Neurological morbidity of surgery for suprasylvian operculoinsular epilepsy

OBJECTIVE

The objective of this study was to identify risk factors associated with surgery-related neurological morbidity in patients with drug-resistant epilepsy undergoing suprasylvian operculoinsular resections. As secondary outcomes, we also analyzed the risk factors for ischemic lesion (IL) of corona radiata and seizure recurrence.

METHODS

A retrospective analysis was conducted on a cohort of patients who underwent suprasylvian operculoinsular resections for drug-resistant epilepsy. The association of several presurgical, surgical, and postsurgical factors with both primary (persistent neurological deficits) and secondary (structural abnormalities on postoperative magnetic resonance imaging [MRI] and seizure recurrence) postoperative outcomes was investigated with univariate and multivariate statistical analysis.

RESULTS

The study included a total of 65 patients; 46.2% of patients exhibited postoperative neurological deficits, but only 12.3% experienced persistent deficits. On postoperative MRI, IL in the corona radiata and corticospinal tract Wallerian degeneration (CSTWd) were seen in 68% and 29% of cases, respectively. Only CSTWd was significantly associated with persistent neurological deficits (relative risk [RR] = 2.6). Combined operculoinsular resection (RR = 3.62) and surgery performed on the left hemisphere (RR = .37) were independently associated with IL in the corona radiata. Variables independently associated with CSTWd were the presence of malacic components in the IL (RR = 1.96), right central operculum resection (RR = 1.79), and increasing age at surgery (RR = 1.03). Sixty-two patients had a postoperative follow-up > 12 months (median = 56, interquartile range = 30.75-73.5), and 62.9% were in Engel class I at last outpatient control. The risk of seizure recurrence was reduced by selective opercular resection (RR = .25) and increased by the histological diagnosis of aspecific gliosis (RR = 1.39).

SIGNIFICANCE

This study provides insights into the risk factors associated with surgery-related neurological morbidity, as well as further evidence on the postoperative occurrence of subcortical injury and seizure recurrence in epileptic patients undergoing suprasylvian operculoinsular resections. The findings highlighted in this study may be useful to better understand the processes supporting the increased surgical risk in the operculoinsular region.

Stereo-electroencephalography (SEEG)-Guided Surgery in Epilepsy With Cingulate Gyrus Involvement: Electrode Implantation Strategies and Postoperative Seizure Outcome

SUMMARY

Surgical treatment of cingulate gyrus epilepsy is associated with good results on seizures despite its rarity and challenging aspects. Invasive EEG monitoring is often mandatory to assess the epileptogenic zone in these patients. To date, only small surgical series have been published, and a consensus about management of these complex cases did not emerge. The authors retrospectively analyzed a large surgical series of patients in whom at least part of the cingulate gyrus was confirmed as included in the epileptogenic zone by means of stereo-electroencephalography and was thus resected. One hundred twenty-seven patients were selected. Stereo-electroencephalography-guided implantation of intracerebral electrodes was performed in the right hemisphere in 62 patients (48.8%) and in the left hemisphere in 44 patients (34.7%), whereas 21 patients (16.5%) underwent bilateral implantations. The median number of implanted electrodes per patient was 13 (interquartile range 12-15). The median number of electrodes targeting the cingulate gyrus was 4 (interquartile range 3-5). The cingulate gyrus was explored bilaterally in 19 patients (15%). Complication rate was 0.8%. A favorable outcome (Engel class I) was obtained in 54.3% of patients, with a median follow-up of 60 months. The chance to obtain seizure freedom increased in cases in whom histologic diagnosis was type-IIb focal cortical dysplasia or tumor (mostly ganglioglioma or dysembryoplastic neuroepithelial tumor) and with male gender. Higher seizure frequency predicted better outcome with a trend toward significance. Our findings suggest that stereo-electroencephalography is a safe and effective methodology in achieving seizure freedom in complex cases of epilepsy with cingulate gyrus involvement.

Stereo-EEG tailored resection in a child with presumed perinatal post-stroke epilepsy: The complex organization of epileptogenic zone

Introduction

Only a few studies have focused on tailored resection in post-stroke epilepsy, in which hemispherectomy and hemispherotomy are the most recognized treatments.

Case description

We describe the case of a patient with drug-resistant, presumed perinatal, post-stroke epilepsy and moderate right hemiparesis. The seizures were stereotyped, both spontaneous and induced by sudden noises and somatosensory stimuli. Considering the discordant anatomic-electro-clinical data - left perisylvian malacic lesion with electrical onset over the left mesial fronto-central leads - and the patient's functional preservation, SEEG was performed. SEEG revealed sub-continuous abnormalities in the perilesional regions. Several seizures were recorded, with onset over the premotor area, rapidly involving the motor and insular-opercular regions. We decided for a combined surgical approach, SEEG-guided radiofrequency thermocoagulation, on the fronto-mesial structure but also on the central operculum, followed by resective surgery including only the fronto-mesial structures.

Discussion and conclusion

The SEEG allowed to localize the epileptogenic zone far away from the anatomical lesion but connected to part of it. A combined surgical approach tailored on SEEG results allowed a good outcome (Engel Ib) without additional deficits.

Validation of SART 3.5D algorithm for cerebrovascular dynamics and artery versus vein classification in presurgical 3D digital subtraction angiographies

Classification of arteries and veins in cerebral angiograms can increase the safety of neurosurgical procedures, such as StereoElectroEncephaloGraphy, and aid the diagnosis of vascular pathologies, as arterovenous malformations. We propose a new method for vessel classification using the contrast medium dynamics in rotational digital subtraction angiography (DSA). After 3D DSA and angiogram segmentation, contrast enhanced projections are processed to suppress soft tissue and bone structures attenuation effect and further enhance the CM flow. For each voxel labelled as vessel, a time intensity curve (TIC) is obtained as a linear combination of temporal basis functions whose weights are addressed by simultaneous algebraic reconstruction technique (SART 3.5D), expanded to include dynamics. Each TIC is classified by comparing the areas under the curve in the arterial and venous phases. Clustering is applied to optimize the classification thresholds. On a dataset of 60 patients, a median value of sensitivity (90%), specificity (91%), and accuracy (92%) were obtained with respect to annotated arterial and venous voxels up to branching order 4–5. Qualitative results are also presented about CM arrival time mapping and its distribution in arteries and veins respectively. In conclusion, this study shows a valuable impact, at no protocol extra-cost or invasiveness, concerning surgical planning related to the enhancement of arteries as major organs at risk. Also, it opens a new scope on the pathophysiology of cerebrovascular dynamics and its anatomical relationships.

Association Between Semiology and Anatomo-Functional Localization in Patients With Cingulate Epilepsy: A Cohort Study

BACKGROUND AND OBJECTIVES

Cingulate epilepsy (CE) is a rare and challenging type of focal epilepsy, due to the polymorphic semiology of the seizures, mimicking other types of epilepsy, and the limited utility of scalp-EEG.

METHODS

We selected consecutive drug-resistant subjects with CE who were seizure-free after surgery, with seizure onset zone (SOZ) confirmed in the CC (cingulate cortex) by histology and/or SEEG. We analysed subjective and objective ictal manifestations using video recordings and correlated semeiology with anatomical CC subregions (anterior, anterior middle, posterior middle and posterior) localization of SOZ.

