Surgery procedures in temporal lobe epilepsies.

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

Long-term deep intracerebral microelectrode recordings in patients with drug-resistant epilepsy: Proposed guidelines based on 10-year experience.

PURPOSE: Human neuronal activity, recorded in vivo from microelectrodes, may offer valuable insights into physiological mechanisms underlying human cognition and pathophysiological mechanisms of brain diseases, in particular epilepsy. Continuous and long-term recordings are necessary to monitor non predictable pathological and physiological activities like seizures or sleep. Because of their high impedance, microelectrodes are more sensitive to noise than macroelectrodes. Low noise levels are crucial to detect action potentials from background noise, and to further isolate single neuron activities. Therefore, long-term recordings of multi-unit activity remains a challenge. We shared here our experience with microelectrode recordings and our efforts to reduce noise levels in order to improve signal quality. We also provided detailed technical guidelines for the connection, recording, imaging and signal analysis of microelectrode recordings. RESULTS: During the last 10 years, we implanted 122 bundles of Behnke-Fried hybrid macro-microelectrodes, in 56 patients with pharmacoresistant focal epilepsy. Microbundles were implanted in the temporal lobe (74%), as well as frontal (15%), parietal (6%) and occipital (5%) lobes. Low noise levels depended on our technical setup. The noise reduction was mainly obtained after electrical insulation of the patient's recording room and the use of a reinforced microelectrode model, reaching median root mean square values of 5.8 µV. Seventy percent of the bundles could record multi-units activities (MUA), on around 3 out of 8 wires per bundle and for an average of 12 days. Seizures were recorded by microelectrodes in 91% of patients, when recorded continuously, and MUA were recorded during seizures for 75 % of the patients after the insulation of the room. Technical guidelines are proposed for (i) electrode tails manipulation and protection during surgical bandage and connection to both clinical and research amplifiers, (ii) electrical insulation of the patient's recording room and shielding, (iii) data acquisition and storage, and (iv) single-units activities analysis. CONCLUSIONS: We progressively improved our recording setup and are now able to record (i) microelectrode signals with low noise level up to 3 weeks duration, and (ii) MUA from an increased number of wires . We built a step by step procedure from electrode trajectory planning to recordings. All these delicate steps are essential for continuous long-term recording of units in order to advance in our understanding of both the pathophysiology of ictogenesis and the neuronal coding of cognitive and physiological functions.

Anterior interhemispheric approach for anterior fossa dural arteriovenous fistulas.

Anterior fossa dural arteriovenous fistulas (AF-DAVF) usually display a cortical venous drainage and are therefore at risk for rupture. Microsurgery is traditionally considered in many centers as the first-line treatment since endovascular treatment (EVT) entails a lower cure rate and significant ophthalmic risks. The anterior interhemispheric approach (AIA), originally described by Mayfrank in 1996, seems to offer the effectiveness of microsurgery while limiting the risks related to subfrontal craniotomy. The objective of this study was to analyze the surgical outcomes of patients who underwent this surgical approach for the treatment of AF-DAVF. We hereby describe our 10 years' experience of patients treated for an AF-DAVF with this technique in our institution and retrospectively analyzed our results. In addition, we describe our operative technique and its specificities. Eleven patients with AF-DAVF were included in our study. The definitive cure of the fistula was confirmed in all cases with postoperative cerebral angiography. All patients had a good neurological outcome and no major complication occurred. Brain retractors were never used during surgery, the frontal sinus was never opened neither, and anosmia was never observed after surgery. Anterior interhemispheric approach seems to be safe and effective to treat AF-DAVF with lower risks than other surgical approaches. This technique could be more widely considered when facing such midline vascular lesion.

Somatic PIK3CA Mutations in Sporadic Cerebral Cavernous Malformations.

