Robot-assisted stereoelectroencephalography

Robot-assisted stereoelectroencephalography

McGovern et al., performed a retrospective, single-center study in consecutive children with medically refractory epilepsy who were undergoing robot-assisted SEEG. Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom. Both univariate and multivariate methods were used to analyze the preoperative and operative factors associated with seizure freedom.

Fifty-seven children underwent a total of 64 robot-assisted procedures. The patients’ mean age was 12 years, an average of 6.4 antiepileptic drugs (AEDs) per patient had failed prior to implantation, and in 56% of the patients the disease was considered nonlesional. On average, children had 12.4 electrodes placed per implantation, with an implantation time of 9.6 minutes per electrode and a 10-day postoperative stay. SEEG analysis yielded a definable epileptogenic zone in 51 (89%) patients; 42 (74%) patients underwent surgery, half of whom were seizure free at last follow-up, 19.6 months from resection. In a multivariate generalized linear model, resective surgery, older age, and shorter SEEG-related hospital length of stay were associated with seizure freedom. In a Cox proportional hazards model including only the children who underwent resective surgery, older age was the only significant factor associated with seizure freedom. Complications related to bleeding were the major contributors to morbidity. One patient (1.5%) had a symptomatic hemorrhage resulting in a permanent neurological deficit.

McGovern et al., reported one of the largest pediatric-specific SEEG series demonstrating that the modern surgical management of medically refractory epilepsy in children can lead to seizure freedom in many patients, while also highlighting the challenges posed by this difficult patient population 1).


Willems et al., analyzed 18 consecutive patients (mean age: 30.5 years, range: 12-46; 61% female) undergoing invasive presurgical video-EEG monitoring via sEEG electrodes (n = 167 implanted electrodes) over a period of 2.5 years with robot-assisted implantation. There were no neurological deficits reported after implantation or explantation in any of the enrolled patients. Postimplantation imaging showed a minimal subclinical subarachnoid hemorrhage in one patient and further workup revealed a previously unknown factor VII deficiency. No injuries or status epilepticus occurred during video-EEG monitoring. In one patient, a seizure-related asymptomatic cross break of two fixation screws was found and led to revision surgery. Unspecific symptoms like headaches or low-grade fever were present in 10 of 18 (56%) patients during the first days of video-EEG monitoring and were transient. Postexplantation imaging showed asymptomatic and small bleedings close to four electrodes (2.8%).

Overall, sEEG is a safe and well-tolerated procedure. Systematic imaging after implantation and explantation helps to identify clinically silent complications of sEEG. In the literature, complication rates of up to 4.4% in sEEG and in 49.9% of subdural EEG are reported; however, systematic imaging after explantation was not performed throughout the studies, which may have led to underreporting of associated complications 2).


2014

Over a period of 4 years, Serletis et al., prospectively identified 200 patients with refractory epilepsy who collectively underwent 2663 tailored SEEG electrode implantations for invasive intracranial EEG monitoring and extraoperative mapping. The first 122 patients underwent conventional Leksell frame-based SEEG electrode placement; the remaining 78 patients underwent frameless stereotaxy under robotic guidance, following acquisition of a stereotactic ROSA robotic device at the authors’ institution. Electrodes were placed according to a preimplantation hypothesis of the presumed epileptogenic zone, based on a standardized preoperative workup including video-EEG monitoring, MRI, PET, ictal SPECT, and neuropsychological assessment. Demographic features, seizure semiology, number and location of implanted SEEG electrodes, and location of the epileptogenic zone were recorded and analyzed for all patients. For patients undergoing subsequent craniotomy for resection, the type of resection and procedure-related complications were prospectively recorded. These results were analyzed and correlated with pathological diagnosis and postoperative seizure outcomes.

The epileptogenic zone was confirmed by SEEG in 154 patients (77%), of which 134 (87%) underwent subsequent craniotomy for epileptogenic zone resection. Within this cohort, 90 patients had a minimum follow-up of at least 12 months; therein, 61 patients (67.8%) remained seizure free, with an average follow-up period of 2.4 years. The most common pathological diagnosis was focal cortical dysplasia Type I (55 patients, 61.1%). Per electrode, the surgical complications included wound infection (0.08%), hemorrhagic complications (0.08%), and a transient neurological deficit (0.04%) in a total of 5 patients (2.5%). One patient (0.5%) ultimately died due to intracerebral hematoma directly ensuing from SEEG electrode placement 3).


