EEG predicts surgical outcome in lesional frontal lobe epilepsy

BACKGROUND: Because of the relatively poor results of frontal lobe epilepsy (FLE) surgery, identification of prognostic factors for surgical outcome is of great importance. METHODS: To identify predictive factors for FLE surgery, we analyzed the data of 61 patients (mean age at surgery 19.2) who had undergone presurgical evaluation and resective surgery in the frontal lobe. Postoperative follow-up ranged from 0.5 to 5 years (mean 1.78). Fifty-nine patients had MRI-detectable lesions. Histopathologic examination showed dysplasia (57.4%), tumor (16.4%), or other lesions (26.2%). Thirty postoperatively seizure-free patients were compared with 31 non-seizure-free patients with respect to clinical history, seizure semiology, EEG and neuroimaging data, resected area, and postoperative data including histopathology. RESULTS: Three preoperative and two postoperative variables were related to poor outcome: generalized epileptiform discharges, generalized slowing, use of intracranial electrodes, incomplete resection detected by MRI, and postoperative epileptiform discharges. The only preoperative factor associated with seizure-free outcome was the absence of generalized EEG signs. Multivariate analysis showed that only the absence of generalized EEG signs predicts the outcome independently. Moreover, the occurrence of a somatosensory aura, secondarily generalized seizures, and negative MRI was identified as additional independent risk factors for poor surgical results. CONCLUSIONS: The absence of generalized EEG signs is the most predictive variable for a seizure-free outcome in FLE surgery. Furthermore, nonlesional MRI, somatosensory aura, and secondarily generalized seizures are risk factors for poor surgical results.     

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.     

Intracranial EEG in predicting surgical outcome in frontal lobe epilepsy

Purpose: Surgery in frontal lobe epilepsy (FLE) has a worse prognosis regarding seizure freedom than anterior lobectomy in temporal lobe epilepsy. The current study aimed to assess whether intracranial interictal and ictal EEG findings in addition to clinical and scalp EEG data help to predict outcome in a series of patients who needed invasive recording for FLE surgery. Methods: Patients with FLE who had resective surgery after chronic intracranial EEG recording were included. Outcome predictors were compared in patients with seizure freedom (group 1) and those with recurrent seizures (group 2) at 19–24 months after surgery. Key Findings: Twenty‐five patients (16 female) were included in this study. Mean age of patients at epilepsy surgery was 32.3 ± 15.6 years (range 12–70); mean duration of epilepsy was 16.9 ± 13.4 years (range 1–48). In each outcome group, magnetic resonance imaging revealed frontal lobe lesions in three patients. Fifteen patients (60%) were seizure‐free (Engel class 1), 10 patients (40%) continued to have seizures (two were class II, three were class III, and five were class IV). Lack of seizure freedom was seen more often in patients with epilepsy surgery on the left frontal lobe (group 1, 13%; group 2, 70%; p = 0.009) and on the dominant (27%; 70%; p = 0.049) hemisphere as well as in patients without aura (29%; 80%; p = 0.036), whereas sex, age at surgery, duration of epilepsy, and presence of an MRI lesion in the frontal lobe or extrafrontal structures were not different between groups. Electroencephalographic characteristics associated with lack of seizure freedom included presence of interictal epileptiform discharges in scalp recordings (31%; 90%; p = 0.01). Detailed analysis of intracranial EEG revealed widespread (>2 cm) (13%; 70%; p = 0.01) in contrast to focal seizure onset as well as shorter latency to onset of seizure spread (5.8 ± 6.1 s; 1.5 ± 2.3 s; p = 0.016) and to ictal involvement of brain structures beyond the frontal lobe (23.5 ± 22.4 s; 5.8 ± 5.4 s; p = 0.025) in patients without seizure freedom. The distribution of ictal onset patterns was similar in both groups, and fast rhythmic activity in the beta to gamma range was found in 57% of seizure‐free patients compared to 70% of patients with recurrent seizures. Analysis of the temporal relation between first clinical alterations and EEG seizure onset did not reveal significant differences between both groups of patients. In multivariate analysis, resection in the left hemisphere (odds ratio [OR] 12.197 95% confidence interval [95% CI] 1.33–111.832; p = 0.027) and onset of seizure spread (odds ratio [OR] 0.733, 95% CI 0.549–0.978, p = 0.035) were independent predictors of ongoing seizures. Significance: Widespread epileptogenicity as indicated by rapid onset of spread of ictal activity likely explains lack of seizure freedom following frontal resective surgery. The negative prognostic effect of surgery on the left hemisphere is less clear. Future study is needed to determine if neuronal network properties in this hemisphere point to intrinsic interhemispheric differences or if neurosurgeons are restrained by proximity to eloquent cortex.     