BACKGROUND: Cerebral cavernous malformations (CCMs) are common sporadic and inherited vascular malformations of the central nervous system. Although familial CCMs are linked to loss-of-function mutations in KRIT1 (CCM1), CCM2, or PDCD10 (CCM3), the genetic cause of sporadic CCMs, representing 80% of cases, remains incompletely understood. METHODS: We developed two mouse models harboring mutations identified in human meningiomas with the use of the prostaglandin D2 synthase (PGDS) promoter. We performed targeted DNA sequencing of surgically resected CCMs from patients and confirmed our findings by droplet digital polymerase-chain-reaction analysis. RESULTS: We found that in mice expressing one of two common genetic drivers of meningioma - Pik3ca H1047R or AKT1 E17K - in PGDS-positive cells, a spectrum of typical CCMs develops (in 22% and 11% of the mice, respectively) instead of meningiomas, which prompted us to analyze tissue samples from sporadic CCMs from 88 patients. We detected somatic activating PIK3CA and AKT1 mutations in 39% and 1%, respectively, of lesion tissue from the patients. Only 10% of lesions harbored mutations in the CCM genes. We analyzed lesions induced by the activating mutations Pik3ca H1074R and AKT1 E17K in mice and identified the PGDS-expressing pericyte as the probable cell of origin. CONCLUSIONS: In tissue samples from sporadic CCMs, mutations in PIK3CA were represented to a greater extent than mutations in any other gene. The contribution of somatic mutations in the genes that cause familial CCMs was comparatively small. (Funded by the Fondation ARC pour la Recherche contre le Cancer and others.).

Intraoperative Ultrasound Shear-Wave Elastography in Focal Cortical Dysplasia Surgery.

Previous studies reported interest in intraoperative shear-wave elastography (SWE) guidance for brain-tumor and epilepsy surgeries. Focal cortical dysplasia (FCD) surgery is one of the most appropriate indications for using SWE guidance. The aim of this study was to evaluate the efficacy of ultrasound SWE techniques for the intraoperative detection of FCDs. We retrospectively analyzed data from 18 adult patients with drug-resistant epilepsy associated with FCD who had undergone SWE-guided surgery. Conventional B-mode images detected FCD in 2 patients (11.1%), while SWE detected FCD in 14 patients (77.8%). The stiffness ratios between MRI-positive and -negative cases were significantly different (3.6 ± 0.4 vs. 2.2 ± 0.6, respectively; p < 0.001). FCDs were significantly more frequently detected by interoperative SWE in women (OR 4.7, 95% CI (1.7-12.7); p = 0.004) and in patients in whom FCD was visible on magnetic resonance imaging (MRI; OR 2.3, 95% CI (1.3-4.3); p = 0.04). At 1 year after surgery and at last follow-up (mean = 21 months), seizure outcome was good (International League Against Epilepsy (ILAE) Class 1 or 2) in 72.2% and 55.6% of patients, respectively. Despite some limitations, our study highlighted the potential of SWE as an intraoperative tool to detect FCD. Future technical developments should allow for optimizing intraoperative surgical-cavity evaluation from the perspective of complete FCD resection. Interobserver reliability of SWE measurements should also be assessed by further studies.

Outpatient vagus nerve stimulation surgery in patients with drug-resistant epilepsy with severe intellectual disability.

PURPOSE: Vagus nerve stimulation (VNS) implantation is increasingly proposed in outpatient procedure. Some epilepsy syndromes are associated with severe neurodevelopmental disabilities (intellectual disability, autism) and often motor or sensory handicaps, making ambulatory surgery more complex. METHODS: We prospectively assessed the feasibility and safety of outpatient VNS implantation in 26 adult patients with drug-resistant epilepsy with severe intellectual disability between December 2017 and October 2020. RESULTS: The male-to-female ratio was 0.9 and the mean age on surgery day was 23.1 years. Seventeen patients (65.4%) suffered from epileptic encephalopathy, 7 (26.9%) from cryptogenic or genetic generalized epilepsy, and 2 (7.7%) from severe multifocal epilepsy. Postoperatively, all patients were discharged the day of surgery. No patient was admitted to a hospital or have consulted within one month due to postoperative complications. There was no surgery-related complication during patients' follow-up. CONCLUSION: Our study highlights the safety and feasibility of VNS surgery in an outpatient setting for patients with severe intellectual disability. We report detailed protocol and preoperative checklist to optimize outpatient VNS surgery in these not able-bodied patients. Severe disabilities or epilepsy-associated handicaps should not be an exclusion criterion when considering ambulatory VNS implantation.

