A scoping review of seizure onset pattern in SEEG and a proposal for morphological classification.

BACKGROUND: Seizure onset pattern (SOP) represents an alteration of electroencephalography (EEG) morphology at the beginning of seizure activity in epilepsy. With stereotactic electroencephalography (SEEG), a method for intracranial EEG evaluation, many morphological SOP classifications have been reported without established consensus. These inconsistent classifications with ambiguous terminology present difficulties to communication among epileptologists. METHODS: We reviewed SOP in SEEG by searching the PubMed database. Reported morphological classifications and the ambiguous terminology used were collected. After thoroughly reviewing all reports, we reconsidered the definitions of these terms and explored a more consistent and simpler morphological SOP classification. RESULTS: Of the 536 studies initially found, 14 studies were finally included after screening and excluding irrelevant studies. We reconsidered the definitions of EEG onset, period for determining type of SOP, core electrode and other terms in SEEG. We proposed a more consistent and simpler morphological SOP classification comprising five major types with two special subtypes. CONCLUSIONS: A scoping review of SOP in SEEG was performed. Our classification may be suitable for describing SOP morphology.

Use of an Endoscope Reduces the Size of Craniotomy Without Increasing Operative Time Compared With Conventional Microscopic Corpus Callosotomy.

BACKGROUND AND OBJECTIVES: Corpus callosotomy (CC) is an epilepsy surgery that disconnects the commissural fibers at the corpus callosum, a structure that often plays a key role in propagating seizure activity. CC is particularly beneficial in patients with drop attacks. Less invasive endoscopic surgeries have recently been introduced to some fields of neurosurgery but have not yet become common in epilepsy surgery. Endoscopic surgeries offer better visualization and require a smaller corridor than conventional microscopic surgeries. Here, we presented a case series comparing endoscopic CC with microscopic CC. METHODS: This 2-center retrospective study involved patients who underwent all types of CC (anterior, total, or posterior CC [pCC]) between January 2014 and May 2022. We excluded patients who underwent additional craniotomy for electrocorticography rather than CC, prior craniotomy, or CC without craniotomy. The primary outcomes were comparing size of craniotomy, operative time, and surgical complications between endoscopic CC and microscopic CC. RESULTS: We included 14 CCs in 11 patients in the endoscopic group and 58 CCs in 55 patients in the microscopic group. No significant difference in age was seen between groups. Craniotomies were significantly smaller in the endoscopic group for anterior (13.36 ± 1.31 cm 2 vs 27.55 ± 3.78 cm 2 ; P = .001), total (14.07 ± 2.54 cm 2 vs 26.63 ± 6.97 cm 2 ; P = .001), and pCC (9.44 ± 1.18 cm 2 vs 30.23 ± 10.76 cm 2 ; P = .002). Moreover, no significant differences in operative time (anterior CC [261 ± 53.11 min vs 298.73 ± 81.08 min, P = .226], total CC [339.5 ± 48.2 min vs 321.39 ± 65.98 min, P = .452], pCC [198 ± 24.73 min vs 242.5 ± 59.12 min, P = .240]), or complication rate were seen. CONCLUSION: Endoscopic CC is a promising technique requiring a smaller craniotomy than microscopic CC, without significantly increasing operative time or complication rate compared with microscopic CC.

Electrode Tip Shift During the Stereotactic Electroencephalography Evaluation Period with Boltless Suture Fixation.

