Intractable occipital lobe epilepsy: clinical characteristics, surgical treatment, and a systematic review of the literature

Seizing Control: Primary Visual Cortex Epilepsy Treated With Resection and Responsive Neurostimulation: 2-Dimensional Operative Video

Occipital lobe epilepsy is a debilitating condition, and surgical resection has been effective, though challenges arise because of the cortex's function. 1-7 Approximately 57% of patients with normal vision experience new visual field deficits postoperatively. 8 A combined approach of resection and responsive neurostimulation (RNS) could aid in decreasing the visual field area severed and the disability tied to it while obtaining seizure freedom. 9,10 We aimed to present a case of medically refractory occipital lobe epilepsy with involvement of the primary visual cortex treated with a combined approach. The patient consented to the procedure and to the publication of his image. Any identifiable individuals consented to publication of his/her image.

A 21-year-old right-handed male experienced refractory epilepsy since age 1 year. His first seizure was a severe refractory status epilepticus which resulted in cardiac arrest. His usual seizure semiology exhibited focal impaired awareness to bilateral tonic-clonic seizures occurring monthly. Noninvasive tests did not provide precise localization, but the intracranial electroencephalogram confirmed seizure onset in the right cuneus with rapid spread to the lingual gyrus and the superior parietal lobe. We performed a corticectomy 11 of the seizure onset zone and used RNS to address spreading areas in the parietal and occipital lobe. A complete lobectomy was avoided to prevent postoperative homonymous hemianopsia in a previously intact patient. The patient was discharged on postoperative day 3 with a nondisabling left inferior quadrantanopia. No clinical seizures were detected after RNS was turned on, rendering so far 8.5 months of seizure freedom.

The combined surgical approach appears promising for medically refractory epilepsy involving functional areas.

Non-ictal, interictal and ictal déjà vu: a systematic review and meta-analysis

Background

Déjà vu, French for "already seen," is a phenomenon most people will experience at least once in their lifetime. Emerging evidence suggests that déjà vu occurs in healthy individuals (as "non-ictal déjà vu") and in epilepsy patients during seizures (as "ictal déjà vu") and between seizures (as "interictal déjà vu"). Although the ILAE has recognized déjà vu as a feature of epileptic seizures, it is notably absent from the ICD-11. A lack of evidence-based research may account for this omission. To our knowledge, this study represents the first systematic review and meta-analysis on déjà vu experiences. Through detailed examinations of non-ictal, interictal and ictal déjà vu, we seek to highlight possible clinical implications. Rethinking the status quo of ictal déjà vu could potentially lead to earlier interventions and improve outcomes for epilepsy patients.

Methods

This study was registered in PROSPERO (ID: CRD42023394239) on 5 February 2023. Systematic searches were conducted across four databases: EMBASE, MEDLINE, PsycINFO, and PubMed, from inception to 1 February 2023, limited to English language and human participants. Studies were included/excluded based on predefined criteria. Data was extracted according to the PICO framework and synthesized through a thematic approach. Meta-analyses were performed to estimate prevalence's of the phenomena. Study quality, heterogeneity, and publication bias were assessed.

Results

Database searching identified 1,677 records, of which 46 studies were included. Meta-analyses of prevalence showed that non-ictal déjà vu was experienced by 0.74 (95% CI [0.67, 0.79], p < 0.001) of healthy individuals, whereas interictal déjà vu was experienced by 0.62 (95% CI [0.48, 0.75], p = 0.099) and ictal déjà vu by 0.22 (95% CI [0.15, 0.32], p = 0.001) of epilepsy patients. Examinations of phenomenological (sex, age, frequency, duration, emotional valence, and dissociative symptoms) and neuroscientific (brain structures and functions) data revealed significant variations between non-ictal, interictal and ictal déjà vu on several domains.

Conclusion

This systematic review and meta-analysis do not support the notion that non-ictal, interictal and ictal déjà vu are homogenous experiences. Instead, it provides insight into ictal déjà vu as a symptom of epilepsy that should be considered included in future revisions of the ICD-11.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=394239, CRD42023394239.

