Prognostic factors in neocortical epilepsy surgery: multivariate analysis

PURPOSE: Defining prognostic factors for neocortical epilepsy surgery is important for the identification of ideal candidates and for predicting the prognosis of individual patients. We use multivariate analysis to identify favorable prognostic factors for neocortical epilepsy surgery. METHODS: One hundred ninety-three neocortical epilepsy patients, including 91 without focal lesions on MRI, were included. Sixty-one had frontal lobe epilepsy (FLE), 80 had neocortical temporal lobe epilepsy (nTLE), 21 had parietal lobe epilepsy (PLE), and 22 had occipital lobe epilepsy (OLE). The primary outcome variable was patient status >or=2 years after surgery (i.e., seizure free or not). Clinical characteristics and the recent presurgical diagnostic modalities were considered as probable prognostic factors. Univariate and standard multiple logistic regression analyses were used to identify favorable prognostic factors. RESULTS: The seizure-free rate was 57.5%. By univariate analysis, a focal lesion on MRI, localized ictal onset on surface EEG, epilepsies other than FLE, localized hypometabolism on fluorodeoxyglucose-positron emission tomography (FDG-PET), and pathologies other than cortical dysplasia were significantly associated with a seizure-free outcome (p<0.05). Multivariate analysis revealed that a focal lesion on MRI (p=0.003), correct localization by FDG-PET (p=0.007), and localized ictal onset on EEG (p=0.01) were independent predictors of a good outcome. CONCLUSIONS: The presence of a focal lesion on MRI, correct localized hypometabolism on FDG-PET, or localized ictal rhythms on EEG were identified as predictors of a seizure-free outcome. Our results suggest that these findings allow the selection of better candidates for neocortical epilepsy surgery.     

Failed surgery for temporal lobe epilepsy: predictors of long-term seizure-free course

OBJECTIVES: To identify prognostic factors which predict the outcome 2 years after TLE surgery in those patients who were not seizure-free at the 6-month postoperative examination. METHODS: We included 86 postoperative TLE patients who had undergone presurgical evaluation, including video-EEG and high-resolution MRI, and who had seizures between the second and sixth postoperative months. RESULTS: 32% of patients were seizure-free in the second postoperative year. We found that normal MRI findings and secondarily generalized seizures (SGTCS) preoperatively were associated with a non-seizure-free outcome, while rare postoperative seizures and ipsilateral temporal IED with seizure-free outcome. Newly administered levetiracetam showed a significant positive effect on the postoperative outcome independent of other prognostic factors. Five of seven patients who received levetiracetam became seizure-free (p = 0.006). CONCLUSION: One-third of patients who did not become seizure-free immediately after surgery, eventually achieved long-term seizure freedom. We suggest watching for long-term seizure freedom after failed epilepsy surgery especially in patients who had rare postoperative seizures, focal MRI abnormality, ipsilateral temporal spikes, or no SGTCS preoperatively. Levetiracetam may have a positive effect on postsurgical seizures.     

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.     

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.     

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.     

Magnetoencephalography source localization and surgical outcome in temporal lobe epilepsy.

OBJECTIVE: We prospectively investigated the role of magnetoencephalography (MEG) in localizing the seizure focus and in predicting outcome to surgical resections for intractable temporal lobe epilepsy (TLE). METHODS: We performed simultaneous interictal EEG and MEG recording (two 37-channel system) in 26 TLE patients followed by MEG source localization. We correlated early modeling dipoles with intracranial EEG, temporal surgical resection and surgical outcome. RESULTS: There were 12 patients who had anterior temporal horizontal or tangential dipoles to the anterior infero-lateral temporal tip cortex. Two patients underwent selective amygdalo-hippocampectomy (SAH) and nine patients had antero-medial temporal lobectomy (AMTL). All patients had successful outcome except for one patient who initially failed SAH, but became seizure-free after AMTL. There were 11 patients who demonstrated anterior temporal vertical or tangential oblique dipoles. Five patients had AMTL and three had SAH; all became seizure free. Five of above 23 patients had invasive EEG and demonstrated mesial seizure onset. Three TLE patients had lateral vertical dipoles that were concordant with intracranial EEG and these became seizure free after temporal neocortical resections. CONCLUSIONS: MEG source analysis produces distinct source patterns that provide useful localizing information, predict surgical outcome, and may aid in planning limited surgical resection in TLE.     

Relationship of flumazenil and glucose PET abnormalities to neocortical epilepsy surgery outcome.

