Significance of postoperative electroencephalograms in patients with extratemporal lesional epilepsy

We retrospectively studied EEGs performed 1 week, 3 months, and 1 year after surgery (lesionectomy or lesion resection with corticectomy) in 24 patients with extratemporal lesional epilepsy who had a mean duration of follow-up of 2.5 years. All patients had intractable partial seizures and underwent a comprehensive presurgical evaluation including long-term EEG monitoring. Twenty of the 24 patients had interictal epileptiform activity (IEA) identified on the preoperative sleep and awake EEG recordings. The presence of IEA 1 year after surgery was associated with recurrent seizure activity (p < 0.05). The postoperative EEG recordings, however, revealed no IEA in the two patients with persistent seizures who had no epileptiform abnormality on the preoperative study. The extent of cortical resection appeared to have no significant effect on the recording of IEA after surgery. One-year postoperative EEG recordings are prognostically useful in patients with extratemporal lesional epilepsy who undergo surgical treatment.     

Discontinuation of antiepileptic drugs after successful epilepsy surgery

OBJECTIVE: To evaluate the frequency and risk factors for seizure recurrence subsequent to antiepileptic drug (AED) withdrawal in patients who underwent surgical treatment for intractable partial epilepsy and were rendered seizure-free. METHODS: The outcome of discontinuation of AED medication was studied retrospectively in 210 consecutive patients who were rendered seizure-free after epilepsy surgery performed between 1989 and 1993. RESULTS: Medical therapy was reduced in 96 patients and discontinued in 84 patients. The seizure recurrence rate after complete AED withdrawal was 14% and 36% at 2 and 5 years. In contrast, only 3% and 7% of the 30 patients who did not alter AED treatment after surgery had recurrent seizures in the same time intervals. After AED discontinuation, seizures tended to recur more often in patients with normal preoperative MRI studies compared with those with focal pathology. However, this difference did not reach significance. Intraoperative electrocorticography, extent of surgical resection, postoperative EEG, and seizure-free duration after surgery were not predictive of seizure outcome after AED withdrawal. CONCLUSIONS: AED withdrawal was associated with seizure recurrence in a significant portion of patients rendered seizure-free by epilepsy surgery. Patients with a normal preoperative MRI study showed a tendency for higher seizure recurrence, whereas the duration of seizure-free postoperative AED treatment interval did not significantly influence the seizure recurrence rate. These results will prove useful in counseling patients about discontinuing AED treatment after successful epilepsy surgery.     

Prognostic factors for surgery of neocortical temporal lobe epilepsy.

OBJECTIVES: In the current classification of epilepsies two forms of temporal lobe epilepsy (TLE) were included: mesial and lateral (neocortical) TLE. We aimed at identifying prognostic factors for the surgical outcome of lesional neocortical TLE. METHODS: We included consecutive patients who had undergone presurgical evaluation including ictal video-EEG and high-resolution MRI, who had TLE due to neocortical lateral epileptogenic lesions, who had a lesionectomy and who had >2-year follow-up. RESULTS: There were 29 patients who met the inclusion criteria. Twenty of them became postoperatively seizure-free. Patients' mean age was 34.8+/-9 years (range 18-52). The age at epilepsy onset was 20.1+/-8 years. We found that left-sided surgery (p=0.048) and focal cortical dysplasia (FCD) on MRI (p=0.005) were associated with non-seizure-free outcome, while lateralized/localized EEG seizure pattern (p=0.032), tumors on the MRI (p=0.013), and a favorable seizure situation at the 6-month postoperative evaluation were associated with 2-year postoperative seizure-freedom (p<0.001). Multivariate analysis indicated that the side of surgery was not an independent predictor. CONCLUSION: More than two-thirds of the patients with neocortical TLE became seizure-free postoperatively. Lateralized/localized EEG seizure pattern and tumors on the MRI were associated with postoperative seizure-freedom, while FCD were associated with a poor outcome. The 6-month postoperative outcome is a reliable predictor for the long-term outcome.     

