Voxel based morphometry of grey matter abnormalities in patients with medically intractable temporal lobe epilepsy: effects of side of seizure onset and epilepsy duration

Regional neocortical thinning in mesial temporal lobe epilepsy

PURPOSE

To determine the nature and extent of regional cortical thinning in patients with mesial temporal lobe epilepsy (MTLE).

METHODS

High-resolution volumetric MRIs were obtained on 21 patients with MTLE and 21 controls. Mean cortical thickness was measured within regions of interest and point-by-point across the neocortex using cortical reconstruction and parcellation software.

RESULTS

Bilateral thinning was observed within frontal and lateral temporal regions in MTLE patients relative to controls. The most striking finding was bilateral cortical thinning in the precentral gyrus and immediately adjacent paracentral region and pars opercularis of the inferior frontal gyrus, extending to the orbital region. Within the temporal lobe, bilateral thinning was observed in Heschl's gyrus only. Ipsilateral only thinning was observed in the superior and middle temporal gyri, as well as in the medial orbital cortex. Greater asymmetries in cortical thickness were observed in medial temporal cortex in patients relative to controls. Individual subject analyses revealed that this asymmetry reflected significant ipsilateral thinning of medial temporal cortex in 33% of patients, whereas it reflected ipsilateral thickening in 20% of MTLEs.

DISCUSSION

Patients with MTLE show widespread, bilateral pathology in neocortical regions that is not appreciated on standard imaging. Future studies are needed that elucidate the clinical implications of neocortical thinning in MTLE.

Extrahippocampal gray matter atrophy and memory impairment in patients with medial temporal lobe epilepsy

Memory impairment observed in patients with medial temporal lobe epilepsy (MTLE) is classically attributed to hippocampal atrophy. The contribution of extrahippocampal structures in shaping memory impairment in patients with MTLE is not yet completely understood, even though atrophy in MTLE extends beyond the hippocampus. We aimed to evaluate the neuropsychological profile of patients with MTLE focusing on memory, and to investigate whether gray matter concentration (GMC) distribution within and outside the medial portion of the temporal lobes would be associated with their neuropsychological performance. We performed a voxel based morphometry study of 36 consecutive patients with MTLE and unilateral hippocampal atrophy. We observed a significant simple regression between general and verbal memory performance based on Wechsler Memory Scale-Revised and the GMC of medial temporal and extratemporal structures in patients with left MTLE. We also performed a "regions of interest analysis" of the medial temporal lobe, and we observed that the GMC of the hippocampus, entorhinal, and perirhinal cortices were consistently associated with general and verbal memory performance in patients with MTLE. We also observed that the GMC of the cingulate and orbito-frontal cortex are independently associated with verbal and general memory performances. Our results suggest that general and verbal memory impairments in patients with left MTLE are associated with atrophy of the hippocampus, the entorhinal, and the perirhinal cortex. We also suggest that atrophy and dysfunction of limbic and frontal structures such as the cingulate and the orbito-frontal cortex contribute to memory impairment in MTLE.

Tractography of the parahippocampal gyrus and material specific memory impairment in unilateral temporal lobe epilepsy

INTRODUCTION

Temporal lobe epilepsy (TLE) is associated with disrupted memory function. The structural changes underlying this memory impairment have not been demonstrated previously with tractography.

METHODS

We performed a tractography analysis of diffusion magnetic resonance imaging scans in 18 patients with unilateral TLE undergoing presurgical evaluation, and in 10 healthy controls. A seed region in the anterior parahippocampal gyrus was selected from which to trace the white matter connections of the medial temporal lobe. A correlation analysis was carried out between volume and mean fractional anisotropy (FA) of the connections, and pre-operative material specific memory performance.

RESULTS

There was no significant difference between the left and right sided connections in controls. In the left TLE patients, the connected regions ipsilateral to the epileptogenic region were found to be significantly reduced in volume and mean FA compared with the contralateral region, and left-sided connections in control subjects. Significant correlations were found in left TLE patients between left and right FA, and verbal and non-verbal memory respectively.

CONCLUSION

Tractography demonstrated the alteration of white matter pathways that may underlie impaired memory function in TLE. A detailed knowledge of the integrity of these connections may be useful in predicting memory decline in chronic temporal lobe epilepsy.

Whole-brain voxel-based morphometry of white matter in medial temporal lobe epilepsy

PURPOSE

The purpose of this study was to analyze whole-brain white matter changes in medial temporal lobe epilepsy (MTLE).

MATERIALS AND METHODS

We studied 23 patients with MTLE and 13 age- and sex-matched healthy control subjects using voxel-based morphometry (VBM) on T1-weighted 3D datasets. The seizure focus was right sided in 11 patients and left sided in 12. The data were collected on a 1.5 T MR system and analyzed by SPM 99 to generate white matter density maps.

RESULTS

Voxel-based morphometry revealed diffusively reduced white matter in MTLE prominently including bilateral frontal lobes, bilateral temporal lobes and corpus callosum. White matter reduction was also found in the bilateral cerebellar hemispheres in the left MTLE group.

CONCLUSION

VBM is a simple and automated approach that is able to identify diffuse whole-brain white matter reduction in MTLE.