Spikes on the postoperative EEG are related to preoperative spike frequency and postoperative seizures

PURPOSE: To investigate the factors which influence the persistence of interictal epileptiform discharges (IED) after epilepsy surgery. METHODS: In this retrospective study we included patients with intractable medial temporal lobe epilepsy (MTLE) who underwent presurgical evaluation including high-resolution MRI and video-EEG monitoring with seizure registration prior to an anterior temporal lobe resection. The postsurgical outcome was assessed by our team 6 months and 2 years after the surgery. RESULTS: One hundred and forty-seven patients fulfilled the inclusion criteria. The mean age of the patients was 31.8 (range 16-59 years). In 22 patients (15%) interictal epileptiform discharges were present on the postoperative routine EEG. We found that both the preoperative spike frequency ( P < 0.001 ) and postoperative seizures ( P = 0.04 ) were independently associated with the presence of IED on the postoperative routine EEG. The preoperative spike frequency was not associated with the postoperative outcome. The extent of resection showed no influence on the presence of postoperative IED. CONCLUSION: We hypothesize that two factors independently influence the presence of postoperative spikes: chronic interictal disturbance (represented as preoperative spike frequency) and the acute (postoperative) seizures. Our study confirmed that persistent postoperative IED had a prognostic value regarding the outcome of the epilepsy surgery.     

Outcome predictors for surgical treatment of temporal lobe epilepsy with hippocampal sclerosis

Purpose: To study long-term postoperative course and identify predictors for postoperative seizure control in patients with medically intractable temporal lobe epilepsy (TLE) associated with hippocampal sclerosis (HS), diagnosed by magnetic resonance imaging (MRI), and ascertained histopathologically. To compare patients becoming seizure-free (i.e., cured from epilepsy) and patients experiencing prolonged seizure-free periods interposed with recurring seizures.
Methods: One hundred thirty-five patients (74 women) underwent complete evaluation for epilepsy surgery. The predictive value of duration of epilepsy, age at onset, age at surgery, gender, febrile convulsion history, ictal dystonic posturing, unilateral interictal electroencephalography (EEG) discharges (IED), preoperative secondarily generalized tonic–clonic seizures (SGTCS), and preoperative seizure frequency for short- and long-term postoperative seizure control were evaluated with two classification systems: Classification 1 (seizure-freedom with or without auras during 12-months before observation points) and the stringent classification 2 [International League Against Epilepsy (ILAE) Ia; absolute absence of seizures and auras after operation].
Results: Unilateral IED at year 1 and 2 (p = 0.037 and p = 0.034), male gender and low seizure frequency at year 2 (p = 0.013 and p = 0.046) were significant predictors for seizure freedom using classification 1. All variables (except male gender at year 2; p = 0.035) lost their predictive power, applying classification 2. The proportion of seizure-free patients remained stable between 70% to 79% with classification 1, but decreased from 64.4% at year 1 to 45.8% at year 5 with classification 2.
Discussion: Positive predictors of short-term outcome do not predict long-term outcome in patients with TLE associated with HS. Absolute freedom of seizures and auras cannot be predicted by conventional preoperative variables.     