Ictal Semiology Important for Electrode Implantation and Interpretation of Stereoelectroencephalography

Scalp video-electroencephalography (video-EEG) monitoring should be analyzed thoroughly to preoperatively evaluate stereoelectroencephalography (SEEG). Formulating the working hypotheses for the epileptogenic zone (EZ) considering "anatomo-electroclinical correlations" is the most crucial step, which determines the placement of SEEG electrodes. If these hypotheses are insufficient, precise EZ identification may not be achieved during SEEG recording.In ictal semiology analysis, temporal and spatial patterns with reference to ictal EEG changes are emphasized. In frontal lobe epilepsy, seizures often begin with relatively widespread synchronous activity, and complex motor symptoms manifest within seconds. Due to the wide area involved and intense interhemispheric connectivity, a comprehensive evaluation is often required. Hypotheses are formulated on the basis of the motor symptoms and emotional manifestations that are related to the prefrontal cortices. In temporal lobe epilepsy, EEG onset often precedes clinical onset. Propagation from the EZ to locations within and outside of the temporal lobe is examined from both the EEG and semiological standpoint. The characteristics of contralateral versive seizures, contralateral tonic seizures, and frequent focal onset bilateral tonic-clonic seizures indicate a higher risk of temporo-perisylvian epilepsy. In parietal/occipital lobe epilepsy, despite that some symptoms result from activity in the immediate vicinity, stronger connectivity with other regions usually contributes to the generation of prominent ictal semiology. Hence, multilobar electrode placement is often useful in practice. For insular epilepsy, it is important to understand the anatomy, function, and networks between other regions. A semiological approach is one of the most important clues for electrode implantation and interpretation of SEEG.

Electrocorticography-Guided Resection Enhances Postoperative Seizure Freedom in Low-Grade Tumor-Associated Epilepsy: A Systematic Review and Meta-Analysis

BACKGROUND

Low-grade cerebral neoplasms are commonly associated with medically intractable epilepsy. Despite increasing evidence that epileptogenic brain regions commonly extend beyond visible tumor margins, the utility of extended surgical resections leveraging intraoperative electrocorticography (ECoG) remains unclear.

OBJECTIVE

To determine whether ECoG-guided surgery is associated with improved postoperative seizure control.

METHODS

We performed a systematic review and meta-analysis encompassing both adult and pediatric populations. The primary outcome measure was postoperative seizure freedom as defined by Engel class I outcome. Class I/II outcome served as a secondary measure. Relevant clinical and operative data were recorded. A random-effects meta-analysis based on the pooled odds ratio (OR) of seizure freedom was performed on studies that reported comparative data between ECoG-guided surgery and lesionectomy.

RESULTS

A total of 31 studies encompassing 1115 patients with medically refractory epilepsy met inclusion criteria. Seven studies reported comparative data between ECoG-guided surgery and lesionectomy for meta-analysis. Tumor resection guided by ECoG was associated with significantly greater postoperative seizure freedom (OR 3.95, 95% CI 2.32-6.72, P < .0001) and class I/II outcome (OR 5.10, 95% CI 1.97-13.18, P = .0008) compared with lesionectomy. Postoperative adverse events were rare in both groups.

CONCLUSION

These findings provide support for the utilization of ECoG-guided surgery to improve postoperative seizure freedom in cases of refractory epilepsy associated with low-grade neoplasms. However, this effect may be attenuated in the presence of concomitant cortical dysplasia, highlighting a need for improved presurgical and intraoperative monitoring for these most challenging cases of localization-related epilepsy.

