Lesional mesial temporal lobe epilepsy and limited resections: prognostic factors and outcome

Surgery procedures in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common cause of refractory epilepsy amenable for surgical treatment and seizure control. Surgery for TLE is a safe and effective strategy. The seizure-free rate after surgical resection in patients with mesial or neocortical TLE is about 70%. Resective surgery has an advantage over stereotactic radiosurgery in terms of seizure outcomes for mesial TLE patients. Both techniques have similar results for safety, cognitive outcomes, and associated costs. Stereotactic radiosurgery should therefore be seen as an alternative to open surgery for patients with contraindications for or with reluctance to undergo open surgery. Laser interstitial thermal therapy (LITT) has also shown promising results as a curative technique in mesial TLE but needs to be more deeply evaluated. Brain-responsive stimulation represents a palliative treatment option for patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior mesial temporal lobe resection. Overall, despite the expansion of innovative techniques in recent years, resective surgery remains the reference treatment for TLE and should be proposed as the first-line surgical modality. In the future, ultrasound therapies could become a credible therapeutic option for refractory TLE patients.

Epilepsy surgery for low-grade epilepsy-associated neuroepithelial tumor of temporal lobe: a single-institution experience of 61 patients

Background

Low-grade epilepsy-associated neuroepithelial tumor (LEAT) is highly responsive to surgery in general. The appropriate surgical strategy remains controversial in temporal LEAT. The aim of this study is to analyze the surgical seizure outcome of temporal LEAT, focusing on the aspects of surgical strategy.

Methods

Sixty-one patients from a single epilepsy center with temporal LEAT underwent surgery. The surgical strategy was according to the multidisciplinary presurgical evaluation. Electrocorticogram (ECoG)-assisted resection was utilized. Surgical extent including lesionectomy and extended resection was described in detail. Seizure outcome was classified as satisfactory (Engel class I) and unsatisfactory (Engel classes II–IV).

Results

After a median follow-up of 36.0 (30.0) months, 83.6% of patients achieved satisfactory outcome, including 72.1% with Engel class Ia. There was 39.3% (24/61) of patients with antiepileptic drug (AED) withdrawal. Use of ECoG (χ2 = 0.000, P > 0.1), preresection spike (χ2 = 0.000, P = 0.763), or spike residue (P = 0.545) was not correlated with the seizure outcome. For lateral temporal LEAT, outcome from lesionectomy was comparable to extended resection (χ2 = 0.499, P > 0.1). For mesial temporal LEAT, 94.7% (18/19) of patients who underwent additional hippocampectomy were satisfactory, whereas only 25% (1/4) of patients who underwent lesionectomy were satisfactory (P = 0.009).

Conclusion

Surgical treatment was highly effective for temporal LEAT. ECoG may not influence the seizure outcome. For lateral temporal LEAT, lesionectomy with or without cortectomy was sufficient in most patients. For mesial temporal LEAT, extended resection was recommended.

Outcome of epilepsy surgery in lesional epilepsy: Experiences from a developing country

BACKGROUND

Our aim was to report the postoperative seizure outcome and associated factors in patients with lesional epilepsy, in a low-income setting.

METHODS

This longitudinal prospective study included patients who underwent epilepsy surgery at Kashani Comprehensive Epilepsy Center between 2014 and 2019. Post-surgical outcomes were reported according to the Engel score, and patients were classified into two groups of seizure free (SF) and not-seizure free (NSF).

RESULTS

A total of 148 adult patients, with a mean age of 30.45 ± 9.23 years were included. The SF outcome was reported in 86.5% of patients and antiepileptic drugs (AEDs) were reduced or discontinued in 45.9%. The mean follow-up duration was 26.7 ± 14.9 months. Temporal lobe lesions (76.3%) and mesial temporal sclerosis (MTS) (56.7%) were the most frequent etiologies. Temporal lesion (Incidence relative risk (IRR): 1.76, 95% CI [1.08-2.87], p = 0.023), prior history of CNS infection (IRR:1.18, 95% CI [1.03-1.35], p = 0.019), use of intra-operative ECoG (IRR:1.73, 95% CI [1.06-2.81], p = 0.028), and absence of IEDs in postoperative EEG (IRR: 1.41, 95% CI [1.18-1.70], p < 0.001) were positive predictors for a favorable outcome.

CONCLUSION

Many patients with drug-resistant lesional epilepsy showed a favorable response to surgery. We believe that resective epilepsy surgery in low-income settings is a major treatment option. The high frequency of patients with drug-resistant epilepsy in developing countries is associated with high rates of morbidity and mortality. Hence, strategies to increase access to epilepsy surgery in these settings are urgently needed.

Highly consistent temporal lobe interictal spike networks revealed from foramen ovale electrodes

OBJECTIVE

A major challenge that limits understanding and treatment of epileptic events from mesial temporal structures comes from our inability to detect and map interictal networks reproducibly using scalp electrodes. Here, we developed a novel approach to map interictal spike networks and demonstrate their relationships to seizure onset and lesions in patients with foramen ovale electrode implantations.

METHODS

We applied the direct Directed Transfer Function to reveal interictal spike propagation from bilateral foramen ovale electrodes on 10 consecutive patients and co-registered spatially with both seizure onset zones and temporal lobe lesions.

RESULTS

Highly reproducible, yet unique interictal spike networks were seen for each patient (correlation: 0.93 ± 0.13). Interictal spikes spread in both anterior and posterior directions within each temporal lobe, often reverberating between sites. Spikes propagated to the opposite temporal lobe predominantly through posterior pathways. Patients with structural lesions (N = 4), including tumors and sclerosis, developed reproducible spike networks adjacent to their lesions that were highly lateralized compared to patients without lesions. Only 5% of mesial temporal lobe spikes were time-locked with scalp electrode spikes. Our preliminary observation on two lesional patients suggested that along with lesion location, Interictal spike networks also partially co-registered with seizure onset zones suggesting interrelationship between seizure onset and a subset of spike networks.

CONCLUSIONS

This is the first demonstration of patient-specific, reproducible interictal spike networks in mesial temporal structures that are closely linked to both temporal lobe lesions and seizure onset zones.

SIGNIFICANCE

Interictal spike connectivity is a novel approach to map epileptic networks that could help advance invasive and non-invasive epilepsy treatments.

Operative variations in temporal lobe epilepsy surgery and seizure and memory outcome in 226 patients suffering from hippocampal sclerosis

Objective: The aim of this retrospective cohort study was to assess seizure and memory outcomes following temporal lobe surgery in patients suffering from medically refractory temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS).Methods: A retrospective monocentric data analysis was performed in consecutive patients who were operated on during 2002-2018. In the first decennium, standard temporal lobe resections (TLR) were predominately performed, and later, antero-temporal lobe resections (ATLR) were mainly performed. Seizure and memory outcomes over time were assessed according to ILAE/Engel classification and the Berlin Amnesia Test (BTA), respectively.Results: Altogether, 231 surgeries were performed on 226 patients (mean age, 40 years [range, 10-68 years]; male: female, 1:1.4; mean seizure duration, 25 years; and mean follow-up duration, 4.75 years [range, 1-16]). Recently, outcomes of 78.3% of the patients in the total cohort were classified as Engel class I, with 54.9% of patients being completely seizure free. The recent cohort of ATLR since 2012 showed significant more completely seizure-free patients than before 2012 (Engel IA 46.6% versus 67.7%, p < 0.0025, χ²), although the Kaplan Meier analysis of all patients favors TLR for better seizure outcome (61% ATLR vs 73% TLR seizure free after 5 yrs, log rank p < 0.001). Verbal memory improved significantly in non-dominant patients. Minor neurological complications were noted (permanent severe complications, 0.4%; temporary severe complications, 4.8%).Conclusion: Significant improvements in seizure and memory outcomes were observed over time, with surgical technique and seizure duration as important prognostic factors. Early admittance for surgery may favor an excellent seizure outcome in patients undergoing temporal lobe resection for HS.

Neuroimaging in pediatric temporal lobe epilepsy: Does neuroimaging accurately predict pathology and surgical outcome?