Focal ictal beta discharge on scalp EEG predicts excellent outcome of frontal lobe epilepsy surgery

PURPOSE: To determine whether a focal beta-frequency discharge at seizure onset on scalp EEG predicts outcome of frontal lobe epilepsy (FLE) surgery. METHODS: We identified 54 consecutive patients with intractable FLE who underwent epilepsy surgery between December 1987 and December 1996. A blind review of EEGs and magnetic resonance images (MRIs) was performed. Lesional epilepsy is defined as presence of an underlying structural abnormality on MRI. RESULTS: Overall, 28 (52%) patients were seizure free, with a mean follow-up of 46.5 months. Presence of a focal beta-frequency discharge at seizure onset on scalp EEG predicted seizure-free outcome in lesional (p = 0.02) and non-lesional (p = 0.01) epilepsy patients. At least 90% of patients who had either lesional or non-lesional epilepsy were seizure free if scalp EEG revealed a focal beta discharge at ictal onset. Moreover, logistic regression analysis showed that focal ictal beta pattern and completeness of lesion resection were independently predictive of seizure-free outcome. Ictal onset with lateralized EEG activity of any kind and postresection electrocorticographic spikes did not predict surgical outcome (p > 0.05). CONCLUSIONS: Only about 25% of FLE surgical patients have a focal beta-frequency discharge at seizure onset on scalp EEG. However, its presence is highly predictive of excellent postsurgical seizure control in either lesional or non-lesional FLE surgical patients.     

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).     

Long term outcome of temporal lobe epilepsy surgery: analyses of 140 consecutive patients

OBJECTIVE: To analyse the long term results of temporal lobe epilepsy surgery in a national epilepsy surgery centre for adults, and to evaluate preoperative factors predicting a good postoperative outcome on long term follow up. METHODS: Longitudinal follow up of 140 consecutive adult patients operated on for drug resistant temporal lobe epilepsy. RESULTS: 46% of patients with unilateral temporal lobe epilepsy became seizure-free, 10% had only postoperative auras, and 15% had rare seizures on follow up for (mean (SD)) 5.4 (2.6) years, range 0.25 to 10.5 years. The best outcome was after introduction of a standardised magnetic resonance (MR) imaging protocol (1993-99): in unilateral temporal lobe epilepsy, 52% of patients became seizure-free, 7% had only postoperative auras, and 17% had rare seizures (median follow up 3.8 years, range 0.25 to 6.5 years); in palliative cases (incomplete removal of focus), a reduction in seizures of at least 80% was achieved in 71% of cases (median follow up 3.1 years, range 1.1 to 6.8 years). Most seizure relapses (86%) occurred within one year of the operation, and outcome at one year did not differ from the long term outcome. Unilateral hippocampal atrophy with or without temporal cortical atrophy on qualitative MR imaging (p < 0.001, odds ratio (OR) 5.2, 95% confidence interval (CI) 2.0 to 13.7), other unitemporal structural lesions on qualitative MR imaging (p < or = 0.001, OR 6.9, 95% CI 2.2 to 21.5), onset of epilepsy before the age of five years (p < 0.05, OR 2.9, 95% CI 1.2 to 7.2), and focal seizures with ictal impairment of consciousness and focal ictal EEG as a predominant seizure type (p < 0.05, OR 3.4, 95% CI 1.2 to 9.1) predicted Engel I-II outcome. Hippocampal volume reduction of at least 1 SD from the mean of controls on the side of the seizure onset (p < 0.05, OR 3.1, 95% CI 1.1 to 9.2) also predicted Engel I-II outcome. CONCLUSIONS: Outcome at one year postoperatively is highly predictive of long term outcome after temporal lobe epilepsy surgery. Unitemporal MR imaging abnormalities, early onset of epilepsy, and seizure type predominance are factors associated with good postoperative outcome.     