2013

Four hundred nineteen procedures were performed in the Claudio Munari Centre for Epilepsy and Parkinson Surgery, Niguarda Ca’ Granda Hospital, Milano, Italy 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).

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.

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 4).

References

1)

McGovern RA, Knight EP, Gupta A, Moosa ANV, Wyllie E, Bingaman WE, Gonzalez-Martinez J. Robot-assisted stereoelectroencephalography in children. J Neurosurg Pediatr. 2018 Dec 7;23(3):288-296. doi: 10.3171/2018.7.PEDS18305. PubMed PMID: 30544342.
2)

Willems LM, Reif PS, Spyrantis A, Cattani A, Freiman TM, Seifert V, Wagner M, You SJ, Schubert-Bast S, Bauer S, Klein KM, Rosenow F, Strzelczyk A. Invasive EEG-electrodes in presurgical evaluation of epilepsies: Systematic analysis of implantation-, video-EEG-monitoring- and explantation-related complications, and review of literature. Epilepsy Behav. 2018 Jun 13. pii: S1525-5050(18)30253-1. doi: 10.1016/j.yebeh.2018.05.012. [Epub ahead of print] PubMed PMID: 29907526.
3)

Serletis D, Bulacio J, Bingaman W, Najm I, González-Martínez J. The stereotactic approach for mapping epileptic networks: a prospective study of 200 patients. J Neurosurg. 2014 Nov;121(5):1239-46. doi: 10.3171/2014.7.JNS132306. PubMed PMID: 25148007.
4)

Cardinale F, Cossu M, Castana L, Casaceli G, Schiariti MP, Miserocchi A, Fuschillo D, Moscato A, Caborni C, Arnulfo G, Lo Russo G. Stereoelectroencephalography: surgical methodology, safety, and stereotactic application accuracy in 500 procedures. Neurosurgery. 2013 Mar;72(3):353-66; discussion 366. doi: 10.1227/NEU.0b013e31827d1161. PubMed PMID: 23168681.

Mesial temporal lobe lesion approaches

Mesial temporal lobe lesion approaches

There are several ways to safely access mesial temporal structures. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. Actual lesions associated with epileptogenesis in focal cortical dysplasia (FCD) may be larger than they appear on magnetic resonance imaging. For this reason, evaluations to locate sufficient epileptogenic foci, including invasive studies, should be completed for FCD, and epilepsy surgery should be performed according to these results. Regardless, the ultimate goal of all epilepsy surgeries is to maximize seizure control while maintaining neurological function. Therefore, a tailored approach based on the properties of the lesion is needed1).

For Campero et al., dividing the mesial temporal region (MTR) into 3 regions allows us to adapt the approach to lesion location. Thus, the anterior sector can be approached via the sylvian fissure, the middle sector can be approached transtemporally, and the posterior sector can be approached via the supracerebellar approach 2).

There are limited reports on the transcortical approach for the resection of tumors within this region.

Morshed et al., from the UCSF Medical Center, described the technical considerations and functional outcomes in patients undergoing transcortical resection of gliomas of the mesial temporal lobe (MTL).

Patients with a glioma (WHO grades I-IV) located within the MTL who had undergone the transcortical approach in the period between 1998 and 2016 were identified through the University of California, San Francisco (UCSF) tumor registry and were classified according to tumor location: preuncus, uncus, hippocampus/parahippocampus, and various combinations of the former groups. Patient and tumor characteristics and outcomes were determined from operative, radiology, pathology, and other clinical reports that were available through the UCSF electronic medical record.