RESULTS

We analysed 122 seizures in 57 patients. Seizures were globally characterized by complex behaviors, typically natural seeming and often accompanied by emotional components.All objective ictal variables considered (pronation of the body or getting up from a lying/sitting position, tonic/dystonic posturing, hand movements, asymmetry, vocalizations, fluidity and repetitiveness of motor manifestations, awareness and emotional and autonomic components) were differently distributed among CC subregions (p<.05) Along the rostro-caudal axis fluidity and repetitiveness of movement, vocalizations, body pronation and emotional components decrease anterior-posteriorly, while tonic/dystonic postures, signs of lateralization and awareness increase.Vestibular and asymmetric somatosensory, somatosensory and epigastric and enteroceptive/autonomic symptoms were distributed differently among CC subregions (p<.05). Along the rostro-caudal axis vestibular, somatosensory and somatosensory asymmetric symptoms increase anterior-posterior.

DISCUSSION

CE is characterized by a spectrum of semeiological manifestations with a topographic distribution. CE semiology could indicate which cingulate sector is mainly involved.

Is the anatomical lesion always guilty?: A case report

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The presence of a lesion on MRI should not be considered as sufficient to identify epileptogenic zone.

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The epileptogenic zone can be independent of the anatomical lesion.

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The presurgical evaluation is a gradual and tailored process on patient’s epilepsy.

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The invasive investigations could clarify the doubts in the epilepsy surgery work-up.

During a presurgical workup, when discordant structural and electroclinical localization is identified, further evaluation with invasive EEG is often necessary. We report a 44-year-old right-handed woman without significant risk factors for epilepsy who presented at 11 years of age with focal seizures manifest as jerking of the left side of her mouth and arm with frequent evolution to bilateral tonic-clonic seizures during sleep with a weekly frequency. During video-EEG monitoring, we observed interictal left fronto-central sharp waves and some independent sharp waves in the right fronto-central region. Habitual seizures were recorded and during the post-ictal state, the patient had left arm weakness for a few minutes. The ictal discharge on EEG was characterized by a bilateral fronto-central rhythmic slow activity more prevalent over the right hemisphere. MRI of the brain revealed a left precentral structural lesion. Considering the discordant structural and electroclinical information, we performed bilateral fronto-central stereo-EEG implantation and demonstrated clear right fronto-central seizure onset. Stereo-EEG-guided radiofrequency thermocoagulation was performed in the right fronto-central leads with subsequent seizure freedom for 9 months. The patient then underwent surgery (right fronto-central cortectomy), and histology revealed focal cortical dysplasia type Ia. The post-surgical outcome was Engel Ia. This case underscores the presence of a structural lesion is not sufficient to define the epileptogenic zone if not supported by clinical and EEG evidence. In such cases, an invasive investigation is typically required.

Investigating visuo-spatial neglect and visual extinction during intracranial electrical stimulations: The role of the right inferior parietal cortex

Both visuo-spatial neglect and visual extinction may occur following right-brain damage. So far, studies on brain-damaged patients have not provided definite evidence about which lesion patterns may lead to the association or dissociation of these deficits. This study was set out to address this issue using Intracranial Electrical Stimulation (IES) in a group of nine patients affected by refractory epilepsy. Cerebral regions associated with visuo-spatial neglect and visual extinction were stimulated, including the right frontal, temporal, and posterior parietal areas. During IES, patients with intracranial implantation involving at least one of these cortical regions were administered with a manual line bisection task (N = 9) to assess visuo-spatial neglect, and a computerized task (N = 8) assessing visual extinction. Results showed that parietal IES induced a rightward bias at the manual bisection task, together with a general improvement in reaction times at bilateral and unilateral visual stimuli detection at the extinction task. The occurrence of visual extinction did not vary across stimulations. By adopting a complementary approach to anatomo-clinical correlation studies, our work corroborates the notion that lesions to the right inferior parietal lobule play a pivotal role in the pathogenesis of visuo-spatial neglect. Importantly, our results also suggest that temporarily interfering with the activity of this region is not sufficient per se to generate visual extinction, which instead may involve a broader and/or different network, possibly extending beyond the cerebral regions considered here, posing important theoretical and clinical implications.

Thalamic and neocortical differences in the relationship between the time course of delta and sigma power during NREM sleep in humans

Sleep spindles and slow waves are the hallmarks of non-rapid eye movement (NREM) sleep and are produced by the dynamic interplay between thalamic and cortical regions. Several studies in both human and animal models have focused their attention on the relationship between electroencephalographic (EEG) spindles and slow waves during NREM, using the power in the sigma and delta bands as a surrogate for the production of spindles and slow waves. A typical report is an overall inverse relationship between the time course of sigma and delta power as measured by a single correlation coefficient both within and across NREM episodes. Here we analysed stereotactically implanted intracerebral electrode (Stereo-EEG [SEEG]) recordings during NREM simultaneously acquired from thalamic and from several neocortical sites in six neurosurgical patients. We investigated the relationship between the time course of delta and sigma power and found that, although at the cortical level it shows the expected inverse relationship, these two frequency bands follow a parallel time course at the thalamic level. Both these observations were consistent across patients and across different cortical as well as thalamic regions. These different temporal dynamics at the neocortical and thalamic level are discussed, considering classical as well as more recent interpretations of the neurophysiological determinants of sleep spindles and slow waves. These findings may also help understanding the regulatory mechanisms of these fundamental sleep EEG graphoelements across different brain compartments.

Tailored multilobar disconnective epilepsy surgery in the posterior quadrant

OBJECTIVE

Surgical treatment of drug-resistant epilepsy originating from the posterior quadrant (PQ) of the brain often requires large multilobar resections, and disconnective techniques have been advocated to limit the risks associated with extensive tissue removal. Few previous studies have described a tailored temporoparietooccipital (TPO) disconnective approach; only small series with short postoperative follow-ups have been reported. The aim of the present study was to present a tailored approach to multilobar PQ disconnections (MPQDs) for epilepsy and to provide details about selection of patients, presurgical investigations, surgical technique, treatment safety profile, and seizure and cognitive outcome in a large, single-center series of patients with a long-term follow-up.

METHODS

In this retrospective longitudinal study, the authors searched their prospectively collected database for patients who underwent MPQD for drug-resistant epilepsy in the period of 2005–2017. Tailored MPQDs were a posteriori grouped as follows: type I (classic full TPO disconnection), type II (partial TPO disconnection), type III (full temporooccipital [TO] disconnection), and type IV (partial TO disconnection), according to the disconnection plane in the occipitoparietal area. A bivariate statistical analysis was carried out to identify possible predictors of seizure outcome (Engel class I vs classes II–IV) among several presurgical, surgical, and postsurgical variables. Preoperative and postoperative cognitive profiles were also collected and evaluated.

RESULTS

Forty-two consecutive patients (29 males, 24 children) met the inclusion criteria. According to the presurgical evaluation (including stereo-electroencephalography in 13 cases), 12 (28.6%), 24 (57.1%), 2 (4.8%), and 4 (9.5%) patients received a type I, II, III, or IV MPQD, respectively. After a mean follow-up of 80.6 months, 76.2% patients were in Engel class I at last contact; at 6 months and 2 and 5 years postoperatively, Engel class I was recorded in 80.9%, 74.5%, and 73.5% of cases, respectively. Factors significantly associated with seizure freedom were the occipital pattern of seizure semiology and the absence of bilateral interictal epileptiform abnormalities at the EEG (p = 0.02). Severe complications occurred in 4.8% of the patients. The available neuropsychological data revealed postsurgical improvement in verbal domains, whereas nonunivocal outcomes were recorded in the other functions.

CONCLUSIONS

The presented data indicate that the use of careful anatomo-electro-clinical criteria in the presurgical evaluation allows for customizing the extent of surgical disconnections in PQ epilepsies, with excellent results on seizures and an acceptable safety profile.