Surgical Treatment for Epilepsy in Cerebral Tuberous Sclerosis

Summary: Tuberous sclerosis (TS) is an autosomal dominant hamartiosis and hamartomatosis with variable expression that is commonly associated with medically intractable seizures. Patients with TS complex (TSC) frequently have multiple brain lesions that can give rise to seizure activity. We report 9 patients with TSC who underwent epilepsy surgery at the Mayo Clinic between 1986 and 1990. Surgical procedures performed included cortical resection (n = 2) and stereotaxic lesionectomy (n = 7). Neuropathologic diagnoses were cortical tubers (n = 7) and glioneural hamartomas (n = 2). Three of 9 patients had multifocal interictal scalp epileptiform EEG activity; however, ictal recordings identified the focus of seizure activity, which in all cases corresponded to a prominent neuroimaging abnormality. Our patients have been followed for 10–72 months (mean 35 months). Four patients are seizure-free with medication, 2 are seizurefree without medication, 2 had >80% reduction in seizure frequency, and 1 experienced only an initial temporary reduction in seizure frequency. Postoperative EEG recordings showed absence of epileptiform abnormalities in the 5 patients who are seizure-free; the other 4 patients continue to have multifocal abnormalities. These data suggest that epilepsy surgery may be beneficial in selected patients with TSC despite multifocal EEG and neuroimaging abnormalities.     

Using recurrence plot for determinism analysis of EEG recordings in genetic absence epilepsy rats

OBJECTIVE: Understanding the transition of brain activity towards an absence seizure is a challenging task. In this paper, we use recurrence quantification analysis to indicate the deterministic dynamics of EEG series at the seizure-free, pre-seizure and seizure states in genetic absence epilepsy rats. METHODS: The determinism measure, DET, based on recurrence plot, was applied to analyse these three EEG datasets, each dataset containing 300 single-channel EEG epochs of 5-s duration. Then, statistical analysis of the DET values in each dataset was carried out to determine whether their distributions over the three groups were significantly different. Furthermore, a surrogate technique was applied to calculate the significance level of determinism measures in EEG recordings. RESULTS: The mean (+/-SD) DET of EEG was 0.177+/-0.045 in pre-seizure intervals. The DET values of pre-seizure EEG data are significantly higher than those of seizure-free intervals, 0.123+/-0.023, (P<0.01), but lower than those of seizure intervals, 0.392+/-0.110, (P<0.01). Using surrogate data methods, the significance of determinism in EEG epochs was present in 25 of 300 (8.3%), 181 of 300 (60.3%) and 289 of 300 (96.3%) in seizure-free, pre-seizure and seizure intervals, respectively. CONCLUSIONS: Results provide some first indications that EEG epochs during pre-seizure intervals exhibit a higher degree of determinism than seizure-free EEG epochs, but lower than those in seizure EEG epochs in absence epilepsy. SIGNIFICANCE: The proposed methods have the potential of detecting the transition between normal brain activity and the absence seizure state, thus opening up the possibility of intervention, whether electrical or pharmacological, to prevent the oncoming seizure.     

Predictive value of early EEG after epilepsy surgery.

To determine whether EEG performed within few months after epilepsy surgery is predictive of seizure outcome, 58 consecutive patients undergoing surgery for presumptive temporal lobe epilepsy (TLE) who had clinical follow-up of at least 2 years and EEG data available both pre- and postoperatively were analyzed. Patients were classified by preoperative brain magnetic resonance imaging into lesional, cryptogenic, and hippocampal sclerosis groups. Seizure outcome was classified according to Engel's outcome scale. Comparison was made between the presence of interictal epileptiform discharges (IEDs) in the postoperative EEG and seizure outcome. Patients who experienced seizures within 2 months after surgery were considered to have early recurrence. The mean follow-up period was 3 years. Sixty percent of patients achieved a class I seizure outcome. Almost all (95%) postoperative EEGs were obtained within 4 months after surgery. IEDs were present in 26% of postoperative EEGs, but were significantly less frequent in EEGs recorded after the first two postoperative months (P = 0.011). The presence of IEDs on postoperative EEGs was not predictive of seizure outcome either in the whole cohort or in any of the subgroups, regardless of whether it was performed within or after the first two postoperative months. It was also not predictive of outcome in the 44 patients (76%) who did not suffer early recurrence. The authors conclude that EEG performed a few months after epilepsy surgery is not useful as a predictor of long-term seizure outcome.     

