Surgical treatment of parietal lobe epilepsy

Postoperative Neurologic Outcome in Patients Undergoing Resective Surgery for Parietal Lobe Epilepsy: A Systematic Review

BACKGROUND AND OBJECTIVES

Parietal lobe epilepsy (PLE) surgery can be an effective treatment for selected patients with intractable epilepsy but can be associated with the risk of serious neurologic deficits. We performed a systematic review of the literature to obtain a comprehensive summary of the frequency and types of new postoperative neurologic deficits in patients undergoing PLE resective surgery.

METHODS

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials for articles published between January 1, 1990, and April 28, 2022. We included studies that reported postoperative neurologic outcome following PLE resective surgery confined to the parietal lobe. We required that studies included ≥5 patients. The data collected included demographic information and specific details of postoperative neurologic deficits. When available, individual patient data were collected. We used the Risk of Bias in Nonrandomized Studies of Interventions tool to assess the risk of bias and Grading of Recommendations Assessment, Development, and Evaluation to assess the quality of the evidence.

RESULTS

Of the 3,461 articles screened, 33 studies met the inclusion criteria. A total of 370 patients were included. One hundred patients (27.0%) had a new deficit noted postoperatively. Approximately half of the patients with deficits experienced only transient deficits. Motor deficits were the most commonly identified deficit. The rates of motor deficits noted after PLE surgery were 5.7%, 3.2%, and 2.2% for transient, long-term, and duration not specified, respectively. Sensory and visual field deficits were also commonly reported. Gerstmann syndrome was noted postoperatively in 4.9% of patients and was almost always transient. Individual patient data added information on parietal lobe subregion postoperative neurologic outcome.

DISCUSSION

Our systematic review provides a comprehensive summary of the frequency and types of neurologic deficits associated with PLE surgery. A significant percentage of postoperative deficits are transient. In addition to the expected sensory and visual deficits, PLE surgery is associated with a notable risk of motor deficits. The available literature has important deficiencies. Our study highlights gaps in the literature and provides recommendations for future directions.

TRIAL REGISTRATION INFORMATION

This systematic review was registered on PROSPERO (CRD42022313108, May 26, 2022).

Gerstmann Syndrome: What is the Possible Role of Deep Brain Stimulation?

Gerstmann syndrome, characterized by a tetrad of symptoms, which are agraphia, acalculia, left-right disorientation, and finger agnosia, presents challenges in both understanding its pathophysiology and establishing effective treatment modalities. Neuroanatomical studies have highlighted the involvement of the dominant parietal lobe, particularly the inferior parietal lobule, in the development of Gerstmann syndrome. Although current treatment options are largely supportive, recent research suggests a potential role for deep brain stimulation (DBS) in managing this condition. DBS, known for its efficacy in various neurological disorders, has been hypothesized to modulate neuronal pathways associated with Gerstmann syndrome. However, clinical evidence supporting DBS in Gerstmann syndrome remains scarce, posing challenges in patient selection and ethical considerations. Future research should prioritize investigating the efficacy and safety of DBS in Gerstmann syndrome to improve patient outcomes and quality of life.

Factors associated with preoperative and postoperative seizures in patients undergoing resection of brain metastases

OBJECTIVE

Epileptic seizures are a common and potentially devastating complication of metastatic brain tumors. Although tumor-related seizures have been described in previous case series, most studies have focused on primary brain tumors and have not differentiated between different types of cerebral metastases. The authors analyzed a large surgical cohort of patients with brain metastases to examine risk factors associated with preoperative and postoperative seizures and to better understand the seizure risk factors of metastatic brain tumors.

METHODS

Patients who underwent resection of a brain metastasis at the University of California, San Francisco (UCSF), were retrospectively reviewed. Patients included in the study were ≥ 18 years of age, required resection of a brain metastasis, and were treated at UCSF. Primary cancers included melanoma, non-small cell lung adenocarcinoma, breast adenocarcinoma, colorectal adenocarcinoma, esophageal adenocarcinoma, gastric adenocarcinoma, renal cell carcinoma, urothelial carcinoma, ovarian carcinoma, cervical squamous cell carcinoma, and endometrial adenocarcinoma. Patients were evaluated for primary cancer type and seizure occurrence, as well as need for use of antiepileptic drugs preoperatively, at time of discharge, and at 6 months postoperatively. Additionally, Engel classification scores were assigned to those patients who initially presented with seizures preoperatively. Univariate and multivariate regression analyses were used to assess the association of tumor type with preoperative seizures.