Stereoelectroencephalography: retrospective analysis of 742 procedures in a single centre

This retrospective description of a surgical series is aimed at reporting on indications, methodology, results on seizures, outcome predictors and complications from a 20-year stereoelectroencephalography (SEEG) activity performed at a single epilepsy surgery centre. Prospectively collected data from a consecutive series of 742 SEEG procedures carried out on 713 patients were reviewed and described. Long-term seizure outcome of SEEG-guided resections was defined as a binomial variable: absence (ILAE classes 1–2) or recurrence (ILAE classes 3–6) of disabling seizures. Predictors of seizure outcome were analysed by preliminary uni/bivariate analyses followed by multivariate logistic regression. Furthermore, results on seizures of these subjects were compared with those obtained in 1128 patients operated on after only non-invasive evaluation. Survival analyses were also carried out, limited to patients with a minimum follow-up of 10 years. Resective surgery has been indicated for 570 patients (79.9%). Two-hundred and seventy-nine of 470 patients operated on (59.4%) were free of disabling seizures at least 2 years after resective surgery. Negative magnetic resonance and post-surgical lesion remnant were significant risk factors for seizure recurrence, while type II focal cortical dysplasia, balloon cells, glioneuronal tumours, hippocampal sclerosis, older age at epilepsy onset and periventricular nodular heterotopy were significantly associated with seizure freedom. Twenty-five of 153 patients who underwent radio-frequency thermal coagulation (16.3%) were optimal responders. Thirteen of 742 (1.8%) procedures were complicated by unexpected events, including three (0.4%) major complications and one fatality (0.1%). In conclusion, SEEG is a safe and efficient methodology for invasive definition of the epileptogenic zone in the most challenging patients. Despite the progressive increase of MRI-negative cases, the proportion of seizure-free patients did not decrease throughout the years.

Experience-based SEEG planning: from retrospective data to automated electrode trajectories suggestions

StereoElectroEncephaloGraphy (SEEG) is a minimally invasive technique that consists of the insertion of multiple intracranial electrodes to precisely identify the epileptogenic focus. The planning of electrode trajectories is a cumbersome and time-consuming task. Current approaches to support the planning focus on electrode trajectory optimisation based on geometrical constraints but are not helpful to produce an initial electrode set to begin with the planning procedure. In this work, the authors propose a methodology that analyses retrospective planning data and builds a set of average trajectories, representing the practice of a clinical centre, which can be mapped to a new patient to initialise planning procedure. They collected and analysed the data from 75 anonymised patients, obtaining 30 exploratory patterns and 61 mean trajectories in an average brain space. A preliminary validation on a test set showed that they were able to correctly map 90% of those trajectories and, after optimisation, they have comparable or better values than manual trajectories in terms of distance from vessels and insertion angle. Finally, by detecting and analysing similar plans, they were able to identify eight planning strategies, which represent the main tailored sets of trajectories that neurosurgeons used to deal with the different patient cases.

A new tool for touch-free patient registration for robot-assisted intracranial surgery: application accuracy from a phantom study and a retrospective surgical series

OBJECTIVE The purpose of this study was to compare the accuracy of Neurolocate frameless registration system and frame-based registration for robotic stereoelectroencephalography (SEEG). METHODS The authors performed a 40-trajectory phantom laboratory study and a 127-trajectory retrospective analysis of a surgical series. The laboratory study was aimed at testing the noninferiority of the Neurolocate system. The analysis of the surgical series compared Neurolocate-based SEEG implantations with a frame-based historical control group. RESULTS The mean localization errors (LE) ± standard deviations (SD) for Neurolocate-based and frame-based trajectories were 0.67 ± 0.29 mm and 0.76 ± 0.34 mm, respectively, in the phantom study (p = 0.35). The median entry point LE was 0.59 mm (interquartile range [IQR] 0.25-0.88 mm) for Neurolocate-registration-based trajectories and 0.78 mm (IQR 0.49-1.08 mm) for frame-registration-based trajectories (p = 0.00002) in the clinical study. The median target point LE was 1.49 mm (IQR 1.06-2.4 mm) for Neurolocate-registration-based trajectories and 1.77 mm (IQR 1.25-2.5 mm) for frame-registration-based trajectories in the clinical study. All the surgical procedures were successful and uneventful. CONCLUSIONS The results of the phantom study demonstrate the noninferiority of Neurolocate frameless registration. The results of the retrospective surgical series analysis suggest that Neurolocate-based procedures can be more accurate than the frame-based ones. The safety profile of Neurolocate-based registration should be similar to that of frame-based registration. The Neurolocate system is comfortable, noninvasive, easy to use, and potentially faster than other registration devices.

Surgical treatment of polymicrogyria-related epilepsy

OBJECTIVE

The role of resective surgery in the treatment of polymicrogyria (PMG)-related focal epilepsy is uncertain. Our aim was to retrospectively evaluate the seizure outcome in a consecutive series of patients with PMG-related epilepsy who received, or did not receive, surgical treatment, and to outline the clinical characteristics of patients who underwent surgery.

METHODS

We evaluated 64 patients with epilepsy associated with magnetic resonance imaging (MRI)-documented PMG. After presurgical evaluation, 32 patients were excluded from surgical treatment and 32 were offered surgery, which was declined by 8 patients. Seizure outcome was assessed in the 40 nonsurgical and 24 surgical patients.

RESULTS

Of 40 nonsurgical patients, 8 (20%) were seizure-free after a mean follow-up of 91.7 ± (standard deviation) 59.5 months. None of the eight patients who declined surgical treatment was seizure-free (mean follow-up: 74.3 ± 60.6 months). These seizure outcomes differ significantly (p = 0.000005 and p = 0.0003, respectively) from that of the 24 surgical patients, 18 of whom (66.7%) were Engel's class I postoperatively (mean follow-up: 66.5 ± 54.0 months). Of the eight patients excluded from surgery for seizure control at first visit, two had seizure recurrence at last contact. At last contact, antiepileptic drugs (AEDs) had been withdrawn in 6 of 24 surgical and in one of 40 nonsurgical cases (p = 0.0092).

SIGNIFICANCE

The present study indicates that, at least in a subset of adequately selected patients with PMG-related epilepsy, surgery may provide excellent seizure outcomes. Furthermore, it suggests that surgery is superior to AEDs for achieving seizure freedom in these cases.

Stereoelectroencephalography-guided radiofrequency thermocoagulation in the epileptogenic zone: a retrospective study on 89 cases

OBJECT

Radiofrequency thermocoagulation (RF-TC) of presumed epileptogenic lesions and/or structures has gained new popularity as a treatment option for drug-resistant focal epilepsy, mainly in patients with mesial temporal lobe epilepsy. The role of this minimally invasive procedure in more complex cases of drug-resistant epilepsy, which may require intracranial electroencephalographic evaluation, has not been fully assessed. This retrospective study reports on a case series of patients with particularly complex focal epilepsy who underwent stereoelectroencephalography (SEEG) evaluation with stereotactically implanted multicontact intracerebral electrodes for the detailed identification of the epileptogenic zone (EZ) and who received RF-TC in their supposed EZ (according to SEEG findings).

METHODS

Eighty-nine patients (49 male and 40 female; age range 2–49 years) who underwent SEEG evaluation and subsequent RF-TC of the presumed EZ at the authors' institution between January 2008 and December 2013 were selected. Brain MRI revealed structural abnormalities in 43 cases and no lesions in 46 cases. After SEEG, 67 patients were judged suitable for resective surgery (Group 1), whereas surgery was excluded for 22 patients (Group 2). Thermocoagulation was performed in each of these patients by using the previously implanted multicontact recording electrodes and delivering RF-generated currents to adjacent electrode contacts.