Early antiepileptic drug reduction following anterior temporal lobectomy for medically intractable complex partial epilepsy.

PURPOSE: To determine the safety, in our practice, of allowing patient preference to influence the timing of antiepileptic drug (AED) reduction, once they became seizure-free after anterior temporal lobectomy (ATL). METHODS: Thirty patients underwent anterior temporal lobectomy for medically intractable complex partial epilepsy at Loma Linda University Medical Center between December 1st 1991 and November 30th 2001. Timing of AED reduction in seizure-free patients was based on patient request. A review of patient records noted seizure status, duration from surgery to AED reduction, AED side effects, seizure recurrence and whether control was regained. RESULTS: Twenty-four (80%) of the 30 patients became seizure-free on their preoperative AEDs after initial ATL; three additional patients after a second operation. AEDs were not reduced in the reoperated patients, the three patients who did not become seizure-free, and in two patients who asked to increase AEDs to control auras. Thus, AEDs were reduced in 22 of the 27 seizure-free patients. Patients were followed an average of 3.4 +/- 2.7 (mean +/- standard deviation) years. AED reduction was initiated 4.6 +/- 7.2 months (range 0-27 months) after surgery. Polytherapy use decreased from 54% preoperatively to 18% at last follow up. Seizures recurred in six patients (27% of 22); three became seizure-free after AED adjustments. CONCLUSIONS: In our practice, using an individualized approach to AED reduction following successful epilepsy surgery resulted in early reduction in AEDs. Our data suggest that early AED reduction can be performed safely and without undue risk of seizure recurrence.     

Postoperative routine EEG correlates with long-term seizure outcome after epilepsy surgery.

We investigated the correlation of interictal epileptiform discharges (IED) in routine EEG 6 and 24 months after epilepsy surgery with regard to long-term seizure outcome. In 148 patients (74% temporal lobe epilepsy (TLE), 26% extratemporal epilepsy) EEG results (IED present or absent) were correlated with the postoperative outcome using the Engel classification 6 and 24 months after resection (PO6m and PO2y, respectively). Self-evaluation was conducted 3 and 5 years after resection (PO3y and PO5y, respectively). Ninety-one patients (62%) were seizure-free 5 years after resection; 88% of them showed no IED in PO6m. Twenty-eight patients (19%) displayed IED in routine EEG 6 months after resection; 61% of them had recurrent seizures at PO5y, whereas of 120 patients without IED only 33% had recurrent seizures at PO5y; p=0.01. Absence of IED in PO6m and PO2y correlated with good outcome: 71% without IED remained seizure-free, whereas only 25% with IED at PO6m and PO2y remained seizure-free; p=0.001. Seizure-free patients (Engel 1) and patients with less favourable outcome (Engel 3-4) at PO6m and PO2y rarely changed categories of outcome during the following years (p<0.001). Half of the patients with favourable seizure reduction (Engel 2) changed to seizure-free (Engel 1) or to a worse outcome category (Engel 3-4). Postoperative routine EEG is a good prognostic instrument for the prediction of long-term seizure outcome, especially for TLE. It predicts the running up and down of fits in patients with rare seizures (Engel 2).     