RESULTS

Data were retrospectively analyzed for 348 consecutive patients who underwent surgical treatment of brain metastases between 1998 and 2019. The cohort had a mean age of 60 years at the time of surgery and was 59% female. The mean and median follow-up durations after the date of surgery for the cohort were 22 months and 10.8 months, respectively. In univariate analysis, frontal lobe location (p = 0.05), melanoma (p = 0.02), KRAS mutation in lung carcinoma (p = 0.04), intratumoral hemorrhage (p = 0.04), and prior radiotherapy (p = 0.04) were associated with seizure presentation. Postoperative checkpoint inhibitor use (p = 0.002), prior radiotherapy (p = 0.05), older age (p = 0.002), distant CNS progression (p = 0.004), and parietal lobe tumor location (p = 0.002) were associated with seizures at 6 months postoperatively. The final multivariate model confirmed the independent effects of tumor location in the frontal lobe and presence of intratumoral hemorrhage as predictors of preoperative seizures, and checkpoint inhibitor use and parietal lobe location were identified as significant predictors of seizures at 6 months postoperatively.

CONCLUSIONS

Within this surgical cohort of patients with brain metastases, seizures were seen in almost a quarter of patients preoperatively. Frontal lobe metastases and hemorrhagic tumors were associated with higher risk of preoperative seizures, whereas checkpoint inhibitor use and parietal lobe tumors appeared to be associated with seizures at 6 months postoperatively. Future research should focus on the effect of metastatic lesion-targeting therapeutic interventions on seizure control in these patients.

The Temporal Lobe as a Symptomatogenic Zone in Medial Parietal Lobe Epilepsy

Some surgical failures after temporal lobe epilepsy surgery may be due to the presence of an extratemporal epileptogenic zone. Of particular interest is the medial parietal lobe due to its robust connectivity with mesial temporal structures. Seizures in that area may be clinically silent before propagating to the symptomatogenic temporal lobe. In this paper, we present an overview of the anatomical connectivity, semiology, radiology, electroencephalography, neuropsychology, and outcomes in medial parietal lobe epilepsy. We also present two illustrative cases of seizures originating from the precuneus and the posterior cingulate cortex. We conclude that the medial parietal lobe should be strongly considered for sampling by intracranial electrodes in individuals with nonlesional temporal lobe epilepsy, especially if scrutinizing the presurgical data produces discordant findings.

POSTERIOR CORTEX SEIZURES - PEDIATRIC CHALLENGES

Posterior cortex seizures have a complex semiologic presentation that is especially challenging in the pediatric population. Therefore, using clinical presentation in localizing ictal involvement is not sufficient in children, thus making this type of epilepsy quite under-recognized. As most of the ictal symptoms are subjective and could well be overshadowed by symptoms arising from adjacent cortices, primarily temporal and central ones, it is necessary not to overlook this large source of pharmacoresistant epilepsies. The parietal lobe as part of an extensive synaptic network is a great imitator, thus quite often producing inaccurate localization readings on scalp electroencephalography (EEG) due to very scattered interictal discharges and uninformative ictal recordings. Using direct cortical recordings in delineating the epileptogenic zone is helpful in some cases but even highly experienced epileptologists may erroneously interpret some features as arising from other localizations, especially the frontal lobe. Epilepsy surgery from the posterior quadrant is still quite rare and relatively unsuccessful, especially in non-lesional epilepsies due to elaborate mechanisms of connectivity, misleading semiology, and non-localizing EEG recordings, possibly due to insufficiency of parietal cortex synchronicity. Applying the aforementioned to the pediatric age makes it perhaps the most difficult challenge for a pediatric epileptologist.

Epilepsy surgery for refractory seizures: a systematic review and meta-analysis in different complications

Background

Nearly one-third of epilepsy patients are refractory/resistant to medical treatment. Developments made in surgical techniques have significantly increased the effectiveness and safety of these techniques, as such techniques have been demonstrated to improve seizure control/freedom outcomes.

Objectives

The aim of this systematic review and meta-analysis was to evaluate the complications of epilepsy surgery.

Patient and methods

The searches were conducted by three independent researchers to find the relevant studies published from January 1, 2009, until the end of January 6, 2019. For English published statistical studies, all studies conducted on epileptic patients who have undergone epilepsy surgery were included.