Temporal lobe epilepsy (TLE) in children is considered different from that in adults. As such, characterizing the structural lesions present in pediatric patients with TLE and their association with long-term seizure control is important. Here, we aimed to assess the concordance between preoperative imaging and postoperative histopathological diagnoses and their associations with seizure outcomes in pediatric patients with TLE undergoing temporal lobe surgery. We retrospectively reviewed the charts of pediatric patients with TLE who underwent surgical treatment between 1988 and 2020 as a part of the Comprehensive Epilepsy Program at the University of Alberta. Demographic, age at seizure onset, age at surgery, preoperative electroencephalography (EEG), long-term video EEG, imaging (magnetic resonance imaging [MRI] and computed tomography), neuropathology, and long-term seizure outcome data were acquired and analyzed. One hundred and seventeen patients underwent surgery for refractory TLE; the preoperative MRI diagnosis was concordant with the histopathological diagnosis in 76 % of cases. Tumors were identified with high accuracy (91 %). Mesial temporal sclerosis (MTS) was strongly associated with an excellent outcome after surgery (94 %). Patients with normal imaging results or non-specific pathologies were more likely to experience poor seizure outcomes after surgery (50 %). The radiological identification of lesions was associated with good long-term seizure outcomes, whereas normal MRI results were associated with significantly poorer long-term seizure outcomes. An accurate preoperative MRI is essential to epilepsy surgery since it impacts all stages of management; these results will thereafter help inform practitioners' efforts to predict seizure outcome.

Risk Factors for Seizure Worsening After Epilepsy Surgery in Children and Adults: A Population-Based Register Study

BACKGROUND

Increased seizure frequency and new-onset tonic-clonic seizures (TCS) have been reported after epilepsy surgery.

OBJECTIVE

To analyze potential risk factors for these outcomes in a large cohort.

METHODS

We studied prospectively collected data in the Swedish National Epilepsy Surgery Register on increased seizure frequency and new-onset TCS after epilepsy surgery 1990-2015.

RESULTS

Two-year seizure outcome was available for 1407 procedures, and data on seizure types for 1372. Increased seizure frequency at follow-up compared to baseline occurred in 56 cases (4.0%) and new-onset TCS in 53 (3.9%; 6.6% of the patients without preoperative TCS). Increased frequency was more common in reoperations compared to first surgeries (7.9% vs 3.1%; P = .001) and so too for new-onset TCS (6.7% vs 3.2%; P = .017). For first surgeries, binary logistic regression was used to analyze predictors for each outcome. In univariable analysis, significant predictors for increased seizure frequency were lower age of onset, lower age at surgery, shorter epilepsy duration, preoperative neurological deficit, intellectual disability, high preoperative seizure frequency, and extratemporal procedures. For new-onset TCS, significant predictors were preoperative deficit, intellectual disability, and nonresective procedures. In multivariable analysis, independent predictors for increased seizure frequency were lower age at surgery (odds ratio (OR) 0.70 per increasing 10-yr interval, 95% CI 0.53-0.93), type of surgery (OR 0.42 for temporal lobe resections compared to other procedures, 95% CI 0.19-0.92), and for new-onset TCS preoperative neurological deficit (OR 2.57, 95% CI 1.32-5.01).

CONCLUSION

Seizure worsening is rare but should be discussed when counseling patients. The identified risk factors may assist informed decision-making before surgery.

Verbal associative memory outcomes in pediatric surgical temporal lobe epilepsy: Exploring the impact of mesial structures

OBJECTIVE

We examined verbal associative memory outcomes in children with left- or right-sided temporal lobe epilepsy (TLE) who received combined lateral and mesial resections versus lateral resections sparing mesial structures. We hypothesized that children who underwent left-sided resections including mesial structures would show the greatest verbal associative memory declines following surgery.

METHOD

We retrospectively analyzed neuropsychology assessment results from a sample of 65 children with TLE who completed pre- and postoperative evaluation at the Hospital for Sick Children in Toronto, Canada. We examined verbal associative memory score changes between groups by laterality (left versus right) and resection type (lateral only versus lateral and mesial resection). We also explored potential associations between certain epilepsy-related characteristics and verbal associative memory changes.

RESULTS

Postoperative decline was found in children with left-sided resections, but not those with right-sided resections. In children who received left-sided resections, there was some suggestion of verbal associative memory decline in those who had both lateral and mesial tissues excised, but not in those with lateral resections only. Notably, there was also a language dominance (typical versus atypical) by resection type interaction. Specifically, for the typical language group, children with left lateral plus mesial resections (but not mesial sparing resections) showed postoperative verbal associative memory declines, whereas the opposite was true for the atypical language group.

SIGNIFICANCE

These data contribute to our growing understanding of verbal memory outcomes following TLE in childhood, with consideration of the extent of resection to mesial structures. Our findings also highlight the importance of language laterality when interpreting neuropsychological assessment findings and making predictions regarding risk of functional loss following surgery.

Are low-grade gliomas of mesial temporal area alone?

Background:

Temporal neocortex which appears normal on magnetic resonance imaging (MRI) may have pathological tissues in low-grade gliomas (LGG) of pure mesial temporal area. Resection of the cortex may be required together with mesial temporal glioma for satisfactory seizure and oncological outcome. The aim of this study was to explore the presence of any pathological tissue on the temporal cortex that appeared normal on preoperative MRI in patients with pure mesial temporal LGGs.

Methods:

This prospective study included 10 patients who underwent surgical resection of temporal lobe for LGG of mesial temporal area. The temporal neocortex with normal appearance on MRI and mesial temporal area were resected separately, and histopathological diagnosis was performed.

Results:

LGGs of the mesial temporal area were diagnosed with glioneuronal tumors in 7 (70%) and low-grade astrocytoma in 2 (20%) patients. Regarding the temporal cortex, gliosis and focal cortical dysplasia were found in 7 (70%) and 2 (20%) patients. In one patient temporal cortex did not contain any pathological tissue. All were seizure-free and no tumor recurrence was noted at the last follow-up.

Conclusion:

Mesial temporal LGGs are not alone and a high proportion of temporal neocortex appeared normal on preoperative MRI, may contain dual pathology. Thus, anterior temporal resection should be performed to have satisfactory seizure and oncological outcomes.

The transcortical equatorial approach for gliomas of the mesial temporal lobe: techniques and functional outcomes

OBJECTIVEMany surgical approaches have been described for lesions within the mesial temporal lobe (MTL), but there are limited reports on the transcortical approach for the resection of tumors within this region. Here, the authors describe the technical considerations and functional outcomes in patients undergoing transcortical resection of gliomas of the MTL.METHODSPatients with a glioma (WHO grades I-IV) located within the MTL who had undergone the transcortical approach in the period between 1998 and 2016 were identified through the University of California, San Francisco (UCSF) tumor registry and were classified according to tumor location: preuncus, uncus, hippocampus/parahippocampus, and various combinations of the former groups. Patient and tumor characteristics and outcomes were determined from operative, radiology, pathology, and other clinical reports that were available through the UCSF electronic medical record.RESULTSFifty patients with low- or high-grade glioma were identified. The mean patient age was 46.8 years, and the mean follow-up was 3 years. Seizures were the presenting symptom in 82% of cases. Schramm types A, C, and D represented 34%, 28%, and 38% of the tumors, and the majority of lesions were located at least in part within the hippocampus/parahippocampus. For preuncus and preuncus/uncus tumors, a transcortical approach through the temporal pole allowed for resection. For most tumors of the uncus and those extending into the hippocampus/parahippocampus, a corticectomy was performed within the middle and/or inferior temporal gyri to approach the lesion. To locate the safest corridor for the corticectomy, language mapping was performed in 96.9% of the left-sided tumor cases, and subcortical motor mapping was performed in 52% of all cases. The mean volumetric extent of resection of low- and high-grade tumors was 89.5% and 96.0%, respectively, and did not differ by tumor location or Schramm type. By 3 months' follow-up, 12 patients (24%) had residual deficits, most of which were visual field deficits. Three patients with left-sided tumors (9.4% of dominant-cortex lesions) experienced word-finding difficulty at 3 months after resection, but 2 of these patients demonstrated complete resolution of symptoms by 1 year.CONCLUSIONSMesial temporal lobe gliomas, including larger Schramm type C and D tumors, can be safely and aggressively resected via a transcortical equatorial approach when used in conjunction with cortical and subcortical mapping.