Voxel-based morphometry of temporal lobe epilepsy: an introduction and review of the literature

We review the applications and results of voxel-based morphometry (VBM) studies that have reported brain changes associated with temporal lobe epilepsy (TLE). A PubMed search yielded 18 applications of VBM to study brain abnormalities in patients with TLE up to May 2007. Across studies, 26 brain regions were found to be significantly reduced in volume relative to healthy controls. There was a strong asymmetrical distribution of temporal lobe abnormalities preferentially observed ipsilateral to the seizure focus, particularly of the hippocampus (82.35% of all studies), parahippocampal gyrus (47.06%), and entorhinal (23.52%) cortex. The contralateral hippocampus was reported as abnormal in 17.65% of studies. There was a much more bilateral distribution of extratemporal lobe atrophy, preferentially affecting the thalamus (ipsilateral = 61.11%, contralateral = 50%) and parietal lobe (ipsilateral = 47.06%, contralateral = 52.94%). VBM generally reveals a distribution of brain abnormalities in patients with TLE consistent with the region-of-interest neuroimaging and postmortem literature. It is unlikely that VBM has any clinical utility given the lack of robustness for individual comparisons. However, VBM may help elucidate some unresolved important research questions such as how recurrent temporal lobe seizures affect hippocampal and extrahippocampal morphology using serial imaging acquisitions.

Distribution of regional gray matter abnormalities in a pediatric population with temporal lobe epilepsy and correlation with neuropsychological performance

OBJECTIVE

The goals of the work described here were to determine if hippocampal and extrahippocampal atrophy in children with temporal lobe epilepsy (TLE) follows a pattern similar to that in adult patients, and to assess the clinical and neuropsychological relevance of regional brain atrophy in pediatric TLE.

METHODS

Children with symptomatic TLE (n=14: 9 with mesial TLE due to hippocampal atrophy and 5 with TLE due to neocortical lesions), healthy children (n=14), and 9 adults with mesial temporal lobe epilepsy (MTLE) were compared using voxel-based morphometry (VBM) of brain magnetic resonance imaging (MRI). The children underwent a comprehensive neuropsychological battery.

RESULTS

Children with MTLE with unilateral hippocampal atrophy (n=9) exhibited a significant reduction in gray matter in the hippocampus ipsilateral to the seizure origin and significant atrophy in the ipsilateral cingulate gyrus and contralateral middle frontal lobe. Children with TLE (n=14) exhibited a significant reduction in the gray matter of the ipsilateral hippocampus and parahippocampal gyrus. There was a correlation between gray matter volume in children with TLE and scores on several neuropsychological tests. Atrophy in pediatric patients with MTLE was less extensive than that in adults, and involved the hippocampi and the frontal cortex.

CONCLUSIONS

Similar to adult MTLE, pediatric MTLE is associated with hippocampal and extrahippocampal cell loss. However, children display less intense quantifiable gray matter atrophy, which affects predominantly frontal lobe areas. There was a significant association between volume of gray matter in medial temporal and frontal regions and scores on neuropsychological tests. In childhood, TLE and the concomitant cognitive/behavior disturbances are the result of a damaged neural network.

Cognitive and magnetic resonance volumetric abnormalities in new-onset pediatric epilepsy

This paper addresses the issue of cognitive morbidity and abnormalities in quantitative MR volumetric in children with new and recent onset idiopathic epilepsy. The available literature suggests that mild diffuse cognitive problems are evident in children with new onset epilepsy in the context of intact whole brain and lobar volumetrics. Subsets of children can be identified with salient academic and volumetric abnormalities. These findings represent the baseline upon which any subsequent effects of chronic epilepsy may accrue.

Growing old with epilepsy: the neglected issue of cognitive and brain health in aging and elder persons with chronic epilepsy

The purpose of this review is to examine what is known about cognitive and brain aging in elders with chronic epilepsy. We contend that much remains to be learned about the ultimate course of cognition and brain structure in persons with chronic epilepsy and concern appears warranted. Individuals with chronic epilepsy are exposed to many risk factors demonstrated to be associated with abnormal cognitive and brain aging in the general population, with many of these risk factors present in persons with chronic epilepsy as early as midlife. We suggest that a research agenda be developed to systematically identify and treat known modifiable risk factors in order to protect and promote cognitive and brain health in aging and elder persons with chronic epilepsy.

Composite voxel-based analysis of volume and T2 relaxometry in temporal lobe epilepsy

Voxel-based analyses of tissue characteristics such as volume and T2 are usually carried out in isolation. However, as the images are analysed in a common voxel-based framework, it is possible to directly assess the spatial relationships of abnormalities detected by each technique. We utilize this approach in well-characterized patients with unilateral temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS). TLE is associated with potentially widespread volume and T2 signal abnormalities in MRI images but the relationship between these two aspects of tissue abnormality is not well understood. Here we use a novel approach of combined univariate and multivariate voxel-wise analysis to investigate the spatial relationship of these abnormalities. We studied 19 TLE patients and compared them to 115 control subjects. Grey matter (GM) and white matter (WM) volume changes were assessed with voxel-based morphometry (VBM), and changes in T2 relaxation times were evaluated with voxel-based relaxometry (VBR). The volume and T2 changes obtained using the combined univariate approach were found in an extensive area, prominently in the ipsilateral hippocampus and amygdala (overlap of GM-VBM and VBR), and in the remaining temporal lobe (overlap of WM-VBR and VBR). Other cortical and subcortical areas showed isolated volume or T2 changes. The multivariate analysis based on the Hotelling T(2) statistic, indicated a similar pattern of distributed changes across the brain but with a greater degree of statistical significance in certain areas. The composite analyses appear to identify a network of affected areas not as easily appreciated by the individual analysis of volume or T2 changes.

