Right Temporal Lobe Epilepsy Research Articles

Frontolimbic brain networks predict depressive symptoms in temporal lobe epilepsy

Psychiatric co-morbidities in epilepsy are of great concern. The current study investigated the relative contribution of structural and functional connectivity (FC) between medial temporal (MT) and prefrontal regions in predicting levels of depressive symptoms in patients with temporal lobe epilepsy (TLE). Twenty-one patients with TLE [11 left TLE (LTLE); 10 right TLE (RTLE)] and 20 controls participated. Diffusion tensor imaging was performed to obtain fractional anisotropy (FA) of the uncinate fasciculus (UF), and mean diffusivity (MD) of the amygdala (AM) and hippocampus (HC). Functional MRI was performed to obtain FC strengths between the AM and HC and prefrontal regions of interest including anterior prefrontal (APF), orbitofrontal, and inferior frontal regions. Participants self-reported depression symptoms on the Beck Depression Inventory-II. Greater depressive symptoms were associated with stronger FC of ipsilateral HC-APF, lower FA of the bilateral UF, and higher MD of the ipsilateral HC in LTLE, and with lower FA of the contralateral UF in RTLE. Regression analyses indicated that FC of the ipsilateral HC-APF was the strongest contributor to depression in LTLE, explaining 68.7% of the variance in depression scores. Both functional and microstructural measures of frontolimbic dysfunction were associated with depressive symptoms. These connectivity variables may be moderating which patients present with depression symptoms. In particular, FC MRI may provide a more sensitive measure of depression-related dysfunction, at least in patients with LTLE. Employing sensitive measures of frontolimbic network dysfunction in TLE may help provide new insight into mood disorders in epilepsy that could eventually guide treatment planning.

Increased microstructural white matter correlations in left, but not right, temporal lobe epilepsy.

Microstructural white matter tract correlations have been shown to reflect known patterns of phylogenetic development and functional specialization in healthy subjects. The aim of this study was to establish intertract correlations in a group of controls and to examine potential deviations from normality in temporal lobe epilepsy (TLE). We investigated intertract correlations in 28 healthy controls, 21 left TLE (LTLE) and 23 right TLE (RTLE). Nine tracts were investigated, comprising the parahippocampal fasciculi, the uncinate fasciculi, the arcuate fasciculi, the frontoparietal tracts, and the fornix. An abnormal increase in tract correlations was observed in LTLE, while RTLE showed intertract correlations similar to controls. In the control group, tract correlations increased with increasing fractional anisotropy (FA), while in the TLE groups tract correlations increased with decreasing FA. Cluster analyses revealed agglomeration of bilateral pairs of homologous tracts in healthy subjects, with such pairs separated in our LTLE and RTLE groups. Discriminant analyses aimed at distinguishing LTLE from RTLE, revealing that tract correlations produce higher rates of accurate group classification than FA values. Our results confirm and extend previous work by showing that LTLE compared to RTLE patients display not only more extensive losses in microstructural orientation but also more aberrant intertract correlations. Aberrant correlations may be related to pathologic processes (i.e., seizure spread) or to adaptive processes aimed at preserving key cognitive functions. Our data suggest that tract correlations may have predictive value in distinguishing LTLE from RTLE, potentially moving diffusion imaging to a place of greater prominence in clinical practice.

Alterations in functional connectivity between the hippocampus and prefrontal cortex as a correlate of depressive symptoms in temporal lobe epilepsy

Depression is a common comorbidity in temporal lobe epilepsy (TLE) that is thought to have a neurobiological basis. This study investigated the functional connectivity (FC) of medial temporal networks in depression symptomatology of TLE and the relative contribution of structural versus FC measures. Volumetric MRI and functional connectivity MRI (fcMRI) were performed on nineteen patients with TLE and 20 controls. The hippocampi and amygdalae were selected as seeds, and five prefrontal and five cingulate regions of interest (ROIs) were selected as targets. Low-frequency blood-oxygen-level-dependent signals were isolated from fcMRI data, and ROIs with synchronous signal fluctuations with the seeds were identified. Depressive symptoms were measured by the Beck Depression Inventory—II. The patients with TLE showed greater ipsilateral hippocampal atrophy (HA) and reduced FC between the ipsilateral hippocampus and the ventral posterior cingulate cortex (vPCC). Neither HA nor hippocampal–vPCC FC asymmetry was a robust contributor to depressive symptoms. Rather, hippocampal–anterior prefrontal FC was a stronger contributor to depressive symptoms in left TLE (LTLE). Conversely, right amygdala FC was correlated with depressive symptoms in both patient groups, with a positive and negative correlation in LTLE and right TLE (RTLE), respectively. Frontolimbic network dysfunction is a strong contributor to levels of depressive symptoms in TLE and a better contributor than HA in LTLE. In addition, the right amygdala may play a role in depression symptomatology regardless of the side of the epileptogenic focus. These findings may inform the treatment of depressive symptoms in TLE and inspire future research to help guide surgical planning.