Surgical Treatment of Lesional Mesial Temporal Lobe Epilepsy

Lesional mesial temporal lobe epilepsy (mTLE) concerns a lesion other than mesial hippocampal sclerosis present in the mesial temporal lobe and causing seizures. The lesions are usually composed of focal cortical dysplasia (FCD) or are tumorous. These are good candidates for surgical treatment. Sometimes, it is difficult to distinguish between tumors and FCD and to determine the extent of required removal. ¹¹C-methionine positron emission tomography (PET) is helpful in differentiating lesions before surgery in lesional mTLE. In ¹¹C-methionine PET imaging, tumors show a hot uptake, whereas FCD does not. In case of tumorous conditions, the removal of only specific lesions may be considered because the seizure outcome is dependent on complete excision of the tumor. There are several ways to safely access mesial temporal structures. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. Actual lesions associated with epileptogenesis in FCD may be larger than they appear on magnetic resonance imaging. For this reason, evaluations to locate sufficient epileptogenic foci, including invasive studies, should be completed for FCD, and epilepsy surgery should be performed according to these results. Regardless, the ultimate goal of all epilepsy surgeries is to maximize seizure control while maintaining neurological function. Therefore, a tailored approach based on the properties of the lesion is needed.

Predictors of outcome of surgery in adults with mesial lesional temporal lobe epilepsy

Background We report the clinical characteristics and outcome of epilepsy surgery in adult patients with intractable epilepsy due to isolated lesional temporal lobe epilepsy (TLE).

Methods Retrospective analysis of clinical and outcome characteristics in 47 consecutive adult patients with intractable epilepsy due to isolated lesional TLE who underwent epilepsy surgery from November 2009 to January 2015 was done to predictors of outcome.

Results The mean age at surgery of the study population was 30.74 ± 10.85 years with 20 (43.5%) women. While the average age at onset of epilepsy was 20.12 ± 12.52 years, average duration of epilepsy was 10.78 ± 7.96 years. Favourable Engels outcome was observed in 39 (84.8%) of the patients. Findings on histopathology reported glioma in 24 (52.0%) of the patients. On comparing patients with favourable outcome (n = 39) with those with unfavourable outcome (n = 7), age at surgery was significantly higher in patients with unfavourable outcome (40.14 ± 11.69 years vs 29.05 ± 9.92 years; p = 0.011). Higher percentage of patients with unfavourable outcome scored poor on pre-surgical IQ tests (42.9% vs 7.7%; p = 0.037). On further analysis for predictors of outcome, age at surgery (β = 0.858; 95% CI 0.738–0.997) significantly predicts outcome (β = 1.166; 95% CI 0.931–1.461; p = 0.182), whereas pre-surgical poor IQ showed a trend towards being associated with unfavourable outcome (β = 0.079; 95% CI 0.005–1.287; p = 0.075).

Conclusion Surgery for intractable epilepsy due to isolated lesional TLE has favourable outcome in vast majority (84.8%) of carefully selected patients. Age at surgery predicts outcome in these patients.

Robot-guided stereoelectroencephalography without a computed tomography scan for referencing: Analysis of accuracy

OBJECTIVE

Recent studies with robot-guided stereotaxy use computed tomography (CT) scans for referencing. We will provide evidence that using preoperative MRI datasets referenced with a laser scan of the patient's face is sufficient for sEEG implantation.

METHODS

In total, 40 sEEG electrodes were implanted in five patients by the robotic surgical assistant (ROSA). The postoperative CT scan for identifying electrode positions was fused with the preoperative MRI-based planning data. The accuracy was determined by the target point error (TPE) and the entry point error (EPE), applying the Euclidean distance.

RESULTS

The mean TPE amounted to 2.96 mm, the mean EPE to 2.53 mm. The accuracy was improved in 1.5 T MRI: the mean TPE amounted to 1.72 mm, the EPE to 0.97 mm. No complications, haemorrhages, infections, etc., were observed.

CONCLUSIONS

Robot-guided sEEG based on 3 T MRI reduces radiation exposure for the patient and can still be performed safely.

Surgical Treatment of Mesiotemporal Lobe Epilepsy: Which Approach is Favorable?

BACKGROUND

Mesiotemporal lobe epilepsy is one of the most frequent causes for pharmacoresistant epilepsy. Different surgical approaches to the mesiotemporal area are used.

OBJECTIVE

To analyze epileptological and neuropsychological results as well as complications of different surgical strategies.

METHODS

This retrospective study is based on a consecutive series of 458 patients all harboring pharmacoresistant mesiotemporal lobe epilepsy. Following procedures were performed: standard anterior temporal lobectomy, anterior temporal or key-hole resection, extended lesionectomy, and transsylvian and subtemporal selective amygdalohippocampectomy. Postoperative outcome was evaluated according to different surgical procedures.

RESULTS

Overall, 1 yr after surgery 315 of 432 patients (72.9%) were classified Engel I; in particular, 72.8% were seizure-free after anterior temporal lobectomy, 76.9% after key-hole resection, 84.4% after extended lesionectomy, 70.3% after transylvian selective amygdalohippocampectomy, and 59.1% after subtemporal selective amygdalohippocampectomy. No significant differences in seizure outcome were found between different resective procedures, neither in short-term nor long-term follow-up. There was no perioperative mortality. Permanent morbidity was encountered in 4.4%. There were no significant differences in complications between different resection types. In the majority of patients, selective attention improved following surgery. Patients after left-sided operations performed significantly worse regarding verbal memory as compared to right-sided procedures. However, surgical approach had no significant effect on memory outcome.

CONCLUSION

Different surgical approaches for mesiotemporal epilepsy analyzed resulted in similar epileptological, neuropsychological results, and complication rates. Therefore, the approach for the individual patient does not only depend on the specific localization of the epileptogenic area, but also on the experience of the surgeon.

Comprehensive preoperative work-up and surgical treatment of low grade tumor/benign lesion related temporal lobe epilepsy

OBJECTIVE

Generally low-grade tumor/benign lesion related temporal lobe epilepsy (LGT/BL-TLE) is considered easier to treat and has better prognosis when compared to non-lesional TLE. However, multiple disputes exist in surgical management of this epilepsy entity. This study aims to discuss comprehensive preoperative work-up, surgical strategies and outcome of it.

METHODS

A retrospective review of sixty LGT/BL-TLE cases which underwent comprehensive preoperative work-up and then resective surgeries was conducted. Surgical strategies were categorized into limited and expanded resections. Surgical efficacy was evaluated using Engel grading after telephone or clinic follow-up and compared statistically.

RESULTS

Preoperative work-up includes magnetic resonance imaging (MRI), conventional electroencephalography, semiology evaluation, positron emission tomography (PET) and 256-channel dense-array electroencephalography source imaging (256-ch dESI). In aspect of concordance with epileptic lesions demonstrated on MRI, 256-ch dESI was more accurate than PET (72.7% vs. 39.4%) (p<0.05). Limited resections were performed in 28 cases while expanded resections in 32 cases. Altogether the surgical efficacy was: Engel grade I 86.7%, I+II 95.0%. Comparison of surgical outcome showed neither the outcome between limited and expanded resection nor the outcome between mesial and neocortical TLE (mTLE & nTLE) undergoing limited resections was significantly different (p>0.05).

CONCLUSIONS

For LGT/BL-TLE, most surgical strategies can be made preoperatively after comprehensive work-up rather than intraoperatively. Limited and expanded strategies yield similar surgical outcome in either nTLE or mTLE as long as comprehensive work-up supports the strategy and the epileptic lesion is totally removed. 256-ch dESI which can visualize both structural and electrophysiological lesions may be contributable to surgical planning of this entity.