Predictive clinical factors for the differential diagnosis of childhood extratemporal seizures

PURPOSE: To describe predictive clinical factors for the differentiation between childhood frontal lobe epilepsy (FLE) and posterior cortex epilepsy (PCE). METHODS: Two independent, blinded investigators analyzed 177 seizures from 35 children (aged 11 months to 12 years) with extratemporal epilepsy selected by postoperative seizure-free outcome. Semiologic seizure components and different periictal signs were observed. Age at onset, auras, seizure frequency, and nocturnal dominance, as well as surgical and histopathologic data, were collected from medical charts. RESULTS: Twenty patients had FLE, and 15 had PCE. Patients from both groups had daily seizures without significant differences in frequency but with higher nocturnal dominance in children with FLE (p < 0.05). Visual aura, nystagmus, and versive seizure were observed exclusively in the PCE group, whereas somatosensory aura and hypermotor seizures appeared only in FLE. Tonic seizures were significantly more frequent in FLE (p < 0.01), whereas the presence of clonic seizure (FLE; p = 0.07) and postictal nose-wiping (PCE; p = 0.05) showed only a trend to localize the seizure-onset zone. Myoclonic seizures, epileptic spasms, psychomotor seizures, atonic seizures, oral and manual automatisms, as well as vocalization and eye deviation appeared in both groups without significant differences in their frequency. CONCLUSIONS: Characteristic features described in adults' extratemporal epilepsies were frequently missing during childhood seizures, especially in infants and preschool children. Ictal features help only a little in differentiating childhood FLE from PCE. Nocturnal appearance and the type of aura have high localizing value; therefore an accurate history taking is still an essential element of pediatric presurgical evaluation.     

鉴别额叶癫痫及颞叶癫痫的临床症状学提示

目的:比较额叶癫痫(FLE)及颞叶癫痫(TLE)的临床症状学区别。方法:纳入2005年10月至2007年3月我院癫痫中心门诊临床诊断为额叶癫痫患者190名,颞叶癫痫患者257名。纳入病例满足发作间期脑电图至少一次具有局限于额叶或颞叶的放电或发作期脑电图明确提示额或颞叶起源;排除所有发作间期脑电图正常、存在多灶或定位不清的脑电异常及影像学检查具有额或颞叶以外的局灶损害者。由两位不知道患者脑电图和影像学结果的临床医生单独分析患者发作情况(先兆、复杂部分发作(CPS)、继发全面强直阵挛发作(SGTC))。用χ2检验统计数据。结果:提示颞叶癫痫最有意义的先兆是经验现象和胃气上升感(P<0.01)。情感表现在TLE中更常见(P<0.05)。口咽自动症与手部自动症是颞叶癫痫患者的典型CPS表现(P<0.01)。而躯体自动症,偏转性强直-肢体与头眼及SGTC、姿势性强直,局部阵挛发作,发作时伴随出声、植物神经症状是额叶癫痫患者的典型CPS表现(P<0.01)。发笑、震颤症状在二类中均可出现,以额叶居多(P<0.05)。言语终止,自言自语,单纯凝视发作对于二者的鉴别意义不大。额叶癫痫组具有两种以上CPS发作的病例更多(P<0.01)。结论:额叶癫痫与颞叶癫痫的症状学特征是不同的,对于临床诊断有重要价值。     

