Neuropsychological outcome after extra-temporal epilepsy surgery

The neuropsychological results of temporal lobe epilepsy surgery are well reported in the literature. The aim of this study was to analyse the neuropsychological outcome in a consecutive series of patients with extra-temporal epilepsy.

Language lateralization correlates with verbal memory performance in children with focal epilepsy

PURPOSE: Assessment of language dominance with functional magnetic resonance imaging (fMRI) and neuropsychological evaluation is often used prior to epilepsy surgery. This study explores whether language lateralization and cognitive performance are systematically related in young patients with focal epilepsy. METHODS: Language fMRI and neuropsychological data (language, visuospatial functions, and memory) of 40 patients (7-18 years of age) with unilateral, refractory focal epilepsy in temporal and/or frontal areas of the left (n = 23) or right hemisphere (n = 17) were analyzed. fMRI data of 18 healthy controls (7-18 years) served as a normative sample. A laterality index was computed to determine the lateralization of activation in three regions of interest (frontal, parietal, and temporal). RESULTS: Atypical language lateralization was demonstrated in 12 (30%) of 40 patients. A correlation between language lateralization and verbal memory performance occurred in patients with left-sided epilepsy over all three regions of interest, with bilateral or right-sided language lateralization being correlated with better verbal memory performance (Word Pairs Recall: frontal r = -0.4, p = 0.016; parietal r = -0.4, p = 0.043; temporal r = -0.4, p = 0.041). Verbal memory performance made the largest contribution to language lateralization, whereas handedness and side of seizures did not contribute to the variance in language lateralization. DISCUSSION: This finding reflects the association between neocortical language and hippocampal memory regions in patients with left-sided epilepsy. Atypical language lateralization is advantageous for verbal memory performance, presumably a result of transfer of verbal memory function. In children with focal epilepsy, verbal memory performance provides a better idea of language lateralization than handedness and side of epilepsy and lesion.

Neuroimaging of epilepsy: lesions, networks, oscillations

While analysis and interpretation of structural epileptogenic lesion is an essential task for the neuroradiologist in clinical practice, a substantial body of epilepsy research has shown that focal lesions influence brain areas beyond the epileptogenic lesion, across ensembles of functionally and anatomically connected brain areas. In this review article, we aim to provide an overview about altered network compositions in epilepsy, as measured with current advanced neuroimaging techniques to characterize the initiation and spread of epileptic activity in the brain with multimodal noninvasive imaging techniques. We focus on resting-state functional magnetic resonance imaging (MRI) and simultaneous electroencephalography/fMRI, and oppose the findings in idiopathic generalized versus focal epilepsies. These data indicate that circumscribed epileptogenic lesions can have extended effects on many brain systems. Although epileptic seizures may involve various brain areas, seizure activity does not spread diffusely throughout the brain but propagates along specific anatomic pathways that characterize the underlying epilepsy syndrome. Such a functionally oriented approach may help to better understand a range of clinical phenomena such as the type of cognitive impairment, the development of pharmacoresistance, the propagation pathways of seizures, or the success of epilepsy surgery.

Dynamic directed interictal connectivity in left and right temporal lobe epilepsy.