Factors predicting the outcome following surgical treatment of mesial temporal epilepsy due to mesial temporal sclerosis

BACKGROUND

Mesial temporal sclerosis (MTS) is the most common disease found in an epilepsy surgery series. Early age of onset, a history of febrile convulsions, epileptiform discharges on EEG, duration of epilepsy, number of generalized seizures and severity of psychiatric disorders are possible prognostic factors in patients with MTS.

OBJECTIVE

The aim of this study is to review the clinical, semiotic, psychological, electrophysiological and neuroradiological researches and relate their findings to the prognosis of patients with MTS who underwent anteromedial temporal lobectomy (ATL).

METHODS

Of 1,214 patients evaluated for surgery in the epilepsy Center of Faculdade de Medicina de São Jose do Rio Preto (FAMERP), a tertiary Brazilian epilepsy center, 400 underwent ATL for MTS. Examinations and clinical data were analyzed and compared with the Engel Outcome Classification.

RESULTS

Of all the items analyzed, the MRI showed the greatest influence on patient outcome. As for the clinical evaluation and pathological antecedents, age at surgery, epilepsy duration, perinatal insults, family history of epilepsy, febrile seizures, neuropsychological abnormalities and presence of generalized tonic-clonic seizure all had statistical significance.

CONCLUSION

In order to identify the most appropriate candidates for ATL, it is very important to consider the prognostic factors associated with a favorable outcome for counseling patients in daily practice.

Surgical strategies for pediatric epilepsy

Pediatric epilepsy is a debilitating condition that impacts millions of patients throughout the world. Approximately 20-30% of children with recurrent seizures have drug-resistant epilepsy (DRE). For these patients, surgery offers the possibility of not just seizure freedom but significantly improved neurocognitive and behavioral outcomes. The spectrum of surgical options is vast, ranging from outpatient procedures such as vagus nerve stimulation to radical interventions including hemispherectomy. The thread connecting all of these interventions is a common goal-seizure freedom, an outcome that can be achieved safely and durably in a large proportion of patients. In this review, we discuss many of the most commonly performed surgical interventions and describe the indications, complications, and outcomes specific to each.

Resective surgery for medically refractory epilepsy using intraoperative MRI and functional neuronavigation: the Erlangen experience of 415 patients

OBJECTIVE

Intraoperative overestimation of resection volume in epilepsy surgery is a well-known problem that can lead to an unfavorable seizure outcome. Intraoperative MRI (iMRI) combined with neuronavigation may help surgeons avoid this pitfall and facilitate visualization and targeting of sometimes ill-defined heterogeneous lesions or epileptogenic zones and may increase the number of complete resections and improve seizure outcome.

METHODS

To investigate this hypothesis, the authors conducted a retrospective clinical study of consecutive surgical procedures performed during a 10-year period for epilepsy in which they used neuronavigation combined with iMRI and functional imaging (functional MRI for speech and motor areas; diffusion tensor imaging for pyramidal, speech, and visual tracts; and magnetoencephalography and electrocorticography for spike detection). Altogether, there were 415 patients (192 female and 223 male, mean age 37.2 years; 41% left-sided lesions and 84.9% temporal epileptogenic zones). The mean preoperative duration of epilepsy was 17.5 years. The most common epilepsy-associated pathologies included hippocampal sclerosis (n = 146 [35.2%]), long-term epilepsy-associated tumor (LEAT) (n = 67 [16.1%]), cavernoma (n = 45 [10.8%]), focal cortical dysplasia (n = 31 [7.5%]), and epilepsy caused by scar tissue (n = 23 [5.5%]).

RESULTS

In 11.8% (n = 49) of the surgeries, an intraoperative second-look surgery (SLS) after incomplete resection verified by iMRI had to be performed. Of those incomplete resections, LEATs were involved most often (40.8% of intraoperative SLSs, 29.9% of patients with LEAT). In addition, 37.5% (6 of 16) of patients in the diffuse glioma group and 12.9% of the patients with focal cortical dysplasia underwent an SLS. Moreover, iMRI provided additional advantages during implantation of grid, strip, and depth electrodes and enabled intraoperative correction of electrode position in 13.0% (3 of 23) of the cases. Altogether, an excellent seizure outcome (Engel Class I) was found in 72.7% of the patients during a mean follow-up of 36 months (range 3 months to 10.8 years). The greatest likelihood of an Engel Class I outcome was found in patients with cavernoma (83.7%), hippocampal sclerosis (78.8%), and LEAT (75.8%). Operative revisions that resulted from infection occurred in 0.3% of the patients, from hematomas in 1.6%, and from hydrocephalus in 0.8%. Severe visual field defects were found in 5.2% of the patients, aphasia in 5.7%, and hemiparesis in 2.7%, and the total mortality rate was 0%.

CONCLUSIONS

Neuronavigation combined with iMRI was beneficial during surgical procedures for epilepsy and led to favorable seizure outcome with few specific complications. A significantly higher resection volume associated with a higher chance of favorable seizure outcome was found, especially in lesional epilepsy involving LEAT or diffuse glioma.

Anterior temporal lobectomy versus selective amygdalohippocampectomy in patients with mesial temporal lobe epilepsy

ABSTRACT Objective To contribute our experience with surgical treatment of patients with mesial temporal lobe epilepsy (mTLE) undergoing anterior temporal lobectomy (ATL) or selective amygdalohippocampectomy (SelAH). Method This is a retrospective observational study. The sample included patients with medically refractory mTLE due to unilateral mesial temporal sclerosis who underwent either ATL or SelAH, at Hospital de Clinicas – UFPR, from 2005 to 2012. We report seizure outcomes, using Engel classification, cognitive outcomes, using measurements of verbal and visuospatial memories, as well as operative complications. Result Sixty-seven patients (33 ATL, 34 SelAH) were studied; median follow-up was 64 months. There was no statistically significant difference in seizure or neuropsychological outcomes, although verbal memory was more negatively affected in ATL operations on patients’ dominant hemispheres. Higher number of major complications was observed in the ATL group (p = 0.004). Conclusion Seizure and neuropsychological outcomes did not differ. ATL appeared to be associated with higher risk of complications.

Predictors of prognosis in patients with temporal lobe epilepsy after anterior temporal lobectomy

The aim of this study was to evaluate the predictive value of prognostic factors for the surgical outcome of patients with mesial temporal lobe epilepsy (MTLE) using Engel seizure classification. The clinical data of 121 patients with MTLE who underwent anterior temporal lobectomy (ATL) and received a 1-year minimum follow-up were collected between January 2005 and December 2008. Patients were divided into seizure and seizure-free groups according to the Engel seizure classification. Univariate analysis and multivariate logistic regression analysis were used to analyze the potential predictive and prognostic factors, including medical history, clinical features of seizures, magnetic resonance imaging (MRI) and video-electroencephalogram (EEG) monitoring results. Univariate analysis indicated no statistically significant differences in gender, age at seizure onset, age at surgery, history of traumatic brain injury, perinatal anoxia, intracranial infection, family history of seizure, auras or site of surgery between the two groups; however, significant differences were detected in pre-surgical seizure duration, history of febrile seizures, seizure types, MRI and video-EEG results. Multivariate logistic regression analysis demonstrated that a pre-surgical seizure duration of <10 years, history of positive febrile seizures, simple complex partial seizure, positive MRI results and unilateral local video-EEG spikes may be considered as predictors of a good prognosis. These results indicate that remission may be achieved in patients with MTLE via the collection of accurate clinical information and adequate pre-surgical evaluation.

Multimodal data and machine learning for surgery outcome prediction in complicated cases of mesial temporal lobe epilepsy

BACKGROUND

This study sought to predict postsurgical seizure freedom from pre-operative diagnostic test results and clinical information using a rapid automated approach, based on supervised learning methods in patients with drug-resistant focal seizures suspected to begin in temporal lobe.

METHOD

We applied machine learning, specifically a combination of mutual information-based feature selection and supervised learning classifiers on multimodal data, to predict surgery outcome retrospectively in 20 presurgical patients (13 female; mean age±SD, in years 33±9.7 for females, and 35.3±9.4 for males) who were diagnosed with mesial temporal lobe epilepsy (MTLE) and subsequently underwent standard anteromesial temporal lobectomy. The main advantage of the present work over previous studies is the inclusion of the extent of ipsilateral neocortical gray matter atrophy and spatiotemporal properties of depth electrode-recorded seizures as training features for individual patient surgery planning.