BACKGROUND: Electrodes for stereotactic electroencephalography (SEEG) are typically fixed to the skull with anchor bolts. When anchor bolts are unavailable, electrodes have to be fixed using other methods, carrying the possibility of electrode shift. This study, therefore, evaluated the characteristics of electrode tip shift during SEEG monitoring in patients with electrodes fixed using the suture technique. METHODS: We retrospectively included patients who underwent SEEG implantation with suture fixation and evaluated the tip shift distance (TSD) of electrodes. Possible influences evaluated included: 1) implantation period, 2) lobe of entry, 3) unilateral or bilateral implantation, 4) electrode length, 5) skull thickness, and 6) scalp thickness difference. RESULTS: A total of 50 electrodes in 7 patients were evaluated. TSD was 1.4 ± 2.0 mm (mean ± standard deviation). Implantation period was 8.1 ± 2.2 days. Entry lobe was frontal for 28 electrodes and temporal for 22 electrodes. Implantation was bilateral for 25 electrodes and unilateral for 25 electrodes. Electrode length was 45.4 ± 14.3 mm. Skull thickness was 6.0 ± 3.7 mm. Scalp thickness difference was -1.5 ± 2.1 mm, which was found greater in temporal lobe entry compared with frontal lobe entry. According to univariate analyses, neither implantation period nor electrode length correlated with TSD. Multivariate regression analysis showed that only greater scalp thickness difference correlated significantly with greater TSD (P = 0.0018). CONCLUSIONS: Greater scalp thickness difference correlated with greater TSD. Surgeons need to consider the degree of scalp thickness difference and electrode shift when using suture fixation, especially with temporal lobe entry.

Intraparenchymal and Subarachnoid Hemorrhage in Stereotactic Electroencephalography Caused by Indirect Adjacent Arterial Injury: Illustrative Case.

The complication rate of stereotactic electroencephalography (SEEG) is generally low, but various types of postoperative hemorrhage have been reported. We presented an unusual hemorrhagic complication after SEEG placement. A 20-year-old man presented with suspected frontal lobe epilepsy. We implanted 11 SEEG electrodes in the bilateral frontal lobes and the left insula. Computed tomography after implantation showed intraparenchymal hemorrhage in the left temporal lobe and insula and subarachnoid hemorrhage in the left Sylvian cistern. Later, the point of vessel injury was revealed from the identification of a pseudoaneurysm, but this location was not along the planned or actual electrode trajectory. The cause of hemorrhage was suggested to be indirect injury from stretching of the arachnoid trabeculae by the puncture needle.

Comparing late-onset epileptic spasm outcomes after corpus callosotomy and subsequent disconnection surgery between post-encephalitis/encephalopathy and non-encephalitis/encephalopathy.

OBJECTIVE: We aimed to analyze the efficiency of corpus callosotomy (CC) and subsequent disconnection surgeries in patients with late-onset epileptic spasms (LOES) by comparing post-encephalitis/encephalopathy (PE) and non-encephalitis/encephalopathy (NE). We hypothesized these surgeries can control potential focal onset epileptic spasms (ES) in the NE group but not in the PE group. METHODS: We retrospectively included 23 patients (12 with PE and 11 with NE) who initially underwent CC and subsequent disconnection surgeries (five NE). We compared the clinical courses, seizure types, MRI, video-EEG, epilepsy surgery, and seizure outcomes between the two groups. RESULTS: The median age of LOES onset in the PE group was 2.8 (range 1.0-10.1 years) and 2.9 years (range 1.1-12.6) in the NE group. Bilateral MRI abnormalities were observed in both groups (PE, n = 12; NE, n = 3; P < 0.05). The PE group presented ES alone (n = 2), ES + focal seizures (FS) (n = 3), ES + generalized seizures (GS) (n = 3), and ES + FS + GS (n = 4) in addition to stimulus-induced startle seizures (SS) (n = 8) (mean 3.1 seizure types/patient). The NE group presented ES alone (n = 1), ES + FS (n = 2), and ES + FS + GS (n = 8) (mean 2.7 seizure types/patient). In the PE group, CC stopped ES (n = 1) and SS (n = 1) and achieved <50% SS (n = 3). In the NE group, CC achieved immediate ES-free status (n = 2) and < 50% ES (n = 1), and additional disconnection surgeries subsided all seizure types (n = 3) based on lateralized interictal/ictal EEG findings. LOES was significantly remitted by surgery in the NE group (6/11 [55%]) compared with the PE group (1/12 [8%]) (P < 0.05). SIGNIFICANCE: LOES is a drug-resistant, focal/generalized/unknown onset ES. Lateralization of ES in NE could be achieved after CC and eliminated by further disconnection surgeries because of potential focal onset ES. LOES in PE had little benefit from CC for generalized onset ES. However, CC might reduce SS in patients in the PE group with multiple seizure types.

