Association of magnetic resonance imaging identification of mesial temporal sclerosis with pathological diagnosis and surgical outcomes in children following epilepsy surgery

Comparison of Hemispheric Surgery Techniques for Pediatric Drug-Resistant Epilepsy: An Individual Patient Data Meta-analysis

BACKGROUND AND OBJECTIVES

Hemispheric surgery effectively treats unihemispheric pediatric drug-resistant epilepsy (DRE) by resecting and/or disconnecting the epileptic hemisphere. Modifications to the original anatomic hemispherectomy have generated multiple functionally equivalent, disconnective techniques for performing hemispheric surgery, termed functional hemispherotomy. While a myriad of hemispherotomy variants exist, all of them can be categorized according to the anatomic plane they are performed in, which includes vertical approaches at or near the interhemispheric fissure and lateral approaches at or near the Sylvian fissure. This meta-analysis of individual patient data (IPD) aimed to compare seizure outcomes and complications between the hemispherotomy approaches to better characterize their relative efficacy and safety in the modern neurosurgical treatment of pediatric DRE, given emerging evidence that outcomes may differ between them.

METHODS

CINAHL, Embase, PubMed, and Web of Science were searched from inception to September 9, 2020, for studies reporting IPD from pediatric patients with DRE who underwent hemispheric surgery. Outcomes of interest were seizure freedom at last follow-up, time-to-seizure recurrence, and complications including hydrocephalus, infection, and mortality. The χ2 test compared the frequency of seizure freedom and complications. Multivariable mixed-effects Cox regression controlling for predictors of seizure outcome was performed on propensity score-matched patients to compare time-to-seizure recurrence between approaches. Kaplan-Meier curves were made to visualize differences in time-to-seizure recurrence.

RESULTS

Fifty-five studies reporting on 686 unique pediatric patients treated with hemispheric surgery were included for meta-analysis. Among the hemispherotomy subgroup, vertical approaches resulted in a greater proportion of seizure free patients (81.2% vs 70.7%, p = 0.014) than lateral approaches. While there were no differences in complications, lateral hemispherotomy had higher rates of revision hemispheric surgery due to incomplete disconnection and/or recurrent seizures than vertical hemispherotomy (16.3% vs 1.2%, p < 0.001). After propensity score matching, vertical hemispherotomy approaches independently conferred longer time-to-seizure recurrence than lateral hemispherotomy approaches (hazard ratio 0.44, 95% CI 0.19-0.98).

DISCUSSION

Among functional hemispherotomy techniques, vertical hemispherotomy approaches confer more durable seizure freedom than lateral approaches without compromising safety. Future prospective studies are required to definitively determine whether vertical approaches are indeed superior and how it should influence clinical guidelines for performing hemispheric surgery.

The Clinical Utility of Inpatient Brain Magnetic Resonance Imaging in Children

The clinical applicability and yield of brain magnetic resonance imaging (MRI) in the setting of an inpatient pediatric department has not been investigated. The authors performed a retrospective chart review of nontraumatic/nonneurosurgical children who underwent brain MRI during their hospitalization in a general pediatric department over a 5-year period. Of the 331 children who underwent brain MRI, 148 (45%) had abnormal findings. High-risk headaches and focal seizures were significantly correlated with findings on brain MRI. Diagnostic and therapeutic yields were most significant in acute demyelinating events, acute cerebrovascular disorders, high-risk headaches when supported by neurologic and ophthalmologic findings, focal seizures with evidence of multifocal epileptic activity on an electroencephalogram and ophthalmic complaints when accompanied by cranial nerve palsy and optic nerve impairment. Since the contributions of a brain MRI in hospitalized children is pivotal in specific clinical situations, a judicious decision-making process should be done before its scheduling, in order to optimize clinical care.

Differential diagnosis of temporal lobe lesions with hyperintense signal on T2-weighted and FLAIR sequences: pictorial essay

Various neuropathologies produce hyperintense signals on T2-weighted or fluid-attenuated inversion recovery sequences of the temporal lobes. Recognition of the distribution pattern and associated findings may narrow the spectrum of differential diagnoses or suggest a specific disease. This pictorial essay aims to illustrate the relatively common diseases that affect the temporal lobe, such as herpes simplex encephalitis, neurosyphilis, limbic encephalitis, postictal edema, neoplasia, and multiple sclerosis, as well as those that are less common, such as myotonic dystrophy type 1, CADASIL, and CARASIL, together with the particularities of each entity.

Utility of Magnetic Resonance Imaging Brain Epilepsy Protocol in New-Onset Seizures: How is it Different in Developing Countries?

Introduction

Magnetic resonance imaging (MRI) is the current imaging tool of choice in the investigation of patients with seizures. The advent of high-resolution MRI with a dedicated seizure protocol has significantly increased the chances of identifying a cause, resulting in a positive clinical impact on the management of these patients.