Statistical analysis

A meta-analysis was conducted in the STATA14 statistical software.

Results

A total of 6735 patients with epilepsy who had undergone the epilepsy surgery were studied. The overall prevalence of complications was 5%. The prevalence of major and minor complications was 5.4% and 3.2% respectively. The prevalence of complications related to the temporal epilepsy surgery and the extra-temporal epilepsy surgery based on 3 studies was 7.9% and 8.2 % respectively. The frequency of neurological and surgical complications after epilepsy surgery was 4.4% and 4.1% respectively.

Conclusion

The overall rate of complications caused by epilepsy surgery was reasonably low (5%), implying that epilepsy surgery especially temporal lobe resection can be safe preferably when performed by an experienced surgeon.

Interictal magnetoencephalography in parietal lobe epilepsy - Comparison of equivalent current dipole and beamformer (SAMepi) analysis

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MEG may aid in the localization of the epileptogenic zone in the parietal lobe.

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SAMepi – a novel kurtosis beamformer – results in localizations similar to those of the ECD analysis.

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A unifocal result in both the ECD and the SAMepi analysis is associated with a good clinical outcome.

Objective

To evaluate a novel analysis method (SAMepi) in the localization of interictal epileptiform magnetoencephalographic (MEG) activity in parietal lobe epilepsy (PLE) patients in comparison with equivalent current dipole (ECD) analysis.

Methods

We analyzed the preoperative interictal MEG of 17 operated PLE patients utilizing visual analysis and: (1) ECD with a spherical conductor model; (2) ECD with a boundary element method (BEM) conductor model; and (3) SAMepi – a kurtosis beamformer method. Localization results were compared between the three methods, to the location of the resection and to the clinical outcome.

Results

Fourteen patients had an epileptiform finding in the visual analysis; SAMepi detected spikes in 11 of them. A unifocal finding in both the ECD and in the SAMepi analysis was associated with a better chance of seizure-freedom (p = 0.02). There was no significant difference in the distances from the unifocal MEG localizations to the nearest border of the resection between the different analysis methods.

Conclusions

Localizations of unifocal interictal spikes detected by SAMepi did not significantly differ from the conventional ECD localizations.

Significance

SAMepi – a novel semiautomatic analysis method – is useful in localizing interictal epileptiform MEG activity in the presurgical evaluation of parietal lobe epilepsy patients.

Outcome of lesional epilepsy surgery: Report of the first comprehensive epilepsy program in Iran

Background

We investigated the utility of epilepsy surgery and postoperative outcome in patients with lesional epilepsy in Iran, a relatively resource-poor setting.

Methods

This prospective longitudinal study was conducted during 2007-2017 in Kashani Comprehensive Epilepsy Center, Isfahan, Iran. Patients with a diagnosis of intractable focal epilepsy, with MRI lesions, who underwent epilepsy surgery and were followed up ≥ 24 months, were included and evaluated for postoperative outcome.

Results

A total of 214 patients, with a mean age of 26.90 ± 9.82 years (59.8% men) were studied. Complex partial seizure was the most common type of seizure (85.9%), and 54.2% of the cases had auras. Temporal lobe lesions (75.2%) and mesial temporal sclerosis (48.1%) were the most frequent etiologies. With a mean follow-up of 62.17 ± 19.33 months, 81.8% of patients became seizure-free postoperatively. Anticonvulsants were reduced in 86% of the cases and discontinued in 40.7%. In keeping with previous studies, we found that seizure freedom rates were lower among patients with longer follow-up periods.

Conclusions

We found high rates of seizure freedom after surgery in lesional epilepsy patients despite limited facilities and infrastructure; antiepileptic medications were successfully tapered in almost half of the patients. Considering the favorable outcome of epilepsy surgery in our series, we believe that it is a major treatment option, even in less resource-intensive settings, and should be encouraged. Strategies to allow larger scale utility of epilepsy surgery in such settings in the developing world and dissemination of such knowledge may be considered an urgent clinical need, given the established mortality and morbidity in refractory epilepsy.