[Surgical Treatment of Mesial Temporal Lobe Epilepsy Focusing on Anatomical Understanding].

Surgical treatment is an effective option for medically intractable epilepsy. Amygdalohippocampectomy for mesial temporal lobe epilepsy is a surgically remediable epileptic syndrome. It is a well-established surgery and various approaches to the mesial temporal lobe have been reported. To reduce the complication rate, surgeons should have sufficient knowledge of anatomy in the mesial temporal region. Here, we summarize the surgical treatments for mesial temporal lobe epilepsy, focusing on anatomical understanding. We described in detail the surgical anatomy of amygdalohippocampectomy and various approaches to the mesial temporal region. In addition, we describe hippocampal transection aimed at preserving memory function, which is an alternative surgery in patients without hippocampal sclerosis. An anatomical understanding of the mesial temporal region helps surgeons not only in the field of epilepsy surgery, but also in other fields of neurosurgery, such as brain tumor and vascular surgery.

Primary Experiences with Robot-assisted Navigation-based Frameless Stereo-electroencephalography: Higher Accuracy than Neuronavigation-guided Manual Adjustment.

The use of robot-assisted frameless stereotactic electroencephalography (SEEG) is becoming more common. Among available robotic arms, Stealth Autoguide (SA) (Medtronic, Minneapolis, MN, USA) functions as an optional instrument of the neuronavigation system. The aims of this study were to present our primary experiences with SEEG using SA and to compare the accuracy of implantation between SA and navigation-guided manual adjustment (MA). Seventeen electrodes from two patients who underwent SEEG with SA and 18 electrodes from four patients with MA were retrospectively reviewed. We measured the distance between the planned location and the actual location at entry (De) and the target (Dt) in each electrode. The length of the trajectory did not show a strong correlation with Dt in SA (Pearson's correlation coefficient [r] = 0.099, p = 0.706) or MA (r = 0.233, p = 0.351). De and Dt in SA were shorter than those in MA (1.99 ± 0.90 vs 4.29 ± 1.92 mm, p = 0.0002; 3.59 ± 2.22 vs 5.12 ± 1.40 mm, p = 0.0065, respectively). SA offered higher accuracy than MA both at entry and target. Surgical times per electrode were 38.9 and 32 min in the two patients with SA and ranged from 51.6 to 88.5 min in the four patients with MA. During the implantation period of 10.3 ± 3.6 days, no patients experienced any complications.

Maximum 11C-methionine PET uptake as a prognostic imaging biomarker for newly diagnosed and untreated astrocytic glioma.

This study aimed whether the uptake of amino tracer positron emission tomography (PET) can be used as an additional imaging biomarker to estimate the prognosis of glioma. Participants comprised 56 adult patients with newly diagnosed and untreated World Health Organization (WHO) grade II-IV astrocytic glioma who underwent surgical excision and were evaluated by 11C-methionine PET prior to the surgical excision at Osaka City University Hospital from July 2011 to March 2018. Clinical and imaging studies were retrospectively reviewed based on medical records at our institution. Preoperative Karnofsky Performance Status (KPS) only influenced progression-free survival (hazard ratio [HR] 0.20; 95% confidence interval [CI] 0.10-0.41, p < 0.0001), whereas histology (anaplastic astrocytoma: HR 5.30, 95% CI 1.23-22.8, p = 0.025; glioblastoma: HR 11.52, 95% CI 2.27-58.47, p = 0.0032), preoperative KPS ≥ 80 (HR 0.23, 95% CI 0.09-0.62, p = 0.004), maximum lesion-to-contralateral normal brain tissue (LN max) ≥ 4.03 (HR 0.24, 95% CI 0.08-0.71, p = 0.01), and isocitrate dehydrogenase (IDH) status (HR 14.06, 95% CI 1.81-109.2, p = 0.011) were factors influencing overall survival (OS) in multivariate Cox regression. OS was shorter in patients with LN max ≥ 4.03 (29.3 months) than in patients with LN max < 4.03 (not reached; p = 0.03). OS differed significantly between patients with IDH mutant/LN max < 4.03 and patients with IDH mutant/LN max ≥ 4.03. LN max using 11C-methionine PET may be used in prognostic markers for newly identified and untreated WHO grade II-IV astrocytic glioma.