Primary Extraosseous Spinal Ewing Sarcomas: Should We Be More Aware About Diagnosis?

STUDY DESIGN: Single-center retrospective study. OBJECTIVE: We discuss the widespread misdiagnosis of primary extraosseous spinal Ewing Sarcomas (PESES) to begnin tumors leading to poor treatment. SUMMARY OF BACKGROUND DATA: PESES is a particular entity of spinal Ewing sarcoma (SES) appearing in a similar shape and features to benign tumors such as schwannomas. This imaging mimicry and subsequent possible misdiagnosis lead to primary surgery, without neoadjuvant chemotherapy, which remains deleterious for survival and progression. METHODS: We identified a total of 13 patients: seven women (53.8%) and six men operated between 2001 and 2018 for PESES and initially misdiagnosed as schwannomas or ependymomas. RESULTS: The mean age of our series was 35.8 years (range, 18.1-47.2 years). The first clinical symptom was neuralgia (61.5%) followed or associated with nerves deficits (38.5%). Median progression-free survival (PFS) was 31.7 months (SD 5.8). Tumor recurrence rates at 1 and 3 years were respectively 21.2% (SD 3.1) and 60.1% (SD 15.8). Median overall survival (OS) was 61.5 months (SD 16.27). The 1-year, 2-year, and 5-year survival estimates were 100.0%, 88.9% (SD 10.5), and 44.4% (SD 16.6). Six patients (46.13%) died following their SES. In univariate analyses, patients with metastastic PESES had a significantly lower OS than others (41.2 months, P = 0.03). CONCLUSION: PESES must be ruled out at diagnosis of a spinal tumor when facing a fast-growing lesion with neurological deficits in a young adult. Thoracoabdominopelvic extension should be carried out. Presurgical biopsy must be performed. In case of PESES, neoadjuvant chemotherapy must be established before considering surgical intervention.Level of Evidence: 4.

Temporal pole epilepsy surgery-Sparing the hippocampus.

Temporal pole epilepsy (TPE) is a poorly known and difficult to individualize subtype of temporal lobe epilepsy. Consequently, in drug-resistant TPE, there is still a debate on the need for a large surgical removal of the temporal pole and mesial temporal structures or a limited resection of the temporal pole. We reviewed all patients who underwent presurgical evaluation for drug-resistant epilepsy over a 17-year period, and report here 19 patients with proven drug-resistant temporal pole epilepsy who underwent a selective temporal pole resection with respect to mesial structures. Most (15) TPE patients exhibited seizures resembling mesiotemporal seizures, whereas the others exhibited nocturnal hyperkinetic seizures or an association of both seizure types. MRI revealed a temporal pole lesion in 58% of patients. Long-term postoperative outcome after a conservative surgery was excellent: 63% of patients were seizure-free (International League Against Epilepsy [ILAE] 1) at 1-year postsurgery and 78% at 5 years. These results show that TPE has no specific electroclinical features but is a distinct type of temporal lobe epilepsy allowing a conservative surgery. Respecting the mesiotemporal structures is a valid surgical approach for drug-resistant temporal pole epilepsy.

Distinct P2Y Receptors Mediate Extension and Retraction of Microglial Processes in Epileptic and Peritumoral Human Tissue.