Multimodal investigation of epileptic networks: The case of insular cortex epilepsy

The insula is a deep cortical structure sharing extensive synaptic connections with a variety of brain regions, including several frontal, temporal, and parietal structures. The identification of the insular connectivity network is obviously valuable for understanding a number of cognitive processes, but also for understanding epilepsy since insular seizures involve a number of remote brain regions. Ultimately, knowledge of the structure and causal relationships within the epileptic networks associated with insular cortex epilepsy can offer deeper insights into this relatively neglected type of epilepsy enabling the refining of the clinical approach in managing patients affected by it. In the present chapter, we first review the multimodal noninvasive tests performed during the presurgical evaluation of epileptic patients with drug refractory focal epilepsy, with particular emphasis on their value for the detection of insular cortex epilepsy. Second, we review the emerging multimodal investigation techniques in the field of epilepsy, that aim to (1) enhance the detection of insular cortex epilepsy and (2) unveil the architecture and causal relationships within epileptic networks. We summarize the results of these approaches with emphasis on the specific case of insular cortex epilepsy.

Mesial Extratemporal Lobe Epilepsy: Clinical Features and Surgical Strategies

BACKGROUND: Extratemporal lobe epilepsy surgery remains a diagnostic and therapeutic challenge. Scalp electroencephalography (EEG) correlates, clinical semiology, and imaging findings are often ambiguous or difficult to interpret, necessitating the need for invasive recordings. This is particularly true for those extratemporal lobe epilepsy cases in which seizures develop from the midline.

OBJECTIVE: The aim of this study was to examine the clinical features and surgical strategies in mesial extratemporal lobe epilepsy.

METHODS: A retrospective study reviewing clinical and surgical characteristics was conducted in 30 patients who underwent epilepsy surgery in mesial extratemporal areas at our institution between 1991 and 2011.

RESULTS: Although the location of the epileptogenic zone was associated with specific seizure types, semiology proved to be heterogeneous. Although scalp EEG was of good lateralizing value, it was poor for localizing the epileptogenic zone, necessitating a frequent need for invasive electroencephalographic recordings.

CONCLUSION: Surgical resections in mesial extratemporal regions were found to be safe and resulted in satisfactory seizure outcomes.

A second chance--reoperation in patients with failed surgery for intractable epilepsy: long-term outcome, neuropsychology and complications

OBJECT

Resective surgery is a safe and effective treatment of drug-resistant epilepsy. If surgery has failed reoperation after careful re-evaluation may be a reasonable option. This study was to summarise the risks and benefits of reoperation in patients with epilepsy.

METHODS

This is a retrospective single centre study comprising clinical data, long-term seizure outcome, neuropsychological outcome and postoperative complications of patients, who had undergone a second resective epilepsy surgery from 1989 to 2009.

RESULTS

A total of 66 patients with median follow-up of 10.3 years were included into the study. Fifty-one patients (77%) had surgery for temporal lobe epilepsy, the remaining 15 cases for extra-temporal lobe epilepsies. The most frequent histological findings were tumours (n=33, 50%), followed by dysplasia, gliosis (n=11, each) and hippocampus sclerosis (n=9). The main reasons for seizure recurrence were incomplete resection (59.1%) of the putative epileptogenic lesion. After reoperation 46 patients (69.7%) were completely seizure-free International League Against Epilepsy 1 (ILAE 1) at the last available follow-up. The neuropsychological evaluation demonstrated that repeated losses in the same cognitive domain, that is, successive changes from better to worse performance categories, were rare and that those losses after first surgery were followed by improvement rather than decline. However, reoperations lead to an increased rate of permanent neurological deficits (9%), overall surgical complications (9%) and visual field deficits (67%).

CONCLUSIONS

Reoperation after failed resective epilepsy surgery led to approximately 70% long-time seizure freedom and reasonable neuropsychological outcome. There is an increased risk of permanent postoperative neurological deficits, which should be taken into consideration when counselling for reoperation.

The role of resting state networks in focal neocortical seizures

Objective

The role of resting state functional networks in epilepsy is incompletely understood. While some pathologic diagnoses have been shown to have maintained but altered resting state connectivity, others have implicated resting state connectivity in disease progression. However little is known about how these resting state networks influence the behavior of a focal neocortical seizure.

Methods

Using data taken from invasively monitored patients with intractable focal neocortical epilepsy, we evaluated network connectivity (as determined by oscillatory covariance of the slow cortical potential (<0.5 Hz)) as it relates to neocortical seizure foci both in the interictal and ictal states.