Medically refractory epilepsy associated with temporal lobe ganglioglioma: characteristics and postoperative outcome

OBJECTIVES: To define the postoperative seizure outcome and its predictors in patients with ganglioglioma-related temporal lobe epilepsy (TLE). PATIENTS AND METHODS: We reviewed the pre- and post-surgical evaluation data of 23 patients with temporal lobe ganglioglioma, who had completed >or=1 year of postoperative follow-up. They comprised 4.9% of the patients with TLE and 67.6% of the tumoral TLE operated in a developing country epilepsy center during an 8-year period. RESULTS: Median age at surgery was 20 years; median duration of epilepsy prior to surgery was 9 years. Magnetic resonance imaging (MRI) revealed tumor in mesial temporal location in 18 patients (78.3%) and in the lateral location in 2; in the remaining 3, involved both mesial and lateral regions. EEG abnormalities were localized to the side of lesion in the majority. Mesial temporal lobe structures were included in the resection, if they were involved by the tumor; otherwise, lesionectomy alone was performed. During a median follow-up of 4 years, 19 (82.6%) patients were completely seizure-free. Epileptiform abnormalities persisting in the 1-year postoperative EEG predicted unfavorable seizure outcome. CONCLUSION: We emphasize that, in patients with temporal lobe ganglioglioma, when the seizures are medically refractory, surgery offers potential for cure of epilepsy in the majority.     

Electro-clinical characteristics and postoperative outcome of medically refractory tumoral temporal lobe epilepsy

BACKGROUND: Very few studies have specifically addressed surgical treatment and outcome of patients with tumor-related temporal lobe epilepsy (TLE). AIM: To define the postoperative seizure outcome and the factors that influenced the outcome of patients with tumor-related TLE. MATERIALS AND METHODS: We selected patients whose surgical pathology revealed a temporal lobe neoplasm and who had completed > 1 year of postoperative follow-up. We reviewed the clinical, EEG, radiological and pathological data, and the seizure outcome of these patients and assessed the factors that influenced the outcome. RESULTS: Out of the 409 patients who underwent surgery for refractory TLE during the 8-year study period, there were 34 (8.3%) patients with temporal lobe neoplasms. The median age at surgery was 20 years and the median duration of epilepsy prior to surgery was 9.0 years. MRI revealed tumor in the mesial location in 21 (61.8%) patients. Interictal and ictal epileptiform EEG abnormalities were localized to the side of th lesion in the majority. Mesial temporal lobe structures were included in the resection, if they were involved by the tumor; otherwise, lesionectomy alone was performed. During a median follow-up of 4 years, 27 (79%) patients were completely seizure-free. The only factor that predicted long-term seizure-free outcome was being seizure-free during the first two postoperative years. CONCLUSIONS: Our results emphasize the fact that in patients with tumoral TLE, when the seizures are medically refractory, surgery offers potential for cure of epilepsy in the majority.     

Postoperative EEG and seizure outcome in temporal lobe epilepsy surgery.

OBJECTIVE: To assess the prognostic value of scalp electroencephalogram (EEG) after epilepsy surgery, we investigated whether postoperative EEG abnormalities (interictal epileptiform discharges, IED; interictal slow activity, ISA) were associated with seizure outcome and other patient characteristics after resective surgery in patients with temporal lobe epilepsy (TLE). METHODS: Sixty-two patients with medically refractory TLE who underwent surgery were studied. Patients were categorized according to etiology (mesiotemporal sclerosis vs. tumors/cortical dysplasias); extent of surgical resection (extensive vs. limited); and amount of preoperative IED on wake EEG (oligospikers, <1 IED/h, vs. spikers). Patients were also classified as seizure-free (SF) or having persistent seizures/auras (not-SF) during follow up visits 1 month and 1 year after surgery. Preoperative 60-min interictal EEGs were evaluated for IED and ISA, and compared to postoperative wake EEGs. RESULTS: Seizures/auras persisted in 16/62 (25.8%) patients at 1 month and in 8/62 (12.9%) at 1 year follow up. ISA was not significantly related to outcome. Of 42 patients with EEG negative for IED at 1 month, 4 were not-SF; at 1 year, one of 44 such patients was not-SF. IED was significantly associated with seizure/aura persistence in patients categorized as mesiotemporal sclerosis and with extensive surgery. Oligospikers and spikers on preoperative EEG showed no differences in the postoperative seizure outcome, excellent in both cases; moreover, the presence of postoperative IEDs indicated auras/seizures persistence apart from the preoperative EEG spike frequency. CONCLUSIONS: Our study showed that the presence of IED of postoperatve EEG strongly indicates seizure/aura persistence. Therefore, serial EEGs should be included in postoperative follow up schedules as a crucial tool in evaluating seizure outcome.     