RESULTS

The mean number of TC sites per patient was 10.6 ± 7.2 (range 1–33). Sustained seizure freedom occurred after TC in 16 patients (18.0%) (13 in Group 1 and 3 in Group 2). A sustained worthwhile improvement was reported by 9 additional patients (10.1%) (3 in Group 1 and 6 in Group 2). As a whole, 25 patients (28.1%) exhibited a persistent significant improvement in their seizures. More favorable results were observed in patients with nodular heterotopy (p = 0.0001389), those with a lesion found on MRI (not significant), and those with hippocampal sclerosis (not significant). Other variables significantly correlated to seizure freedom were the patient's age (p = 0.02885) and number of intralesional TC sites (p = 0.0271). The patients in Group 1 who did not benefit at all (21 patients) or who experienced only a transient benefit (30 patients) from TC underwent microsurgical resection of their EZ. Thermocoagulation was followed by severe permanent neurological deficits in 2 patients (an unexpected complex neuropsychological syndrome in one patient and an expected and anticipated permanent motor deficit in the other).

CONCLUSIONS

This study provides evidence that SEEG-guided TC in the EZ may be a treatment option for particularly complex drug-resistant focal epilepsy that requires invasive evaluation. A small subset of patients who achieve seizure freedom or worthwhile improvement may avoid open surgery or take advantage of an otherwise unexpected treatment if resection is not an option. Patients with epileptogenic nodular heterotopy are probably ideal candidates for this treatment.

Cerebral Angiography for Multimodal Surgical Planning in Epilepsy Surgery: Description of a New Three-Dimensional Technique and Literature Review

OBJECTIVE

Cerebrovascular imaging is critical for safe and accurate planning of Stereo-ElectroEncephaloGraphy (SEEG) electrode trajectory. We developed a new technique for Cone Beam Computed Tomography (CBCT) Three-Dimensional Digital Subtraction Angiography (3D DSA).

METHODS

The workflow core is the acquisition of computed tomography datasets without (bone mask) and with selective injection of contrast medium in the main brain-feeding arteries, followed by dataset registration and subtraction. The images were acquired with the O-armTM 1000 System (Medtronic). Images were postprocessed with FSL software package. We retrospectively analyzed 191 3D DSA procedures and qualitatively analyzed the quality of each 3D DSA dataset.

RESULTS

The quality of 3D DSA was good in 150 procedures, sufficient in 37, and poor in 4. 3D rendering of the vascular tree was helpful for both SEEG implantation and resective surgery planning. Angiography complications occurred in only one procedure that was aborted due to a major allergic reaction to contrast medium. No other complications directly related to 3D DSA occurred. Minor intracerebral hemorrhage occurred in 2/191 patients after SEEG implantation, with no permanent sequelae.

CONCLUSIONS

CBCT 3D DSA is a safe diagnostic procedure for SEEG electrode trajectory planning and for 3D reconstructions of the vascular tree in multimodal scenes for resections. The high fidelity and geometric accuracy contribute to the safety of electrode implantation.

Stereo-EEG-guided radio-frequency thermocoagulations of epileptogenic grey-matter nodular heterotopy

OBJECTIVE

To retrospectively evaluate seizure outcome in a case-series of patients with nodular heterotopy (NH)-related epilepsy treated by stereo-EEG (SEEG)-guided radio-frequency thermocoagulation (RF-THC) of the NH.

METHODS

Five patients (three male, age 5-33 years) with drug-resistant focal epilepsy presented a single NH at brain MRI. Following video-EEG monitoring, patients underwent SEEG recording to better identify the epileptogenic zone. All patients received RF-THC of the NH, using contiguous contacts of the electrodes employed for recording. The contacts for RF-THC lesions were chosen according to anatomical (intranodular position) and electrical (intranodular ictal low-voltage fast activity) criteria.

RESULTS

At SEEG recordings, ictal discharge originated from the NH alone in three cases and from the NH and ipsilateral hippocampus in one case. In the remaining case, different sites of ictal onset, including the NH, were identified within the left frontal lobe. No adverse effects related to the RF-THC procedures were observed, apart from a habitual seizure that occurred during coagulation in one patient. Postprocedural sustained seizure freedom was detected in four cases (mean follow-up 33.5 months). In the case with left frontal multifocal ictal activity, RF-THC of the NH provided no benefit on seizures, and the patient is seizure-free after left frontal lobe resection.

CONCLUSIONS

SEEG-guided RF-THC proved to be a safe and effective option in our small case-series of NH-related focal epilepsy. The indications to this treatment were strictly dependent on findings of intracerebral recording by SEEG, which can define the role of the NH in the generation of the ictal discharge.

Multi-trajectories automatic planner for StereoElectroEncephaloGraphy (SEEG)

PURPOSE

StereoElectroEncephaloGraphy (SEEG) is done to identify the epileptogenic zone of the brain using several multi-lead electrodes whose positions in the brain are pre-operatively defined. Intracranial hemorrhages due to disruption of blood vessels can cause major complications of this procedure ([Formula: see text]1%). In order to increase the intervention safety, we developed and tested planning tools to assist neurosurgeons in choosing the best trajectory configuration.

METHODS

An automated planning method was developed that maximizes the distance of the electrode from the vessels and avoids the sulci as entry points. The angle of the guiding screws is optimized to reduce positioning error. The planner was quantitatively and qualitatively compared with manually computed trajectories on 26 electrodes planned for three patients undergoing SEEG by four neurosurgeons. Quantitative comparison was performed computing for each trajectory using (a) the Euclidean distance from the closest vessel and (b) the incidence angle.

RESULTS

Quantitative evaluation shows that automatic planned trajectories are safer in terms of distance from the closest vessel with respect to manually planned trajectories. Qualitative evaluation performed by four neurosurgeons showed that the automatically computed trajectories would have been preferred to manually computed ones in 30% of the cases and were judged good or acceptable in about 86% of the cases. A significant reduction in time required for planning was observed with the automated system (approximately 1/10).

CONCLUSION

The automatic SEEG electrode planner satisfied the essential clinical requirements, by providing safe trajectories in an efficient timeframe.

Stereoelectroencephalography: surgical methodology, safety, and stereotactic application accuracy in 500 procedures

BACKGROUND

Stereoelectroencephalography (SEEG) methodology, originally developed by Talairach and Bancaud, is progressively gaining popularity for the presurgical invasive evaluation of drug-resistant epilepsies.

OBJECTIVE

To describe recent SEEG methodological implementations carried out in our center, to evaluate safety, and to analyze in vivo application accuracy in a consecutive series of 500 procedures with a total of 6496 implanted electrodes.

METHODS

Four hundred nineteen procedures were performed with the traditional 2-step surgical workflow, which was modified for the subsequent 81 procedures. The new workflow entailed acquisition of brain 3-dimensional angiography and magnetic resonance imaging in frameless and markerless conditions, advanced multimodal planning, and robot-assisted implantation. Quantitative analysis for in vivo entry point and target point localization error was performed on a sub--data set of 118 procedures (1567 electrodes).

RESULTS

The methodology allowed successful implantation in all cases. Major complication rate was 12 of 500 (2.4%), including 1 death for indirect morbidity. Median entry point localization error was 1.43 mm (interquartile range, 0.91-2.21 mm) with the traditional workflow and 0.78 mm (interquartile range, 0.49-1.08 mm) with the new one (P < 2.2 × 10). Median target point localization errors were 2.69 mm (interquartile range, 1.89-3.67 mm) and 1.77 mm (interquartile range, 1.25-2.51 mm; P < 2.2 × 10), respectively.