Seizure outcomes following multilobar epilepsy surgery

Purpose: Outcomes following unilobar surgeries for refractory epilepsy have been well described. However, little is known about long‐term seizure outcomes following multilobar resections. The aim of the current study was to identify long‐term seizure control and predictors of seizure recurrence in this patient population. Methods: Records of patients who underwent multilobar epilepsy surgery at the Cleveland Clinic between 1994 and 2010 were retrospectively reviewed. A postoperative follow‐up of at least 6 months was required. Patients were classified as seizure free if they achieved an Engel class I at last follow‐up. Long‐term chances of seizure freedom were illustrated using a survival analysis, and predictors of recurrence were identified using Cox proportional hazard modeling. Key Findings: Sixty‐three patients with medically intractable epilepsy underwent multilobar surgical resections during the study period (mean follow‐up of 4.6 years). Predominant resection types included extended occipital (temporoparietooccipital, parietooccipital, temporooccipital: 57%), frontotemporal (21%), and temporoparietal (17%). Mean age at surgery was 21.4 years and mean age at seizure onset was 10.1 years. Fifty‐six percent of the patients underwent extraoperative invasive electroencephalography (EEG) evaluations. At 6 postoperative months, 71% (95% confidence interval (CI) 65–77) were seizure‐free (SF), 64% (CI 58–70) were SF at 1 year, 52% (CI 46–59) were SF at 5 years, and 41% (CI 32–50) remained SF at 10 years. Forty‐one patients had at least one breakthrough seizure after surgery (median timing of recurrence 6.1 months), with an Engel class 1 achieved again by last follow‐up in 12 of these 41 cases. Nine patients required a reoperation. Patients who underwent extended occipital/posterior quadrant resections had more favorable outcomes as compared to the other groups. With multivariate analysis, the type of resection (p = 0.03), preoperative auras (p = 0.03), an incomplete resection (0.03), and the presence of postoperative spikes (p = 0.0003) correlated with seizure recurrence. The risk of seizure recurrence for an incomplete resection was 2.3 (CI 1.53–3.36), preoperative aura 2.3 (CI 1.34–3.87), and postoperative spikes on surface EEG 2.5 (CI 1.29–4.71). Significance: A favorable outcome can be achieved in 41% of patients undergoing multilobar resections for epilepsy surgery at 10 years of follow‐up. Close to one‐third of patients who have breakthrough seizures after surgery are able to regain seizure freedom by last follow‐up. Predictors of recurrence include resection type (frontotemporal and parietotemporal resections did worse), presence of preoperative aura, an incomplete surgical resection, and the presence of postoperative interictal discharges on EEG.     

Nichtinvasives Video-EEG-Monitoring in der Diagnostik fokaler Epilepsien und als Prädiktor für das postoperative Ergebnis

Video-documented seizure semiology and non-invasive EEG are mandatory elements of presurgical epilepsy diagnosis. Non-invasive interictal and ictal EEG invaluably contribute to the diagnosis and prognosis of non-tumoral mesial temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). The semiology of auras and seizures help to lateralize FLE and TLE, and add to the consistency of various methods. In posterior epilepsy, the semiology of auras and seizures provides important information on localization and prognosis as opposed to non-invasive EEG.¶???During the first two years after surgery, routine EEG helps to predict the long-term seizure outcome. Further studies about long-term seizure outcome over more than five years are necessary.¶ ???Beyond the scope of this review about non-invasive video/ EEG monitoring, a multitude of other non-invasive methods are used which would deserve seperate consideration.     

Seizure outcome and its predictors after temporal lobe epilepsy surgery in patients with normal MRI