MEG predicts outcome following surgery for intractable epilepsy in children with normal or nonfocal MRI findings

PURPOSE: To identify the predictors of postsurgical seizure freedom in children with refractory epilepsy and normal or nonfocal MRI findings. METHODS: We analyzed 22 children with normal or subtle and nonfocal MRI findings, who underwent surgery for intractable epilepsy following extraoperative intracranial EEG. We compared clinical profiles, neurophysiological data (scalp EEG, magnetoencephalography (MEG) and intracranial EEG), completeness of surgical resection and pathology to postoperative seizure outcomes. RESULTS: Seventeen children (77%) had a good postsurgical outcome (defined as Engel class IIIA or better), which included eight (36%) seizure-free children. All children with postsurgical seizure freedom had an MEG cluster in the final resection area. Postsurgical seizure freedom was obtained in none of the children who had bilateral MEG dipole clusters (3) or only scattered dipoles (1). All five children in whom ictal onset zones were confined to < or = 5 adjacent intracranial electrodes achieved seizure freedom compared to three of 17 children with ictal onset zones that extended over >5 electrodes (p = 0.002). None of six children with more than one type of seizure became seizure-free, compared to eight of 16 children with a single seizure type (p = 0.04). Complete resection of the preoperatively localized epileptogenic zone resulted in seizure remission in 63% (5/8) and incomplete resections, in 21% (3/14) (p = 0.06). Age of onset, duration of epilepsy, number of lobes involved in resection, and pathology failed to correlate with seizure freedom. CONCLUSIONS: Surgery for intractable epilepsy in children with normal MRI findings provided good postsurgical outcomes in the majority of our patients. As well, restricted ictal onset zone predicted postoperative seizure freedom. Postoperative seizure freedom was less likely to occur in children with bilateral MEG dipole clusters or only scattered dipoles, multiple seizure types and incomplete resection of the proposed epileptogenic zone. Seizure freedom was most likely to occur when there was concordance between EEG and MEG localization and least likely to occur when these results were divergent.     

Clinical adult outcome 11–30 years after pediatric epilepsy surgery: Complications and other surgical adverse events,seizure control,and cure of epilepsy

Objective

Pediatric epilepsy surgery promises seizure freedom or even cure of epilepsy. We evaluated the long-term (≥10 years) adult clinical outcome including surgery-related adverse events and complications, which are generally underreported.

Methods

A monocentric, single-arm, questionnaire study in now adult patients who underwent epilepsy surgery during childhood. A novel ad hoc parental/patient questionnaire, which addressed diverse outcome domains was applied.

Results

From a total of 353 eligible patients, 203 could be contacted (3 patients died of causes unknown) and 101 (50%) returned appropriately filled-in surveys. No evidence for a survey-response bias was found. The rate of surgical complications according to the patient records was 9%. As regards the survey, half of the parents/patients reported surgical adverse events (expected and unexpected issues) and one-third reported permanent aversive sequels. Two-thirds of the patients were seizure-free during the last year before follow-up; 63% were Engel class 1A; favorable seizure outcomes (including auras only) were obtained in 73%; and 54% were seizure-free and off antiseizure medicine (ASM), that is, cured of epilepsy. In non–seizure-free patients, seizure relapse occurred at any time during the follow-up interval but 87% of those with a seizure-free first postoperative year were seizure-free at follow-up. One patient experienced a seizure relapse during the ASM withdrawal trial but became seizure-free again with ASMs. Eleven patients reported an increased number of ASMs as compared to the time before surgery. Earlier focal surgery did not affect the long-term clinical outcome.