Sulcal variability, stereological measurement and asymmetry of Broca's area on MR images

Leftward volume asymmetry of the pars opercularis and pars triangularis may exist in the human brain, frequently referred to as Broca's area, given the functional asymmetries observed in this region with regard to language expression. However, post-mortem and magnetic resonance imaging (MRI) studies have failed to consistently identify such a volumetric asymmetry. In the present study, an analysis of the asymmetry of sulco-gyral anatomy and volume of this anterior speech region was performed in combination with an analysis of the morphology and volume asymmetry of the planum temporale, located within the posterior speech region, in 50 healthy subjects using MRI. Variations in sulcal anatomy were documented according to strict classification schemes and volume estimation of the grey matter within the brain structures was performed using the Cavalieri method of stereology. Results indicated great variation in the morphology of and connectivity between the inferior frontal, inferior precentral and diagonal sulci. There were significant inter-hemispheric differences in the presence of (1) the diagonal sulcus within the pars opercularis, and (2) horizontal termination of the posterior Sylvian fissure (relative to upward oblique termination), both with an increased leftward incidence. Double parallel inferior precentral sulci and absent anterior rami of the Sylvian fissure prevented stereological measurements in five subjects. Therefore volumes were obtained from 45 subjects. There was a significant leftward volume asymmetry of the pars opercularis (P = 0.02), which was significantly related to the asymmetrical presence of the diagonal sulcus (P < 0.01). Group-wise pars opercularis volume asymmetry did not exist when a diagonal sulcus was present in both or neither hemispheres. There was no significant volume asymmetry of the pars triangularis. There was a significant leftward volume asymmetry of the planum temporale (P < 0.001), which was significantly associated with the shape of the posterior Sylvian fissure as a unilateral right or left upward oblique termination was always associated with leftward or rightward volume asymmetry respectively (P < 0.01). There was no relationship between volume asymmetries of the anterior and posterior speech regions. Our findings illustrate the extent of morphological variability of the anterior speech region and demonstrate the difficulties encountered when determining volumetric asymmetries of the inferior frontal gyrus, particularly when sulci are discontinuous, absent or bifid. When the intrasulcal grey matter of this region is exhaustively sampled according to strict anatomical landmarks, the volume of the pars opercularis is leftward asymmetrical. This manuscript illustrates the importance of simultaneous consideration of brain morphology and morphometry in studies of cerebral asymmetry.

Cerebral cortical gyrification: a preliminary investigation in temporal lobe epilepsy

PURPOSE

To introduce a measure of global cortical folding in epilepsy by using stereology. Subtle developmental abnormalities associated with temporal lobe epilepsy may encompass brain morphologic changes such as an aberrant degree of cortical folding.

METHODS

Stereologic methods of volume and surface-area estimation were applied to in vivo MR brain-image data of a cohort of 20 temporal lobe epilepsy (TLE) patients (10 men, 10 women), and 20 neurologically normal controls (10 men, 10 women). Indices of cerebral gyrification and cerebral atrophy were generated. The impact of side of seizure onset, age at onset, history of febrile seizures, presence or absence of lesions, and presence or absence of secondarily generalized seizures on cerebral gyrification was assessed.

RESULTS

Although no significant group mean difference was found in the degree of cerebral gyrification between patients and controls, five of 10 of male patients had an abnormal gyrification when compared with male controls. One female patient had a significant change in gyrification compared with female controls. In general, patients with TLE demonstrated a significant degree of global cerebral atrophy compared with controls. Clinical factors were not demonstrated to affect significantly any of the quantitative parameters.

CONCLUSIONS

The results of this study suggest that an aberrant degree of global cerebral gyrification may occur in certain clinical groups of TLE patients. These findings have implications for general theories of developmental susceptibility in TLE.

Evaluation of quantitative magnetic resonance imaging contrasts in MRI-negative refractory focal epilepsy

PURPOSE

Conventional optimal MRI is unremarkable in 20%-30% of patients with intractable focal epilepsy. These MRI-negative patients are the most challenging in surgical programs. Our aim was to evaluate the yield and utility of quantitative MRI with novel contrasts in MRI-negative patients with refractory focal epilepsy, who were potential surgical candidates.

METHODS

Ninety-three consecutive potential surgical candidates with refractory focal epilepsy, 44 with temporal lobe epilepsy, and 49 with frontal lobe epilepsy as determined with ictal scalp video-EEG; and normal optimal conventional MRI, including hippocampal volumes and T2 measures were investigated with quantitative MRI contrasts. The contrasts comprised fast fluid attenuated inversion recovery based T2 measurement (FFT2), double inversion recovery (DIR), magnetization transfer ratio (MTR), and voxel-based morphometry of gray matter (VBM). Voxel-based analyses of whole brain data were used to compare each patient with a control group.