Purpose: To characterize seizure outcomes following temporal lobe epilepsy (TLE) surgery in patients with normal preoperative brain magnetic resonance imaging (MRI). Methods: We reviewed adult patients with pharmacoresistant epilepsy and normal MRI who underwent TLE surgery (1996–2009). Seizure outcomes were analyzed using survival and multivariate regression with Cox proportional hazard modeling. Two analyses were performed using two favorable outcome definitions: complete seizure freedom and Engel classification. Key Findings: Sixty‐four patients were analyzed (mean follow‐up 4.1 years; range 1–14.5 years). Most had a standard anterior temporal lobectomy (84%) and unremarkable pathology (45%). At 1 year, the chance of complete seizure freedom was 76% [95% confidence interval (CI) 71–81%] comparable to an 81% (95% CI 76–86%) chance of Engel score of 1. With longer follow‐up, a progressively broadening significant discrepancy between the two outcome measures was observed. The chance of complete seizure freedom was 66% (95% CI 61–71%) at 2 years, and 47% (95% CI 40–54%) at 7 years and beyond, whereas the respective chances of achieving an Engel 1 classification were 76% (95% CI 70–82%), and 69% (95% CI 63–75%) at similar time points. Seizure outcome as defined by either measure was worse in patients with higher baseline seizure frequency (adjusted risk‐ratio 2.7 when >12 seizures/month; p = 0.01) and with preoperative generalized tonic–clonic seizures (adjusted risk ratio 10.8; p = 0.0006). Memory measures declined with dominant hippocampus resections. Significance: A normal MRI should not prevent presurgical evaluations in patients with suspected TLE, as favorable long‐term postoperative seizure outcomes are possible. Proposed mechanisms of epileptogenicity and seizure recurrence in this group are discussed.     

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.     

Frontal lobe epilepsy: Clinical characteristics, surgical outcomes and diagnostic modalities.

OBJECTIVE: To identify surgical prognostic factors and to characterize clinical features according to the location of the intracranial ictal onset zone of frontal lobe epilepsy (FLE) in order to assess the role of various diagnostic modalities, including concordances with presurgical evaluations. METHODS: We studied 71 FLE patients who underwent epilepsy surgery and whose outcomes were followed for more than 2 years. Diagnoses were established by standard presurgical evaluation. RESULTS: Clinical manifestations could be categorized into six types: initial focal motor (9 patients), initial versive seizure (15), frontal lobe complex partial seizure (14), complex partial seizure mimicking temporal lobe epilepsy (18), initial tonic elevation of arms (11), and sudden secondary generalized tonic-clonic seizure (4). Thirty-seven patients became seizure-free after surgery. Five patients were deleted in the analysis because of incomplete resection of ictal onset zones. The positive predictive value of interictal EEG, ictal EEG, MRI, PET, and ictal SPECT, respectively were 62.5%, 56.4%, 73.9%, 63.2%, and 63.6%, and the negative predictive value were 46.0%, 44.4%, 53.5%, 44.7%, and 51.7%. No significant relationship was found between the diagnostic accuracy of these modalities and surgical outcome, with the exception of MRI (p=0.029). Significant concordance of two or more modalities was observed in patients who became seizure-free (p=0.011). We could not find any clinical characteristic related to surgical outcome besides seizure frequency. No definite relationship was found between the location of intracranial ictal onset zone and clinical semiology. CONCLUSION: Although various diagnostic methods can be useful in the diagnosis of FLE, only MRI can predict surgical outcome. Concordance between presurgical evaluations indicates a better surgical outcome.     

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.     

Predictors of epilepsy surgery outcome: a meta-analysis

The potential efficacy of temporal and extratemporal resection in patients with partial epilepsy uncontrolled by anti-epileptic drugs is undisputed. However, there are still uncertainties about which patients will benefit most. A systematic review of the available literature has been undertaken by four pairs of reviewers to assess the overall outcome of epilepsy surgery and to identify factors better correlated to seizure outcome. A Medline search for studies on epilepsy surgery published since 1984 was performed. Studies were included if they had a well-defined population and design, a sample size of at least 30 patients, an MRI performed in least 90% of cases, an expected duration of follow-up of at least one year, and a post-operative outcome measured as seizure remission. A good outcome was considered as seizure control or seizure-free status for at least one year or Engel class I. Based on the review of 47 articles meeting all the eligibility criteria, febrile seizures (odds ratio, OR, 0.48; 95% confidence interval, CI, 0.27-0.83), mesial temporal sclerosis (OR 0.47; 95% CI 0.35-0.64), tumors (OR 0.58; 95% CI 0.42-0.80), abnormal MRI (OR 0.44; 95% CI 0.29-0.65), EEG/MRI concordance (OR 0.52; 95% CI 0.32-0.83), and extensive surgical resection (OR 0.24; 95% CI 0.16-0.36) were the strongest prognostic indicators of seizure remission (positive predictors); by contrast, post-operative discharges (OR 2.41; 95% CI 1.37-4.27) and intracranial monitoring (OR 2.72; 95% CI 1.60-4.60) predicted an unfavorable prognosis (negative predictors). Firm conclusions cannot be drawn for extent of resection, EEG/MRI concordance and post-operative discharges for the heterogeneity of study results. Neuromigrational defects, CNS infections, vascular lesions, interictal spikes, and side of resection did not affect the chance of seizure remission after surgery. Despite a number of limitations, the results of the review provide some insight into the selection of the best surgical candidates in clinical practice but raise concerns on the quality of published reports, and may serve as the basis for the identification of better standards to assess surgical outcome in observational studies.     