Fifty patients with low- or high grade glioma were identified. The mean patient age was 46.8 years, and the mean follow-up was 3 years. Seizures were the presenting symptom in 82% of cases. Schramm classification types A, C, and D represented 34%, 28%, and 38% of the tumors, and the majority of lesions were located at least in part within the hippocampus/parahippocampus. For preuncus and preuncus/uncus tumors, a transcortical approach through the temporal pole allowed for resection. For most tumors of the uncus and those extending into the hippocampus/parahippocampus, a corticectomy was performed within the middle and/or inferior temporal gyri to approach the lesion. To locate the safest corridor for the corticectomy, language mapping was performed in 96.9% of the left-sided tumor cases, and subcortical motor mapping was performed in 52% of all cases. The mean volumetric extent of resection of low- and high-grade tumors was 89.5% and 96.0%, respectively, and did not differ by tumor location or Schramm type. By 3 months’ follow-up, 12 patients (24%) had residual deficits, most of which were visual field deficits. Three patients with left-sided tumors (9.4% of dominant-cortex lesions) experienced word-finding difficulty at 3 months after resection, but 2 of these patients demonstrated complete resolution of symptoms by 1 year.

Mesial temporal lobe gliomas, including larger Schramm type C and D tumors, can be safely and aggressively resected via a transcortical equatorial approach when used in conjunction with cortical and subcortical mapping 3).


Microsurgery was performed via transsylviantranstemporal, or subtemporal approaches on 62 patients with mesial temporal lobe gliomas, 33 with localized tumors within the mesial temporal structures (type A), 19 in anterior portion (type A1), and 14 extending to posterior portion (type A2); 19 patients with multicompartmental tumors involving the mesial temporal lobe, insular lobe, and posterior frontorbital gurus (type B); 14 patients with tumors involving the temporal pole and lateral areas of the temporal horn (type C); and 6 patients with tumors infiltrating the brain stem, basal nuclei and thalamus (type D).

Trans-sylvian approach was performed in 25 cases of which total tumor removal was achieved in 14 cases, subtotal removal in 6 cases, and gross removal in 5 cases. Primary visual deficits worsened after surgery in 5 cases. Trans-temporal approach was used in 23 cases of which total tumor resection was achieved in 15 cases, subtotal resection in 5 cases, and gross resection in 3 cases. Primary visual deficits worsened after surgery in 5 cases. Four patients in which preoperative vision were good presented with visual deficits postoperatively. Subtemporal approach was used in 14 cases of which total tumor removal was achieved in 10 cases, and subtotal removal in 4 cases. All 14 patients did not develop worsened vision after surgery.

Trans-sylvian and subtemporal approaches can reduce possible harm to parenchyma and optic radiation, whereas approaches to the temporal horn through the superior and middle temporal gyri will induce damage to parenchyma and optic radiation 4).


The aim of Faust et al., was to categorize temporal lobe tumors based on anatomical, functional, and vascular considerations and to devise a systematic field manual of surgical approaches.

Tumors were classified into four main types with assigned approaches: Type I-lateral: transcortical; type II-polar: pterional/transcortical; type III-central: transsylvian/transopercular; type IV-mesial: transsylvian/trans-cisternal if more anterior (=Type IV A), and supratentorial/infraoccipital if more posterior (=type IV B). 105 patients have been operated on prospectively using the advocated guidelines. Outcomes were evaluated.

Systematic application of the proposed classification facilitated a tailored approach, with gross total tumor resection of 88 %. Neurological and surgical morbidity were less than 10 %. The proposed classification may prove a valuable tool for surgical planning 5).


Twenty formalin-fixed, adult cadaveric specimens were studied. Ten brains provided measurements to compare different surgical strategies. Approaches were demonstrated using 10 silicon-injected cadaveric heads. Surgical cases were used to illustrate the results by the different approaches. Transverse lines at the level of the inferior choroidal point and quadrigeminal plate were used to divide the medial temporal region into anterior, middle, and posterior portions. Surgical approaches to the medial temporal region were classified into four groups: superior, lateral, basal, and medial, based on the surface of the lobe through which the approach was directed. The approaches through the medial group were subdivided further into an anterior approach, the transsylvian transcisternal approach, and two posterior approaches, the occipital interhemispheric and supracerebellar transtentorial approaches.

The anterior portion of the medial temporal region can be reached through the superior, lateral, and basal surfaces of the lobe and the anterior variant of the approach through the medial surface. The posterior group of approaches directed through the medial surface are useful for lesions located in the posterior portion. The middle part of the medial temporal region is the most challenging area to expose, where the approach must be tailored according to the nature of the lesion and its extension to other medial temporal areas.