OBJECTIVE There is increasing evidence that epileptic activity involves widespread brain networks rather than single sources and that these networks contribute to interictal brain dysfunction. We investigated the fast-varying behavior of epileptic networks during interictal spikes in right and left temporal lobe epilepsy (RTLE and LTLE) at a whole-brain scale using directed connectivity. METHODS In 16 patients, 8 with LTLE and 8 with RTLE, we estimated the electrical source activity in 82 cortical regions of interest (ROIs) using high-density electroencephalography (EEG), individual head models, and a distributed linear inverse solution. A multivariate, time-varying, and frequency-resolved Granger-causal modeling (weighted Partial Directed Coherence) was applied to the source signal of all ROIs. A nonparametric statistical test assessed differences between spike and baseline epochs. Connectivity results between RTLE and LTLE were compared between RTLE and LTLE and with neuropsychological impairments. RESULTS Ipsilateral anterior temporal structures were identified as key drivers for both groups, concordant with the epileptogenic zone estimated invasively. We observed an increase in outflow from the key driver already before the spike. There were also important temporal and extratemporal ipsilateral drivers in both conditions, and contralateral only in RTLE. A different network pattern between LTLE and RTLE was found: in RTLE there was a much more prominent ipsilateral to contralateral pattern than in LTLE. Half of the RTLE patients but none of the LTLE patients had neuropsychological deficits consistent with contralateral temporal lobe dysfunction, suggesting a relationship between connectivity changes and cognitive deficits. SIGNIFICANCE The different patterns of time-varying connectivity in LTLE and RTLE suggest that they are not symmetrical entities, in line with our neuropsychological results. The highest outflow region was concordant with invasive validation of the epileptogenic zone. This enhanced characterization of dynamic connectivity patterns could better explain cognitive deficits and help the management of epilepsy surgery candidates.

Hippocampal functional connectivity reflects verbal episodic memory network integrity

Using functional magnetic resonance imaging during a verbal memory task, we investigated correlations of signal fluctuations within the hippocampus and ipsilateral frontal as well as temporal areas in temporal lobe epilepsy patients. Declarative memory abilities were additionally examined before and after temporal lobe epilepsy surgery. A significant difference exists in functional connectivity between patients whose mnemonic functions deteriorated and those who remained stable or improved. Univariate analyses showed significantly higher preoperative coupling between the hippocampus and Brodmann area 22 for the group that decreased in verbal learning. We suggest greater coupling to reflect higher functional network integrity. Postoperatively reduced learning ability in patients with higher preoperative coupling underlines the importance of hippocampal interaction with cortical areas for successful memory formation.

Mapping epileptic activity: sources or networks for the clinicians?

Epileptic seizures of focal origin are classically considered to arise from a focal epileptogenic zone and then spread to other brain regions. This is a key concept for semiological electro-clinical correlations, localization of relevant structural lesions, and selection of patients for epilepsy surgery. Recent development in neuro-imaging and electro-physiology and combinations, thereof, have been validated as contributory tools for focus localization. In parallel, these techniques have revealed that widespread networks of brain regions, rather than a single epileptogenic region, are implicated in focal epileptic activity. Sophisticated multimodal imaging and analysis strategies of brain connectivity patterns have been developed to characterize the spatio-temporal relationships within these networks by combining the strength of both techniques to optimize spatial and temporal resolution with whole-brain coverage and directional connectivity. In this paper, we review the potential clinical contribution of these functional mapping techniques as well as invasive electrophysiology in human beings and animal models for characterizing network connectivity.

New-onset epilepsy: considerations for initial and follow-up MRI to detect brain tumor

Seizures are often the presenting symptoms of a cerebral tumor and may precede its diagnosis by many years. The article under evaluation searched two large English registries for patients admitted for new-onset epilepsy. The risk of subsequently being diagnosed with a malignant brain tumor was found to be 26-fold higher compared with controls, persisted over many years and was accentuated in young patients. Recently, surgical advances have led to a significant decrease in surgical morbidities, making surgery the first treatment option for gliomas, especially low-grade gliomas. This paradigm shift warrants a consequent diagnostic workup (MRI) in patients at risk for low-grade glioma - that is, patients with new-onset epilepsy. The study is discussed in the context of the ongoing debate on neuroimaging after new-onset epilepsy.

Can postictal memory predict postoperative memory in patients with temporal lobe epilepsy?