Results

Similar to what has been shown in the past for sleep and anesthesia, electophysiologic resting state networks that are defined by this slow cortical potential covariance maintain their topographic correlation structure throughout an ictal event. Moreover, in the context of focal epilepsy in which the seizure has a specific site of onset, seizure propagation is not chaotic or random. Rather, the seizure (reflected by an elevation of high frequency power) preferentially propagates along the network that contains the seizure onset zone.

Significance

Taken together, these findings further undergird the fundamental role of resting state networks, provide novel insights into the network-influenced behavior of seizures, and potentially identify additional targets for surgical disconnection including informing the location for the completion of multiple subpial transections (MSPTs).

Evolution of cranial epilepsy surgery complication rates: a 32-year systematic review and meta-analysis

Object

Surgical interventions for medically refractory epilepsy are effective in selected patients, but they are underutilized. There remains a lack of pooled data on complication rates and their changes over a period of multiple decades. The authors performed a systematic review and meta-analysis of reported complications from intracranial epilepsy surgery from 1980 to 2012.

Methods

A literature search was performed to find articles published between 1980 and 2012 that contained at least 2 patients. Patients were divided into 3 groups depending on the procedure they underwent: A) temporal lobectomy with or without amygdalohippocampectomy, B) extratemporal lobar or multilobar resections, or C) invasive electrode placement. Articles were divided into 2 time periods, 1980–1995 and 1996–2012.

Results

Sixty-one articles with a total of 5623 patients met the study's eligibility criteria. Based on the 2 time periods, neurological deficits decreased dramatically from 41.8% to 5.2% in Group A and from 30.2% to 19.5% in Group B. Persistent neurological deficits in these 2 groups decreased from 9.7% to 0.8% and from 9.0% to 3.2%, respectively. Wound infections/meningitis decreased from 2.5% to 1.1% in Group A and from 5.3% to 1.9% in Group B. Persistent neurological deficits were uncommon in Group C, although wound infections/meningitis and hemorrhage/hematoma increased over time from 2.3% to 4.3% and from 1.9% to 4.2%, respectively. These complication rates are additive in patients undergoing implantation followed by resection.

Conclusions

Complication rates have decreased dramatically over the last 30 years, particularly for temporal lobectomy, but they remain an unavoidable consequence of epilepsy surgery. Permanent neurological deficits are rare following epilepsy surgery compared with the long-term risks of intractable epilepsy.

Current management and surgical outcomes of medically intractable epilepsy

Epilepsy is one of the most common neurologic disorders in the world. While anti-epileptic drugs (AEDs) are the mainstay of treatment in most cases, as many as one-third of patients will have a refractory form of disease indicating the need for a neurosurgical evaluation. Ever since the first half of the twentieth century, surgery has been a major treatment option for epilepsy, but the last 10-15 years in particular has seen several major advances. As shown in relatively recent studies, resection is more effective for medically intractable epilepsy (MIE) than AED treatment alone, which is why most clinicians now endorse a neurosurgical consultation after approximately two failed regimens of AEDs, ultimately leading to decreased healthcare costs and increased quality of life. Temporal lobe epilepsy (TLE) is the most common form of MIE and comprises about 80% of epilepsy surgeries with the majority of patients gaining complete seizure-freedom. As the number of procedures and different approaches continues to grow, temporal lobectomy remains consistently focused on resection of mesial structures such as the amygdala, hippocampus, and parahippocampal gyrus while preserving as much of the neocortex as possible resulting in optimum seizure control with minimal neurological deficits. MIE originating outside the temporal lobe is also effectively treated with resection. Though not as successful as TLE surgery because of their frequent proximity to eloquent brain structures and more diffuse pathology, epileptogenic foci located extratemporally also benefit from resection. Favorable seizure outcome in each of these procedures has heavily relied on pre-operative imaging, especially since the massive surge in MRI technology just over 20 years ago. However, in the absence of visible lesions on MRI, recent improvements in secondary imaging modalities such as fluorodeoxyglucose positron emission computed tomography (FDG-PET) and single-photon emission computed tomography (SPECT) have lead to progressively better long-term seizure outcomes by increasing the neurosurgeon's visualization of supposed non-lesional foci. Additionally, being historically viewed as a drastic surgical intervention for MIE, hemispherectomy has been extensively used quite successfully for diffuse epilepsies often found in pediatric patients. Although total anatomic hemispherectomy is not utilized as commonly today, it has given rise to current disconnective techniques such as hemispherotomy. Therefore, severe forms of hemispheric developmental epilepsy can now be surgically treated while substantially decreasing the amount of potential long-term complications resulting from cavitation of the brain following anatomical hemispherectomy. Despite the rapid pace at which we are gaining further knowledge about epilepsy and its surgical treatment, there remains a sizeable underutilization of such procedures. By reviewing the recent literature on resective treatment of MIE, we provide a recent up-date on epilepsy surgery while focusing on historical perspectives, techniques, prognostic indicators, outcomes, and complications associated with several different types of procedures.