RESULTS

In patients with a putative single focus on scalp video-EEG telemetry, 16% had concordant FFT2 abnormalities, as did 16% with DIR, 5% with MTR and 9% with VBM. The greatest agreement in the localization of abnormalities was between FFT2 and DIR. Altogether, 31% patients had a focal abnormality with at least one contrast in the lobe of seizure onset. Signal changes outside the lobe of the putative focus were found with FFT2 in 36% patients, with DIR in 42%, with MTR in 6% and with VBM in 7%.

DISCUSSION

Quantitative analysis of MRI contrasts had a low yield of identifying focal abnormalities concordant with putative epileptic foci in patients with unremarkable conventional MRI. Specificity was low for FFT2 and DIR. With the low specificity, data must be interpreted with caution, but in some patients may assist in creating a hypothesis for testing with intracranial electrodes.

Frontal and temporal volumes in children with epilepsy

This study examined if children with cryptogenic epilepsy and complex partial seizures (CPS) have smaller total brain, frontal, and temporal lobe volumes than normal children and how this is related to seizure, cognitive, psychiatric, and demographic variables. Forty-four children with CPS and 38 normal children, aged 5-16 years, underwent brain MRI scans at 1.5 T. Tissue was segmented, and total brain, frontal lobe, frontal parcellation, and temporal lobe volumes were computed. Other than significantly larger temporal lobe white matter volumes in the CPS group, there were no significant differences in brain volumes between the CPS and normal groups. Earlier onset, longer duration of illness, younger chronological age, and presence of a psychiatric diagnosis were significantly related to smaller frontotemporal volumes in subjects with CPS. Although these findings suggest that CPS might affect development of the temporal and frontal regions, we are unable to rule out the possibility that smaller frontotemporal volumes might predispose children to CPS. These findings highlight the need to control for seizure, cognitive, psychiatric, and demographic variables in studies of frontotemporal volumes in pediatric CPS.

VBM lesion detection depends on the normalization template: a study using simulated atrophy

Structural neuroimaging studies are of great interest for neuroscientists, which are reflected in the rising number of papers using voxel-based morphometry (VBM). One major step in VBM is the transformation of images to a standard template, a spatial normalization necessary to ensure that homologous regions are compared while interindividual characteristics are maintained. Templates can be created in different ways, and this may affect the likelihood that differences in gray/white matter density between groups are detected. However, studies investigating the interaction of normalization template and VBM accuracy are sparse. Existing work is based on patient-control group comparisons, and the emerging results are inconclusive. The present paper therefore used simulated atrophy in a simplified one-lesion model to systematically study template effects of VBM analyses implemented in SPM. This allowed us to characterize template-specific biases in reference to a set of prespecified parameters of anatomical difference. The data suggest that the likelihood of correctly detecting the prespecified lesion is modulated by the normalization template. Thereby, the relationship between template-related VBM accuracy and specific group/study characteristics is complex, and there does not appear to be one 'best template.' Our data show that template effects are critical and clearly suggest that the choice of template needs careful consideration in relation to the specific research question and study constraints.

Persistent seizures following left temporal lobe surgery are associated with posterior and bilateral structural and functional brain abnormalities

PURPOSE

To perform a quantitative MRI and retrospective electrophysiological study to investigate whether persistent post-surgical seizures may be due to brain structural and functional abnormalities in temporal lobe cortex beyond the margins of resection and/or bilateral abnormalities in patients with temporal lobe epilepsy (TLE).

METHODS

In 22 patients with left TLE and histopathological evidence of hippocampal sclerosis, we compared pre-surgical brain morphology between patients surgically remedied (Engel's I) and patients with persistent post-surgical seizures (PPS, Engel's II-IV) using voxel-based morphometry (VBM). Routine pre-surgical EEG and invasive and non-invasive telemetry investigations were additionally compared between patient groups.

RESULTS

Results indicated widespread structural and functional abnormalities in patients with PPS relative to surgically remedied patients. In particular, patients with PPS had significantly reduced volume of the ipsilateral posterior medial temporal lobe and contralateral medial temporal lobe relative to surgically remedied patients. Furthermore, successful surgery was associated with clear anterior (89%) and unilateral (100%) temporal lobe EEG abnormalities, whilst PPS were associated with widespread ipsilateral (91%) and bilateral (82%) temporal lobe abnormalities.

DISCUSSION

We suggest that these preliminary data support the hypothesis that PPS after temporal lobe surgery are due to functionally connected epileptogenic cortex remaining in the ipsilateral posterior temporal lobe and/or in temporal lobe contralateral to resection.

Asymmetrical extra-hippocampal grey matter loss related to hippocampal atrophy in patients with medial temporal lobe epilepsy

BACKGROUND

Structural neuroimaging studies have consistently shown a pattern of extra-hippocampal atrophy in patients with left and right drug-refractory medial temporal lobe epilepsy (MTLE). However, it is not yet completely understood how extra-hippocampal atrophy is related to hippocampal atrophy. Moreover, patients with left MTLE often exhibit more intense cognitive impairment, and subtle brain asymmetries have been reported in patients with left MTLE versus right MTLE but have not been explored in a controlled study.