Significance

Pediatric epilepsy surgery was capable of curing epilepsy in about one-half of the children and to significantly control seizures in about three-fourths. Long-term success of focal surgery did not depend on age at surgery or duration of epilepsy. Surgical adverse events including complications may be underreported and must be assessed more thoroughly.     

Seizure recurrence after planned discontinuation of antiepileptic drugs in seizure-free patients after epilepsy surgery: a review of current clinical experience

PURPOSE: Although epilepsy surgery, especially temporal lobe epilepsy surgery, is well established to control seizures in patients remaining on antiepileptic drug (AED) treatment, less information is available about how many seizure-free surgical patients will relapse after discontinuation of AEDs under medical supervision. METHODS: A literature review yielded six retrospective clinical observations. RESULTS: After planned discontinuation of AEDs in patients rendered seizure free after epilepsy surgery, most often various forms of temporal lobe surgery, the mean percentage recurrence rate in adults in four studies was 33.8%[95% confidence interval (CI), 32.4-35.2%], with maximum follow-up ranging from 1 to 5 years. Seizure recurrence increased during the follow-up of 1 to 3 years and occurred within 3 years of AED discontinuation. In one study of children with temporal lobe epilepsy, the recurrence rate was 20%. More than 90% of adult patients with seizure recurrence regained seizure control with reinstitution of previous AED therapy. Seizure recurrence was unaffected by the duration of postoperative AED treatment; as a consequence, delaying discontinuation beyond 1 to 2 years of complete postoperative seizure control seems to have no added benefit. The occurrence of rare seizures or auras after surgery did not eliminate the possibility of eventual successful AED discontinuation. CONCLUSIONS: AED discontinuation is associated with a seizure recurrence in one in three patients rendered seizure free by epilepsy surgery. These results will be useful in counseling patients about discontinuing AED treatment after successful epilepsy surgery.     

Topiramate: effect on EEG interictal abnormalities and background activity in patients affected by focal epilepsy

PURPOSE: To evaluate the effects of topiramate (TPM) on interictal epileptiform abnormalities (IEA) and background activity by means of a computerized EEG analysis, in adult patients affected by focal epilepsy, with or without secondarily generalization, treated with TPM as adjunctive therapy or monotherapy. METHODS: Twenty-four patients affected by symptomatic or cryptogenic focal epilepsy underwent long-term video-EEG recording before and after TPM addition (mean dose 175+/-25 mg per day). RESULTS: TPM addition induced a significant reduction of both partial and secondarily generalized tonic-clonic (SGTC) seizures; treatment responder patients (seizure reduction > or = 50%) were 19 out of 24 patients (79.1%), of whom 5 were seizure-free. Quantitative analysis of IEA showed a significant decrease in the mean number of spikes/10 min during TPM therapy ( 4.2+/-4.2 versus 2.2+/-4.4; P<0.003 ). The analysis of spatial distribution of interictal spikes showed that such reduction was more evident at the level of the epileptogenic area rather than on the spreading component. Statistical analysis revealed only a significant decrease of mean relative power of alpha band in the EEG spectral content, recorded at rest in a group of 18 out of 24 epileptic patients during TPM therapy. In addition, during TPM treatment we observed a significant reduction in alpha reactivity without any important changes of alpha indexes (peak frequency and median frequency). CONCLUSION: These findings suggest that TPM has a strong inhibitory effect on IEA, probably acting on the generating processes, and, if used at low dosage and gradually titrated, seems to have only mild interferences with EEG background activity.     