RESULTS

A maximum relevance minimum redundancy (mRMR) feature selector identified the following features as the most informative predictors of postsurgical seizure freedom in this study's sample of patients: family history of epilepsy, ictal EEG onset pattern (positive correlation with seizure freedom), MRI-based gray matter thickness reduction in the hemisphere ipsilateral to seizure onset, proportion of seizures that first appeared in ipsilateral amygdala to total seizures, age, epilepsy duration, delay in the spread of ipsilateral ictal discharges from site of onset, gender, and number of electrode contacts at seizure onset (negative correlation with seizure freedom). Using these features in combination with a least square support vector machine (LS-SVM) classifier compared to other commonly used classifiers resulted in very high surgical outcome prediction accuracy (95%).

CONCLUSIONS

Supervised machine learning using multimodal compared to unimodal data accurately predicted postsurgical outcome in patients with atypical MTLE.

Seizure outcome in surgically treated drug-resistant mesial temporal lobe epilepsy based on the recent histopathological classifications

OBJECT

The study was performed to investigate the relation between seizure outcome after surgical treatment of mesial temporal lobe epilepsy (MTLE) and pathological findings, classified according to the recently proposed classifications of mesial temporal sclerosis (MTS), granule cell pathology (GCP), focal cortical dysplasia (FCD) and epilepsy-associated low-grade tumors (ELGT).

METHODS

The authors analyzed data obtained in 120 consecutive cases involving patients presenting with drug-resistant MTLE, who underwent tailored anteromesial temporal lobe resection, and correlated seizure outcome with pathological findings. They identified 5 histopathological groups: Group 1-ELGT, alone or associated with other lesions (30 cases); Group 2-isolated FCD (17 cases); Group 3-MTS, with or without GCP (28 cases); Group 4-MTS associated with FCD, with or without GCP (37 cases); Group 5-other lesions (8 cases).

RESULTS

Engel Class I outcome was observed in 83% of patients with ELGT (Class IA in 63%); in 59% of patients with isolated FCD, with FCD Type II showing a better prognosis than FCD Type I; in 82% of patients with isolated MTS (Class IA in 50%), with MTS Type 1a and MTS Type 1b showing a better prognosis than MTS Type 2 and patients with MTS and GCP having better postsurgical results than those with MTS without GCP. Engel Class I outcome was also achieved in 84% of patients with FCD associated with MTS (Engel Class IA in 62%); also in this group MTS 1a and MTS 1b associated with FCD showed a better prognosis than FCD associated with MTS 2. Finally, Engel Class I was also achieved in 2 patients with vascular malformation and in 1 with a temporal pole encephalocele.

CONCLUSIONS

Patients with MTLE and ELGT, MTS, or MTS associated with FCD showed the best postsurgical seizure outcome (Engel Class I in more than 80% of cases), whereas only 63% of patients with isolated FCD achieved the same type of outcome. Interestingly, the analysis of seizure outcome in histopathological subtypes of FCD and of MTS showed different prognoses in the different pathological subgroups, with worse outcomes for atypical MTS, absence of GCP, and isolated FCD Type I.

Seizure outcome of surgical treatment of focal epilepsy associated with low-grade tumors in children

OBJECT

Low-grade tumor (LGT) is an increasingly recognized cause of focal epilepsies, particularly in children and young adults, and is frequently associated with cortical dysplasia. The optimal surgical treatment of epileptogenic LGTs in pediatric patients has not been fully established.

METHODS

In the present study, the authors retrospectively reviewed 30 patients (age range 3-18 years) who underwent surgery for histopathologically confirmed LGTs, in which seizures were the only clinical manifestation. The patients were divided into 2 groups according to the type of surgical treatment: patients in Group A (20 cases) underwent only tumor removal (lesionectomy), whereas patients in Group B (11 cases) underwent removal of the tumor and the adjacent epileptogenic zone (tailored surgery). One of the patients, who underwent 2 operations, is included in both groups. Follow-up ranged from 1 to 17 years.

RESULTS

Sixteen (80%) of 20 patients in Group A had an Engel Class I outcome. In this group, 3 of 4 patients who were in Engel Classes II and III had temporomesial lesions. All patients in Group B had temporomesial tumors and were seizure free (Engel Class I). In this series, in temporolateral and extratemporal tumor locations, lesionectomy yielded a good seizure outcome. In addition, a young age at seizure onset (in particular < 4 years) was associated with a poor seizure outcome.

CONCLUSIONS

Tailored resection in temporomesial LGTs was associated with excellent seizure outcome, indicating that an adequate presurgical evaluation including extensive neurophysiological evaluation (long-term videoelectroencephalography monitoring) to plan appropriate surgical strategy is advised.

Pediatric temporal lobe epilepsy surgery: resection based on etiology and anatomical location

Advances in electrophysiological assessment with improved structural and functional neuroimaging have been very helpful in the use of surgery as a tool for drug-resistant epilepsy. Increasing interest in epilepsy surgery has had a major impact on adult patients; a refined evaluation process and new criteria for drug resistance combined with refined surgical techniques resulted in large surgical series in many centers. Pediatric surgery has lagged behind this evolution, possibly because of the diverse semiology and electrophysiology of pediatric epilepsy obscuring the focal nature of the seizures and frustrating the treatment of catastrophic epileptic syndromes specific to children. Unfortunately, refractory -epilepsy is more -devastating in children than in adults as it interferes with all aspects of neural development. Nevertheless, during the last few decades, the efforts of a small number of centers with encouraging results in pediatric epilepsy surgery have motivated pediatric neurologists to gain interest. Although well behind in the number of patients compared with that of adults, pediatric series are increasing exponentially. While temporal lobe epilepsy is the focus of interest in adults, with almost 70 % of resections in the temporal lobe, the pediatric epilepsy spectrum is different. Resective or functional surgery techniques devoted to resistant extratemporal epilepsy are the major improvements in pediatric epilepsy surgery. Temporal lobe epilepsy in adults has been studied extensively but only recently has begun to receive attention in children. Several aspects of temporal lobe epilepsy in childhood remain unclear or controversial in terms of seizure semiology and its pathology. This is reflected in the surgical treatment. Information on the major contributors to a favorable outcome, such as type or extent of resection, in terms of seizure control and morbidity is not available as in adult temporal lobe epilepsy. This chapter discusses the major discrepancies between adult and pediatric temporal lobe epilepsy and outlines the current concepts in surgical treatment. The resection strategy based on the different substrates at different locations in the temporal lobe causing seizures is emphasized with respect to available literature.

Language mapping in temporal lobe epilepsy in children: special considerations

Temporal lobe epilepsy (TLE) in children is a slightly different entity than TLE in adults not only because of its semiology and pathology but also because of the different approach to surgical treatment. Presurgical investigations for eloquent cortex, especially language, must take these differences into account. Most diagnostic tests were created for adults, and many of the assessment tools need to be adapted for children because they are not just small adults. This paper will highlight the specific challenges and solutions in mapping language in a pediatric population with TLE.

Surgical management of glioneuronal tumors with drug-resistant epilepsy

In this review, we discuss the options for the surgical management of glioneuronal tumors (GNTs) associated with drug-resistant epilepsy, with an emphasis on the surgical issues involved in addressing the epileptogenic nature of these lesions. We briefly summarize the pathological hallmarks of these lesions in order to outline how these tumors contribute to seizure activity. Understanding the pathophysiology of these lesions is important in discussing the advantages and disadvantages of different surgical strategies. There have been a number of studies that have investigated the utility of different surgical approaches in improving seizure outcome, and we highlight some of these studies in order to shed light on surgical issues related to these tumors.

Transsylvian-transcisternal selective lesionectomy for pediatric lesional mesial temporal lobe epilepsy

BACKGROUND

The optimal extent of resection for surgical treatment of lesional epilepsy is a controversial issue.