BACKGROUND: Cortical areas showing abnormal glucose metabolism and [(11)C]flumazenil (FMZ) binding are commonly seen on PET scans of patients with intractable partial epilepsy, but it is unclear whether these must be totally resected to achieve seizure control. OBJECTIVE: To analyze whether the extent of cortex showing 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) or FMZ PET abnormalities correlates with the outcome of resective epilepsy surgery. METHODS: Cortical FDG and FMZ PET abnormalities in 15 young patients (mean age, 12.2 +/- 7.0 years) with intractable partial epilepsy of neocortical origin were marked as regions with abnormal asymmetry using an objective semiautomated software package. These marked regions were then projected and measured on the brain surface reconstructed from the coregistered high-resolution MRI. Following cortical resection, the size of nonresected cortex with preoperative PET abnormalities was also measured (calculated separately for marked areas in the lobe of seizure onset as defined by long-term video EEG monitoring, and in remote cortical areas). Extent of preoperative PET abnormalities and postoperative nonresected cortex abnormalities on PET were correlated with outcome scores. RESULTS: Large preoperative FMZ PET abnormalities were associated with poor outcome (r = 0.57; p = 0.025). Larger areas of nonresected cortex with preoperative FMZ PET abnormalities in the lobe of seizure onset were also associated with worse outcome in the whole group (r = 0.66; p = 0.007) as well as in patients with extratemporal resection (r = 0.73; p = 0.007), and in those with no lesion on MRI (r = 0.60; p = 0.049). Patients with seizure-free outcome had significantly smaller nonresected cortex with preoperative FMZ PET abnormalities than those who continued to have seizures (p = 0.022). No significant correlations between nonresected FDG PET abnormalities and surgical outcome were found. CONCLUSIONS: Extensive cortical abnormalities on FMZ PET predict poor outcome in neocortical epilepsy surgery. Resection of FMZ abnormalities in the lobe of seizure onset is associated with excellent outcome even in the absence of a structural lesion. In contrast, although FDG PET abnormalities regionalized the epileptogenic area, their size was not related to the extent of epileptogenic tissue to be removed.     

The prognostic significance of interictal epileptiform activity in postoperative EEGs of patients with mesial temporal lobe epilepsy.

It has not been established whether electroencephalography (EEG) is a contributing factor in predicting the outcome of surgery for epilepsy. We conducted a prospective study on 26 patients (M/F 14/12, age: 33 +/- 7.5 years, range 19-48) with mesial temporal lobe epilepsy (MTLE) who were followed for 2 years after surgery and who underwent routine EEG recordings 5.6 +/- 3 months (range 3-12) postoperatively. Interictal epileptiform activity (IEA) on the EEG was compared in 17 seizure-free patients to 9 patients with recurrent seizures. The two groups were similar in gender, age, febrile convulsions, trauma, family history, seizure frequency prior to surgery, epilepsy duration and number of antiepileptic drugs. Following surgery, 17 study patients (65%) became seizure free; 9 (35%) had seizure recurrence. Post-operative EEG recordings showed IEA in 8/26 study patients (31%), 3 of whom were from the seizure-free group (3/17, 18%); 5 had seizure recurrence (5/9, 56%) (p=0.078). IEAs in postoperative EEGs were less frequently demonstrated in patients who were seizure free, but the presence of postoperative IEAs does not preclude successful surgical 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.     

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).     

Comparison of Mesial Versus Neocortical Onset Temporal Lobe Seizures: Neurodiagnostic Findings and Surgical Outcome

Summary: We compared historical features, surface EEG findings, results of intracarotid sodium amobarbital memory testing (IAT), and outcome after anterotemporal lobectomy (ATL) in patients with mesiotemporal lobe seizure onset with those with more diffuse temporal lobe seizure onset (intracranial EEG). Forty-eight patients evaluated consecutively between July 1985 and October 1991 with both scalp/sphenoidal and intracranial EEG were shown to have seizures originating in one temporal lobe. No patients had temporal lobe tumor or vascular malformation. Thirty-seven of the 48 patients had seizure onset in the amygdale/hippocampus (amyg/hipp). Eleven of the 48 had either temporal neocortical onset or simultaneous amydhipp and neocortical onset. Patients with mesial onset seizures were more likely to have lateralized memory impairment on I AT (p = 0.05). We noted a trend toward a difference in age of first risk for epilepsy between the two groups (p = 0.09) but not for a difference in any specific risk factor. There were no significant differences in surface EEG interictal findings. Unlike in previous studies, comparison of outcome between the two groups showed no difference in seizure-free outcome. Sudden unexpected death (SUD) was more frequent in neocortical seizure patients who were not seizure-free (p < 0.05).     

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.     

Hyperkinetic seizures in patients with temporal lobe epilepsy: clinical features and outcome after temporal lobe resection

Purpose: Temporal lobe epilepsy (TLE) is usually associated with automatisms. Hyperkinetic seizures are supposed to be unusual. Because we witnessed several patients with TLE and ictal hyperkinetic symptoms, we retrospectively assessed the number, clinical findings, and seizure outcome in such patients who had undergone temporal lobe resection. Methods: We reviewed medical history, video–electroencephalography (EEG) recording and neuroimaging of adult patients who underwent epilepsy surgery for TLE at the Kork Epilepsy Center over the last 20 years with a minimum postoperative follow‐up of 12 months. Key Findings: Among 294 patients who were resected exclusively in the temporal region, we identified 17 (6%) who presented with hyperkinetic semiology such as violent vocalization, complex movements of the proximal segments of the limbs, rotation of the trunk, pelvic thrusting, or early tonic or dystonic posturing. Most of the patients had a preceding aura. Ictal EEG activity was located in the corresponding temporal region, usually with a wide distribution over temporal electrodes with fast spread to unilateral frontal electrodes and to the contralateral side. Neuroimaging revealed extended lesions in the temporal lobe involving mesial and neocortical structures. Most of the patients underwent classical anterior temporal lobe resection including amygdalo‐hippocampectomy. Fourteen patients (82%) became completely seizure‐free (Engel class Ia). Histopathology showed mainly focal cortical dysplasia plus hippocampal sclerosis. Significance: Hyperkinetic seizure semiology may occasionally occur in patients with TLE and is, therefore, no contradiction to the hypothesis of TLE if scalp EEG patterns and neuroimaging findings correspond. The postoperative seizure outcome is favorable in such patients and not different from outcome data in classical TLE.     