Computer-Aided Diagnosis and Localization of Lateralized Temporal Lobe Epilepsy Using Interictal FDG-PET.

Interictal FDG-PET (iPET) is a core tool for localizing the epileptogenic focus, potentially before structural MRI, that does not require rare and transient epileptiform discharges or seizures on EEG. The visual interpretation of iPET is challenging and requires years of epilepsy-specific expertise. We have developed an automated computer-aided diagnostic (CAD) tool that has the potential to work both independent of and synergistically with expert analysis. Our tool operates on distributed metabolic changes across the whole brain measured by iPET to both diagnose and lateralize temporal lobe epilepsy (TLE). When diagnosing left TLE (LTLE) or right TLE (RTLE) vs. non-epileptic seizures (NES), our accuracy in reproducing the results of the gold standard long term video-EEG monitoring was 82% [95% confidence interval (CI) 69–90%] or 88% (95% CI 76–94%), respectively. The classifier that both diagnosed and lateralized the disease had overall accuracy of 76% (95% CI 66–84%), where 89% (95% CI 77–96%) of patients correctly identified with epilepsy were correctly lateralized. When identifying LTLE, our CAD tool utilized metabolic changes across the entire brain. By contrast, only temporal regions and the right frontal lobe cortex, were needed to identify RTLE accurately, a finding consistent with clinical observations and indicative of a potential pathophysiological difference between RTLE and LTLE. The goal of CADs is to complement – not replace – expert analysis. In our dataset, the accuracy of manual analysis (MA) of iPET (∼80%) was similar to CAD. The square correlation between our CAD tool and MA, however, was only 30%, indicating that our CAD tool does not recreate MA. The addition of clinical information to our CAD, however, did not substantively change performance. These results suggest that automated analysis might provide clinically valuable information to focus treatment more effectively.

A Study on Material Functional Connectivity of the Human Brain via Granger Causality

16-channel EEG data during intermittent episodes of epilepsy is recoded and analyzed to find the lesions source for temporal lobe epilepsy by Granger causality. And the analysis of EEG with the lesions of temporal lobe epilepsy and non-lesions area of relationship between cause and effects is focused on, exploring temporal lobe epilepsy with lesions in other regions of the information transduction relationship for the clinical determination of temporal lobe epileptic focus to provide a theoretical the support. There are 8 cases patients which 6 cases patients of left-temporal lobe epilepsy and 2 cases patients of right-temporal lobe epilepsy in this work, Sampling frequency fs=200Hz，time t=20s (Sampling points N=4000). Granger causality is used to direction of the information transduction between each channel of the EEG signals. Autoregressive methods of EEG analysis for multi-channel data and determination of the coefficient of the matrix A, and proportion of operations on the matrix A is applied to get the result of matrix I which can reflect the causal relationship between each channel. The result shows that Granger causality can test the location of the lesions source and the areas that the information was reached. The results are consistent with the diagnosis of the EEG and CT. Granger causality not only can analyze the causal relationship of EEG, and it can calculate the multi-channel information transduction between the directions of EEG, which can provide support in the clinic for determine the source of seizure.

Topiramate and its effect on fMRI of language in patients with right or left temporal lobe epilepsy