CONCLUSION

SEEG is a safe and accurate procedure for the invasive assessment of the epileptogenic zone. Traditional Talairach methodology, implemented by multimodal planning and robot-assisted surgery, allows direct electrical recording from superficial and deep-seated brain structures, providing essential information in the most complex cases of drug-resistant epilepsy.

Long-duration epilepsy affects cell morphology and glutamatergic synapses in type IIB focal cortical dysplasia

To investigate hypothesized effects of severe epilepsy on malformed cortex, we analyzed surgical samples from eight patients with type IIB focal cortical dysplasia (FCD) in comparison with samples from nine non-dysplastic controls. We investigated, using stereological quantification methods, where appropriate, dysplastic neurons, neuronal density, balloon cells, glia, glutamatergic synaptic input, and the expression of N-methyl-D-aspartate (NMDA) receptor subunits and associated membrane-associated guanylate kinase (MAGUK). In all FCD patients, the dysplastic areas giving rise to epileptic discharges were characterized by larger dysmorphic neurons, reduced neuronal density, and increased glutamatergic inputs, compared to adjacent areas with normal cytology. The duration of epilepsy was found to correlate directly (a) with dysmorphic neuron size, (b) reduced neuronal cell density, and (c) extent of reactive gliosis in epileptogenic/dysplastic areas. Consistent with increased glutamatergic input, western blot revealed that NMDA regulatory subunits and related MAGUK proteins were up-regulated in epileptogenic/dysplastic areas of all FCD patients examined. Taken together, these results support the hypothesis that epilepsy itself alters morphology-and probably also function-in the malformed epileptic brain. They also suggest that glutamate/NMDA/MAGUK dysregulation might be the intracellular trigger that modifies brain morphology and induces cell death.

Automatic trajectory planner for StereoElectroEncephaloGraphy procedures: a retrospective study

In StereoElectroEncephaloGraphy (SEEG) procedures, intracerebral electrodes are implanted in order to identify the epileptogenic zone in drug-resistant epileptic patients. This paper presents an automatic multitrajectory planner that computes the best trajectory in terms of distance from vessels and guiding screws angle, once the candidate entry and target regions are quickly and roughly defined. The planning process is designed also to spare some brain structures, such as cella media and trigone of the lateral ventricles and brain stem. The planner was retrospectively evaluated on 15 patients who had previously undergone SEEG investigation. Quantitative comparison was performed computing for each patient and for each electrode trajectory 1) the Euclidean distance from the closest vessel; 2) the trajectory incidence angle (guiding screws angle); and 3) the sulcality value. The automatic planner proved to satisfy the clinical requirements, planning safe trajectories in a clinical-compatible timeframe. Qualitative evaluation performed by three neurosurgeons showed that the automatically computed trajectories would have been accepted by them.

Stereoelectroencephalography in the presurgical evaluation of focal epilepsy in infancy and early childhood

OBJECT

The authors report on the use of stereoelectroencephalography (stereo-EEG) in the presurgical electroclinical evaluation of infants and very young children with focal drug-resistant epilepsy.

METHODS

Fifteen patients (9 girls and 6 boys, mean age 34.1 ± 7.3 months, range 21-45 months), potentially candidates to receive surgical treatment for their focal drug-resistant epilepsy, were evaluated using stereo-EEG recording for a detailed definition of the epileptogenic zone. Stereoelectroencephalography was indicated because neuroradiological (brain MRI) and video-EEG data failed to adequately localize the epileptogenic zone. Stereotactic placement of multicontact intracerebral electrodes was preceded by the acquisition of all pertinent anatomical information from structural and functional MRI and from brain angiography, enabling the accurate targeting of desired structures through avascular trajectories. Stereoelectroencephalography monitoring attempted to record habitual seizures; electrical stimulations were performed to induce seizures and for the functional mapping of eloquent areas. Stereoelectroencephalography-guided microsurgery, when indicated, pointed to removal of the epileptogenic zone and seizure control.

RESULTS

Brain MRI revealed an anatomical lesion in 13 patients (lobar in 2 cases, multilobar or hemispheric in 11 cases) and was unremarkable in 2 patients. One patient underwent 2 stereo-EEG studies. The arrangement of the intracerebral electrodes was unilateral in all but 1 case. One patient died the day following electrode placement due to massive brain edema and profound hyponatremia of undetermined cause. In 8 cases intracerebral electrical stimulations allowed mapping of functionally critical areas; in 3 other cases that received purposeful placement of electrodes in presumably eloquent areas, no functional response was obtained. Of the 14 patients who completed stereo-EEG monitoring, 1 was excluded from surgery for multifocality of seizures and 13 underwent operations. Postoperatively, 2 patients exhibited an anticipated, permanent motor deficit, 3 experienced a transient motor deficit, and 2 experienced transient worsening of a preexisting motor deficit. Three patients developed a permanent homonymous hemianopia after posterior resections. Histological analysis revealed cortical malformations in 10 cases. Of the 10 patients with a postoperative follow-up of at least 12 months, 6 (60%) were seizure-free (Engel Class Ia), 2 (20%) experienced a significant reduction of seizures (Engel Class II), and 2 (20%) were unchanged (Engel Class IV).

CONCLUSIONS

The present study indicates that stereo-EEG plays a prominent role in the presurgical evaluation of focal epilepsies also in the first years of life and that it may offer a surgical option in particularly complex cases that would have scarcely benefitted from further medical treatment. Results of stereo-EEG-guided resective surgery were excellent, with 80% of patients exhibiting a substantial improvement in seizures. In consideration of the potentially life-threatening risks of major intracranial surgery in this specific age group, the authors recommend reserving stereo-EEG evaluations for infants with realistic chances of benefiting from surgery.

One-year postsurgical follow-up of 12 subjects with epilepsy and interictal psychosis

We describe the 1-year follow-up after epilepsy surgery of 12 patients with chronic interictal psychosis and medically intractable epilepsy. The 12 cases described were part of a sample of 350 subjects who concluded a 1-year psychiatric follow-up from a total of 504 subjects operated on for medically intractable epilepsy between 2002 and 2009. Outcome was Engel class IA for five of these patients, IB for one, ID for one, IIB for one, IIIA for three, and IVA for one. Four patients had a worsening of psychotic symptoms at 6 months, but showed improvement after 1 year; two subjects had a worsening of psychotic symptoms at both 6 months and 1 year. Despite the severity of symptoms, compliance with preoperative assessment, surgical programs, and follow-up was satisfactory.

Features of somatosensory manifestations induced by intracranial electrical stimulations of the human insula

OBJECTIVE

To study the clinical manifestations induced by intracranial electrical stimulation of the insular cortex in epileptic patients submitted to invasive stereo-electroencephalography (SEEG) recordings.

METHODS

We retrospectively studied the clinical manifestations induced by intracerebral electrical stimulations of the insular cortex in 96 patients. In order to precisely localize the position of the electrodes a postoperative 3D CT scan or a 3D MRI was obtained and then the images were merged with the preoperative MRI in the same stereotactic referenced system.

RESULTS

A total of 341 electrical bipolar stimulations were performed. The most frequently induced symptom was a somatosensory manifestation (70%), mainly tingling and electric sensation involving the contralateral face and arm. Motor responses represented the 8% of the total amount, as well as auditory phenomena. Language dysfunction accounted for 2% of responses. Autonomic and gustatory phenomena represented respectively 1% of responses.

CONCLUSIONS

We found a great prevalence of somatosensory manifestations whereas other types of clinical modifications were extremely infrequent.