OBJECTIVES

To investigate the association between extra-hippocampal and hippocampal atrophy in patients with MTLE, and the effect of side of hippocampal atrophy on extra-hippocampal atrophy.

METHODS

Voxel-based morphometry analyses of magnetic resonance images of the brain were performed to determine the correlation between regional extra-hippocampal grey matter volume and hippocampal grey matter volume. The results from 36 patients with right and left MTLE were compared, and results from the two groups were compared with those from 49 healthy controls.

RESULTS

Compared with controls, patients with MTLE showed a more intense correlation between hippocampal grey matter volume and regional grey matter volume in locations such as the contralateral hippocampus, bilateral parahippocampal gyri and frontal and parietal areas. Compared with right MTLE, patients with left MTLE exhibited a wider area of atrophy related to hippocampal grey matter loss, encompassing both the contralateral and ipsilateral hemispheres, particularly affecting the contralateral hippocampus.

CONCLUSIONS

Our results suggest that left hippocampal atrophy is associated with a larger degree of extra-hippocampal atrophy. This may help to explain the more intense cognitive impairment usually observed in these patients.

The seizure outcome after amygdalohippocampectomy and temporal lobectomy

The aim of this study was to compare the seizure outcome of two different types of epilepsy surgery, selective amygdalohippocampectomy (AHE) and anterior temporal lobectomy (ATLE) in patients with temporal lobe epilepsy. We included 114 patients who had mesio-temporal lobe epilepsy and hippocampal sclerosis or gliosis on histology. Patients had ATLE if the non-dominant hemisphere was affected or if the whole temporal lobe was atrophic. Patients had AHE if the dominant hemisphere was affected. Standardized seizure outcome at 1 year following surgery was used. Overall 40% of the 114 patients who had temporal lobe epilepsy surgery were seizure-free at 1-year (Engel's class Ia). A good outcome (Engel's classes I and II) was significantly more frequent in ATLE than in AHE. (66% and 44%, respectively, P = 0.03). ATLE had a better seizure outcome than AHE.

Reduced Neocortical Thickness and Complexity Mapped in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis

We mapped the profile of neocortical thickness and complexity in patients with mesial temporal lobe epilepsy (MTLE) and hippocampal sclerosis. Thirty preoperative high-resolution magnetic resonance imaging scans were acquired from 15 right (mean age: 31.9 +/- 9.7 standard deviation [SD] years) and 15 left (mean age: 30.8 +/- 8.4 SD years) MTLE patients who were seizure-free for 2 years after anteriomesial temporal resection. Nineteen healthy controls were also scanned (mean age: 24.8 +/- 3.9 SD years). A cortical pattern matching technique mapped thickness across the entire neocortex. Mesial temporal structures were not included in this analysis. Cortical models were remeshed in frequency space to compute their fractal dimension (surface complexity). Both MTLE groups showed up to 30% bilateral decrease in cortical thickness, in the frontal poles, frontal operculum, orbitofrontal, lateral temporal, and occipital regions. In both groups, cortical complexity was decreased in multiple lobar regions. Significant linkages were found relating longer duration of epilepsy to greater cortical thickness reduction in the superior frontal and parahippocampal gyrus ipsilateral to the side of seizure onset. The pervasive extrahippocampal structural deficits may result from chronic seizure propagation or may reflect other causes such as initial precipitating factors leading to MTLE.

Neural correlates of verbal semantic memory in patients with temporal lobe epilepsy

Functional imaging data suggest that the core network engaged in verbal semantic memory (SM) processing encompasses frontal and temporal lobe structures, with a strong left lateralization in normal right handers. The impact of long term temporal lobe epilepsy (TLE) on this network has only partly been elucidated. We studied verbal SM in 50 patients with chronic, intractable TLE (left TLE=26, right TLE=24) and 35 right handed normal controls using a verbal fMRI semantic decision paradigm. All patients had language lateralized to the left hemisphere, as verified by the intracarotid amobarbital procedure. Within and between group analyses showed remarkable, group-specific activation profiles. The control group activated frontal and temporal areas bilaterally, with a strong left predominance. Left TLE patients showed a shift of activations of left frontal and medial temporal areas to homologous regions in the right hemisphere. Furthermore, left TLE subjects utilized subcortical structures such as the thalamus and putamen to accomplish the verbal SM task. Contrastively, the activation pattern of right TLE patients resembled that of normal controls, but exhibited "hypofrontality" with a shift from frontal to posterior regions in the temporal, parietal and occipital lobe. Our results show that chronic epileptic activity originating from temporal seizure foci is associated with an alteration of neural circuits which support semantic language processing and that side of seizure focus has a specific impact on the resulting activation network. These findings presumably result from morphological changes and from functional reorganization which are both inherent to chronic TLE.