Topiramate (TPM) is well recognized for its negative effects oncognition, language performance and lateralization results on the intracarotid amobarbital procedure (IAP). But, the effects of TPM on functional MRI (fMRI) of language and the fMRI signals are less clear. Functional MRI is increasingly used for presurgical evaluation of epilepsy patients in place of IAP for language lateralization. Thus, the goal of this study was to assess the effects of TPM on fMRI signals. In this study, we included 8 patients with right temporal lobe epilepsy (RTLE) and 8 with left temporal lobe epilepsy (LTLE) taking TPM (+TPM). Matched to them for age, handedness and side of seizure onset were 8 patients with RTLE and 8 with LTLE not taking TPM (−TPM). Matched for age and handedness to the patients with TLE were 32 healthy controls. The fMRI paradigm involved semantic decision/tone decision task (in-scanner behavioral data were collected). All epilepsy patients received a standard neuropsychological language battery. One sample t-tests were performed within each group to assess task-specific activations. Functional MRI data random-effects analysis was performed to determine significant group activation differences and to assess the effect of TPM dose on task activation. Direct group comparisons of fMRI, language and demographic data between patients with R/L TLE +TPM vs. −TPM and the analysis of the effects of TPM on blood oxygenation level-dependent (BOLD) signal were performed. Groups were matched for age, handedness and, within the R/L TLE groups, for the age of epilepsy onset/duration and the number of AEDs/TPM dose. The in-scanner language performance of patients was worse when compared to healthy controls — all p<0.044. While all groups showed fMRI activation typical for this task, regression analyses comparing L/R TLE +TPM vs. −TPM showed significant fMRI signal differences between groups (increases in left cingulate gyrus and decreases in left superior temporal gyrus in the patients with LTLE +TPM; increases in the right BA 10 and left visual cortex and decreases in the left BA 47 in +TPM RTLE). Further, TPM dose showed positive relationship with activation in the basal ganglia and negative associations with activation in anterior cingulate and posterior visual cortex. Thus, TPM appears to have a different effect on fMRI language distribution in patients with R/L TLE and a dose-dependent effect on fMRI signals. These findings may, in part, explain the negative effects of TPM on cognition and language performance and support the notion that TPM may affect the results of language fMRI lateralization/localization.

MRI analysis in temporal lobe epilepsy: Cortical thinning and white matter disruptions are related to side of seizure onset

Past studies reported more widespread structural brain abnormalities in patients with left compared to right temporal lobe epilepsy (TLE), but the profile of these differences remains unknown. This study investigated the relationship between cortical thinning, white matter compromise, epilepsy variables, and the side of seizure onset, in patients with TLE. We performed diffusion tensor imaging tractography and cortical thickness analyses of 18 patients with left TLE (LTLE), 18 patients with right TLE (RTLE), and 36 controls. We investigated the relationship among brain structural abnormalities, side of seizure onset, age of seizure onset, and disease duration. Patients with TLE displayed cortical thinning and white matter compromise, predominately on the side ipsilateral to the seizure onset. Relative to RTLE, patients with LTLE showed more widespread abnormalities, particularly in white matter fiber tracts. Greater compromise in white matter integrity was associated with earlier age of seizure onset, whereas cortical thinning was marginally associated with disease duration. These data support previous findings of LTLE showing greater structural compromise than RTLE, and suggest that mechanisms may not be uniform for gray and white matter compromise in patients with LTLE and RTLE. These results may indicate that LTLE is different from RTLE, possibly due to greater vulnerability of the left hemisphere to early injury and the progressive effects of seizures.

Increased temporolimbic cortical folding complexity in temporal lobe epilepsy

Converging evidence suggests that abnormalities of brain development may play a role in the pathogenesis of temporal lobe epilepsy (TLE). As sulco-gyral patterns are thought to be a footprint of cortical development, we set out to quantitatively map folding complexity across the neocortex in TLE. Additionally, we tested whether there was a relationship between cortical complexity and features of hippocampal maldevelopment, commonly referred to as malrotation. To quantify folding complexity, we obtained whole-brain surface-based measures of absolute mean cortical curvature from MRI scans acquired in 43 drug-resistant patients with TLE with unilateral hippocampal atrophy, and 40 age- and sex-matched healthy controls. In patients, we correlated changes in cortical curvature with 3-dimensional measures of hippocampal positioning. We found increased folding complexity in the temporolimbic cortices encompassing parahippocampal, temporopolar, insular, and fronto-opercular regions. Increased complexity was observed ipsilateral to the seizure focus in patients with left TLE (LTLE), whereas these changes were bilateral in patients with right TLE (RTLE). In both TLE groups, increased temporolimbic complexity was associated with increased hippocampal malrotation. We found tendencies for increased complexity in bilateral posterior temporal cortices in LTLE and contralateral parahippocampal cortices in RTLE to be predictive of unfavorable seizure outcome after surgery. The anatomic distribution of increased cortical complexity overlapping with limbic seizure networks in TLE and its association with hippocampal maldevelopment further imply that neurodevelopmental factors may play a role in the epileptogenic process of TLE.