SIGNIFICANCE

Our data support a prominent somatosensory role of the human insular cortex and provide a precise characterization of the different types of sensory manifestations induced by intracranial electrical stimulation of the human insula.

Seizure outcome of epilepsy surgery in focal epilepsies associated with temporomesial glioneuronal tumors: lesionectomy compared with tailored resection

OBJECT

The authors retrospectively analyzed and compared seizure outcome in a series of 28 patients with temporomesial glioneuronal tumors associated with epilepsy who underwent 1 of 2 different epilepsy surgery procedures: lesionectomy or tailored resection.

METHODS

The 28 patients were divided into 2 groups, with 14 cases in each group. In Group A, surgery was limited to the tumor (lesionectomy), whereas Group B patients underwent tailored resection involving removal of the tumor and the epileptogenic zone as identified by a neurophysiological noninvasive presurgical study.

RESULTS

In Group A (10 male and 4 female patients) the interval between onset of seizures and surgery ranged from 1 to 33 years (mean 10.6 years). Patients' ages ranged from 3 to 61 years (mean 23.1 years). The epileptogenic lesion was on the left side in 6 patients and the right in 8 patients. Mean follow-up was 9.8 years (range 6.5-15 years). The Engel classification system, used to determine postoperative seizure outcome, showed 6 patients (42.8%) were Engel Class I and 8 (57.1%) were Engel Class II. In Group B (6 male and 8 female patients) the interval between onset of seizures and surgery ranged from 0.5 to 25 years (mean 8.6 years). Patients' ages ranged from 3 to 48 years (mean 22.3 years). The tumor and associated epileptogenic area was on the right side in 8 patients and the left in 6 patients. Mean follow-up duration was 3.5 years (range 1-6.5 years). Postoperative seizure outcome was Engel Class I in 13 patients (93%) and Engel Class II in 1 (7.1%).

CONCLUSIONS

The authors' results demonstrate a better seizure outcome for temporomesial glioneuronal tumors associated with epilepsy in patients who underwent tailored resection rather than simple lesionectomy (p = 0.005). For temporomesial glioneuronal tumors associated with epilepsy, performing a presurgical noninvasive neurophysiological study intended to identify the epileptogenic zone is necessary for planning a tailored surgery. Using this surgical strategy, the presence of temporomesial glioneuronal tumors constitutes a predictive factor of excellent seizure outcome, and therefore surgical treatment can be offered early to avoid both the consequences of uncontrolled seizures as well as the side effects of pharmacological therapy.

Taylor's focal cortical dysplasia increases the risk of sleep-related epilepsy

PURPOSE

To analyze the topography of the epileptogenic zone (EZ) and the etiologic substrate as risk factors for sleep-related focal epilepsy.

METHODS

Three hundred three patients (172 males and 131 females, mean age at surgery 25.6 +/- 13.1 years), who were seizure-free after resective surgery for drug-resistant focal epilepsy, were retrospectively reviewed. Statistical analysis was conducted to evaluate the risk of presenting sleep-related epilepsy (SRE) against topography of resection (assumed to correspond or to include the EZ) and results of histology.

RESULTS

Thirty-nine patients (12.8%) presented with an SRE. At bivariate analysis, a higher frequency of SRE was associated with a frontal lobe EZ (p = 1.94 x 10(-9)) and Taylor's FCD (TFCD, p = 2.20 x 10(-16)), whereas architectural FCD (p = 0.00977), ganglioglioma (p = 0.02508), and mesial temporal sclerosis (p = 2.47 x 10(-5)) were correlated with a reduced frequency of SRE. Multivariate analysis demonstrated that the only variable significantly associated with SRE was the presence of a TFCD, which increased 14-fold the risk of SRE [p = 1.66 x 10(-10); risk ratio (RR) = 14.44].

DISCUSSION

In this study, we have demonstrated a significant and strong association between SRE and TFCD in a select population of patients with drug-resistant focal epilepsy submitted to surgical resection of the EZ. Although our results cannot be applied to the entire spectrum of SRE, the presence of TFCD as the underlying etiology should be considered when evaluating patients with SRE, because surgery can provide excellent results on seizures in these cases.

A survey of Italian cases of dystonia treated by deep brain stimulation

AIM

The aim of this study was to report on Italian cases of dystonia treated by deep brain stimulation up to the end of 2005.

METHODS

Retrospective survey. Presentation of data collection among all Italian neurosurgical institutions.

RESULTS

Seven out of 123 Italian neurosurgical centres were enrolled. Sixty-nine patients were operated. According to different classification criteria, cases were grouped as follows: 37 primary and 32 secondary dystonia; 61 generalized and 8 focal dystonia; 16 patients aged at onset <2 years, 22 aged 3-12 years, 14 aged 13-20 years, 17 aged >20 years. Primary dystonia (DYT) mutation 1 was identified in 21% of primary generalized dystonia. Age at surgery was <15 years in 21.7% of cases (N.=15). Mean time between clinical onset and surgery was 17 years. Globus pallidus internus (GPi) was chosen for implantation in all cases. Type of anesthesia, method of target localization, lead and implanted pulse generator (IPG) model differed among centres. Surgical complications occurred in 19% of patients, but at a higher rate (33%) in the pediatric subgroup. Stimulation parameters varied among centres, but the main scheme was 90-120 micros and 130 Hz. Follow-up duration ranged from 3 to 84 months (longer than 24 months in 50% of patients). Mean Burke-Fahn-Marsden scale (BFM) improvement was 42% for both severity and disability score, ranging from 0% to 92%. Improvement of at least 50% in BFM severity score has been reached by 45% of primary and 37% of secondary dystonia. Clinical results were better in the DYT1 subgroup, with 60% of cases improving more than 50%. Among secondary dystonia, the drug-induced group had very good results too. On the contrary delayed surgery and presence of comorbidity were negatively correlated to the outcome.

CONCLUSION

In this series, primary generalized dystonia has a better outcome, especially if associated to DYT1 mutation. Among secondary dystonia, the drug-induced group has very good

RESULTS

Correlation analysis of time to surgery and associated comorbidity suggests that earlier surgery is advisable.

Epilepsy surgery in children: results and predictors of outcome on seizures

PURPOSE

To retrospectively analyze the results on seizures of surgery in children with drug-resistant focal epilepsy. To identify the factors predicting seizure control among several presurgical, surgical, and postsurgical variables.

METHODS

One hundred thirteen patients (67 male, 46 female), younger than 16 years, operated on from 1996 to 2004 and followed-up for at least 2 years were identified. Individualized microsurgical resections, aimed at removal of the epileptogenic zone, were performed according to the results of tailored presurgical evaluations, which included stereo-electroencephalographic recording with intracerebral electrodes when needed. Risk of seizure recurrence was assessed for the considered variables by bivariate and multivariate analysis.

RESULTS

Mean age at surgery was 8.8 years, mean duration of epilepsy was 5.7 years, and mean age at seizure onset was 3.1 years. One hundred eight patients (96%) had an abnormal magnetic resonance imaging. At postoperative follow-up (mean duration 55.1 month), 77 patients (68%) were in Engel's class I, with 68 patients (60%) being seizure free (Engel's classes Ia and Ic). At multivariate analysis, variables associated with a significantly lower risk of seizure recurrence were unifocal lesion at MRI and older age at seizure onset (presurgical variables), temporal unilobar resection and complete lesionectomy (surgical variables), diagnosis of glial-neuronal tumors (postsurgical variables).