Microglia exhibit multiple, phenotype-dependent motility patterns often triggered by purinergic stimuli. However, little data exist on motility of human microglia in pathological situations. Here we examine motility of microglia stained with a fluorescent lectin in tissue slices from female and male epileptic patients diagnosed with mesial temporal lobe epilepsy or cortical glioma (peritumoral cortex). Microglial shape varied from ramified to amoeboid cells predominantly in regions of high neuronal loss or closer to a tumor. Live imaging revealed unstimulated or purine-induced microglial motilities, including surveillance movements, membrane ruffling, and process extension or retraction. At different concentrations, ADP triggered opposing motilities. Low doses triggered process extension. It was suppressed by P2Y12 receptor antagonists, which also reduced process length and surveillance movements. Higher purine doses caused process retraction and membrane ruffling, which were blocked by joint application of P2Y1 and P2Y13 receptor antagonists. Purinergic effects on motility were similar for all microglia tested. Both amoeboid and ramified cells from mesial temporal lobe epilepsy or peritumoral cortex tissue expressed P2Y12 receptors. A minority of microglia expressed the adenosine A2A receptor, which has been linked with process withdrawal of rodent cells. Laser-mediated tissue damage let us test the functional significance of these effects. Moderate damage induced microglial process extension, which was blocked by P2Y12 receptor antagonists. Overall, the purine-induced motility of human microglia in epileptic tissue is similar to that of rodent microglia in that the P2Y12 receptor initiates process extension. It differs in that retraction is triggered by joint activation of P2Y1/P2Y13 receptors.SIGNIFICANCE STATEMENT Microglial cells are brain-resident immune cells with multiple functions in healthy or diseased brains. These diverse functions are associated with distinct phenotypes, including different microglial shapes. In the rodent, purinergic signaling is associated with changes in cell shape, such as process extension toward tissue damage. However, there are little data on living human microglia, especially in diseased states. We developed a reliable technique to stain microglia from epileptic and glioma patients to examine responses to purines. Low-intensity purinergic stimuli induced process extension, as in rodents. In contrast, high-intensity stimuli triggered a process withdrawal mediated by both P2Y1 and P2Y13 receptors. P2Y1/P2Y13 receptor activation has not previously been linked to microglial morphological changes.

Conscious and unconscious expectancy effects: A behavioral, scalp and intracranial electroencephalography study.

OBJECTIVE: The scope of unconscious cognition stretched its limits dramatically during the last 40 years, yet most unconscious processes and representations that have been described so far are fleeting and very short-lived, whereas conscious representations can be actively maintained in working memory for a virtually unlimited period. In the present work we aimed at exploring conscious and unconscious lasting (>1 second) expectancy effects. METHODS: In a series of four experiments we engaged participants in the foreperiod paradigm while using both unmasked and masked cues that were informative about the presence/absence of an upcoming target. We recorded behavioral responses, high-density scalp EEG (Exp. 2a), and intra-cranial EEG (Exp. 2b). RESULTS: While conscious expectancy was associated with a large behavioral effect (~150 ms), unconscious expectancy effect was significant but much smaller (4 ms). Both conscious and unconscious expectancy Contingent Negative Variations (CNVs) originated from temporal cortices, but only the late component of conscious CNV originated from an additional source located in the vicinity of mesio-frontal areas and supplementary motor areas. Finally, only conscious expectancy was accessible to introspection. CONCLUSIONS: Both unmasked and masked cues had an impact on response times and on brain activity. SIGNIFICANCE: These results support a two-stage model of the underlying mechanisms of expectancy.

Intraoperative real-time guidance using ShearWave Elastography for epilepsy surgery.

PURPOSE: In epilepsy surgery, seizure outcome is determined by the integrity of epileptogenic zone resection. ShearWave elastography (SWE) is a noninvasive imaging technique that generates a quantitative assessment of elasticity values permitting intraoperative real time tissue mapping by differentiating normal and pathological epileptogenic tissue. The aim of this study was to evaluate the contribution of SWE intraoperative guidance on the advancement of epileptogenic zone detection in epilepsy surgery. METHODS: We prospectively analyzed epileptogenic zone resections using SWE guidance for 28 patients with severe and/or disabling drug-resistant focal epilepsy. RESULTS: Conventional B-mode images visualized echogenicity differences between the epileptogenic lesion and normal brain tissue in 71.4% of cases, while SWE detected a significant difference in stiffness in 92.8% of cases (p = 0.02). Regarding cryptogenic epilepsy, none of the 4 MRI-negative focal cortical dysplasias was visualized by B-mode images, while 3 cases were detected by SWE. Postoperative brain MRI showed a complete resection of the epileptogenic zone in all MRI-positive cases. One year after the surgery, 85.7% of the patients were seizure free (ILAE class 1). CONCLUSION: Despite some technical limitations, SWE improves the intraoperative detection of epileptogenic lesions and should be considered for all patients with cryptogenic and lesional epilepsy. Naturally this ought to be confirmed by larger case series additionally investigating long-term seizure outcome.