Clinical Impacts of Stereotactic Electroencephalography on Epilepsy Surgery and Associated Issues in the Current Situation in Japan

Stereotactic electroencephalography (SEEG) is receiving increasing attention as a safe and effective technique in the invasive evaluation for epileptogenic zone (EZ) detection. The main clinical question is whether the use of SEEG truly improves outcomes. Herein, we compared outcomes in our patients after three types of intracranial EEG (iEEG): SEEG, the subdural electrode (SDE), and a combined method using depth and strip electrodes. We present here our preliminary results from two demonstrative cases. Several international reports from large epilepsy centers found the following clinical advantages of SEEG: 1) three-dimensional analysis of structures, including bilateral and multilobar structures; 2) low rate of complications; 3) less pneumoencephalopathy and less patient burden during postoperative course, which allows the initiation of video-EEG monitoring immediately after implantation and does not require resection to be performed in the same hospitalization; and 4) a higher rate of good seizure control after resection. In other words, SEEG more accurately identified the EZ than the SDE method. We obtained similar results in our preliminary experiences under limited conditions. In Japan, as of August 2022, dedicated electrodes and SEEG accessories have not been approved and the use of the robot arm is not widespread. The Japanese medical community is hopeful that these issues will soon be resolved and that the experience with SEEG in Japan will align with that of large epilepsy centers internationally.

[Intraoperative visual evoked potential recording in occipital tumor surgery]

Currently, visual field defects are considered as an inevitable consequence of occipital lobe surgery. However, recent advances in neuroimaging techniques, such as diffusion tensor tractography allowing better visualization of optic radiation and its relationship with occipital lobe tumors, as well as intraoperative monitoring of cortical visual evoked potentials (cVEPs) can contribute to correct planning of surgery and minimizing the risk of visual field defects after surgery.

OBJECTIVE

To evaluate the effectiveness of intraoperative monitoring of cVEP in patients with occipital lobe tumors.

MATERIAL AND METHODS

Ten patients with occipital lobe tumors have undergone surgery with neurophysiological monitoring since 2020. Mean age of patients was 57 years. There were 6 women and 4 men. In 7 patients, neoplasms were located in the right hemisphere, in 3 patients - in the left hemisphere. According to preoperative automatic perimetry data, 7 patients had various visual field defects, and other ones had intact visual fields. All patients underwent pre- and postoperative MRI for visualization of optic radiation, its relationship with tumor and control of resection quality. Intraoperative monitoring of cVEPs was performed in all patients.

RESULTS

Biopsy verified glioblastoma in 5 cases, metastasis of adenocarcinoma - 2 cases, diffuse glioma - 1 case, ganglioglioma - 1 case, CNS lymphoma - 1 case. Postoperative MRI confirmed total or subtotal resection of tumor in all cases. Enlargement of visual fields occurred in 3 patients after surgery. Two ones had deterioration and/or new homonymous defect. No changes of visual fields was observed in other cases. Analysis of visual field defects after surgery found no correlation with functional state of visual tract according to fractional anisotropy before and after surgery.

CONCLUSION

MR tractography of optic radiation and intraoperative monitoring of cVEP allow choosing the safest approach for resection of occipital tumor and minimizing the risk of damage to visual cortex and optic radiation fibers. In most cases, postoperative visual functions do not worsen after intraoperative mapping of visual cortex and determining the safest trajectory for resection of occipital lobe tumors. Moreover, improvement is observed in some cases.

Impact of intraoperative direct cortical stimulation dynamics on perioperative seizures and afterdischarge frequency in patients undergoing awake craniotomy

OBJECTIVE

Intraoperative stimulation is used as a crucial adjunct in neurosurgical oncology, allowing for greater extent of resection while minimizing morbidity. However, limited data exist regarding the impact of cortical stimulation on the frequency of perioperative seizures in these patients.

METHODS

A retrospective chart review of patients undergoing awake craniotomy with electrocorticography data by a single surgeon at the authors' institution between 2013 and 2020 was conducted. Eighty-three patients were identified, and electrocorticography, stimulation, and afterdischarge (AD)/seizure data were collected and analyzed. Stimulation characteristics (number, amplitude, density [stimulations per minute], composite score [amplitude × density], total and average stimulation duration, and number of positive stimulation sites) were analyzed for association with intraoperative seizures (ISs), ADs, and postoperative clinical seizures.