OBJECTIVE

For patients with mesial temporal lobe lesions visible on magnetic resonance imaging, we compared the surgical outcome of selective lesionectomy with that of standard anterior temporal lobectomy (ATL) and amygdalohippocampectomy.

METHODS

We conducted a retrospective analysis of the seizure outcome of 40 patients treated for lesional mesial temporal lobe epilepsy between 1993 and 2008. Before 2006, patients were managed by ATL (n=29) and from 2006 onward, by selective lesionectomy via the transsylvian-transcisternal approach (n=11).

RESULTS

The postoperative seizure-free rates for the 2 groups were comparable: 93% (27/29) for the ATL group and 91% (10/11) for the selective lesionectomy group (P=.814). In both groups, patients with persistent seizures commonly showed incomplete lesion resection, with complete resection often improving seizure outcome. Postoperative visual field defects were more common in the ATL group (21%) than in the selective lesionectomy group (0%) (P=.102).

CONCLUSION

Transsylvian-transcisternal selective lesionectomy is an effective and safe therapeutic modality in children with lesional mesial temporal lobe epilepsy. Completeness of resection is an important variable for seizure control regardless of surgical modality.

Through the choroidal fissure: a quantitative anatomic comparison of 2 incisions and trajectories (transsylvian transchoroidal and lateral transtemporal)

BACKGROUND

We compared the transsylvian transchoroidal (TSTC) approach with the lateral transtemporal (LTT) approach. Both approaches proceed through the choroidal fissure but through different incisions and along different trajectories.

METHODS

Four fixed, silicon-injected heads (8 sides) were used. Nine strategic anatomic points within the dissections were compared between the TSTC and LTT approaches in 7 other silicon-injected heads (14 sides). Neuronavigation was used to gather coordinates from selected points of both approaches to calculate surgical angles and distances to common targets.

RESULTS

The surgical angle of the TSTC approach for the inferior choroidal point was wider compared with the LTT approach (P < .05). The surgical angles for the P2a-P2p point were similar for both approaches. In the TSTC approach, the P2-P3 point angle was smaller than in the LTT approach (P < .05). The TSTC approach provided (except for the P2-P3 point) significantly shorter distances to all defined anatomic targets compared with the LTT approach. When the posterior cerebral artery was the target in the TSTC approach, the hippocampus was retracted 3 to 8 mm compared with 8 to 13 mm in the LTT approach.

CONCLUSION

We quantitatively described anatomic features of the TSTC approach and compared them with the LTT approach. For approaching the mesial temporal region, the TSTC approach offers an adequate surgical angle and shorter or similar distances proximal to P2-P3 and requires less temporal lobe and hippocampal retraction than the LTT approach. Such information can help surgeons select the optimal approach to the mesial temporal lobe and its surrounding structures. The TSTC approach should be considered for lesions located in the medial temporal region.

Long-term surgical outcomes of temporal lobe epilepsy associated with low-grade brain tumors

BACKGROUND

Tumor-related temporal lobe epilepsy (TLE) has a high likelihood of medical intractability and requires surgical treatment. The aims of this study were to analyze the long-term surgical outcomes of and to present appropriate surgical strategies for tumor-related TLE.

METHODS

The clinical data of 87 consecutive patients diagnosed with tumor-related TLE were analyzed. The median age at surgery was 22 years. Sixteen patients had a tumor confined to the amygdala or the parahippocampal gyrus, and 10 of them received a tailored lesionectomy without hippocampectomy. The surgical outcome was evaluated based on 3 aspects: seizure control, tumor control, and discontinuation of antiepileptic drugs (AEDs).

RESULTS

The actuarial seizure and tumor control rates at the fifth year postoperatively were 79% and 90%, respectively. Seizure control was highly correlated with tumor control. The following factors were found to be significantly associated with poor seizure control: duration of epilepsy>10 years, presence of a remote focus on surface electroencephalography, and incomplete tumor removal. The actuarial AED maintenance rates were 47% at the second year and 11% at the fifth year. The median time to AED discontinuation was 22 months. A younger age at surgery was found to be significantly associated with an increased chance of AED discontinuation. Tailored resection focusing on the tumor resulted in a favorable outcome, even for tumors confined to the amygdala or the parahippocampal gyrus.

CONCLUSIONS

Surgical treatment of tumor-related TLE resulted in long-term seizure control in the majority of patients. Maximal tumor removal can be recommended for tumor-related TLE.

Microneurosurgical management of temporal lobe epilepsy by amygdalohippocampectomy (AH) plus standard anterior temporal lobectomy (ATL): a report of our initial five cases in Bangladesh

Patient presenting as a case of Temporal Lobe Epilepsy (TLE) are usually resistant to antiepileptic drugs and surgery is the treatment of choice. This type of epilepsy may be due to Mesial Temporal Sclerosis (MTS), tumors [i.e. low grade glioma, Arterio-Venous Malformation (AVM) etc], trauma, infection (Tuberculosis) etc. Here we report five cases of surgically treated TLE that were due to a MTS, MTS with arachnoid cyst, low grade ganglioglioma, high grade ganglioglioma and a tuberculoma in the department of neurosurgery, Dhaka Medical College Hospital and Islami Bank Central Hospital, Dhaka, Bangladesh from August 2009 to February 2010. In all cases the only presenting symptoms was complex partial seizures (psychomotor epilepsy) for which all underwent scalp EEG (Electro Encephalogram) and MRI (Magnetic Resonance Imaging) of Brain. All patients were managed by amygdalohippocampectomy plus standard anterior lobectomy. One patient with high grade ganglioglioma recurred within two months of operation and expired within five months. The rest of the cases are seizure and disease free till the last follow up.

Seizures in patients with low-grade gliomas--incidence, pathogenesis, surgical management, and pharmacotherapy

Seizures complicate the clinical course of > 80% of patients with low-grade gliomas. Patients with some tumor variants almost always have epilepsy. Diffuse low-grade gliomas (LGG) are believed to cause epilepsy through partial deafferentiation of nearby brain cortex (denervation hypersensitivity). Glioneural tumors may interfere with local neurotransmitter levels and are sometimes associated with structural abnormalities of the brain which may produce seizures. The severity of tumor associated epilepsy varies considerably between patients. Some cases may present with a first seizure. Others suffer from long-standing pharmacoresistant epilepsy. Seizure control rates of > 70-80% can be expected after complete tumor resections. Patients with drug-resistant epilepsy require a comprehensive preoperative epileptological work-up which may include the placement of subdural (and intraparenchymal) electrodes or intraoperative electrocorticography (ECoG) for the delineation of extratumoral seizure foci. Partial and subtotal tumor resections are helpful in selected cases, i.e. for gliomas involving the insula. In one series, 40% of patients presented for surgery with uncontrolled seizures, i.e. medical therapy alone often fails to control tumor-related epilepsy. Use of the newer (second generation) non-enzyme inducing antiepileptic drugs (non-EIAED) is encouraged since they seem to have lesser interactions with other medications (e.g. chemotherapy). Chemotherapy and irradiation may have some minor beneficial effects on the patients' seizure disorder. Overall 60-70% of patients may experience recurrent epilepsy during long-term follow-up. Recurrent seizures (not infrequently heralding tumor recurrence) after surgery continue to pose significant clinical problems.

Dysembryoplastic neuroepithelial tumors in pediatric patients

OBJECTIVE

Dysembryoplastic neuroepithelial tumors (DNTs) are benign cortical tumors that are frequently associated with the medically intractable focal epilepsy. In this study, the authors delineate the clinical characteristics of DNTs in children and evaluate the role of cortical dysplasia (CD) in the epileptogenicity to find out the optimum surgical strategy.

METHODS

A retrospective analysis was performed for clinical data of children with DNT, who underwent surgery between 1996 and 2006. The adopted surgical methods were uniform according to the tumor location and included intraoperative electrocorticography (ECoG)-guided resection. The prognostic factors were evaluated for the two prognostic group categorized by the seizure outcome at one year after surgery.