Implantable stimulator for epileptic seizure suppression with loading impedance adaptability

The implantable stimulator for epileptic seizure suppression with loading impedance adaptability was proposed in this work. The stimulator consisted of the high voltage generator, output driver, adaptor, and switches, can constantly provide the required 40-μA stimulus currents, as the loading impedance varied within 10 kΩ -300 kΩ. The performances of this design have been successfully verified in silicon chip fabricated by a 0.35- μm 3.3-V/24-V CMOS process. The power consumption of this work was only 1.1 mW-1.4 mW. The animal test results with the fabricated chip of proposed design have successfully verified in the Long-Evans rats with epileptic seizures.

Integration of functional neuronavigation and intraoperative MRI in surgery for drug-resistant extratemporal epilepsy close to eloquent brain areas

Object

The authors performed a retrospective study to assess the impact of functional neuronavigation and intraoperative MRI (iMRI) on surgery of extratemporal epileptogenic lesions on postsurgical morbidity and seizure control.

Methods

Twenty-five patients (14 females and 11 males) underwent extratemporal resections for drug-resistant epilepsy close to speech/motor brain areas or adjacent to white matter tracts. The mean age at surgery was 34 years (range 12–67 years). The preoperative mean disease duration was 13.2 years. To avoid awake craniotomy, cortical motor-sensory representation was mapped during preoperative evaluation in 14 patients and speech representation was mapped in 15 patients using functional MRI. In addition, visualization of the pyramidal tract was performed in 11 patients, of the arcuate fascicle in 7 patients, and of the visual tract in 6 patients using diffusion tensor imaging. The mean minimum distance of tailored resection between the eloquent brain areas was 5.6 mm. During surgery, blood oxygen level–dependent imaging and diffusion tensor imaging data were integrated into neuronavigation and displayed through the operating microscope. The postoperative mean follow-up was 44.2 months.

Results

In 20% of these patients, further intraoperative resection was performed because of intraoperatively documented residual lesions according to iMRI findings. At the end of resection, the final iMRI scans confirmed achievement of total resection of the putative epileptogenic lesion in all patients. Postoperatively, transient complications and permanent complications were observed in 20% and 12% of patients, respectively. Favorable postoperative seizure control (Engel Classes I and II) was achieved in 84% and seizure freedom in 72% of these consecutive surgical patients.

Conclusions

By using functional neuronavigation and iMRI for treatment of epileptogenic brain lesions, the authors achieved a maximum extent of resection despite the lesions' proximity to eloquent brain cortex and fiber tracts in all cases. The authors' results underline possible benefits of this technique leading to a favorable seizure outcome with acceptable neurological deficit rates in difficult-to-treat extratemporal epilepsy.

A primer on brain-machine interfaces, concepts, and technology: a key element in the future of functional neurorestoration

Conventionally, the practice of neurosurgery has been characterized by the removal of pathology, congenital or acquired. The emerging complement to the removal of pathology is surgery for the specific purpose of restoration of function. Advents in neuroscience, technology, and the understanding of neural circuitry are creating opportunities to intervene in disease processes in a reparative manner, thereby advancing toward the long-sought-after concept of neurorestoration. Approaching the issue of neurorestoration from a biomedical engineering perspective is the rapidly growing arena of implantable devices. Implantable devices are becoming more common in medicine and are making significant advancements to improve a patient's functional outcome. Devices such as deep brain stimulators, vagus nerve stimulators, and spinal cord stimulators are now becoming more commonplace in neurosurgery as we utilize our understanding of the nervous system to interpret neural activity and restore function. One of the most exciting prospects in neurosurgery is the technologically driven field of brain-machine interface, also known as brain-computer interface, or neuroprosthetics. The successful development of this technology will have far-reaching implications for patients suffering from a great number of diseases, including but not limited to spinal cord injury, paralysis, stroke, or loss of limb. This article provides an overview of the issues related to neurorestoration using implantable devices with a specific focus on brain-machine interface technology.