RESULTS

Total stimulation duration (p = 0.005), average stimulation duration (p = 0.010), and number of stimulations (p = 0.020) were found to significantly impact AD incidence. A total stimulation duration of more than 145 seconds (p = 0.04) and more than 60 total stimulations (p = 0.03) resulted in significantly higher rates of ADs. The total number of positive stimulation sites was associated with increased IS (p = 0.048). Lesions located within the insula (p = 0.027) were associated with increased incidence of ADs. Patients undergoing repeat awake craniotomy were more likely to experience IS (p = 0.013). Preoperative antiepileptic drug use, seizure history, and number of prior resections of any type showed no impact on the outcomes considered. The charge transferred to the cortex per second during mapping was significantly higher in the 10 seconds leading to AD than at any other time point examined in patients experiencing ADs, and was significantly higher than any time point in patients not experiencing ADs or ISs. Although the rate of transfer for patients experiencing ISs was highest in the 10 seconds prior to the seizure, it was not significantly different from those who did not experience an AD or IS.

CONCLUSIONS

The data suggest that intraoperative cortical stimulation is a safe and effective technique in maximizing extent of resection while minimizing neurological morbidity in patients undergoing awake craniotomies, and that surgeons may avoid ADs and ISs by minimizing duration and total number of stimulations and by decreasing the overall charge transferred to the cortex during mapping procedures.

Resection of bilateral occipital lobe lesions during a single operation as a treatment for bilateral occipital lobe epilepsy

BACKGROUND

Neurosurgical treatment of severe bilateral occipital lobe epilepsy usually involves two operations several mos apart.

AIM

To evaluate surgical resection of bilateral occipital lobe lesions during a single operation as a treatment for bilateral occipital lobe epilepsy.

METHODS

This retrospective case series included patients with drug-refractory bilateral occipital lobe epilepsy treated surgically between March 2006 and November 2015.

RESULTS

Preoperative evaluation included scalp video-electroencephalography (EEG), magnetic resonance imaging, and PET-CT. During surgery (bilateral occipital craniotomy), epileptic foci and important functional areas were identified by EEG (intracranial cortical electrodes) and cortical functional mapping, respectively. Patients were followed up for at least 5 years to evaluate treatment outcome (Engel grade) and visual function. The 20 patients (12 males) were aged 4-30 years (median age, 12 years). Time since onset was 3-20 years (median, 8 years), and episode frequency was 4-270/mo (median, 15/mo). Common manifestations were elementary visual hallucinations (65.0%), flashing lights (30.0%), blurred vision (20.0%) and visual field defects (20.0%). Most patients were free of disabling seizures (Engel grade I) postoperatively (18/20, 90.0%) and at 1 year (18/20, 90.0%), 3 years (17/20, 85.0%) and ≥ 5 years (17/20, 85.0%). No patients were classified Engel grade IV (no worthwhile improvement). After surgery, there was no change in visual function in 13/20 (65.0%), development of a new visual field defect in 3/20 (15.0%), and worsening of a preexisting defect in 4/20 (20.0%).

CONCLUSION

Resection of bilateral occipital lobe lesions during a single operation may be applicable in bilateral occipital lobe epilepsy.

Okzipitallappenepilepsie und Parietallappenepilepsie – eine Maskerade

Wir berichten über ein 7‑jähriges Mädchen mit therapierefraktärer Okzipitallappenepilepsie, welche zu Beginn als Migräne fehlinterpretiert wurde. In weiterer Folge diskutieren wir die klinische Semiologie, die Elektrophysiologie und die Bildgebung v. a. im Hinblick auf die Differenzialdiagnose zur Parietallappenepilepsie.