RESULTS

Of 22 patients, the overall seizure free rate was 90.9% and the other two patients belonged to Engel class II during the mean follow-up period of 44.1 months. There was no worsening of the seizure after one year of surgery. Associated CD was found in 18 cases (81.8%) and in the 80% (8 of 10 cases) of the additionally resected areas according to the electrophysiologic studies.

CONCLUSIONS

The CD associated with DNT appears to have its own epileptogenicity. Therefore, complete removal of the CD with tumor itself is important for patient outcome. A thorough surgical approach can be accomplished by comprehensive presurgical evaluations and extensive surgery with the aid of the intraoperative ECoG or intracranial recording.

Brain tumors in the mesial temporal lobe: long-term oncological outcome

OBJECT

Surgical treatment of brain tumors in the mesial temporal lobe (MTL) is a highly demanding procedure. Only a few studies describing the surgery of MTL tumors have been reported, and they have been focused on the operative techniques and immediate results of the surgery. The authors have analyzed the long-term oncological outcome in patients with MTL tumors.

METHODS

Thirty-six patients with an MTL tumor were studied. The mean patient age at surgery was 32 years (range 13-62 years). The tumors were confined to the MTL (Schramm Type A) in 25 patients (69%). Extension of the tumor into the fusiform gyrus (Schramm Type C) and temporal stem (Schramm Type D) was observed in 4 and 7 patients (11 and 19%), respectively. There was a significant difference in the tumor size according to Schramm types (p = 0.001). Complete tumor resection was achieved in 26 patients (72%). All tumors were low-grade lesions except for 1 anaplastic astrocytoma.

RESULTS

After a median follow-up period of 50.5 months, 7 patients showed progression of the disease. The actuarial progression-free survival rates were 97% in the 1st year, 84% in the 2nd year, and 80% in the 5th year. The degree of tumor resection was significantly related to the tumor control failure (p < 0.001) and malignant transformation of a low-grade tumor (p < 0.001). Univariate analyses using a Cox proportional hazards model showed that the following factors were significantly associated with a failure to control the tumor: 1) extent of the tumor (Schramm Type D; p = 0.003, relative risk [RR] 12.04); 2) size of the tumor (p = 0.033, RR 1.052/mm); 3) patient age at surgery >or= 50 years (p = 0.007, RR 8.312); and 4) short duration of epilepsy (< 6 months; p = 0.001, RR 21.54).

CONCLUSIONS

Surgery is the principal treatment for MTL tumors, despite its technical difficulty. Complete tumor resection is strongly recommended for long-term tumor control. The MTL tumors are heterogeneous in their prognosis. Older age, short duration of epilepsy, and tumor size are all associated with poor outcome. Patients with these characteristics may have a more aggressive form of the disease than those with MTL tumors associated with chronic epilepsy.

Hippocampal volumetry and functional MRI of memory in temporal lobe epilepsy

This study examined the utility of structural and functional MRI at 1.5 and 3T in the presurgical evaluation and prediction of postsurgical cognitive outcome in temporal lobe epilepsy (TLE). Forty-nine patients undergoing presurgical evaluation for temporal lobe (TL) resection and 25 control subjects were studied. Patients completed standard presurgical evaluations, including the intracarotid amobarbital test (IAT) and neuropsychological testing. During functional imaging, subjects performed a complex visual scene-encoding task. High-resolution structural MRI scans were used to quantify hippocampal volumes. Both structural and functional imaging successfully lateralized the seizure focus and correlated with IAT memory lateralization, with improvement for functional imaging at 3T as compared with 1.5 T. Ipsilateral structural and functional MRI data were related to cognitive outcome, and greater functional asymmetry was related to earlier age at onset. These findings support continued investigation of the utility of MRI and fMRI in the presurgical evaluation of TLE.

Role of proton magnetic resonance spectroscopy in preoperative evaluation of patients with mesial temporal lobe epilepsy

A retrospective study was conducted for evaluation of the role of single-voxel proton magnetic resonance spectroscopy (1H-MRS) in preoperative investigation of patients with mesial temporal lobe epilepsy (MTLE). Eighteen cases, including both non-lesional and lesional MTLE, were analyzed. Selective amygdalohippocampectomy was performed in 8 cases, selective amygdalohippocampectomy combined with lesionectomy in 6 cases, lesionectomy in 3 cases, and anterior temporal lobe resection in one case. The length of follow-up varied from 24 to 71 months (median, 35 months). Before surgery, (1)H-MRS disclosed decrease of N-acetylaspartate (NAA) content (P=0.01) and more frequent (P=0.07) presence of lactate (Lac) on the side of the epileptogenic zone. Decrease of NAA content below 0.75 and/or unilateral presence of Lac provided 86% (95% CI: 68%-100%) lateralization accuracy. Metabolic parameters did not differ in subgroups with hippocampal sclerosis and brain tumors. On the long-term follow-up 12 patients (67%) were free of disabling seizures. There was a trend (P=0.05) for worse seizure outcome in cases with significant bilateral metabolic alterations characterized by predominance of choline-containing compounds' peak on 1H-MR spectra on both sides. In conclusion, 1H-MRS-detected reduction of NAA content and unilateral presence of Lac in the mesial temporal lobe structures may serve as additional diagnostic clues for lateralization of the epileptogenic zone in MTLE. Metabolic imaging has limited usefulness for differentiation of the hippocampal sclerosis and low-grade intraaxial brain tumor. Presence of significant bilateral metabolic alterations in the mesial temporal lobe structures is associated with worse postoperative seizure control.

Neuropathology of focal epilepsies: a critical review

A broad spectrum of structural lesions can be histopathologically identified in surgical brain specimens obtained from patients with focal, therapy-refractory epilepsies. In our experience with 4512 tissue samples collected at the German Neuropathological Reference Center for Epilepsy Surgery, three clinicopathological entities are most common: mesial temporal sclerosis (40%), long-term epilepsy-associated tumors (27%), and malformations of cortical development (13%). Notwithstanding, a systematic histopathological and molecular-genetic analysis is mandatory to unravel the underlying pathogenic mechanism of epilepsy-associated lesions and may contribute to our current understanding of pharmacoresistance and epileptogenesis. However, an interdisciplinary approach is necessary to further explore predictive parameters with respect to postsurgical seizure relief and memory impairment, and also to identify new pharmacological targets.

High frequency oscillations in intracranial EEGs mark epileptogenicity rather than lesion type

High frequency oscillations (HFOs) called ripples (80-250 Hz) and fast ripples (FR, 250-500 Hz) can be recorded from intracerebral EEG macroelectrodes in patients with intractable epilepsy. HFOs occur predominantly in the seizure onset zone (SOZ) but their relationship to the underlying pathology is unknown. It was the aim of this study to investigate whether HFOs are specific to the SOZ or result from pathologically changed tissue, whether or not it is epileptogenic. Patients with different lesion types, namely mesial temporal atrophy (MTA), focal cortical dysplasia (FCD) and nodular heterotopias (NH) were investigated. Intracranial EEG was recorded from depth macroelectrodes with a sampling rate of 2000 Hz. Ripples (80-250 Hz) and Fast Ripples (250-500 Hz) were visually marked in 12 patients: five with MTA, four with FCD and three with NH. Rates of events were statistically compared in channels in four areas: lesional SOZ, non-lesional SOZ, lesional non-SOZ and non-lesional non-SOZ. HFO rates were clearly more linked to the SOZ than to the lesion. They were highest in areas in which lesion and SOZ overlap, but in patients with a SOZ outside the lesion, such as in NHs, HFO rates were clearly higher in the non-lesional SOZ than in the inactive lesions. No specific HFO pattern could be identified for the different lesion types. The findings suggest that HFOs represent a marker for SOZ areas independent of the underlying pathology and that pathologic tissue changes alone do not lead to high rates of HFOs.