Gray matter atrophy associated with duration of temporal lobe epilepsy

Hippocampal sclerosis is the most common abnormality associated with medial temporal lobe epilepsy (MTLE). Converging evidence supports that hippocampal sclerosis progresses with time. However, it is unclear whether extrahippocampal atrophy in patients with MTLE, similarly to hippocampal sclerosis, is an unremitting progressive process. In this article, we investigate the relationship between duration of epilepsy and gray matter concentration reduction in patients with MTLE within and outside the hippocampus. We employed a voxel-based morphometry study of MRI of the entire brain of 36 patients with drug refractory MTLE and 49 neurologically healthy age-matched controls. We performed a voxel-based parametric and nonparametric investigation of the association between gray matter concentration, age and duration of epilepsy. We complemented the investigation by extracting the gray matter concentration of regions of interest (ROIs) within the limbic system, and we investigated the association between the gray matter concentration on the ROIs and duration of epilepsy. Patients with MTLE exhibited gray matter concentration reduction that is negatively correlated with the duration of epilepsy within the ipsilateral hippocampus, temporal lobes as well as extratemporal limbic structures that are closely connected with the hippocampus. In conclusion, longer duration of refractory epilepsy was associated with a more intense hippocampal and extrahippocampal atrophy in patients with MTLE. The mechanism of progressive neuronal damage in MTLE may be related to active seizure activity within a limbic network, and early seizure control may prevent further brain atrophy in patients with refractory MTLE.

Hippocampal volume in childhood complex partial seizures

PURPOSE

This study compared hippocampal volume in children with cryptogenic epilepsy, all of whom had complex partial seizures (CPS), and age and gender matched normal children controlling for between group differences in IQ and demographic variables (e.g., age, gender, ethnicity, socioeconomic status). It also examined the relationship between hippocampal volumes and seizure variables in the patients.

METHODS

Using quantitative magnetic resonance imaging (MRI), we compared the hippocampal volumes of 19 medically treated children with CPS, aged 6-14 years, to 21 age and gender matched normal children.

RESULTS

The children with CPS had significantly smaller total hippocampal volumes than the normal children. This finding was accounted for primarily by significantly smaller anterior hippocampal volumes. Within the CPS group, smaller total and posterior hippocampus volumes were significantly associated with longer duration of illness. Anterior hippocampal volumes, however, were unrelated to seizure variables.

CONCLUSIONS

These findings imply impaired development of the hippocampus, particularly the anterior hippocampus, and a differential effect of the underlying illness and on-going seizures on hippocampal development in medically controlled pediatric CPS.

Voxel-based optimized morphometry (VBM) of gray and white matter in temporal lobe epilepsy (TLE) with and without mesial temporal sclerosis

PURPOSE

In temporal lobe epilepsy (TLE) with evidence of hippocampal sclerosis (TLE-MTS) volumetric gray (GM) and white (WM) matter abnormalities are not restricted to the hippocampus but also are found in extrahippocampal structures. Less is known about extrahippocampal volumetric abnormalities in TLE without hippocampal sclerosis (TLE-no). In this study, we used optimized voxel-based morphometry (VBM) with and without modulation with the following aims: (a) to identify WM and GM abnormalities beyond the hippocampus in TLE-MTS and TLE-no; and (b) to determine whether extratemporal WM and GM abnormalities differ between TLE-MTS and TLE-no.

METHODS

Optimized VBM of GM and WM with and without modulation was performed in 26 TLE-MTS (mean age, 35.6 +/- 9.7 years), 17 TLE-no (mean age, 35.6 +/- 11.1 years), and 30 healthy controls (mean age, 30.3 +/- 11.1 years).

RESULTS

In TLE-MTS, GM/WM volume and concentration reductions were found in the ipsilateral limbic system, ipsi- and contralateral neocortical regions, thalamus, cerebellum, internal capsule, and brainstem when compared with controls. In contrast, no differences of GM/WM volumes/concentrations were found between TLE-no and controls or between TLE-no and TLE-MTS.

CONCLUSIONS

In TLE-MTS, optimized VBM showed extensive GM and WM volume reductions in the ipsilateral hippocampus and in ipsi- and contralateral extrahippocampal regions. In contrast, no GM/WM volume or concentration reductions were found in TLE-no. This further supports the hypothesis that TLE-no is a distinct clinicopathologic entity from TLE-MTS and probably heterogeneous in itself.

Degree of hippocampal atrophy is related to side of seizure onset in temporal lobe epilepsy

BACKGROUND AND PURPOSE

Temporal lobe epilepsy (TLE) is associated with pathologic changes in hippocampal physiology and morphology. Our aim was to quantify volume reduction of the right and left hippocampus in patients with TLE and to investigate whether the degree of hippocampal atrophy is related to the side of seizure onset.

METHODS

The volume of the right and left hippocampus was estimated for 50 controls and 101 patients with TLE, by applying the unbiased Cavalieri method on MR images.

RESULTS

Pairwise comparisons, within a multivariate analysis of variance and adjusted by using the Bonferroni correction, revealed that both right and left hippocampal volumes were, on average, significantly smaller in patients with right-sided seizure onset (R-patients) relative to those of controls (P < .001 and P = .04, respectively). Furthermore, left hippocampal volume was significantly smaller in patients with left-sided seizure onset (L-patients) compared with controls (P < .001), but the right-sided hippocampal volume was not significantly smaller (P = .71). Moreover, a correlation analysis revealed that the strong linear association between the right and left hippocampal volumes existing in the control population (r = 0.73) is partially lost in patients with TLE (r < or = 0.48), and this loss in correlation appears to be more pronounced in L-patients than in R-patients.