[Occipital gliomas. Case report and literature review]

The authors report intraoperative mapping with cortical visual evoked potentials during occipital tumor resection. This approach was valuable to reduce the risk of visual cortex and visual pathways damage and, accordingly, the likelihood of postoperative visual impairment. The peculiarity of this case is registration of clear cortical visual evoked potentials in various positions before and after tumor resection. Intraoperative monitoring was valuable to avoid damage to visual cortex and visual pathways during tumor resection. There was no postoperative visual deterioration. Moreover, we observed partial recovery of visual fields after resection of occipital malignant tumor.

Evolution of patients with surgically treated drug-resistant occipital lobe epilepsy

Background

This study was to describe the evolution of patients who underwent surgical treatment of drug- resistant occipital lobe epilepsy (OLE) at our institution.

Methods

We performed a retrospective analysis of data collected from electronic and paper clinical records of 20 patients who were diagnosed of OLE and underwent epilepsy surgery at our institution between 1998 and 2018. We also contacted patients by telephone and asked them to fill out a questionnaire about quality of life in epilepsy (QOLIE-10). Assembled data were analyzed using descriptive statistics.

Results

The age at surgery ranged between 19 and 55 years. The period encompassing epilepsy onset and the date of surgery was variable. Semiology of seizures included visual symptoms in 75% of patients. In 90% of cases subdural grids, depth electrodes or a combination of both were used to plan the surgery. The most frequent neuroimaging and histopathological finding was cortical dysplasia (55%). The postoperative follow-up period was up to 15 years. The most common score on the Engel scale was I (70%). Visual deficits increased after surgery. Median score on QOLIE-10 questionnaire was 82.5 (interquartile range: 32.5).

Conclusion

Surgical treatment of drug-resistant OLE offers hopeful results to those patients who have run out of pharmacological options and leads to postoperative deficits that are deemed expectable and occasionally acceptable.

Ictal blinking in focal seizures: Insights from SEEG recordings

PURPOSE

Ictal blinking may be observed in various forms of epilepsies. In the context of presurgical assessment of drug-resistant focal epilepsies, its semiological value is poorly understood. Our aims were to determine the prevalence and localizing value of ictal blinking.

METHODS

We reviewed our cohort of more than 300 patients explored by SEEG, searching for ictal blinking. We defined seizure onset zone (SOZ) using visual analysis complemented by a quantified method (epileptogenicity index). We analysed the features of ictal blinking and the associated signs. We tested for statistically significant associations with the underlying SOZ.

RESULTS

We found that about 8% of our patients exhibited ictal blinking, mostly bilateral. Ictal blinking was seen mostly in four types of SOZ: occipital, occipito-temporal, temporal mesial, and insulo-opercular. It was significantly over-represented in occipito-temporal and occipital SOZ. Eye blinking was fastest in insulo-opercular SOZ and slowest in temporal mesial SOZ. Nystagmus and tonic eye deviation were associated with SOZ involving the occipital lobe.

CONCLUSION

Ictal blinking is not uncommon in the population of patients with drug-resistant focal epilepsies. It is mostly associated with four types of SOZ: occipital, occipito-temporal, temporal mesial, and insulo-opercular. Some features of ictal blinking, as well as the analysis of the associated signs, allow to orient clinical hypotheses toward some specific SOZ.

Awake perimetry testing for occipital epilepsy surgery

With the patient awake during surgery, the authors used a simple technique to determine which part of a patient's brain was essential for vision. This technique allows the surgeon to remove as much as the seizure-producing brain as possible by avoiding the areas that are critical for vision.

Tonic Upward Eyeball Deviation Mimicking Non-Convulsive Occipital Lobe Status Epilepticus That Was Induced by Hydrocephalus