The surgery of epilepsy

The idea of surgical treatment for epilepsy is not new. However, widespread use and general acceptance of this treatment has only been achieved during the past three decades. A crucial step in this direction was the development of video electroencephalographic monitoring. Improvements in imaging resulted in an increased ability for preoperative identification of intracerebral and potentially epileptogenic lesions. High resolution magnetic resonance imaging plays a major role in structural and functional imaging; other functional imaging techniques (e.g., positron emission tomography and single-photon emission computed tomography) provide complementary data and, together with corresponding electroencephalographic findings, result in a hypothesis of the epileptogenic lesion, epileptogenic zone, and the functional deficit zone. The development of microneurosurgical techniques was a prerequisite for the general acceptance of elective intracranial surgery. New less invasive and safer resection techniques have been developed, and new palliative and augmentative techniques have been introduced. Today, epilepsy surgery is more effective and conveys a better seizure control rate. It has become safer and less invasive, with lower morbidity and mortality rates. This article summarizes the various developments of the past three decades and describes the present tools for presurgical evaluation and surgical strategy, as well as ideas and future perspectives for epilepsy surgery.

Trephine Epilepsy Surgery: The Inferior Temporal Gyrus Approach

Objective:

To describe our technique for temporal lobe epilepsy surgery using a minimal-access approach.

Methods:

Our epilepsy surgery registry was reviewed, and all patients with at least 2 years follow-up were queried. Clinical data included age, sex, side of lesion, presence of mesial temporal sclerosis, surgical complications, and Engel class outcome. Our operation was performed through a 6- to 8-cm linear vertical incision extending upward from just anterior to the tragus. An oval trephine (2×3 cm) craniotomy was performed flush with the middle fossa floor. Resection of part of the inferior temporal gyrus provided a corridor to the mesial temporal lobe. Identification of the temporal horn of the lateral ventricle was followed by resection of the parahippocampal gyrus, the amygdala, and the uncus. Segregation of the hippocampus and its subsequent resection in subpial fashion preserved perimesencephalic vasculature. Use of a fine suture for skin closure produced a cosmetic result.

Results:

In our 8-year series of 201 patients with a minimum follow-up duration of 2 years, we have observed a low number (1.5%) of complications and a 78% rate of Engel Class I seizure-free outcome. Surgery times were short (average, 2–5 h; range, 2 h 20 min-4 h 10 min) and hospital stays brief (&lt;3 d; range, 1–4 d).

Conclusion:

Our results suggest that the trephine craniotomy with the inferior temporal gyrus approach has the advantage of minimal invasiveness, including brief operative times and postoperative stays, and also effectively reduces or eradicates medically intractable seizures.

Prognosis after temporal lobe epilepsy surgery: the value of combining predictors

PURPOSE

Although several independent predictors of seizure freedom after temporal lobe epilepsy surgery have been identified, their combined predictive value is largely unknown. Using a large database of operated patients, we assessed the combined predictive value of previously reported predictors included in a single multivariable model.

METHODS

The database comprised a cohort of 484 patients who underwent temporal lobe surgery for drug-resistant epilepsy. Good outcome was defined as Engel class 1, one year after surgery. Previously reported independent predictors were tested in this cohort. To be included in our final prediction model, predictors had to show a multivariable p-value of <0.20.

RESULTS

The final multivariable model included predictors obtained from the patient's history (absence of tonic-clonic seizures, absence of status epilepticus), magnetic resonance imaging [MRI; ipsilateral mesial temporal sclerosis (MTS), space occupying lesion], video electroencephalography (EEG; absence of ictal dystonic posturing, concordance between MRI and ictal EEG), and fluorodeoxyglucose positron emission tomography (FDG-PET; unilateral temporal abnormalities), that were related to seizure freedom in our data. The model showed an expected receiver-operating characteristic curve (ROC) area of 0.63 [95% confidence interval (CI) 0.57-0.68] for new patient populations. Intracranial monitoring and surgery-related parameters (including histology) were not important predictors of seizure freedom. Among patients with a high probability of seizure freedom, 85% were seizure-free one year after surgery; however, among patients with a high risk of not becoming seizure-free, still 40% were seizure-free one year after surgery.

CONCLUSION

We could only moderately predict seizure freedom after temporal lobe epilepsy surgery. It is particularly difficult to predict who will not become seizure-free after surgery.

The Children's Cancer and Leukaemia Group guidelines for the diagnosis and management of dysembryoplastic neuroepithelial tumours

Dysembryoplastic neuroepithelial tumours (DNETs) were incorporated into the new World Health Organization classification of brain tumours as part of the group of glioneuronal tumours in 1993. Large series of patients with DNETs and pharmaco-resistant epilepsy have been reported. DNETs are most often located in the temporal lobe, occurring in both mesial and lateral temporal locations. DNETs have also been reported in the insular cortex, brain stem, cerebellum, occipital lobe and striatum. Approximately 40% of DNETs are cystic, and solitary nodular, multinodular or diffuse forms have been recognized. Approximately 30% of DNETs are associated with subtle cortical dysplastic changes in the adjacent cortex. DNET nodules usually look like oligodendroglioma, whilst between the nodules it may be possible to recognize vertical columns of neurons surrounded by oligodendrocyte-like cells. Cytologically, oligodendroglial-like cells of DNETs are distinguished from oligodendroglioma by larger nuclei with frequent nuclear indentations and multiple, small nucleoli, whilst oligodendrogliomas consistently show nuclear roundness with one or two occasional nucleoli. Very rare cases of malignant transformation have been reported. DNETs are hypodense on CT and demonstrate decreased signal on the T1-weighted images and a hyper-intense signal on T2-weighted MRI. DNETs associated with pharmaco-resistant epilepsy should be removed early to achieve seizure freedom and prevent tumour progression. The surgical approach should be that of an extended lesionectomy, i.e. excision of the lesion and the abnormal dysplastic cortex around it. Use of MRI-based image guidance (neuronavigation) as a surgical tool to identify this area of abnormal cortex is very helpful to ensure that the extended lesionectomy includes any visibly dysplastic cortex. It is not advocated to use a stereotactic biopsy only, as this may generate an unrepresentative tissue sample consisting of an oligodendroglial component only and may lead to an incorrect diagnosis.

Neuropsychological features of lesion-related epilepsy in adults: an overview

Lesional epilepsy is thought to be a direct consequence of focal brain lesions of dysgenetic, neoplastic, vascular, or traumatic origin. It has been estimated that at least half of all epilepsies are the result of such lesions. The current discussion includes an overview of the cognitive and behavioral presentations in adults with epilepsy secondary to focal pathology. The neuropsychological presentation in this population is influenced by many factors, including the location and nature of the underlying lesion, seizure characteristics, the effects of treatment, and patient variables. Few studies attempt to disentangle the specific contributions of these variables to cognitive performance. However, where available studies examining the separable effects of seizure-related variables on cognitive functioning in individuals with lesional epilepsy are also reviewed. This overview includes a discussion of focal malformations of cortical and vascular development and select foreign tissue and acquired lesions.

Preserved proper naming following left anterior temporal lobectomy is associated with early age of seizure onset

PURPOSE

Anterior temporal lobectomy (ATL) is an effective surgical option for managing pharmacoresistant temporal lobe epilepsy. Many patients with left ATL develop postsurgical difficulties with proper name retrieval, although curiously, some patients have entirely intact proper naming following left ATL. Here, we tested the hypothesis that early age of seizure onset would be a reliable factor "protecting" patients from developing proper naming defects following left ATL.

METHODS

Proper naming of unique persons (Famous Faces Test, 155 items) and places (Landmark Test, 65 items) was measured in 23 patients who had undergone left ATL for pharmacoresistant epilepsy. Data were collected for a number of variables, including age of seizure onset, age at surgery, handedness, IQ, and seizure outcome. The patients were sorted into two groups based on proper naming performance: (1) Unimpaired: 7 patients performed normally on both the Faces and Landmark tests; (2) Impaired: 16 patients performed abnormally on one or both of the tests.

RESULTS

In support of our hypothesis, the Unimpaired group had a significantly earlier age of seizure onset (M = 2.1 years) than the Impaired group (M = 15.1 years). Moreover, a correlation analysis indicated a strong association between age of seizure onset and naming outcome (R =-0.569). The groups were comparable (and statistically indistinguishable) on nearly all other variables.

CONCLUSIONS

These findings document the importance of age of seizure onset in predicting proper naming outcome following left ATL (with earlier being better), and extend understanding of brain reorganization and plasticity.