Drug‐resistant parietal lobe epilepsy: clinical manifestations and surgery outcome

Aim. We reviewed a large surgical cohort to investigate the clinical manifestations, EEG and neuroimaging findings, and postoperative seizure outcome in patients with drug‐resistant parietal lobe epilepsy (PLE). Methods. All drug‐resistant PLE patients, who were investigated for epilepsy surgery at Jefferson Comprehensive Epilepsy Center between 1986 and 2015, were identified. Demographic data, seizure data, EEG recordings, brain MRI, pathological findings, and postsurgical seizure outcome were reviewed. Results. In total, 18 patients (11 males and seven females) were identified. Sixteen patients (88%) had tonic‐clonic seizures, 12 (66%) had focal seizures with impaired awareness, and 13 (72%) described auras. Among 15 patients who had brain MRI, 14 patients (93%) had parietal lobe lesions. Only three of 15 patients (20%) who had interictal scalp EEG recordings showed parietal interictal spikes. Of 12 patients with available ictal surface EEG recordings, only three patients (25%) had parietal ictal EEG onset. After a mean follow‐up duration of 8.6 years, 14 patients (77.7%) showed a favourable postoperative seizure outcome. Conclusion. In patients with PLE, semiology and EEG may be misleading and brain MRI is the most valuable tool to localize the epileptogenic zone. Postsurgical seizure outcome was favourable in our patients with drug‐resistant parietal lobe epilepsy.     

Significance of Sharp Waves in Routine EEGs After Epilepsy Surgery

We retrospectively analyzed the presence of sharp waves in 2-h EEGs performed 6 months after epilepsy surgery in 59 patients. To study the significance of the postoperative interictal epileptiform activity in the tissue remaining after resection, we included only patients with a single epileptic focus (as defined preoperatively by prolonged video/EEG recordings and subdural electrode arrays studies) and no progressive structural lesions. Temporal lobectomy was performed in 51 patients (86%); extratemporal resections were performed in the remainder. The epileptogenic focus was completely resected in 26 patients (44%). The immediate postoperative electrocorticograms (EcoG) showed spikes in 13 patients (22%). At 6-month follow-up, 43 patients (73%) were seizure-free or had auras only and 12 patients (20%) had epileptiform activity on EEG. A significant correlation was noted between presence of sharp waves in the 6-month postoperative EEG and recurrence of seizures (Fisher's exact test p = 0.011) and also with the extent of the resection (complete vs. incomplete p = 0.042). We noted no correlation between postoperative epileptiform activity and location of the resection (temporal vs. extratemporal), presence of spikes in immediate postoperative EcoG, or occurrence of auras only at 6-month follow-up.     

Occipital lobe epilepsy: clinical characteristics, surgical outcome, and role of diagnostic modalities

PURPOSE: To assess the role of various diagnostic modalities, to identify surgical prognostic factors and concordances with presurgical evaluations, and to characterize the clinical features of occipital lobe epilepsy (OLE), we studied 26 patients who were diagnosed as having OLE and underwent epilepsy surgery. METHODS: Diagnoses were established by standard presurgical evaluations, which included magnetic resonance imaging (MRI), fluorodeoxyglucose-positron emission tomography (FDG-PET), ictal single-photon emission computed tomography (SPECT), scalp video-EEG monitoring, and intracranial EEG monitoring. After epilepsy surgery, patients were followed up for >2 years. RESULTS: Sixteen (61.5%) of the 26 became seizure free after surgery, and another eight patients had a favorable outcome. Sixteen of the 26 patients experienced a type of visual aura (i.e., visual hallucination, visual illusion, blindness, or a field defect). Nine patients had both automotor seizures and secondary generalized tonic-clonic seizures at different times. Interictal EEG showed correctly localizing spikes in 10 of the 16 patients who became seizure free, and in three of the 10 non-seizure-free patients. MRI correctly localized the lesion in seven of these 16 seizure-free patients, and in three of the 10 non-seizure-free patients. FDG-PET correctly localized the lesion in eight of the 16 seizure-free patients, and in three of nine non-seizure-free patients. Ictal SPECT was performed in 19 patients and correctly localized the lesion in only three of 12 seizure-free patients, and in four of seven non-seizure-free patients. Ictal EEG correctly localized the lesion in 13 of the 16 seizure-free patients, and in five of the 10 non-seizure-free patients. No significant relation was found between the diagnostic accuracy of any modality and surgical outcome. The localizations of epileptogenic zones by these different diagnostic methods were complementary. The concordance of three or more modalities was significantly observed in seizure-free patients (p = 0.042). However, no definite relation was observed between the presence of lateralizing clinical seizure manifestation and surgical outcome (p = 0.108). CONCLUSIONS: Some specific auras indicated an occipital epilepsy onset. Various diagnostic methods can be useful to diagnose OLE, and a greater concordance between presurgical evaluation modalities indicates a better surgical outcome.     