Several seizure-like symptoms are difficult to differentiate from epileptic convulsion, and then if they were misdiagnosed, they could be led to grave prognosis. A 41-year-old man was referred to the emergency room due to unconsciousness. Brain computed tomography (CT) revealed acute subdural hemorrhage along the left frontal lobe, and intraparenchymal hemorrhage in the left temporo-occipital lobe. After emergent decompressive craniectomy, he recovered an alert mental state but became progressively drowsy. Four days later, virtually continuous tonic upward eyeball deviation was observed. He had been taking antiepileptic drugs following an occipital lobectomy 20 years prior due to intractable epilepsy, and we assumed these upward eyeball deviations were symptoms of non-convulsive occipital lobe status epilepticus. Hence, doses and classes of antiepileptic drugs were modified, but clinical manifestations did not improve. Follow-up brain CT revealed newly developed hydrocephalus and compression of the mesencephalon. His symptoms fully resolved after a ventriculo-peritoneal shunt operation. In this case report, we describe the case of a patient exhibiting tonic upward eyeball deviation induced by hydrocephalus that was not associated with a seizure.

Seizure Outcomes in Occipital Lobe and Posterior Quadrant Epilepsy Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

Occipital lobe epilepsy (OLE) is an uncommon but debilitating focal epilepsy syndrome with seizures often refractory to medical management. While surgical resection has proven a viable treatment, previous studies examining postoperative seizure freedom rates are limited by small sample size and patient heterogeneity, thus exhibiting significant variability in their results.

OBJECTIVE

To review the medical literature on OLE so as to investigate rates and predictors of both seizure freedom and visual outcomes following surgery.

METHODS

We reviewed manuscripts exploring surgical resection for drug-resistant OLE published between January 1990 and June 2015 on PubMed. Seizure freedom rates were analyzed and potential predictors were evaluated with separate meta-analyses. Postoperative visual outcomes were also examined.

RESULTS

We identified 27 case series comprising 584 patients with greater than 1 yr of follow-up. Postoperative seizure freedom (Engel class I outcome) was observed in 65% of patients, and was significantly predicted by age less than 18 yr (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.13-2.18), focal lesion on pathological analysis (OR 2.08, 95% CI 1.58-2.89), and abnormal preoperative magnetic resonance imaging (OR 3.24, 95% 2.03-6.55). Of these patients, 175 also had visual outcomes reported with 57% demonstrating some degree of visual decline following surgery. We did not find any relationship between postoperative visual and seizure outcomes.

CONCLUSION

Surgical resection for OLE is associated with favorable outcomes with nearly two-thirds of patients achieving postoperative seizure freedom. However, patients must be counseled regarding the risk of visual decline following surgery.

Relationship between cortical resection and visual function after occipital lobe epilepsy surgery

OBJECTIVE In this study, the authors investigated long-term clinical and visual outcomes of patients after occipital lobe epilepsy (OLE) surgery and analyzed the relationship between visual cortical resection and visual function after OLE surgery. METHODS A total of 42 consecutive patients who were diagnosed with OLE and underwent occipital lobe resection between June 1995 and November 2013 were included. Clinical, radiological, and histopathological data were reviewed retrospectively. Seizure outcomes were categorized according to the Engel classification. Visual function after surgery was assessed using the National Eye Institute Visual Functioning Questionnaire 25. The relationship between the resected area of the visual cortex and visual function was demonstrated by multivariate linear regression models. RESULTS After a mean follow-up period of 102.2 months, 27 (64.3%) patients were seizure free, and 6 (14.3%) patients had an Engel Class II outcome. Nineteen (57.6%) of 33 patients had a normal visual field or quadrantanopia after surgery (normal and quadrantanopia groups). Patients in the normal and quadrantanopia groups had better vision-related quality of life than those in the hemianopsia group. The resection of lateral occipital areas 1 and 2 of the occipital lobe was significantly associated with difficulties in general vision, peripheral vision, and vision-specific roles. In addition, the resection of intraparietal sulcus 3 or 4 was significantly associated with decreased social functioning. CONCLUSIONS The authors found a favorable seizure control rate (Engel Class I or II) of 78.6%, and 57.6% of the subjects had good visual function (normal vision or quadrantanopia) after OLE surgery. Lateral occipital cortical resection had a significant effect on visual function despite preservation of the visual field.