Stimulus type affects Wada memory performance

The effects of amytal injection side, seizure focus laterality, and stimulus type (real and line-drawn objects, printed words, and faces) on recognition memory were studied during the Wada procedure. To-be-remembered stimuli were presented during cerebral anesthesia to 35 patients with left temporal lobe epilepsy (LTLE) and 28 patients with right temporal lobe epilepsy (RTLE), all with left hemisphere language dominance. In both groups, recognition of real and line-drawn objects was best after anesthetization of the lesional hemisphere. Recognition of faces was poor after either injection in patients with RTLE, but only after right injection in patients with LTLE. Conversely, recognition of words by patients with LTLE was impaired equally after either injection, but more so after left than right injection in patients with RTLE. The findings suggest that (1) real and line-drawn objects are "dually encoded" and memory accuracy depends on seizure focus laterality, and (2) accuracy in recognition of words and faces is related to seizure focus laterality, but may also depend on the language dominance of the hemisphere being assessed.

Predicting epileptic seizures with a mental simulation task: A prospective study

The unpredictability of seizures is one of the most disabling aspects of epilepsy. We assessed the possibility of forecasting seizure onset by means of a behavioral task using mental simulation of biological and nonbiological movements. Four patients with epilepsy were included in a longitudinal study. In two patients with right temporal lobe epilepsy (RTLE), performance of the task changed depending on the epileptic cycle. In the preictal phase, timing precision decreased during simulation of biological movements and increased during simulation of nonbiological movements. In two other patients, the timing precision during simulation of biological movements was chronically decreased. The observed phase dependency of performance in patients with RTLE may indicate changes in brain states hours in advance of seizure onset. We suggest that our paradigm might be a simple and accurate method for the prediction of epileptic seizures. The validity of the approach for different types of epilepsy should be assessed in future studies.

Face Memory in MRI‐Positive and MRI‐Negative Temporal Lobe Epilepsy

Effects of MRI-positive (MRI(+)) as compared to MRI-negative (MRI(-)) temporal lobe epilepsy (TLE) on face memory are not yet known. We studied 24 MRI(-) (11 right/13 left) and 20 MRI(+) (13 right/7 left) TLE patients, 12 generalized epilepsy patients, and 12 healthy subjects undergoing diagnostic workup with 24-72-h Video-EEG-monitoring. Twenty faces were shown, and had to be recognized from 40 faces immediately and after a 24-h delay. MRI(+) and MRI(-) right TLE (RTLE) patients showed deficits in face recognition compared to controls or generalized epilepsy, consistent with right temporal lobe dominance for face recognition. MRI(+) RTLE patients had deficits in both immediate and delayed recognition, while MRI(-) RTLE patients showed delayed recognition deficits only. The RTLE groups showed comparable delayed recognition deficits. Separate analyses in which the MRI(+) group included patients with hippocampal sclerosis only, did not alter results. Furthermore, MRI(-) RTLE had a worse delayed recognition than MRI(-) left TLE (LTLE). On the other hand, MRI(+) RTLE did not differ from MRI(+) LTLE in delayed recognition. Combining MRI(-) and MRI(+) TLE groups, we found differences between RTLE and LTLE in delayed, but not immediate face recognition. Our results suggest that a delayed recognition condition might be superior to immediate recognition tests in detecting face memory deficits in MRI(-) RTLE patients. This might explain why former studies in preoperative patients did not observe an immediate face recognition dominance of the right temporal lobe when combining MRI(-) and MRI(+) TLE patients. Our data further point to an important role of the right mesial temporal region in face recognition in TLE.

Global/local scoring modifications for the Rey-Osterrieth Complex Figure: Relation to unilateral temporal lobe epilepsy patients

Observation of figural reproductions of right temporal lobe epilepsy (RTLE) patients have revealed overall configuration errors, whereas in left temporal lobe epilepsy (LTLE) patients, the global aspect of performance is generally preserved. This study compared performance of individuals with temporal lobe epilepsy (LTLE, n=83; RTLE, n=63) on a global/local modification of the Rey-Osterrieth Complex Figure Test (RCFT). In Phase I, neuropsychologists (n=6) and neuropsychology fellows (n=3) completed a survey identifying the global and local aspects of the RCFT. Questionnaire responses were used to categorize a list of global and local items (five global, five local) for re-scoring the protocols of TLE patients during study Phase II. Results showed that the RTLE and LTLE groups were not differentiated according to the global or local indices F(1,141) = .385; p = not significant. There were lower local scores for both groups in the copy F(1,142) = 5.23; p = .024, immediate F(1,142) = 445.26; p < .001, and delay trials F(1,142) = 427.82; p < .001, indicating less retention of local information over time. Results suggest general declines in figural memory for local stimulus properties in both unilateral TLE groups. However, this relationship was weakened after controlling for global and local item verbalizability.