Epilepsy surgery of the cingulate gyrus and the frontomesial cortex

BACKGROUND

Epilepsy surgery involving the cingulate gyrus has been mostly presented as case reports, and larger series with long-term follow-up are not published yet.

OBJECTIVE

To report our experience with focal epilepsy arising from the cingulate gyrus and surrounding structures and its surgical treatment.

METHODS

Twenty-two patients (mean age, 36; range, 12-63) with a mean seizure history of 23 years (range, 2-52) were retrospectively analyzed. We report presurgical diagnostics, surgical strategy, and postoperative follow-up concerning functional morbidity and seizures (mean follow-up, 86 months; range, 25-174).

RESULTS

Nineteen patients showed potential epileptogenic lesions on preoperative magnetic resonance imaging (MRI). All patients had noninvasive presurgical workup; 15 (68%) underwent invasive Video-electroencephalogram (EEG)-Monitoring. In 12 patients we performed extended lesionectomy according to MRI; an extension with regard to EEG results was done in 6 patients. In 4 patients, the resection was incomplete because of the involvement of eloquent areas according to functional mapping results. Eight pure cingulate resections (36%, 3 in the posterior cingulate gyrus) and 14 extended supracingular frontal resections were performed. Nine patients experienced temporary postoperative supplementary motor area syndrome after resection in the superior frontal gyrus. Two patients retained a persistent mild hand or leg paresis, respectively. Postoperatively, 62% of patients were seizure-free (International League Against Epilepsy [ILAE] 1), and 76% had a satisfactory seizure outcome (ILAE 1-3).

CONCLUSION

Epilepsy surgery for lesions involving the cingulate gyrus represents a small fraction of all epilepsy surgery cases, with good seizure outcome and low rates of postoperative permanent deficits. In case of extended supracingular resection, supplementary motor area syndrome should be considered.

Lateral extratemporal resections in adults

The presurgical evaluation in cases of extratemporal epilepsy is much less stereotypic than it is for mesial temporal lobe epilepsy. The finding of even a tiny structural lesion may be relevant but needs verification that it matches the seizure onset zone. Often invasive analysis is necessary to produce such evidence and to assess the relationship to adjacent eloquent cortex. Invasive analysis exposes the patient to an additional surgical procedure and to the morbidity associated with it. Therapeutic resections may comprise lesionectomy, topectomy, or lobectomy. Epileptogenic cortex that coincides with indispensable eloquent cortex can be treated with multiple subpial transections. A large variety of lesions may be epileptogenic, ranging from posttraumatic gliosis, over dysplasias and vascular malformations, to low-grade tumors. Intraoperative monitoring of adjacent brain functions under anesthesia or awake surgery may be used. Unless a circumscribed lesionectomy is possible, results in extratemporal epilepsy tend to be less favorable than in mesial temporal lobe epilepsy.

Adverse events occurring during invasive electroencephalogram recordings in children

BACKGROUND

In cryptogenic epilepsy or when multifocal seizure onset is suspected, intracranial monitoring of the EEG is required.

OBJECTIVE

To report on the adverse events related to electroencephalogram (EEG) intracranial recording in one of the largest pediatric series published and to discuss the avoidance of adverse events in our experience and with respect to a review of the literature.

METHODS

A retrospective analysis of our department database and hospital charts of 95 children operated on between 1994 and 2009 was performed.

RESULTS

Invasive recording was uneventful in 51.1% of cases. Observed frequency of infection was 14.9%, cerebrospinal fluid leak was 10.6%, brain swelling was 6.4%, and hemorrhage was 17%. Brain swelling was more frequent in older patients, whereas the length of recording, number of electrode contacts used, and presence of depth electrodes were not relevant. Cerebrospinal fluid leakage was completely prevented by the routine introduction of dural graft substitutes in 2003.

CONCLUSION

Invasive recordings carry a noticeable rate of adverse events but provide invaluable information in delineating the epileptogenic zone. The low incidence of such events among younger children suggests that invasive recordings can be successfully performed with low morbidity in this age group.

Epilepsy and brain tumors

PURPOSE OF REVIEW

To present an overview of the recent findings in pathophysiology and management of epileptic seizures in patients with brain tumors.