Disconnection surgery to cure or palliate medically intractable epileptic spasms: a retrospective study.

OBJECTIVE: Surgery is a treatment option for medically intractable epileptic spasms (ESs). However, outcomes of ES after surgery are not well understood, especially when surgeries aimed at seizure palliation are included. The purpose of the present study was to 1) investigate the proportion of favorable postoperative ES outcomes, 2) explore the preoperative factors related to favorable postoperative ES outcomes, and 3) examine the timing of ES recurrence after disconnection surgeries, including both curative and palliative indications. METHODS: This retrospective study included patients who underwent disconnection surgery for medically intractable ES at the authors' institution between May 2015 and April 2021. Patients with suggested focal-onset ES based on preoperative evaluations initially underwent lobar disconnection. Patients with suggested generalized or unknown-onset ES underwent corpus callosotomy (CC). If evaluations after initial CC showed focalized or lateralized change, they were considered secondarily revealed focal-onset ES, and lobar disconnection was performed. ES outcomes were evaluated using the International League Against Epilepsy classification. ES outcomes were divided into classes 1-4 as favorable outcomes and classes 5 and 6 as unfavorable outcomes. The relationship between the favorable postoperative ES outcomes and the following preoperative factors was analyzed: sex, age at onset (< or > 1 year), duration between seizure onset and initial surgery (< or > 2 years), type of seizure at onset (ES or others), presence of other types of seizures, substrate, hypsarrhythmia, and MRI abnormalities. The period between the last surgery and ES recurrence was also analyzed. RESULTS: A total of 41 patients were included, of whom 75.6% achieved favorable ES outcomes. A longer seizure duration between seizure onset and initial surgery, presence of hypsarrhythmia, and positive MRI findings led to poorer postoperative ES outcomes (p = 0.0028, p = 0.0041, and p = 0.0241, respectively). A total of 60.9% of patients had ES recurrence during the follow-up period, and their ES recurred within 13 months after the last surgery. CONCLUSIONS: Disconnection surgery is an effective treatment option for medically intractable ES, even when the preoperative evaluation suggests a generalized or unknown onset.

Surgical Aspects of Corpus Callosotomy.

Corpus callosotomy (CC) is one of the options in epilepsy surgeries to palliate patient seizures, and is typically applied for drop attacks. The mechanisms of seizure palliation involve disrupting the propagation of epileptic activity to the contralateral side of the brain. This review article focuses on the surgical aspects of CC. As a variations of CC, anterior two-thirds, posterior one-third, and total callosotomy are described with intraoperative photographs. As less-invasive surgical variations, recent progress in endoscopic CC, and CC without craniotomy, is described. CC remains acceptable under the low prevalence of complications, and surgeons should make the maximum effort to minimize the complication rate.

Diagnostic Performance of [11C]Methionine Positron Emission Tomography in Newly Diagnosed and Untreated Glioma Based on the Revised World Health Organization 2016 Classification.