CONCLUSION

Our MR imaging results suggest that although the major damage in patients with TLE is located in the hippocampus ipsilateral to the side of seizure onset, R-patients are more likely to have bilateral hippocampal volume reduction. These findings support the hypothesis that cerebral hemispheres may not only differ in their functionality organization but also in their vulnerability to a neurologic insult.

Quantitative MRI biomarkers of cognitive morbidity in temporal lobe epilepsy

PURPOSE

To determine the relation between neuropsychological morbidity, quantitative magnetic resonance imaging (MRI) measures of whole brain structure, and clinical seizure factors reflecting epilepsy cause, course, and treatment.

METHODS

Quantitative MRI measurements of total (whole brain) cerebrospinal fluid (CSF) and gray- and white-matter volumes and clinical seizure features were examined in relation to summary indices of cognitive morbidity in 96 patients with temporal lobe epilepsy. MRI volumes were adjusted for intracranial volume (ICV), and cognitive scores were adjusted for age, education, and gender, based on a sample of 82 healthy controls.

RESULTS

Whole-brain volumes (gray, white, and CSF) were abnormal in chronic temporal lobe epilepsy patients compared with controls and were related significantly to neuropsychological morbidity, especially total CSF. Statistical modeling demonstrated that markers of total atrophy (CSF) was the primary mediator of the relation between clinical seizure variables and neuropsychological morbidity.

CONCLUSIONS

Quantitative measurements of overall brain abnormality (atrophy) in temporal lobe epilepsy are clinically meaningful markers that are associated with increased cognitive morbidity. These biomarkers appear to mediate the adverse effects of some clinical seizure variables on cognition.

Hippocampal Sclerosis in Children with Lesional Epilepsy Is Influenced by Age at Seizure Onset

PURPOSE

Hippocampal sclerosis (HS) is the most common lesion underlying drug-resistant temporal lobe epilepsy. Whether HS is a developmental or acquired pathology remains unclear. Whereas HS has been causally linked to prolonged febrile convulsions in childhood, evidence also exists that it may coexist with extrahippocampal abnormalities, the concept of "dual pathology." The aims of this study were to address whether hippocampal abnormality consistent with HS (a) occurs in children with lesional extrahippocampal epilepsy, (b) is more commonly seen in association with developmental rather than acquired extrahippocampal pathologies, and (c) whether any effect of age at seizure onset is found on the occurrence of HS in lesional extrahippocampal epilepsy.

METHODS

Clinical and histopathologic data of patients having resective surgery for extrahippocampal epilepsy that included the hippocampus were investigated.

RESULTS

Twenty-nine children were retrospectively included in this study, and 21 (72%) of 29 were found to have a hippocampal abnormality consistent with HS. No relation was noted between developmental or acquired extrahippocampal pathologies and the presence of hippocampal abnormality. Children with normal hippocampi on visual histologic assessment had a significantly younger age at seizure onset (p < 0.001). Duration of epilepsy was not correlated with the presence of hippocampal abnormality.

CONCLUSIONS

Hippocampal abnormalities are seen in similar proportions with both acquired and developmental extra-hippocampal pathologies, suggesting that these abnormalities are the result of seizures from the focus that is remote from the hippocampus. In addition, children who have their initial seizure at an early age are less likely to develop seizure-induced hippocampal injury.

Distinct right frontal lobe activation in language processing following left hemisphere injury

Right hemisphere activation during functional imaging studies of language has frequently been reported following left hemisphere injury. Few studies have anatomically characterized the specific right hemisphere structures engaged. We used functional MRI (fMRI) with verbal fluency tasks in 12 right-handed patients with left temporal lobe epilepsy (LTLE) and 12 right-handed healthy controls to localize language-related activity in the right inferior frontal gyrus (RIFG). During the phonemic task, LTLE patients activated a significantly more posterior region of the right anterior insula/frontal operculum than healthy controls (P = 0.02). Activation of the left inferior frontal gyrus (LIFG) did not differ significantly between the two groups. This suggests that, following left hemisphere injury, language-related processing in the right hemisphere differs from that with a functionally normal left hemisphere. The localization of activation in the left and right inferior frontal gyri was determined with respect to the anatomical sub-regions pars opercularis (Pop), pars triangularis (Ptr) and pars orbitalis (Por). In the LIFG, both healthy controls (8 out of 12) and LTLE patients (9 out of 12) engaged primarily Pop during phonemic fluency. Activations in the RIFG, however, were located mostly in the anterior insula/frontal operculum in both healthy controls (8 out of 12) and LTLE patients (8 out of 12), albeit in distinct regions. Mapping the locations of peak voxels in relation to previously obtained cytoarchitectonic maps of Broca's area confirmed lack of homology between activation regions in the left and right IFG. Verbal fluency-related activation in the RIFG was not anatomically homologous to LIFG activation in either patients or controls. To test more directly whether RIFG activation shifts in a potentially adaptive manner after left hemisphere injury, fMRI studies were performed in a patient prior to and following anatomical left hemispherectomy for the treatment of Rasmussen's encephalitis. An increase in activation magnitude and posterior shift in location were found in the RIFG after hemispherectomy for both phonemic and semantic tasks. Together, these results suggest that left temporal lobe injury is associated with potentially adaptive changes in right inferior frontal lobe functions in processing related to expressive language.

