for medically intractable partial epilepsy in selected patients usually results in dramatically improved seizure control. However, the authors present six patients who, after surgery for refractory complex partial seizures, postoperatively experienced pseudoseizures (also known as nonepileptic seizures), confirmed with EEG monitoring. Three of these patients also had nonepileptic seizures preoperatively that coexisted with their partial epilepsy. Psychiatric assessment revealed that this patient group had several characteristics in common, which suggests that preoperative psychiatric consultation may help identify those patients at risk for developing nonepileptic seizures. Treatment strategies with anticonvulsant medications and behavioral therapy are reviewed.

Interchannel coherence is a measure of spatial extent of and timing relationships among cerebral electroencephalogram (EEG) generators. Interchannel coherence of referentially recorded potentials includes components due to volume conduction and reference site activity. The laplacian of the potential is reference independent and decreases the contribution of volume conduction. Interchannel coherences of the laplacian should, therefore, be less than those of referentially recorded potentials. However, methods used to compute the laplacian involve forming linear combinations of multiple recorded potentials, which may inflate interchannel coherences. WE compared 3 methods of computing the laplacian: (1) modified Hjorth (4 equidistant neighbors to each electrode), (2) Taylor's series (4 nonequidistant neighbors), and (3) spherical harmonic expansion (SHE). Average interchannel coherence introduced by computing the laplacian was less for nearest-neighbor methods (0.0207 +/- 0.0766) but still acceptable for the SHE method (0.0337 +/- 0.0865). Average interchannel coherence for simulated EEG (random data plus a common 10 Hz signal) was less for laplacian than for referential data because of removal of the common referential signal. Interchannel coherences of background EEG and partial seizure activity were less with the laplacian (any method) than with referential recordings. Laplacians calculated from the SHE do not demonstrate excessively large interchannel coherences, as have been reported for laplacians from spherical splines.

Objective: To analyze the effect of nimodipine in patients with intractable epilepsy., Design: We conducted a double-blind placebo-controlled crossover study in 95 patients., Material and Methods: The dihydropyridine calcium antagonist nimodipine was used as add-on therapy (60 mg four times a day) in a 1-year placebo-controlled crossover study in 71 patients with localization-related epilepsy and 24 with generalized seizure disorders. Of the 95 patients, 81 were receiving two or more antiepileptic drugs. Patients diaries were used to record the number of seizures and any side effects., Results: Nimodipine seemed to be well tolerated during the study; only two patients were unable to complete the study because of probable adverse effects. The trial demonstrated no significant crossover effect and no significant effect of nimodipine on either the mean or the median number of seizures or seizure days. The peak median serum nimodipine level was less than 5 ng/mL in the 78 patients who completed the study., Conclusion: This clinical trial found no beneficial effect with use of nimodipine as add-on therapy for intractable epilepsy. Potential reasons for the absence of efficacy of nimodipine may be the inclusion of patients with very refractory seizure disorders or the relatively low serum nimodipine concentrations related to the pharmacokinetic effect of concurrent antiepileptic medication.

This study investigates the relationship between hippocampal volume and seizure control following temporal lobectomy in patients with volumetrically symmetric hippocampi. Forty-six patients who underwent temporal lobectomy for nonlesional temporal-lobe-onset seizures, and in whom the volumes of the two hippocampi were roughly equal (ie, the difference of the right minus the left hippocampal volume fell between -0.1 and 0.3 cm3), were included. We graded postoperative seizure control on a four-point scale according to criteria defined by Engel. We found no relationship between the hippocampal sum (sum of the right plus left hippocampal volumes normalized for cranial size) and operative outcome. A satisfactory operative outcome is possible in patients with bilaterally symmetric mesial temporal sclerosis by MRI criteria.

We investigated the relationship between electrocorticography (ECoG), quantitative magnetic resonance imaging (MRI), and surgical outcome in 165 patients with intractable nonlesional temporal lobe epilepsy (NLTLE). A standard mesial temporal resection was performed in all patients. Patients with an operative follow-up < 1 year were excluded from the study. The extent of the lateral temporal neocortex resection (LCR) was guided by ECoG and the side of surgery. The extent of the LCR was not predictive of seizure outcome in patients with or without hippocampal formation atrophy (p > 0.5). Patients undergoing a right anterior temporal lobectomy had a larger LCR (p < 0.0001), but the side of surgery was not of predictive value in determining seizure outcome (p > 0.1). The topography of the acute intracranial spikes did not correlate with operative outcome (p > 0.5) and was independent of hippocampal volumetric studies (p > 0.5). The postexcision ECoG was also shown not to be of prognostic importance (p > 0.5). Our results indicates that the extent of the lateral temporal cortical resection and the ECoG findings are not important determinants of surgical outcome in patients with NLTLE.

We performed a retrospective study of 30 patients with presumed intractable temporal lobe epilepsy (TLE) who underwent chronic intracranial EEG monitoring (CIEM). Multicontact depth electrodes were stereotactically implanted through the medial occipital lobe into amygdala and hippocampus. All patients had previously undergone extracranial ictal EEG monitoring that proved inadequate to localize the epileptogenic zone. No morbidity was associated with CIEM in the 30 patients. Twenty-five patients were shown to have exclusively or predominantly unilateral temporal lobe seizures, and 5 patients had bitemporal seizures without unilateral predominance; 24 patients subsequently underwent an anterotemporal lobe cortical resection. Twenty-one patients have been followed a minimum of 1 year postoperatively. Nine patients (43%) had a class I outcome (seizure-free, auras only, or provoked seizures), 3 patients (14%) had a class II outcome (> or = 95% seizure reduction), 4 patients (19%) had a class III outcome (> or = 50% seizure reduction); and 5 patients (24%) had a class IV outcome (< 50% seizure reduction or no change). A prolonged interhemispheric propagation time (p < 0.01) and magnetic resonance imaging (MRI)-identified hippocampal atrophy (p < 0.01) correlated with a favorable surgical outcome. Results of this study may prove useful in counseling patients who undergo CIEM before temporal lobe surgery.