BACKGROUND: The relationship between uptake of amino acid tracer with positron emission tomography (PET) and glioma subtypes/gene status is still unclear. OBJECTIVE: To assess the relationship between uptake of [11C]methionine using PET and pathology, IDH (isocitrate dehydrogenase) mutation, 1p/19q codeletion, and TERT (telomerase reverse transcriptase) promoter status in gliomas. METHODS: The participants were 68 patients with newly diagnosed and untreated glioma who underwent surgical excision and preoperative [11C]methionine PET examination at Osaka City University Hospital between July 2011 and March 2018. Clinical and imaging studies were reviewed retrospectively based on the medical records at our institution. RESULTS: The mean lesion/contralateral normal brain tissue (L/N) ratio of diffuse astrocytomas was significantly lower than that of anaplastic astrocytomas (P = 0.00155), glioblastoma (P < 0.001), and oligodendrogliomas (P = 0.0157). The mean L/N ratio of IDH mutant gliomas was significantly lower than that of IDH wild-type gliomas (median 1.75 vs. 2.61; P = 0.00162). A mean L/N ratio of 2.05 provided the best sensitivity and specificity for distinguishing between IDH mutant and IDH wild-type gliomas (69.2% and 76.2%, respectively). The mean L/N ratio of TERT promoter mutant gliomas was significantly higher than that of TERT promoter wild-type gliomas (P = 0.0147). Multiple regression analysis showed that pathologic diagnosis was the only influential factor on L/N ratio. CONCLUSIONS: Distinguishing glioma subtypes based on the revised 2016 World Health Organization classification of the central nervous system tumors on the basis of [11C]methionine PET alone seems to be difficult. However, [11C]methionine PET might be useful for predicting the IDH mutation status in newly diagnosed and untreated gliomas noninvasively before tumor resection.

Comparison of the keyhole trans-middle temporal gyrus approach and transsylvian approach for selective amygdalohippocampectomy: A single-center experience.

Several approach routes exist for selective amygdalohippocampectomy (SAH); however, previous reports regarding a comparison of these routes are limited. Here, we compared trans-middle temporal gyrus (T2) SAH and transsylvian (TS) SAH in terms of seizure outcome, visual-field defect, memory function, and operation time in our institution. This retrospective study examined the data of 16 patients with medically intractable mesial temporal lobe epilepsy. Six patients underwent trans-T2 SAH and 10 patients underwent TS SAH between July 2014 and February 2019 in Osaka City University Hospital. In trans-T2 SAH, we performed a keyhole temporal craniotomy and a small corticotomy on T2. In TS SAH, we performed a 1.5 cm corticotomy along the inferior periinsular sulcus after opening the sylvian fissure. Amygdalohippocampectomy after reaching the inferior horn of the lateral ventricle was performed in the same manner in both procedures. The seizure outcome, visual-field defect, memory function, and operation time were retrospectively compared between the procedures. Seizure-free outcomes were achieved for six patients in the trans-T2 SAH and eight patients in the TS SAH group. There were no significant differences in the seizure outcome, visual-field defect, and memory function. The operation time was significantly shorter for trans-T2 SAH than TS SAH. The postoperative scar was less conspicuous for trans-T2 SAH. Trans-T2 SAH and TS SAH were comparable in terms of the seizure outcome, visual-field defect, and memory function. The operation time and length of the skin incision were shorter for trans-T2 SAH, suggesting that it may be preferable for general epilepsy surgeons.

Anatomic Understanding of Subtotal Hemispherotomy Using Cadaveric Brain, 3-Dimensional Simulation Models, and Intraoperative Photographs.