When is a postoperative seizure equivalent to “epilepsy recurrence” after epilepsy surgery?

Purpose: Up to one‐half of epilepsy surgery patients will have at least one seizure after surgery. We aim to characterize the prognosis following a first postoperative seizure, and provide criteria allowing early identification of recurrent refractory epilepsy. Methods: Analyzing 915 epilepsy surgery patients operated on between 1990 and 2007, we studied 276 who had ≥1 seizure beyond the immediate postoperative period. The probability of subsequent seizures was calculated using survival analysis. Patients were divided into seizure‐free (no seizures for ≥1 year) and refractory (persistent seizures) and analyzed using multivariate regression analysis. Results: After a first seizure, 50% had a recurrence within 1 month and 77% within a year before the risk slowed down to additional 2–3% increments every two subsequent years. After a second seizure, 50% had a recurrence within 2 weeks, 78% within 2 months, and 83% within 6 months. Having both the first and second seizures within six postoperative months [odds ratio (OR) 4.04; 95% confidence interval (CI) 2.05–8.40; p = 0.0001], an unprovoked initial recurrence (OR 3.92; 95% CI 2.13–7.30; p < 0.0001), and ipsilateral spikes on a 6‐months postoperative electroencephalography (EEG) (OR 2.05; 95% CI 1.10–3.88; p = 0.025) predicted a poorer outcome, with 95% of patients who had all three risk factors becoming refractory. All patients with cryptogenic epilepsy and recurrent seizures developed refractoriness. Discussion: Seizures will recur in most patients who present with their first postoperative event, with one‐third eventually regaining seizure‐freedom. Etiology and early and unprovoked postoperative seizures with epileptiform activity on EEG at six postoperative months may predict recurrent medical refractoriness.     

Scalp-EEG Recording via Methohexital Narcosis

This study sought to compare the localization of methohexital induced activation in the epileptogenic zone between scalp derived and subdural electrode ECoG recordings and to correlate with seizure outcome after epilepsy surgery. Electroencephalogram (EEG) and ECoG recordings of 15 patients (15–53 years of age, mean: 34 years) with a preoperative methohexital narcosis (low dose 40–50 mg and high dose 80–100 mg) were postoperatively analyzed. Six out of eight patients with both scalp recordings and ECoG recordings showed congruous epileptogenic zone activation (temporal/frontal) in noninvasive and invasive recordings. All improved postoperatively 1, 2. Five postoperatively improved patients (two with ECoG and three with EEG) had an additional temporal spike induction opposite the operated hemisphere 1, 3. One postoperatively seizure-free patient had no temporal activation in EEG but did in ECoG 1, 4. In none of the postoperatively improved patients was EEG falsely localizing [2]. Five of seven patients with scalp-EEG recording showed exclusive activation, one patient predominant activation of the temporal epileptogenic zone. All of these patients improved postoperatively [3]. Postoperatively, all but one patient were seizure-free or had > 75% improvement. One patient with an EEG activation incongruous with the side of operation had no postoperative improvement. Methohexital induced activation of epileptogenic foci is congruent in EEG and ECoG and is a reliable method for lateralization and localization of the epileptogenic zone.