Classification of epilepsy types through global network analysis of scalp electroencephalograms

Epilepsy is a dynamic disease in which self-organization and emergent structures occur dynamically at multiple levels of neuronal integration. Therefore, the transient relationship within multichannel electroencephalograms (EEGs) is crucial for understanding epileptic processes. In this paper, we show that the global relationship within multichannel EEGs provides us with more useful information in classifying two different epilepsy types than pairwise relationships such as cross correlation. To demonstrate this, we determine the global network structure within channels of the scalp EEG based on the minimum spanning tree method. The topological dissimilarity of the network structures from different types of temporal lobe epilepsy is described in the form of the divergence rate and is computed for 11 patients with left (LTLE) and right temporal lobe epilepsy (RTLE). We find that patients with LTLE and RTLE exhibit different large scale network structures, which emerge at the epoch immediately before the seizure onset, not in the preceding epochs. Our results suggest that patients with the two different epilepsy types display distinct large scale dynamical networks with characteristic epileptic network structures.

Effects of lateralisation and gender on temporal lobe ictal behaviour associated with hippocampal sclerosis

Introduction: Information derived from animal models and neuroradiological studies in humans indicates that males and females exhibit differences in the functional and anatomical organisation of the brain. This study aimed to evaluate the effect of gender in ictal behaviour considering lateralisation in a group with homogeneous pathology. Methods: Patients with hippocampal seizures who underwent temporal lobectomy and who were seizure-free during one year of follow-up were selected. Surgery was performed on the right side in 27 patients and on the left side in 21. Videotape recordings of the patients were reviewed in order to investigate ictal behaviour. There were 42 seizure episodes in 20 males and 40 in 21 females. For auras, 48 patients’ data were reviewed. Ictal behaviour was evaluated taking into consideration the lateralisation of seizures and gender differences. Results: Ictal vocalisation was significantly higher in females with right temporal lobe epilepsy (RTLE) ( P<0.05). Forced head deviation was significantly higher in males with left temporal lobe epilepsy (LTLE) ( P<0.03) and in females with RTLE ( P<0.0001). Unforced head deviation was significantly higher in males with RTLE ( P<0.002). Ipsilateral eye deviation was significantly higher in RTLE, with no differences between males and females. Postictal coughing was significantly higher in RTLE, again with no differences between males and females ( P<0.03). With regard to automatisms, posturing and nose wiping, there was no difference between right and left temporal lobe seizures or between genders. Conclusions: To the best of our knowledge, this study is the first demonstrating differences in ictal behaviour between females and males, thus showing that gender is related to different functional and anatomical organisations of the human brain.

Contralateral medial temporal lobe damage in right but not left temporal lobe epilepsy: a 1H magnetic resonance spectroscopy study

Background: Proton magnetic resonance spectroscopy (MRS) of the hippocampus is useful in lateralising the epileptic focus in temporal lobe epilepsy for subsequent surgical resection. Previous studies have reported abnormal contralateral...

Pseudoword and Real Word Memory in Unilateral Temporal Lobe Epilepsy

Recognition memory for pronounceable pseudowords (PWs), real words, and degraded photographs of unfamiliar faces, was examined in 45 patients with unilateral temporal lobe epilepsy (TLE), before and after Anterior Temporal Lobectomy, to test predictions from two accounts of hemispheric differences in memory functioning: (1) The ‘material-specific’ account predicts that left TLE (LTLE) patients would be impaired in memory for both familiar (real words) and unfamiliar (PWs) verbal stimuli, while memory for novel complex visual stimuli (unfamiliar faces) would be impaired in right TLE (RTLE) patients. (2) The ‘familiarity’ account predicts that memory for familiar stimuli (such as words) will be impaired in LTLE patients, while memory for both linguistic and nonlinguistic unfamiliar stimuli should be disrupted in RTLE patients. Results were consistent with the ‘material-specific’ hypothesis suggesting that both familiar and unfamiliar linguistic stimuli are processed for memory in the left medial temporal lobe (MTL), whereas unfamiliar nonverbal stimuli are processed for memory in the right MTL.