Stereoelectroencephalography: Indication and Efficacy

Stereoelectroencephalography (SEEG) is a method for invasive study of patients with refractory epilepsy. Localization of the epileptogenic zone in SEEG relied on the hypothesis of anatomo-electro-clinical analysis limited by X-ray, analog electroencephalography (EEG), and seizure semiology in the 1950s. Modern neuroimaging studies and digital video-EEG have developed the hypothesis aiming at more precise localization of the epileptic network. Certain clinical scenarios favor SEEG over subdural EEG (SDEEG). SEEG can cover extensive areas of bilateral hemispheres with highly accurate sampling from sulcal areas and deep brain structures. A hybrid technique of SEEG and subdural strip electrode placement has been reported to overcome the SEEG limitations of poor functional mapping. Technological advances including acquisition of three-dimensional angiography and magnetic resonance image (MRI) in frameless conditions, advanced multimodal planning, and robot-assisted implantation have contributed to the accuracy and safety of electrode implantation in a simplified fashion. A recent meta-analysis of the safety of SEEG concluded the low value of the pooled prevalence for all complications. The complications of SEEG were significantly less than those of SDEEG. The removal of electrodes for SEEG was much simpler than for SDEEG and allowed sufficient time for data analysis, discussion, and consensus for both patients and physicians before the proceeding treatment. Furthermore, SEEG is applicable as a therapeutic alternative for deep-seated lesions, e.g., nodular heterotopia, in nonoperative epilepsies using SEEG-guided radiofrequency thermocoagulation. We review the SEEG method with technological advances for planning and implantation of electrodes. We highlight the indication and efficacy, advantages and disadvantages of SEEG compared with SDEEG.

Improvement of visual field defects after focal resection for occipital lobe epilepsy: case report

Improvement of visual field defects after surgical treatment for occipital lobe epilepsy is rare. Here, the authors report on a 24-year-old man with a 15-year history of refractory epilepsy that developed after he had undergone an occipital craniotomy to remove a cerebellar astrocytoma at the age of 4. His seizures started with an elementary visual aura, followed by secondary generalized tonic-clonic convulsion. Perimetry revealed left-sided incomplete hemianopia, and MRI showed an old contusion in the right occipital lobe. After evaluation with ictal video-electroencephalography, electrocorticography, and mapping of the visual cortex with subdural electrodes, the patient underwent resection of the scarred tissue, including the epileptic focus at the occipital lobe. After surgery, he became seizure free and his visual field defect improved gradually. In addition, postoperative ¹²³I-iomazenil (IMZ) SPECT showed partly normalized IMZ uptake in the visual cortex. This case is a practical example suggesting that neurological deficits attributable to the functional deficit zone can be remedied by successful focal resection.

Three-dimensional intracranial EEG monitoring in presurgical assessment of MRI-negative frontal lobe epilepsy

Magnetic resonance imaging (MRI)-negative epilepsy is associated with poor clinical outcomes prognosis. The present study was aimed to assess whether intracranial 3D interictal and ictal electroencephalography (EEG) findings, a combination of EEG at a different depth, in addition to clinical, scalp EEG, and positron emission tomography-computed tomography (PETCT) data help to predict outcome in a series of patients with MRI-negative frontal lobe epilepsy (FLE) after surgery.Patients with MRI-negative FLE who were presurgically evaluated by 3D-intracranial EEG (3D-iEEG) recording were included. Outcome predictors were compared in patients with seizure freedom (group 1) and those with recurrent seizures (group 2) at least 24 months after surgery.Forty-seven patients (15 female) were included in this study. MRI was found normal in 38 patients, whereas a focal or regional hypometabolism was observed in 33 cases. Twenty-three patients (48.9%) were seizure-free (Engel class I), and 24 patients (51.1%) continued to have seizures (12 were class II, 7 were class III, and 5 were class IV). Detailed analysis of intracranial EEG revealed widespread (>2 cm) (17.4%:75%; P = 0.01) in contrast to focal seizure onset as well as shorter latency to onset of seizure spread (5.9 ± 7.1 s; 1.4 ± 2.9 s; P = 0.016) and to ictal involvement of brain structures beyond the frontal lobe (21.8 ± 20.3 s; 4.9 ± 5.1 s; P = 0.025) in patients without seizure freedom.The results suggest that presurgical evaluation using 3D-iEEG monitoring lead to a better surgical outcome as seizure free in MRI-negative FLE patients.