Microglial phenotypes in the human epileptic temporal lobe.

Microglia, the immune cells of the brain, are highly plastic and possess multiple functional phenotypes. Differences in phenotype in different regions and different states of epileptic human brain have been little studied. Here we use transcriptomics, anatomy, imaging of living cells and ELISA measurements of cytokine release to examine microglia from patients with temporal lobe epilepsies. Two distinct microglial phenotypes were explored. First we asked how microglial phenotype differs between regions of high and low neuronal loss in the same brain. Second, we asked how microglial phenotype is changed by a recent seizure. In sclerotic areas with few neurons, microglia have an amoeboid rather than ramified shape, express activation markers and respond faster to purinergic stimuli. The repairing interleukin, IL-10, regulates the basal phenotype of microglia in the CA1 and CA3 regions with neuronal loss and gliosis. To understand changes in phenotype induced by a seizure, we estimated the delay from the last seizure until tissue collection from changes in reads for immediate early gene transcripts. Pseudotime ordering of these data was validated by comparison with results from kainate-treated mice. It revealed a local and transient phenotype in which microglia secrete the human interleukin CXCL8, IL-1B and other cytokines. This secretory response is mediated in part via the NRLP3 inflammasome.

New clinicopathological associations and histoprognostic markers in ILAE types of hippocampal sclerosis.

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is a heterogeneous syndrome. Surgery results in seizure freedom for most pharmacoresistant patients, but the epileptic and cognitive prognosis remains variable. The 2013 International League Against Epilepsy (ILAE) histopathological classification of hippocampal sclerosis (HS) has fostered research to understand MTLE-HS heterogeneity. We investigated the associations between histopathological features (ILAE types, hypertrophic CA4 neurons, granule cell layer alterations, CD34 immunopositive cells) and clinical features (presurgical history, postsurgical outcome) in a monocentric series of 247 MTLE-HS patients treated by surgery. NeuN, GFAP and CD34 immunostainings and a double independent pathological examination were performed. 186 samples were type 1, 47 type 2, 7 type 3 and 7 samples were gliosis only but no neuronal loss (noHS). In the type 1, hypertrophic CA4 neurons were associated with a worse postsurgical outcome and granule cell layer duplication was associated with generalized seizures and episodes of status epilepticus. In the type 2, granule cell layer duplication was associated with generalized seizures. CD34+ stellate cells were more frequent in the type 2, type 3 and in noHS. These cells had a Nestin and SOX2 positive, immature neural immunophenotype. Patients with nodules of CD34+ cells had more frequent dysmnesic auras. CD34+ stellate cells in scarce pattern were associated with higher ratio of normal MRI and of stereo-electroencephalographic studies. CD34+ cells were associated with a trend for a better postsurgical outcome. Among CD34+ cases, we proposed a new entity of BRAF V600E positive HS and we described three hippocampal multinodular and vacuolating neuronal tumors. To conclude, our data identified new clinicopathological associations with ILAE types. They showed the prognostic value of CA4 hypertrophic neurons. They highlighted CD34+ stellate cells and BRAF V600E as biomarkers to further decipher MTLE-HS heterogeneity.

Imaging pathological activities of human brain tissue in organotypic culture.