Assessing nonverbal memory with the Biber Figure Learning Test—Extended in temporal lobe epilepsy patients

Material-specific memory dysfunction was assessed using a nonverbal, visuospatial, supraspan learning test, the Biber Figure Learning Test-Extended (BFLT-E), in 71 left-hemisphere language-dominant epilepsy patients prior to anterior temporal lobectomy (ATL) and in 48 age-matched healthy subjects. Two matched forms of the BFLT-E yielded comparable scores, indicating that this task may be used to track memory performance over time in individual patients. Right temporal lobe epilepsy (RTLE) and left temporal lobe epilepsy (LTLE) patients performed below healthy subjects on all free-recall measures. RTLE, but not LTLE, patients also differed from healthy subjects in recognition memory discrimination. Furthermore, the RTLE patients performed below LTLE patients on measures specific to long-term memory abilities. The BFLT-E appears to be a useful clinical tool for assessing different components of visuospatial memory in patients with lateralized mesial temporal lobe (MTL) dysfunction. The test is sensitive to visuoconstructional problems associated with various types of brain damage, but it also distinguishes material-specific, nonverbal, visuospatial memory impairments in patients with neurological dysfunction in the non language-dominant right temporal lobe.

Assessing nonverbal memory with the Biber Figure Learning Test--Extended in temporal lobe epilepsy patients

Material-specific memory dysfunction was assessed using a nonverbal, visuospatial, supraspan learning test, the Biber Figure Learning Test-Extended (BFLT-E), in 71 left-hemisphere language-dominant epilepsy patients prior to anterior temporal lobectomy (ATL) and in 48 age-matched healthy subjects. Two matched forms of the BFLT-E yielded comparable scores, indicating that this task may be used to track memory performance over time in individual patients. Right temporal lobe epilepsy (RTLE) and left temporal lobe epilepsy (LTLE) patients performed below healthy subjects on all free-recall measures. RTLE, but not LTLE, patients also differed from healthy subjects in recognition memory discrimination. Furthermore, the RTLE patients performed below LTLE patients on measures specific to long-term memory abilities. The BFLT-E appears to be a useful clinical tool for assessing different components of visuospatial memory in patients with lateralized mesial temporal lobe (MTL) dysfunction. The test is sensitive to visuoconstructional problems associated with various types of brain damage, but it also distinguishes material-specific, nonverbal, visuospatial memory impairments in patients with neurological dysfunction in the non language-dominant right temporal lobe.

Interictal 99mTc-HMPAO SPECT in temporal lobe epilepsy: relation to clinical variables.

Factors affecting blood flow observed by interictal single-photon emission computed tomography (SPECT) images in temporal lobe epilepsy (TLE) have not been systematically studied or consistently demonstrated. We evaluated interictal SPECT results with respect to many clinical variables in a large population of TLE patients, all of whom underwent temporal lobectomy. Interictal 99mTc-HMPAO SPECT scans from 61 TLE patients were obtained before an anterior temporal lobectomy. SPECT was analyzed using a region of interest analysis (ROI) in the cerebellum, anterior temporal lobe, lateral temporal lobe, mesial temporal lobe, whole temporal lobe, and inferior frontal lobe. Asymmetry indices (AIs) were calculated. Correlative analysis of AIs and clinical variables was performed. The AIs from TLE patients differed significantly from those of controls in the anterior temporal (p < 0.01), lateral temporal (p < 0.001), and whole temporal (p < 0.01) regions. No consistent overall correlation between the AIs and clinical variables existed. In right TLE (RTLE) only, AIs in the lateral and whole temporal lobe were positively correlated with age of onset (r = 0.470, p < 0.05; r = 0.548, p < 0.01, respectively). Similarly, in RTLE only, duration of epilepsy was negatively correlated with the anterior (r = -0.395, p < 0.05) and mesial (r = -0.45, p < 0.05) temporal lobe AI. No correlations were found between clinical variables and AIs in left TLE (LTLE) patients. Significant correlation of age at onset and duration of epilepsy with AIs in RTLE but not LTLE suggests physiologic processes may be determined in part by laterality of TLE. Clinical applications are problematic.

Right hippocampal contribution to visual memory: a presurgical and postsurgical study in patients with temporal lobe epilepsy

OBJECTIVESExisting speculations regarding the cognitive functions of the right hippocampus suggest a special involvement in non-verbal memory functions. However, all supporting evidence in epileptic patients came from postoperative studies that...