Implications of Seizure Termination Location in Temporal Lobe Epilepsy

Summary: Where propagating symptomatic seizures terminate has not been studied, but might provide insight into mechanisms of seizure termination as well as localization of epileptogenic tissue. We investigated location of seizure termination in 50 refractory temporal lobe epilepsy (TLE) patients who had intracranial EEG recording of spontaneous seizures and subsequent temporal lobe resection with > 1–year follow-up. Only seizures that had onset in the resected temporal lobe were included. Location of the electrical termination for each seizure in each patient was categorized as diffuse, localized to the onset location, or localized elsewhere. The proportion of all seizures in each patient in each category was analyzed with respect to the outcome of surgery. Outcome was classified as seizure-free or persistent seizures. Diffuse seizure termination was noted equally frequently in both outcome groups. However, the 27 patients without seizures postoperatively had a significantly greater proportion of seizures with termination in the onset location (67%) than did the 23 patients with persistent seizures (36%, p < 0.01). The seizure-free patients also had a significantly lower proportion of seizures with localized termination elsewhere than the onset site (13%) than did patients with persistent seizures (45%, p < 0.005). Localization of the site of termination of seizures of focal origin to cortical regions other than the onset is associated with a poorer surgical prognosis. This observation raises the possibility of additional abnormal epileptogenic cortical regions with impaired seizure-terminating capabilities.     

The localizing value of the abdominal aura and its evolution: a study in focal epilepsies.

OBJECTIVE: To evaluate the localizing value of abdominal aura and its evolution into other seizure types. METHODS: The seizures of 491 consecutive patients with focal epilepsies were prospectively classified according to a recently introduced semiologic seizure classification. All patients underwent prolonged EEG video monitoring and MRI scan. Two hundred twenty-three patients (45%) had temporal lobe epilepsies (TLE); 113 patients (23%) had extratemporal epilepsies; and for 155 (32%) patients, the epilepsy could not be localized to one lobe. RESULTS: Abdominal auras were more frequent with TLE (117 of 223 patients, 52%) than in extratemporal epilepsy (13 of 113 patients, 12%, p < 0.0001) and more frequent in mesial TLE (70 of 110 patients, 64%) than in neocortical TLE (16 of 41 patients, 39%, p = 0.007). No preponderance to one side existed. Abdominal auras were followed by ictal oral and manual automatisms (automotor seizure) in at least one seizure evolution in all patients with TLE (117 patients, 100%). In contrast, only two patients with extratemporal epilepsy (2 of 13 patients, 15%, p < 0.0001) had abdominal auras evolving into automotor seizures. An abdominal aura is associated with TLE with a probability of 73.6%. The evolution of an abdominal aura into an automotor seizure, however, increases the probability of TLE to 98.3%. CONCLUSIONS: These results demonstrate that evolution of abdominal aura into automotor seizure permits differentiation between temporal lobe epilepsy and extratemporal epilepsy, showing that analysis of seizure evolution provides more localizing information than does the frequency of particular seizure types.     

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.     

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.     

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.     

Surgical outcome and predictive factors in adult patients with intractable epilepsy and focal cortical dysplasia

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.     

EEG and Seizure Outcome After Epilepsy Surgery

Summary: The significance of the EEG after epilepsy surgery is not fully understood. We investigated the as- sociation between postoperative EEG abnormalities and persistent seizures after epilepsy surgery as they relate to pathologic lesions. Among 254 patients who underwent epilepsy surgery between 1987 and 1991, we identified 78 patients who had mesiotemporal sclerosis (MTS) and 47 patients who had low-grade brain tumors, all of whom had 6-to 18-month postoperative follow-up including EEG. Patients who had other pathology, multiple operations, callosotomy, or hemispherectomy, or who were aged <18 years or who had insufficient EEG data, were excluded. Patients were classified as having persistent seizures or being seizure-free since operation. EEG abnormalities were abstracted from EEG reports 6–18 months postoperatively. Seizures persisted in 24% of the MTS group and in 27% of the tumor group. Of those with normal EEGs, none of the MTS patients and only 1 of the tumor patients had persistent seizures (p = 0.03 for MTS and p = 0.42 for tumor). Epileptiform discharges and focal slowing were associated with seizure persistence in both groups, but to a significant extent only in the MTS group. In the MTS group, patients who had both epileptiform discharges and focal slowing were more likely to have persistent seizures than were those with either abnormality alone.