RECENT FINDINGS

Low-grade gliomas are the most epileptogenic brain tumors. Regarding pathophysiology, the role of peritumoral changes [hypoxia and acidosis, blood-brain barrier (BBB) disruption, increase or decrease of neurotransmitters and receptors] are of increasing importance. Tumor-associated epilepsy and tumor growth could have some common molecular pathways. Total/subtotal surgical resection (with or without epilepsy surgery) allows a seizure control in a high percentage of patients. Radiotherapy and chemotherapy as well have a role. New antiepileptic drugs are promising, both in terms of efficacy and tolerability. The resistance to antiepileptic drugs is still a major problem: new insights into pathogenesis are needed to develop strategies to manipulate the pharmakoresistance.

SUMMARY

Epileptic seizures in brain tumors have been definitely recognized as one of the major problems in patients with brain tumors, and need specific and multidisciplinary approaches.

Continuous motor monitoring enhances functional preservation and seizure-free outcome in surgery for intractable focal epilepsy

PURPOSE

Complete yet safe resection close to motor areas in medically intractable epilepsy requires functional information. New deficit may occur despite preservation of motor cortex, e.g., through vascular compromise. Here, we explore for the first time the feasibility, safety, and the clinical value of continuous motor-evoked potential (MEP) monitoring in focal epilepsy surgery.

METHODS

High-frequency stimulation for MEP monitoring was performed during 100 consecutive lesionectomies critically related to motor areas and pathways. Extraoperative motor cortex mapping was performed in 27 of these cases via chronically implanted subdural grid electrodes. MEP monitoring results, postoperative motor outcome, and seizure control were correlated in a prospective observational design.

RESULTS

Reliable MEP monitoring was achieved in 86 cases. Young age was the only discernible cause of unsuccessful recordings. Seizures from cortex stimulation did not occur. MEP changes (36%) predicted new motor deficit (17%) in all cases except purely cortical lesions. MEP changes predicted occurrence and permanence of new pareses. New deficit was significantly more frequent without (as compared with) successful monitoring (43% vs. 17%); permanently severe pareses from ischemia occurred only without MEPs (21% vs. 0%). Complete seizure control was significantly more frequent in successfully monitored cases (60% vs. 31%). Even with extraoperative motor mapping, severe paresis occurred only among cases with unsuccessful MEPs.

CONCLUSIONS

Continuous MEP monitoring in epilepsy surgery is feasible and safe. It reflects motor function complementarily to the localizing motor mapping results. Successful MEP monitoring correlates with unimpaired motor outcome and full seizure control.

Surgery for extratemporal nonlesional epilepsy in children: a meta-analysis

PURPOSE

Previous small studies have demonstrated that seizure outcomes following surgery for extratemporal lobe epilepsy (ETLE) in children are worse than those for temporal lobe epilepsy. We have conducted a meta-analysis of the available literature to better understand ETLE surgical outcomes in children.

METHODS

We searched PubMed (1990-2009) for appropriate studies using the following terms: ETLE, ETLE surgery, ETLE surgery outcome, frontal lobe epilepsy, occipital lobe epilepsy, and parietal lobe epilepsy. Our collected data included patient age at seizure onset and surgery, the cerebral lobe involved with epileptogenesis, MRI findings, predominant seizure semiology, intracranial monitoring use (electrode implantation), epileptic region histopathology, and postoperative seizure outcome. Statistical analysis was performed to determine associations among these variables and postoperative outcome.

RESULTS

Ninety-five patients from 17 studies satisfied the inclusion criteria. Pathological findings (p = 0.039) and seizure type (p = 0.025) were significantly associated with outcome: A larger proportion of patients with cortical dysplasia and complex partial seizures experienced better outcomes. Age at surgery (p = 0.073) and the cerebral resection site (p = 0.059) were marginally associated with seizure outcome.

CONCLUSIONS

This study confirms previous reports: Surgical outcomes for ETLE epilepsy are significantly worse than those for temporal lobe epilepsy. The reasons for this difference may include the diffuse nature of the pathology involved in ETLE, difficulty in localizing the seizure focus in young children, and involvement of "eloquent" nonresectable cortex in epileptogenesis. Because of the reporting variability among different epilepsy centers, more uniform protocols are necessary for fair evaluation and comparison of outcomes among the different centers.