CONCLUSIONS

Surgery is a valuable option for children with drug-resistant focal epilepsies which may provide excellent results in a considerable amount of cases. Since results of surgery for epilepsy strongly depend on the presurgical identification of the Epileptogenic Zone, future work should be focused on refinement and implementation of diagnostic strategies.

COMPARISON OF TWO TECHNIQUES TO POSTOPERATIVELY LOCALIZE THE ELECTRODE CONTACTS USED FOR SUBTHALAMIC NUCLEUS STIMULATION

OBJECTIVE

Cerebral ventriculography (Vg) and magnetic resonance imaging (MRI) scanning are routine procedures to determine the implanted electrode placement into the subthalamic nucleus (STN) and are used in several centers that provide deep brain stimulation for Parkinson's disease patients. However, because of image distortion, MRI scan accuracy in determining electrode placement is still matter of debate. The objectives of this study were to verify the expected localization of the electrode contacts within the STN and to compare the stereotactic coordinates of these contacts determined intraoperatively by Vg with those calculated postoperatively by MRI scans. To our knowledge, this is the first study attempting to compare the "gold standard" of stereotactic accuracy (Vg) with the anatomic resolution provided by MRI scans.

METHODS

Images from 18 patients with Parkinson's disease who underwent bilateral operation were used in this study. Among the 36 chronically stimulated contacts, 28 contacts (78%) were localized in the dorsolateral part of the STN. The remaining eight contacts (22%) were located more dorsally in the zona incerta, close to the upper border of the STN.

RESULTS

Significant differences were found between Vg and MRI scans regarding the mediolateral x coordinate of the contacts for both left and right electrodes and regarding the right-sided anteroposterior y coordinate. No statistical difference was found for the left-sided y coordinate and the dorsoventral z coordinate for both sides.

CONCLUSION

If we assume that Vg is an imaging gold standard, our results suggest that postoperative MRI scanning may induce a slight image translation compared with Vg. However, MRI scans allowed localization of most of the contacts within the STN.

Surgical treatment of drug-resistant nocturnal frontal lobe epilepsy

Of the cases with nocturnal frontal lobe epilepsy (NFLE) approximately 30% are refractory to antiepileptic medication, with several patients suffering from the effects of both ongoing seizures and disrupted sleep. From a consecutive series of 522 patients operated on for drug-resistant focal epilepsy, 21 cases (4%), whose frontal lobe seizures occurred almost exclusively (>90%) during sleep, were selected. All patients underwent a comprehensive pre-surgical evaluation, which included history, interictal EEG, scalp video-EEG monitoring, high-resolution MRI and, when indicated, invasive recording by stereo-EEG (SEEG). There were 11 males and 10 females, whose mean age at seizure onset was 6.2 years, mean age at surgery was 24.7 years and seizure frequency ranged from <20/month to >300/month. Nine patients reported excessive daytime sleepiness (EDS). Prevalent ictal clinical signs were represented by asymmetric posturing (6 cases), hyperkinetic automatisms (10 cases), combined tonic posturing and hyperkinetic automatisms (4 cases) and mimetic automatisms (1 case). All patients reported some kind of subjective manifestations. Interictal and ictal EEG provided lateralizing or localizing information in most patients. MRI was unrevealing in 10 cases and it showed a focal anatomical abnormality in one frontal lobe in 11 cases. Eighteen patients underwent a SEEG evaluation to better define the epileptogenic zone (EZ). All patients received a microsurgical resection in one frontal lobe, tailored according to pre-surgical evaluations. Two patients were operated on twice owing to poor results after the first resection. Histology demonstrated a Taylor-type focal cortical dysplasia (FCD) in 16 patients and an architectural FCD in 4. In one case no histological change was found. After a post-operative follow-up of at least 12 months (mean 42.5 months) all the 16 patients with a Taylor's FCD were in Engel's Class Ia and the other 5 patients were in Engel's Classes II or III. After 6 months post-surgery EDS had disappeared in the 9 patients who presented this complaint pre-operatively. It is concluded that patients with drug-resistant, disabling sleep-related seizures of frontal lobe origin should be considered for resective surgery, which may provide excellent results both on seizures and on epilepsy-related sleep disturbances. An accurate pre-surgical evaluation, which often requires invasive EEG recording, is mandatory to define the EZ. Further investigation is needed to explain the possible causal relationships between FCD, particularly Taylor-type, and sleep-related seizures, as observed in this cohort of NFLE patients.

Sleep-related Minor Motor Events in Nocturnal Frontal Lobe Epilepsy

PURPOSE

Nocturnal frontal lobe epilepsy (NFLE) is characterized by a wide spectrum of sleep-related motor manifestations of increasing complexity, ranging from major episodes to brief motor events (minor motor events, MMEs). NFLE patients may exhibit a large quantity of MMEs in the form of short-lasting stereotyped movements. Whereas major episodes are considered epileptiform manifestations, it remains unclear whether the MMEs are related to epileptiform discharges (EDs).

METHODS

To study the relation between EDs and the occurrence of MMEs, we report a detailed neurophysiolgical evaluation in NFLE subjects explored by using implanted electrodes.

RESULTS

The median value of ED-related movements was 71.8%. Motor expression in relation to epileptiform discharge was surprisingly variable; no peculiar expression of MMEs could be attributed to the presence of EDs.

CONCLUSIONS

Our data suggest that ED-associated MMEs are extremely polymorphous, and no univocal relation to EDs can be identified. We hypothesize that MMEs are not a direct effect of epileptiform discharge (i.e., not epileptic in origin), but the result of aspecific disinhibition of innate motor patterns. We warn clinicians that the epileptic nature of minimal motor phenomena in NFLE cannot be established on the clinical phenomenology of the event.

Stereo-EEG in children

BACKGROUND

Stereotactic placement of intracerebral multilead electrodes for chronic EEG recording of seizures or stereoelectroencephalography (SEEG) was introduced 50 years ago at Saint Anne Hospital in Paris, France for the presurgical evaluation of patients with drug-resistant focal epilepsy. SEEG explorations are indicated whenever the noninvasive tests fail to adequately localize the epileptogenic zone (EZ).

INDICATIONS

Currently, approximately 35% of our operated-on children require a SEEG evaluation. Arrangement of electrodes is individualized according to the peculiar needs of each child, to verify a predetermined hypothesis of localization of the EZ based on pre-SEEG anatomo-electro-clinical findings. Multilead intracerebral electrodes are designed to sample cortical structures on the lateral, intermediate, and mesial aspect of the hemisphere, as well as deep-seated lesions. Stereotactic stereoscopic teleangiograms and coregistered 3-D MRI are employed to plan avascular trajectories and to accurately target the desired structures. Pre-SEEG stereotactic neuroradiology and electrode implantation are usually performed in separate procedures. Electrodes are removed once video-SEEG monitoring is completed.

INTRACEREBRAL ELECTRICAL STIMULATIONS

Intracerebral electrical stimulations are used to better define the EZ and to obtain a detailed functional mapping of critical cortical and subcortical regions.

MORBIDITY

Surgical morbidity of SEEG is definitely low in children. SEEG-GUIDED RESECTIVE SURGERY: In 90% of evaluated children, SEEG provides a guide for extratemporal or multilobar resections. SEEG-guided resective surgery may yield excellent results on seizures with 60% of patients in Engel's Class I.

Stereoelectroencephalography in the presurgical evaluation of focal epilepsy: a retrospective analysis of 215 procedures

OBJECTIVE

To report on indications, surgical technique, results, and morbidity of stereoelectroencephalography (SEEG) in the presurgical evaluation of patients with drug-resistant focal epilepsy.