Each approach to medial temporal lesions has technical or functional drawbacks that should be considered when selecting a surgical treatment for a given patient. Dividing the medial temporal region into smaller areas allows for a more precise analysis, not only of the expected anatomic relationships, but also of the possible choices for the safe resection of the lesion. The systematization used here also provides the basis for selection of a combination of approaches 6).


Germano described a transsulcal temporal approach to mesiotemporal lesions and its application in three patients. Gross-total resection of the lesion was accomplished in all cases. An anatomical cadaveric study was also performed to delineate the microsurgical anatomy of this approach. Precise knowledge of temporal intraventricular landmarks allows navigation to the lesion without the need for a navigational system. This approach is helpful for neurologically intact patients with mesiotemporal lesions 7).

References

1)

Chong S, Phi JH, Lee JY, Kim SK. Surgical Treatment of Lesional Mesial Temporal Lobe Epilepsy. J Epilepsy Res. 2018 Jun 30;8(1):6-11. doi: 10.14581/jer.18002. eCollection 2018 Jun. Review. PubMed PMID: 30090756; PubMed Central PMCID: PMC6066696.
2)

Campero A, Ajler P, Rica C, Rhoton A Jr. Cavernomas and Arteriovenous Malformations in the Mesial Temporal Region: Microsurgical Anatomy and Approaches. Oper Neurosurg (Hagerstown). 2017 Feb 1;13(1):113-123. doi: 10.1227/NEU.0000000000001239. PubMed PMID: 28931254.
3)

Morshed RA, Young JS, Han SJ, Hervey-Jumper SL, Berger MS. The transcortical equatorial approach for gliomas of the mesial temporal lobe: techniques and functional outcomes. J Neurosurg. 2018 Apr 20:1-9. doi: 10.3171/2017.10.JNS172055. [Epub ahead of print] PubMed PMID: 29676697.
4)

Jiang ZL, Wang ZC, Jiang T. [Surgical outcomes of different approaches for mesial temporal lobe gliomas]. Zhonghua Yi Xue Za Zhi. 2005 Sep 7;85(34):2428-32. Chinese. PubMed PMID: 16321253.
5)

Faust K, Schmiedek P, Vajkoczy P. Approaches to temporal lobe lesions: a proposal for classification. Acta Neurochir (Wien). 2014 Feb;156(2):409-13. doi: 10.1007/s00701-013-1917-4. Epub 2013 Nov 8. Review. PubMed PMID: 24201756.
6)

Campero A, Tróccoli G, Martins C, Fernandez-Miranda JC, Yasuda A, Rhoton AL Jr. Microsurgical approaches to the medial temporal region: an anatomical study. Neurosurgery. 2006 Oct;59(4 Suppl 2):ONS279-307; discussion ONS307-8. PubMed PMID: 17041498.
7)

Germano IM. Transsulcal approach to mesiotemporal lesions. Anatomy, technique, and report of three cases. Neurosurg Focus. 1996 Nov 15;1(5):e4. PubMed PMID: 15099055.

DNET-like neoplasms of the septum pellucidum

DNET-like neoplasms of the septum pellucidum

Rare midline neoplasms with similar histological features to those found in DNETs have been described near the septum pellucidum and termed ‘DNET-like neoplasms of the septum pellucidum‘. Due to their rarity, these tumors have been described in just a few reports and their genetic alterations sought only in small series

Chiang et al., collected 20 of these tumors for a comprehensive study of their clinical, radiological and pathological features. RNA sequencing or targeted DNA sequencing was undertaken on 18 tumors, and genome-wide DNA methylation profiling was possible with 11 tumors. Published cases (n=22) were also reviewed for comparative purposes.

The commonest presenting symptoms and signs were related to raised intracranial pressure; 40% of cases required cerebrospinal fluid diversion. Epilepsy was seen in approximately one third of cases. All patients had an indolent disease course, despite metastasis within the neuraxis in a few cases. Radiologically, the septum verum / septal nuclei were involved in all cases and are the proposed site of origin for septal DNET (sDNET). sDNET showed a high frequency (~80%) of PDGFRA mutations, and alterations in FGFR1 and NF1 were also identified. In a genomic DNA methylation analysis alongside other neural tumors, sDNETs formed a separate molecular group.

