Kristina Malmgren

Epileptic Seizures and Epilepsy: Definitions Proposed by the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE)

The International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE) have come to consensus definitions for the terms epileptic seizure and epilepsy. An epileptic seizure is a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychological, and social consequences of this condition. The definition of epilepsy requires the occurrence of at least one epileptic seizure.

Recommendation for a definition of acute symptomatic seizure.

Purpose:  To consider the definition of acute symptomatic seizures for epidemiological studies, and to refine the criteria used to distinguish these seizures from unprovoked seizures for specific etiologies.

Hippocampal sclerosis—Origins and imaging

The association between hippocampal sclerosis (HS) and epilepsy has been known for almost two centuries. For many years, HS was studied in postmortem series; however, since the mid‐20th century, surgical specimens from temporal lobe resections have provided important new knowledge. HS is the most common pathology underlying drug‐resistant mesial temporal lobe epilepsy (MTLE), a syndrome with a characteristic history and seizure semiology. In the early 1990s, it was recognized that magnetic resonance imaging (MRI) could detect HS. The standard MRI protocol for temporal lobe abnormalities uses coronal slices perpendicular to the long axis of the hippocampus. The MRI features of HS include reduced hippocampal volume, increased signal intensity on T2‐weighted imaging, and disturbed internal architecture. The histopathologic diagnosis of HS is usually straightforward, with neuronal loss and chronic fibrillary gliosis centered on the pyramidal cell layer. There are several patterns or subtypes of HS recognized from surgical series based on qualitative or quantified assessments of regional neuronal loss. The pathologic changes of HS include granule cell dispersion, mossy fiber sprouting, and alterations to interneurons. There may also be more extensive sclerosis of adjacent structures in the medial temporal lobe, including the amygdala and parahippocampal gyrus. Subtle cortical neuropathologies may accompany HS. The revised classification of dysplasias in epilepsy denotes these as focal cortical dysplasias type IIIa. Sometimes, HS occurs with a second lesion, either in the temporal lobe or extratemporal, most often ipsilateral to the HS. HS on preoperative MRI strongly predicts good seizure outcome following temporal lobe resection (TLR). If adequate MRI shows no structural correlate in patients with MTLE, functional imaging studies are valuable, especially if they are in agreement with ictal electroencephalography (EEG) findings. Focal hypometabolism on 18F‐fluorodeoxyglucose–positron emission tomography (FDG‐PET) ipsilateral to the symptomatic temporal lobe predicts a good surgical outcome; the added value of 11C‐Flumazenil‐PET (FMZ‐PET) and proton magnetic resonance spectroscopy (MRS) is less clear. Surgical methods have evolved, particularly resecting less tissue, aiming to preserve function without compromising seizure outcome. Around two thirds of patients operated for MTLE with HS obtain seizure freedom. However, the best surgical approach to optimize seizure outcome remains controversial.

Health-Related Quality of Life After Epilepsy Surgery: A Swedish Multicenter Study

Summary: Purpose: To investigate health‐related quality of life (HRQOL) in relation to seizure outcome as part of a multicenter follow‐up of epilepsy surgery in Sweden.

Vigabatrin Visual Toxicity: Evolution and Dose Dependence

Summary:  Purpose: To investigate the prevalence and prognosis of visual field defects (VFDs) in epilepsy patients with and without vigabatrin (VGB) treatment; to investigate the possible relationship between VFDs and cumulative VGB dose, and to characterise the evolution of VFDs.

Intersubject variability in the anterior extent of the optic radiation assessed by tractography.

INTRODUCTION Temporal lobe resection for epilepsy involves a risk of damaging the anterior part of the optic radiation, Meyers loop, causing a contralateral upper quadrant visual field defect. This study aims to assess the intersubject variability in the course of Meyers loop in vivo by diffusion tensor imaging and tractography. METHODS Seven healthy volunteers and two patients with previous temporal lobe resection were recruited. Diffusion tensor imaging and tractography were used to visualize the optic radiation. The distances from the anterior edge of Meyers loop to landmarks in the temporal lobe were calculated. RESULTS In the healthy subjects, the mean distance between the most anterior part of Meyers loop and the temporal pole was 44 mm (range 34-51 mm). Meyers loop did not reach the tip of the temporal horn in any subject. A disruption in Meyers loop could be demonstrated in the patient with quadrantanopia after temporal lobe resection. CONCLUSIONS Meyers loop has a considerable variability in its anterior extent. Tractography may be a useful method to visualize Meyers loop, and assess the risk of a visual field defect, prior to temporal lobe resection.