Occipital and occipital "plus" epilepsies: A study of involved epileptogenic networks through SEEG quantification

Compared with temporal or frontal lobe epilepsies, the occipital lobe epilepsies (OLE) remain poorly characterized. In this study, we aimed at classifying the ictal networks involving OLE and investigated clinical features of the OLE network subtypes. We studied 194 seizures from 29 consecutive patients presenting with OLE and investigated by stereoelectroencephalography (SEEG). Epileptogenicity of occipital and extraoccipital regions was quantified according to the 'epileptogenicity index' (EI) method. We found that 79% of patients showed widespread epileptogenic zone organization, involving parietal or temporal regions in addition to the occipital lobe. Two main groups of epileptogenic zone organization within occipital lobe seizures were identified: a pure occipital group and an occipital "plus" group, the latter including two further subgroups, occipitotemporal and occipitoparietal. In 29% of patients, the epileptogenic zone was found to have a bilateral organization. The most epileptogenic structure was the fusiform gyrus (mean EI: 0.53). Surgery was proposed in 18/29 patients, leading to seizure freedom in 55% (Engel Class I). Results suggest that, in patient candidates for surgery, the majority of cases are characterized by complex organization of the EZ, corresponding to the occipital plus group.

Review of seizure outcomes after surgical resection of dysembryoplastic neuroepithelial tumors

Dysembryoplastic neuroepithelial tumors (DNETs) are rare tumors that present with seizures in the majority of cases. We report the results of a review of seizure freedom rates following resection of these benign lesions. We searched the English literature using PubMed for articles presenting seizure freedom rates for DNETs as a unique entity. Patient demographics, tumor characteristics, and operative variables were assessed across selected studies. Twenty-nine articles were included in the analysis. The mean age at surgery across studies was a median of 18 years (interquartile range 11-25 years). The mean duration of epilepsy pre-operatively was a median 7 years (interquartile range 3-11 years). Median reported gross-total resection rate across studies was 79% (interquartile range 62-92%). Authors variously chose lesionectomy or extended lesionectomy operations within and across studies. The median seizure freedom rate was 86% (interquartile range 77-93%) with only one study reporting fewer than 60% of patients seizure free. Seizure outcomes were either reported at 1 year of follow-up or at last follow-up, which occurred at a median of 4 years (interquartile range 3-7 years). The number of seizure-free patients who discontinued anti-epileptic drugs varied widely from zero to all patients. Greater extent of resection was associated with seizure freedom in four studies.

The Classical Pathways of Occipital Lobe Epileptic Propagation Revised in the Light of White Matter Dissection

The clinical evidences of variable epileptic propagation in occipital lobe epilepsy (OLE) have been demonstrated by several studies. However the exact localization of the epileptic focus sometimes represents a problem because of the rapid propagation to frontal, parietal, or temporal regions. Each white matter pathway close to the supposed initial focus can lead the propagation towards a specific direction, explaining the variable semiology of these rare epilepsy syndromes. Some new insights in occipital white matter anatomy are herein described by means of white matter dissection and compared to the classical epileptic patterns, mostly based on the central position of the primary visual cortex. The dissections showed a complex white matter architecture composed by vertical and longitudinal bundles, which are closely interconnected and segregated and are able to support specific high order functions with parallel bidirectional propagation of the electric signal. The same sublobar lesions may hyperactivate different white matter bundles reemphasizing the importance of the ictal semiology as a specific clinical demonstration of the subcortical networks recruited. Merging semiology, white matter anatomy, and electrophysiology may lead us to a better understanding of these complex syndromes and tailored therapeutic options based on individual white matter connectivity.