Resection of Frontal Encephalomalacias for Intractable Epilepsy: Outcome and Prognostic Factors

Summary: 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 β 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 β 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.     

Lack of aura experience correlates with bitemporal dysfunction in mesial temporal lobe epilepsy

The diagnostic value of lack of aura experience in patients with temporal lobe epilepsy (TLE) is unclear. PURPOSE: To evaluate possible factors of bitemporal dysfunction in patients with mesial TLE who did not experience an aura in electroencephalography EEG/video monitoring for epilepsy surgery. METHODS: Ictal scalp EEG propagation patterns of 347 seizures of 58 patients with mesial temporal lobe sclerosis or non-lesional mesial TLE, interictal epileptiform discharges (IED), presence of unilateral mesial temporal lobe sclerosis in visual magnetic resonance imaging (MRI) analysis, prose memory performance, history or not of an aura, and postictal memory or absence of an aura were analyzed. The ictal EEG was categorized as follows. EEG seizure: (a) remaining regionalized, (b) non-lateralized, (c) showing later switch of lateralization or bitemporal asynchronous ictal patterns. RESULTS: Absent aura in monitoring was significantly correlated with absence of unitemporal MRI sclerosis (P=0.004), bitemporal IED (P=0.008), and propagation of the ictal EEG to the contralateral temporal lobe (P=0.001). Other historical data and interictal prose memory performance were not significantly correlated with absent aura. Ten of 11 patients without aura in monitoring also had absent or rare auras in their history. CONCLUSIONS: Lack of aura experience strongly correlates with indicators of bitemporal dysfunction such as bitemporal interictal sharp waves and bitemporal ictal propagation in scalp EEG, and absence of lateralized MRI sclerosis in patients with mesial TLE. The fact that absent auras are not correlated with episodic memory suggests a transient memory deficit, probably because of rapid propagation to the contralateral mesial temporal lobe.     

Postsurgical outcome of children and adolescents with medically refractory frontal lobe epilepsies

OBJECTS: In the adult population surgical treatment is generally less favorable for refractory frontal lobe epilepsy (FLE) than for temporal lobe epilepsy (TLE). Predictive factors and outcome of FLE surgery had not previously been described for the pediatric and adolescent population. Therefore, 32 children and adolescents who underwent FLE surgery were analyzed in this study. METHODS: Medical records were reviewed for demographic data, presurgical evaluation procedures, surgical procedures, pathological findings and follow-up. RESULTS: Mean age at operation was 10.8 years, with seizure onset at 4.6 years. Excellent outcomes were observed in 21 of the 32 patients following evaluation a mean of 34.5 months after surgery. Nineteen of 22 patients became seizure free after tailored resections, versus 2 out of 10 after lobectomy. Transient neurological and surgical complications occurred in 4 patients. Focal neoplastic lesions detectable by MRI were associated with a favorable outcome. CONCLUSIONS: As seen in adult FLE series, the detection of a resectable ictal neoplastic lesion on preoperative MRI is associated with an excellent outcome comparable to that of TLE surgery.