METHODS

Two-hundred fifteen stereotactic implantations of multilead intracerebral electrodes were performed in 211 patients (4 patients were explored twice), who showed variable patterns of localizing incoherence among electrical (interictal/ictal scalp electroencephalography), clinical (ictal semeiology), and anatomic (magnetic resonance imaging [MRI]) investigations. MRI scanning showed a lesion in 134 patients (63%; associated with mesial temporal sclerosis in 7) and no lesion in 77 patients (37%; with mesial temporal sclerosis in 14 patients). A total of 2666 electrodes (mean, 12.4 per patient) were implanted (unilaterally in 175 procedures and bilaterally in 40). For electrode targeting, stereotactic stereoscopic cerebral angiograms were used in all patients, coupled with a coregistered three-dimensional MRI scan in 108 patients.

RESULTS

One hundred eighty-three patients (87%) were scheduled for resective surgery after SEEG recording, and 174 have undergone surgery thus far. Resections sites were temporal in 47 patients (27%), frontal in 55 patients (31.6%), parietal in 14 patients (8%), occipital in one patient (0.6%), rolandic in one patient (0.6%), and multilobar in 56 patients (32.2%). Outcome on seizures (Engel's classification) in 165 patients with a follow-up period of more than 12 months was: Class I, 56.4%; Class II, 15.1%; Class III, 10.9%; and Class IV, 17.6%. Outcome was significantly associated with the results of MRI scanning (P = 0.0001) and with completeness of lesion removal (P = 0.038). Morbidity related to electrode implantation occurred in 12 procedures (5.6%), with severe permanent deficits from intracerebral hemorrhage in 2 (1%) patients.

CONCLUSION

SEEG is a useful and relatively safe tool in the evaluation of surgical candidates when noninvasive investigations fail to localize the epileptogenic zone. SEEG-based resective surgery may provide excellent results in particularly complex drug-resistant epilepsies.

Intracerebral recordings of minor motor events, paroxysmal arousals and major seizures in nocturnal frontal lobe epilepsy

The clinical features of nocturnal frontal lobe epilepsy (NFLE) consist of a spectrum of paroxysmal motor manifestations ranging from minor motor events (MMEs) to paroxysmal arousals (PAs) and major seizures. During MMEs and PAs scalp EEG generally does not show definite ictal abnormalities. We describe the clinical and electrophysiological features of three patients affected by drug-resistant NFLE studied with intracerebral electrodes during a presurgical evaluation. The stereo-EEG (SEEG) investigation revealed that MMEs can be fragments of the major seizure and occur during a brief epileptic discharge or on the following arousal. PAs, in the same subject, do not show a definite stereotypy despite the morphological and topographic similarity of the epileptic discharges, thus indicating that other variables may influence the clinical features of PAs.

Sleep-related hyperkinetic seizures: always a frontal onset?

Hyperkinetic seizures are considered a typical manifestation of nocturnal frontal lobe epilepsy (NFLE). Patients with temporal lobe epilepsy with mainly sleep-related seizures have been described; however they commonly lack hyperkinetic activity and seizure frequency is low. We retrospectively analysed our population of 442 consecutive patients surgically treated between January 1996 and January 2004. Among these there were 25 patients with sleep-related hyperkinetic epileptic seizures, with a frontal lobe onset in 18 cases and a temporal lobe onset in 7. Patients with sleep-related hyperkinetic seizures with temporal lobe origin had anamnestic and clinical features strikingly similar to those with a frontal onset, with agitated movements, high seizure frequency and no history of febrile convulsions. We confirm our previous findings that this kind of epileptic manifestation is not only peculiar to frontal lobe epilepsy.

Sleep-related hyperkinetic seizures of temporal lobe origin

Sleep-related hyperkinetic seizures are a common feature of nocturnal frontal lobe epilepsy. Although sleep-related seizures with a temporal lobe origin have been reported, they commonly lack hyperkinetic activity. The authors describe three patients with sleep-related seizures characterized by frenetic, agitated, hyperactive movements (bimanual/bipedal activity, rocking, axial, pelvic, and hemiballistic movements), in whom stereo-EEG investigation and surgical outcome demonstrated a temporal lobe origin of the attacks.

Nocturnal frontal lobe epilepsy: intracerebral recordings of paroxysmal motor attacks with increasing complexity

PURPOSES

To show the results of the investigation conducted with intracerebral electrodes in a patient with drug-resistant nocturnal frontal lobe epilepsy, characterized by sleep-related paroxysmal motor attacks of increasing complexity ranging from simple and brief stereotyped motor events to paroxysmal arousals and major attacks.

METHODS

The patient was studied with long-term video-stereo-electroencephalographic monitoring by means of stereotactically implanted intracerebral electrodes.

RESULTS

Video-stereo-electroencephalography demonstrated that minor events and paroxysmal arousals, as well as major attacks, were correlated with a discharge in the right supplementary motor area and central cingulate gyms. The increasing complexity of these sleep-related ictal motor behaviors reflected a different pattern of discharge, with a progressive spread to other frontal and extrafrontal areas in the fully developed attacks. Surgical resection of the right supplementary motor area and central cingulate gyrus was performed. In the 5 years since the operation, the patient has remained completely seizure free.

CONCLUSION

This study clearly demonstrates the ictal origin of minor events in nocturnal frontal lobe epilepsy. The increasing complexity of the motor behaviors from minor to major attacks reflects different duration, amplitude, and spread of the epileptic discharge.

Focal cortical resection in malformations of cortical development

Malformations of cortical development may be associated with drug-resistant partial epilepsy suitable for surgical therapy. From the anatomopathological point of view, this categorisation has been used in reference to a wide range of alterations of the cortical mantle. Focal cortical dysplasias represent the main group of malformations of cortical development, but there are also other types of alterations, such as heterotopias, double cortex or polymicrogyria. Defining candidacy for surgical therapy and tailored resection requires thorough pre-surgical evaluation so that the approach will be individualised for each patient. We present our series of 126 patients with malformation of cortical development selected from 321 consecutively operated patients. Within this group encompassing different types of malformation of cortical development, including periventricular heterotopia (nine patients), polymicrogyria (three patients), hemimegalencephaly (one patient) and subcortical band heterotopia (one patient), the largest group was 81 individuals with focal cortical dysplasia. For this last group, we propose a simplified classification defining 42 architectural dysplasias, 12 cytoarchitectural dysplasias and 27 Taylor's focal cortical dysplasias. In addition, at routine neuropathological investigation, the only morphological alteration shown by 31 patients was diffuse neuronal heterotopia. All patients underwent scalp EEG and video-EEG, and 75 patients (59.5%) also underwent stereo-EEG. Magnetic resonance imaging and stereotactic stereoscopic angiography represented the indispensable premises for further studies, in particular stereo-EEG, and for planning surgery and tailoring resection. Magnetic resonance imaging was unhelpful in 17 out of 81 patients with focal cortical dysplasia and in seven out of 31 with neuronal heterotopia, while signal alterations were present in all other cases. Common characteristics corresponding to clinical-histopathological homogeneous subgroups were found within the focal cortical dysplasia group. In patients with architectural dysplasia, the epileptogenic zone was mainly in the temporal lobe and there was a lower seizure frequency than in patients with Taylor's focal cortical dysplasia. Patients with Taylor's type had an epileptogenic zone that was mainly extra-temporal, and a distinctive interictal stereo-EEG. The best outcome was observed in patients with Taylor's type dysplasia: 69% seizure-free (Engel class Ia) after at least 1 year of follow-up, compared with 45% of cytoarchitectural dysplasia and 49% of architectural dysplasia patients.