BACKGROUND: Insights into human brain diseases may emerge from tissue obtained after operations on patients. However techniques requiring transduction of transgenes carried by viral vectors cannot be applied to acute human tissue. NEW METHOD: We show that organotypic culture techniques can be used to maintain tissue from patients with three different neurological syndromes for several weeks in vitro. Optimized viral vector techniques and promoters for transgene expression are described. RESULTS: Region-specific differences in neuronal form, firing pattern and organization as well as pathological activities were maintained over 40-50 days in culture. Both adeno-associated virus and lentivirus based vectors were persistently expressed from ∼10 days after application, providing 30-40 days to exploit genetically expressed constructs. Different promoters, including hSyn, e/hSyn, CMV and CaMKII, provided cell-type specific transgene expression. The Ca probe GCaMP let us explore epileptogenic synchrony and a FRET-based probe was used to follow activity of the kinase mTORC1. COMPARISON WITH EXISTING METHODS: The use of a defined culture medium, with low concentrations of amino acids and no growth factors, permitted organotypic culture of tissue from humans aged 3-62 years. Epileptic activity was maintained and excitability changed relatively little until ∼6 weeks in culture. CONCLUSIONS: Characteristic morphology and region-specific neuronal activities are maintained in organotypic culture of tissue from patients diagnosed with mesial temporal lobe epilepsy, cortical dysplasia and cortical glioblastoma. Viral vector techniques permit expression of probes for long-term measurements of multi-cellular activity and intra-cellular signaling.

Complication Risk Factors in Anterior Choroidal Artery Aneurysm Treatment.

OBJECT: The anterior choroidal artery (AChoA) is a rare location for intracranial aneurysms. The treatment of these aneurysms may be challenging due to the risk of occlusion of such a small and eloquent artery as the AChoA. We aimed to evaluate the risk factors for complications in AChoA aneurysm treatment. METHODS: We retrospectively analyzed 47 consecutive AChoA aneurysms in 40 patients treated in our institution from 1999 and 2014 by endovascular means (87%) or surgical clipping (13%). Minor (transient or minor neurological deficits) and major complications (severe permanent neurological deficits or death) were systematically recorded. The influence of patient age, sex, aneurysm size, neck size, shape, dome-to-neck ratio and treatment technique on the occurrence of procedure-related complications was evaluated. RESULTS: Of the patients 11 experienced procedure-related complications (5 major, 6 minor). Aneurysms with multilobed shape were significantly associated with a higher procedure-related complication rate. There was a tendency for higher major procedure-related complication rate in small volume aneurysms. We did not find any association between the other factors analyzed and occurrence of procedure-related complications. CONCLUSION: Treatment of AChoA aneurysms has an acceptable complication risk. We did not find any significant differences between surgical and endovascular treatment in terms of procedure-related complication rates. Multilobed aneurysms were significantly associated with a higher procedure-related complication rate.

Surgical technique.

In SEEG, as for any surgical procedure, the benefit/risk ratio is a key-point. This implies rigorous clinical practice in terms of indication, information delivered to the patient, and surgical technique. Numerous technical options may be used to achieve this goal. All are valuable, as long as they are executed with rigor and consistency. Intracranial bleeding represents the main risk of the procedure (1-4% of cases). The procedure also carries a risk of infection (0.8%), death (total of 6 reported cases in all the literature, <0.002%), and of minor and transient side effects. SEEG is performed under general anesthesia. MRI is the gold standard morphological imaging, used for targeting and for trajectory calculations. It is strictly necessary to use some form of vascular imaging to minimize the peroperative bleeding risk. SEEG can be performed on a frame-based, or frameless, basis, using stereotactic instrumentation, or a neurosurgical robot. Literature does not provide any data in favour of one of these techniques compared to the other. The minimal acceptable bone thickness is considered to be 2mm. Postoperatively, as soon as any non-preexisting neurological deficit is noticed, neuroimaging must immediately be performed. It is recommended to perform a postoperative imaging during the 24hours after implantation. The numerous current possibilities, in terms of imaging and technology, give rise to many possible stereotactic strategies for performing SEEG implantation. None of these strategies can be considered as superior to the other. The guarantee of the best possible result is provided by the care with which these procedures are done.