Aims

The aims of this study were to evaluate the diagnostic efficacy of standard MRI, identify whether there is an increase in the diagnostic yield with the addition of dedicated seizure protocol, and compare the diagnostic yields of MRI and electroencephalogram (EEG) individually and in combination.

Subjects and Methods

This is a prospective study of 129 consecutive patients who presented with new-onset seizures over an 18-month period. The MRI scans performed on 1.5T were reviewed for their diagnostic yield and their association with abnormal electrical activity on EEG. Chi-square test of significance (P < 0.05) was used to test for the difference in proportion. The correlation between MRI brain and EEG was studied using McNemer test.

Results

MRI detected potentially epileptogenic lesions in 59 patients (47%). The frequency of epileptogenic lesions was highest in patients who had focal-onset seizures (81%). The most common lesion type was infection and inflammation (28%), with neurocysticercosis being the most common, followed by mesial temporal sclerosis, ischemia, and tumor. About 37% of epileptogenic lesions were missed by standard protocol, which were detected on a dedicated seizure protocol MRI. The diagnostic yield of EEG was 31%. Abnormal MRI and EEG were concordant in 18% of patients, with EEG being normal in 37% of patients with epileptogenic lesions.

Conclusions

MRI detects epileptogenic lesions in almost one half who presented with new-onset seizures and of these, more than third of them were detected using a "dedicated seizure protocol." While almost 50% with seizures will have a cause identified on MRI, the sensitivity can be substantially improved by utilizing a dedicated seizure protocol.

The use of hippocampal volumetric measurements to improve diagnostic accuracy in pediatric patients with mesial temporal sclerosis

OBJECTIVE Many patients with medically intractable epilepsy have mesial temporal sclerosis (MTS), which significantly affects their quality of life. The surgical excision of MTS lesions can result in marked improvement or even complete resolution of the epileptic episodes. Reliable radiological diagnosis of MTS is a clinical challenge. The purpose of this study was to evaluate the utility of volumetric mapping of the hippocampi for the identification of MTS in a case-controlled series of pediatric patients who underwent resection for medically refractory epilepsy, using pathology as a gold standard. METHODS A cohort of 57 pediatric patients who underwent resection for medically intractable epilepsy between 2005 and 2015 was evaluated. On pathological investigation, this group included 24 patients with MTS and 33 patients with non-MTS findings. Retrospective quantitative volumetric measurements of the hippocampi were acquired for 37 of these 57 patients. Two neuroradiologists with more than 10 years of experience who were blinded to the patients' MTS status performed the retrospective review of MR images. To produce the volumetric data, MR scans were parcellated and segmented using the FreeSurfer software suite. Hippocampal regions of interest were compared against an age-weighted local regression curve generated with data from the pediatric normal cohort. Standard deviations and percentiles of specific subjects were calculated. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined for the original clinical read and the expert readers. Receiver operating characteristic curves were generated for the methods of classification to compare results from the readers with the authors' results, and an optimal threshold was determined. From that threshold the sensitivity, specificity, PPV, and NPV were calculated for the volumetric analysis. RESULTS With the use of quantitative volumetry, a sensitivity of 72%, a specificity of 95%, a PPV of 93%, an NPV of 78%, and an area under the curve of 0.84 were obtained using a percentage difference of normalized hippocampal volume. The resulting specificity (95%) and PPV (93%) are superior to the original clinical read and to Reader A and Reader B's findings (range for specificity 74%-86% and for PPV 64%-71%). The sensitivity (72%) and NPV (78%) are comparable to Reader A's findings (73% and 81%, respectively) and are better than those of the original clinical read and of Reader B (sensitivity 45% and 63% and NPV 71% and 70%, respectively). CONCLUSIONS Volumetric measurement of the hippocampi outperforms expert readers in specificity and PPV, and it demonstrates comparable to superior sensitivity and NPV. Volumetric measurements can complement anatomical imaging for the identification of MTS, much like a computer-aided detection tool would. The implementation of this approach in the daily clinical workflow could significantly improve diagnostic accuracy.

Imaging of intractable paediatric epilepsy

Approximately 20% of paediatric patients with epilepsy are refractory to medical therapies. In this subgroup of patients, neuroimaging plays an important role in identifying an epileptogenic focus. Successful identification of a structural lesion results in a better outcome following epilepsy surgery. Advances in imaging technologies, methods of epileptogenic region localisation and refinement of clinical evaluation of this group of patients in epilepsy centres have helped to widen the spectrum of children who could potentially benefit from surgical treatment. In this review, we discuss ways to optimise imaging techniques, list typical imaging features of common pathologies that can cause epilepsy, and potential pitfalls to be aware of whilst reviewing imaging studies in this challenging group of patients. The importance of multidisciplinary meetings to analyse and synthesise all the non-invasive data is emphasised. Our objectives are: to describe the four phases of evaluation of children with drug-resistant localisation-related epilepsy; to describe optimal imaging techniques that can help maximise detection of epileptogenic foci; to describe a systematic approach to reviewing magnetic resonance imaging of children with intractable epilepsy; to describe the features of common epileptogenic substrates; to list potential pitfalls whilst reviewing imaging studies in these patients; and to highlight the value of multimodality and interdisciplinary approaches to the management of this group of children.