BACKGROUND: When the epileptogenic foci skip the motor area, the epilepsy can be cured by surgery while preserving the motor function. This surgery has been reported as subtotal hemispherectomy. The disconnective variant of this surgery, subtotal hemispherotomy, is described. OBJECTIVE: To demonstrate each step clearly, a cadaveric brain, 3-dimensional reconstruction and simulation model, and intraoperative photographs were used. METHODS: A formalin-fixed cadaveric brain was dissected to show each step of this surgery. For the 3-dimensional model, several brain structures were reconstructed from preoperative images, and the surgery was simulated. Intraoperative photographs and postoperative magnetic resonance images were taken from the representative cases. RESULTS: Temporo-parieto-occipital disconnection is performed to disconnect these lobes and the insula, limbic system, and splenium of the corpus callosum. The postcentral sulcus is the anterior border of the disconnection. Next, prefrontal disconnection is performed to disconnect the frontal lobe and the insula, frontal lobe and basal ganglia, and the anterior part of the corpus callosum. The precentral sulcus is the posterior border of the disconnection. Finally, corpus callosotomy of the central part is performed. After these steps, subtotal hemispherotomy, with preservation of the pre- and postcentral gyrus, is achieved. The 3-dimensional model clearly shows the anatomic relationships between deep brain structures. In the representative cases, postoperative motor deterioration was transient or none, and seizure-free status was achieved after surgery. CONCLUSION: Subtotal hemispherotomy is generally difficult because of the complicated anatomy and narrow and deep surgical corridors. Combined use of these methods facilitates a clearer understanding of this surgery.

Adult-Onset Mixed Germ Cell Tumor Composed Mainly of Yolk Sac Tumor Around the Pineal Gland: A Case Report and Review of the Literature.

BACKGROUND: Mixed germ cell tumors (MGCTs) usually occur in children. In the present report, we discuss an extremely rare case of adult-onset MGCT composed mainly of yolk sac tumor (YST) around the pineal gland. CASE DESCRIPTION: A 54-year-old Japanese man presented with disturbance of consciousness, Parinaud's syndrome, and gait disturbance. Magnetic resonance imaging revealed a pineal mass lesion, and subtotal resection of the tumor was achieved. The histologic diagnosis was MGCT, consisting mainly of YST. Although he underwent 5 courses of chemotherapy and craniospinal irradiation after surgery, tumor dissemination could not be controlled, and he died 10 months postoperatively. CONCLUSION: The present case highlights the need for clinicians to include YST in the differential diagnosis of acute progressive lesions around the pineal region, even in adult patients.

Anatomic Understanding of Posterior Quadrant Disconnection from Cadaveric Brain, 3D Reconstruction and Simulation Model, and Intraoperative Photographs.

BACKGROUND: Posterior quadrant disconnection is a surgery for refractory unilateral temporoparieto-occipital epilepsy to limit propagation of epileptic discharges. As incomplete disconnection can lead to residual seizures, detailed procedures are presented using a cadaveric brain, three-dimensional (3D) reconstruction and simulation models, and intraoperative photographs. METHODS: A formalin-fixed adult cadaveric brain was dissected to show each step in posterior quadrant disconnection. Using 3D preoperative planning software, we reconstructed 3D models of operative views from computed tomography and magnetic resonance imaging. Intraoperative photographs were taken from the case of a 7-year-old girl with temporoparieto-occipital epilepsy. RESULTS: Frontotemporoparietal craniotomy was performed. The Sylvian fissure was widely dissected, and the insular cortex was exposed. The temporal stem was disconnected along the inferior peri-insular sulcus. The disconnection was extended from the limen insulae to the atrium of the lateral ventricle. The fibers between the head of the hippocampus and the amygdala were disconnected. The parietal lobe was disconnected along the postcentral sulcus, and the disconnection was connected to the atrium of the lateral ventricle. At the medial surface of the parietal lobe, the disconnection was continued to the corpus callosum. The splenium of the corpus callosum was disconnected via the medial wall of the lateral ventricle. The fornix was divided in the atrium of the lateral ventricle. After these steps, disconnection of the unilateral tempoparieto-occipital lobe was achieved while preserving the arteries and veins. CONCLUSIONS: Inclusion of views from cadaveric brain, 3D reconstruction and simulation models, and intraoperative photographs facilitates a clearer anatomic understanding of posterior quadrant disconnection.