We investigated the contribution of postictal memory testing for lateralizing the epileptic focus and predicting memory outcome after surgery for temporal lobe epilepsy (TLE). Forty-five patients with TLE underwent interictal, postictal, and postoperative assessment of verbal and nonverbal memory. Surgery consisted of anterior temporal lobectomy (36), selective isolated amygdalohippocampectomy (6), or amygdalohippocampectomy coupled to lesionectomy (3). Postictal and postoperative but not interictal memory were significantly lower in left TLE than in right TLE. Nonverbal memory showed no significant difference in left TLE versus right TLE in all conditions. Postictal memory was significantly correlated with postoperative memory, but the effect disappeared when the lateralization of the focus was considered. Postictal verbal memory is a useful bedside tool that can help lateralize the epileptic focus. Larger studies are needed to further estimate its predictive value of the postoperative outcome.

Differences between RNA and DNA due to RNA editing in temporal lobe epilepsy

To investigate whether alterations in RNA editing (an enzymatic base-specific change to the RNA sequence during primary transcript formation from DNA) of neurotransmitter receptor genes and of transmembrane ion channel genes play a role in human temporal lobe epilepsy (TLE), this exploratory study analyzed 14 known cerebral editing sites in RNA extracted from the brain tissue of 41 patients who underwent surgery for mesial TLE, 23 with hippocampal sclerosis (MTLE+HS). Because intraoperatively sampled RNA cannot be obtained from healthy controls and the best feasible control is identically sampled RNA from patients with a clinically shorter history of epilepsy, the primary aim of the study was to assess the correlation between epilepsy duration and RNA editing in the homogenous group of MTLE+HS. At the functionally relevant I/V site of the voltage-gated potassium channel Kv1.1, an inverse correlation of RNA editing was found with epilepsy duration (r=-0.52, p=0.01) but not with patient age at surgery, suggesting a specific association with either the epileptic process itself or its antiepileptic medication history. No significant correlations were found between RNA editing and clinical parameters at other sites within glutamate receptor or serotonin 2C receptor gene transcripts. An "all-or-none" (≥95% or ≤5%) editing pattern at most or all sites was discovered in 2 patients. As a secondary part of the study, RNA editing was also analyzed as in the previous literature where up to now, few single editing sites were compared with differently obtained RNA from inhomogenous patient groups and autopsies, and by measuring editing changes in our mouse model. The present screening study is first to identify an editing site correlating with a clinical parameter, and to also provide an estimate of the possible effect size at other sites, which is a prerequisite for power analysis needed in planning future studies.

Comparison of voxel-based 3-D MRI analysis and subtraction ictal SPECT coregistered to MRI in focal epilepsy

While voxel-based 3-D MRI analysis methods as well as assessment of subtracted ictal versus interictal perfusion studies (SISCOM) have proven their potential in the detection of lesions in focal epilepsy, a combined approach has not yet been reported. The present study investigates if individual automated voxel-based 3-D MRI analyses combined with SISCOM studies contribute to an enhanced detection of mesiotemporal epileptogenic foci. Seven consecutive patients with refractory complex partial epilepsy were prospectively evaluated by SISCOM and voxel-based 3-D MRI analysis. The functional perfusion maps and voxel-based statistical maps were coregistered in 3-D space. In five patients with temporal lobe epilepsy (TLE), the area of ictal hyperperfusion and corresponding structural abnormalities detected by 3-D MRI analysis were identified within the same temporal lobe. In two patients, additional structural and functional abnormalities were detected beyond the mesial temporal lobe. Five patients with TLE underwent epileptic surgery with favourable postoperative outcome (Engel class Ia and Ib) after 3-5 years of follow-up, while two patients remained on conservative treatment. In summary, multimodal assessment of structural abnormalities by voxel-based analysis and SISCOM may contribute to advanced observer-independent preoperative assessment of seizure origin.

Percutaneous access of the epicardial space for mapping ventricular and supraventricular arrhythmias in patients with and without prior cardiac surgery

There is a paucity of data on the success rates of achieving percutaneous epicardial access in different groups of patients.

Early 4-Week Cardiac Rehabilitation Exercise Training in Elderly Patients After Heart Surgery

The aim of this study was to assess the effects on exercise performance of supplementing a standard cardiac rehabilitation program with additional exercise programming compared to the standard cardiac rehabilitation program alone in elderly patients after heart surgery.