Surgical treatment of epilepsy ‐ clinical, radiological and histopathological findings in 139 children and adults

The present study relates clinical and radiological data to histopathological diagnoses in the first 139 patients (children and adults) in the Göteborg Epilepsy Surgery series. Temporal lobe resections were most common (54.0%) followed by frontal lobe (18.0%) and multilobar resections (11.5%). All histopathological specimens were re‐evaluated in connection with this study. Parenchymal malformations and atrophic‐gliotic lesions were the most common histopathological findings. Microdysgenesis was more common than major malformations (24.5% versus 11.5%). When the MRI scans were blindly re‐evaluated the MRI findings correlated with histopathological diagnosis in all of the vascular malformations, in 77.8% of the tumours, in 76.5% of the cases with hippocampal sclerosis but only in 28.6% of the major cortical development malformations. Hemispherectomies carried the best seizure outcome prognosis followed by temporal lobe resections (75.0% versus 57.3% seizure free 2 years after surgery). Vascular malformations carried the best, and microdysgenesis the worst prognosis (76.9% versus 39.4% seizure free).

Long term follow-up of the first 70 operated adults in the Göteborg Epilepsy Surgery Series with respect to seizures, psychosocial outcome and use of antiepileptic drugs

Objective: To compare long term (10 years) seizure outcome, psychosocial outcome and use of antiepileptic drugs (AED) with the 2 year follow-up in adults after resective epilepsy surgery. Methods: All adults (n = 70) who underwent resective epilepsy surgery from 1987 to 1995 in the Göteborg Epilepsy Surgery Series were included. Fifty-four had undergone temporal lobe resections and 16 extratemporal resections (12 frontal). A cross-sectional follow-up in the form of a semistructured interview was performed in late 2003. Results: Mean follow-up was 12.4 years (range 8.6–16.2). Of the 70 patients (51% males), five (7%) were dead (three as a result of non-epilepsy related causes). Of the 65 patients interviewed, 38 (58%) were seizure-free at the long term follow-up: 65% of the patients with temporal lobe resections and 36% of the patients with extratemporal resections. Of the 35 patients who were seizure-free at the 2 year follow-up, 3 (9%) had seizures at the long term follow-up. Of the 30 patients who had seizures at the 2 year follow-up, 6 (20%) were seizure-free at the long term follow-up. Of all 65 patients, 45 (69%) had the same seizure status as the 2 year follow-up. Sixteen (25%) had an improved seizure status and 4 (6%) had a worsened status. Of the seizure-free patients, 11 (29%) had ceased taking AED, 28 (74%) were working and 25 (66%) had a driving license. Conclusions: Adult patients who are seizure-free 2 years after resective epilepsy surgery are most likely to still be seizure-free 10 years later. Most are working and have obtained a driving license.

Long-term outcomes of epilepsy surgery in Sweden A national prospective and longitudinal study

Objective: To investigate prospective, population-based long-term outcomes concerning seizures and antiepileptic drug (AED) treatment after resective epilepsy surgery in Sweden. Methods: Ten- and 5-year follow-ups were performed in 2005 to 2007 for 278/327 patients after resective epilepsy surgery from 1995 to 1997 and 2000 to 2002, respectively. All patients had been prospectively followed in the Swedish National Epilepsy Surgery Register. Ninety-three patients, who were presurgically evaluated but not operated, served as controls. Results: In the long term (mean 7.6 years), 62% of operated adults and 50% of operated children were seizure-free, compared to 14% of nonoperated adults (p < 0.001) and 38% of nonoperated children (not significant). Forty-one percent of operated adults and 44% of operated children had sustained seizure freedom since surgery, compared to none of the controls (p < 0.0005). Multivariate analysis identified ≥30 seizures/month at baseline and long epilepsy duration as negative predictors and positive MRI to be a positive predictor of long-term seizure-free outcome. Ten years after surgery, 86% of seizure-free children and 43% of seizure-free adults had stopped AEDs in the surgery groups compared to none of the controls (p < 0.0005). Conclusions: This population-based, prospective study shows good long-term seizure outcomes after resective epilepsy surgery. The majority of the patients who are seizure-free after 5 and 10 years have sustained seizure freedom since surgery. Many patients who gain seizure freedom can successfully discontinue AEDs, more often children than adults. Classification of evidence: This study provides Class III evidence that more patients are seizure-free and have stopped AED treatment in the long term after resective epilepsy surgery than nonoperated epilepsy patients.

Visual field defects after temporal lobectomy – comparing methods and analysing resection size

Objectives – The frequency of visual field defects (VFD) after temporal lobe resections (TLR) was compared for two types of TLR and VFD frequency was correlated to resection size.