Genetic alterations that are different from those of cerebral DNETs and a distinct methylome profile support the proposal that sDNET is a distinct disease entity. 1).


Gessi et al., described the neuroradiologic, histopathologic, and molecular features of 7 cases (4 female and 3 male; patient age range, 3 to 34 y; mean age, 16.7 y). The tumors, all localized near the supratentorial midline structures in proximity to the foramen of Monro and septum pellucidum, appeared in magnetic resonance imaging as well-delimited cystic lesions with cerebrospinal fluid-like signal on T1-weighted and T2-weighted images, some of them with typical fluid-attenuated inversion recovery ring sign. Histologically, they shared features with classic cortical DNTs but did not display aspects of multinodularity. From a molecular point of view the cases investigated did not show KIAA1549-BRAF fusions or FGFR1 mutations, alterations otherwise observed in pilocytic astrocytomas, or MYB and MYBL1 alterations that have been identified in a large group of pediatric low-grade gliomas. Moreover, BRAF mutations, which so far represent the most common molecular alteration found in cortical DNTs, were absent in this group of rare periventricular tumors 2).


Baisden et al., reported a series of 10 low-grade neoplasms arising in the midline anteriorly in the region of the septum pellucidum with many of the histologic features of dysembryoplastic neuroepithelial tumor (DNT). The patients (five female, five male) ranged in age from 6 to 35 years (mean age, 21.5 years). The most common presenting symptoms were headache, nausea and vomiting, and visual disturbances. Radiographically, the tumors extended into the lateral ventricles from the septal region and obstructed the foramen of Monro. Varying degrees of hydrocephalus were present. The lesions were lobular, well-delineated, hypointense to brain on T1-weighted magnetic resonance imaging, and hyperintense on T2-weighted images. They were uniformly nonenhancing or showed only minimal peripheral enhancement. The tumors, in aggregate, had the histologic features of DNT. These included a mucin-rich background, oligodendrocyte-like cells, “floating neurons,” and a “specific glioneuronal element.” Seven patients underwent gross total resection and two underwent subtotal resection. No patients received adjuvant chemotherapy or radiotherapy. On follow-up (n = 6; median, 14 months), all tumors had either not recurred or were radiologically stable. On the basis of both neuroimaging and histopathology, DNT-like lesions should be considered in the differential diagnosis of midline intraventricular tumors in children and young adults. Distinction from more aggressive neoplasms is essential because these tumors appear to behave in a benign fashion 3).

References

1)

Chiang JCH, Harreld JH, Tanaka R, Li X, Wen J, Zhang C, Boué DR, Rauch TM, Boyd JT, Chen J, Corbo JC, Bouldin TW, Elton SW, Liu LL, Schofield D, Lee SC, Bouffard JP, Georgescu MM, Dossani RH, Aguiar MA, Sances RA, Saad AG, Boop FA, Qaddoumi I, Ellison DW. Septal Dysembryoplastic Neuroepithelial Tumor: A Comprehensive Clinical, Imaging, Histopathologic and Molecular Analysis. Neuro Oncol. 2019 Feb 6. doi: 10.1093/neuonc/noz037. [Epub ahead of print] PubMed PMID: 30726976.
2)

Gessi M, Hattingen E, Dörner E, Goschzik T, Dreschmann V, Waha A, Pietsch T. Dysembryoplastic Neuroepithelial Tumor of the Septum Pellucidum and the Supratentorial Midline: Histopathologic, Neuroradiologic, and Molecular Features of 7 Cases. Am J Surg Pathol. 2016 Jun;40(6):806-11. doi: 10.1097/PAS.0000000000000600. PubMed PMID: 26796505.
3)

Baisden BL, Brat DJ, Melhem ER, Rosenblum MK, King AP, Burger PC. Dysembryoplastic neuroepithelial tumor-like neoplasm of the septum pellucidum: a lesion often misdiagnosed as glioma: report of 10 cases. Am J Surg Pathol. 2001 Apr;25(4):494-9. PubMed PMID: 11257624.
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