Hippocampal volumetry: Normative data in the Indian population

BACKGROUND

Mesial temporal sclerosis (MTS) is the most common cause of temporal lobe epilepsy. Quantitative analysis of the hippocampus using volumetry is commonly being used in the diagnosis of MTS and is being used as a marker in prognostication of seizure control. Although normative data for hippocampal volume (HV) is available for the western population, no such data is available for the Indian population.

AIM

The aim of the study was to establish normative data for HV for the Indian population, which can aid in the accurate diagnosis of MTS.

MATERIALS AND METHODS

Magnetic resonance imaging (MRI) scans of 200 healthy volunteers were acquired using a 3 Tesla (3T) MRI scanner. Manual segmentation and volumetry was done using Siemens Syngo software. The data was analyzed using two tailed t-test to detect associations between HV and age, gender, and education. The data so obtained was also correlated with the data available from the rest of the world.

RESULTS

A mean HV of 2.411 cm(3) (standard deviation -0.299) was found in the study, which was significantly smaller when compared to the data from the western population. The right hippocampus was larger than the left, with a mean volume of 2.424 cm(3) and 2.398 cm(3), respectively. HV was detected to be significantly higher in males. No association was found between HV and age and education.

CONCLUSION

The values obtained in this study may be adopted as a standard in the evaluation of patients with intractable epilepsy.

Seizure outcomes after temporal lobectomy in pediatric patients

Temporal lobe epilepsy (TLE) is the most common form of epilepsy in adults and is responsible for 15%-20% of epilepsy cases in children. Class I evidence strongly supports the use of temporal lobectomy for intractable TLE in adults, but fewer studies have examined seizure outcomes and predictors of seizure freedom after temporal lobectomy in pediatric patients. The authors performed a systematic review and meta-analysis of studies including 10 or more pediatric patients (age ≤ 19 years) published over the last 20 years examining seizure outcomes after temporal lobectomy for TLE. Thirty-six studies met their inclusion criteria. These 36 studies included 1318 pediatric patients with a mean age (± SEM) of 10.7 ± 0.3 years. Overall, seizure freedom (Engel Class I outcome) was achieved in 1002 cases (76%); 316 patients (24%) continued to have seizures (Engel Class II-IV outcome). All patients had at least 1 year of follow-up. Statistically significant predictors of seizure freedom after surgery included lesional epilepsy etiology (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.15), abnormal findings on preoperative MRI (OR 1.27, 95% CI 1.16-1.40), and lack of generalized seizures (OR 1.36, 95% CI 1.20-1.56). Among lesional epilepsy cases, there was a trend toward better outcome with gross-total lesionectomy than with subtotal resection. Approximately three-fourths of pediatric patients with TLE attain seizure freedom after temporal lobectomy. Favorable outcomes may be predicted by lesional epilepsy etiology, abnormal MRI, and lack of generalized seizures. Pediatric patients with medically refractory TLE should be referred to a comprehensive pediatric epilepsy center for surgical evaluation.

Long-term surgical outcomes in patients with drug-resistant temporal lobe epilepsy and no histological abnormalities

INTRODUCTION

Reports on surgical outcomes in patients with drug-resistant temporal lobe epilepsy without histological abnormalities are scarce.

METHODS

Retrospective review of data from patients with drug-resistant temporal lobe epilepsy and no histopathological alterations who underwent anterior mesial temporal lobectomy. We analysed the following variables: age, sex, age at seizure onset, age at surgery, time elapsed between diagnosis and the date of the surgery, follow-up time, and classification according to the Engel rating scale.

RESULTS

From a database of 256 temporal lobectomies, 21 were identified as meeting the inclusion criteria. The average age upon diagnosis of epilepsy was 8.3 years and average age at time of surgery was 28.6 years. The mean time elapsed between diagnosis and surgery was 20.2 years. After a mean follow-up of 6.5 years, 90.5% of the patients showed favourable outcomes (classes i and ii) and 42.9% were seizure-free (class IA). Comparative analysis of the variables revealed that average age at seizure onset was the only statistically significant difference between groups, with age at onset being lower in patients with favourable outcomes.

CONCLUSION

Although long-term surgical outcomes were favourable for a large majority of patients, the percentage of seizure-free patients is lower than in patients with lesional epilepsy and comparable to that previously reported in the literature.