Extra-hippocampal grey matter density abnormalities in paediatric mesial temporal sclerosis

The aim of this study was to identify grey matter density abnormalities in children with temporal lobe epilepsy and mesial temporal sclerosis. Magnetic resonance T1 weighted 3D datasets were obtained in children with temporal lobe epilepsy (20 left and 10 right sided, mean age 11.9 years, range 6.6-17.5) and compared to scans obtained from age-matched controls (n = 22, mean age 12.8 years, range 7.1-17.5) using voxel-based morphometry. This method detected reduced grey matter ipsilateral to the seizure focus not only in the hippocampus, but also in the lateral temporal lobe and in extra-temporal regions including the thalamus, posterior cingulate cortex and cerebellum. Bilateral differences were present in the frontal and parietal opercular cortices and lateral temporal regions. These grey matter density reductions broadly reflect the pattern of hippocampal connections and may be caused by the disruption of cortical development by the recurrent seizures, as well as by loss of functional input from the sclerotic hippocampus.

Stereological analysis of forebrain regions in kainate-treated epileptic rats

Patients and models of temporal lobe epilepsy display neuron loss in the hippocampal formation, but neuropathological changes also occur in other forebrain regions. We sought to evaluate the specificity and extent of volume loss of the major forebrain regions in epileptic rats months after kainate-induced status epilepticus. In systematic series of Nissl-stained sections, the areas of major forebrain regions were measured, and volumes were estimated using the Cavalieri principle. In some regions, the optical fractionator method was used to estimate neuron numbers. Most kainate-treated rats showed significant volume loss in the amygdala, olfactory cortex, and septal region, but others displayed different patterns, with significant loss only in the hippocampus or thalamus, for example. Average volume loss was most severe in the amygdala and olfactory cortex (82-83% of controls), especially the caudal parts of both regions. In the piriform cortex (including the endopiriform nucleus) of epileptic rats, an average of approximately one-third of Nissl-stained neurons and one-third of the GABAergic interneurons labeled by in situ hybridization for GAD67 mRNA were lost, and the extent of neuron loss was correlated with the extent of volume loss. Volumetric analysis of major forebrain regions was insensitive to specific neuron loss in subregions such as layer III of the entorhinal cortex and the hilus of the dentate gyrus. These findings provide quantitative evidence that kainate-treated rats tend to display extensive neuron and volume loss in the amygdala and olfactory cortex, although the patterns and extent of loss in forebrain regions vary considerably among individuals. In this status epilepticus-based model, extrahippocampal damage appears to be more extensive and hippocampal damage appears to be less extensive than that reported for patients with temporal lobe epilepsy.

Hippocampal atrophy in temporal lobe epilepsy is correlated with limbic systems atrophy

Hippocampal sclerosis in temporal lobe epilepsy (TLE) is often associated with hippocampal atrophy. This study assessed whether such atrophy is correlated with loss of gray matter volume in other brain regions. In 16 patients with TLE and clear magnetic resonance imaging-based evidence of hippocampal sclerosis, hippocampal volumes were determined manually and the local gray matter (LGM) amount was estimated throughout the entire brain using voxel-based morphometry. Voxelwise correlations between the volume of the sclerotic hippocampus and LGM were computed. The pattern of voxels whose LGM correlated with hippocampal volume outlined remarkably well the anatomy of the extended limbic system and included the parahippocampal region, cingulate gyrus throughout its extent, basal forebrain, thalamic nuclei, medial orbitofrontal areas and the insula. These correlations emerged mainly on the side ipsilateral to the affected hippocampus but were also found contralaterally. No such correlations were found in a group of 16 healthy controls. The present data show that hippocampal volume loss in TLE is associated with a widespread limbic systems atrophy. These findings are helpful to better understand the functional deficit and reorganization often found in temporal lobe epilepsy and will also provide a basis to assess neural plasticity in the limbic system for those patients who will undergo curative temporal lobe surgery.

Voxel-based morphometry of the thalamus in patients with refractory medial temporal lobe epilepsy

Previous research has suggested that patients with refractory medial temporal lobe epilepsy (MTLE) show gray matter atrophy both within the temporal lobes as well as in the thalamus. However, these studies have not distinguished between different nuclei within the thalamus. We examined whether thalamic atrophy correlates with the nuclei's connections to other regions in the limbic system. T1-weighted MRI scans were obtained from 49 neurologically healthy control subjects and 43 patients diagnosed with chronic refractory MTLE that was unilateral in origin (as measured by ictal EEG and hippocampal atrophy observed on MRI). Measurements of gray matter concentration (GMC) were made using automated segmentation algorithms. GMC was analyzed both voxel-by-voxel (preserving spatial precision) as well as using predefined regions of interest. Voxel-based morphometry revealed intense GMC reduction in the anterior portion relative to posterior thalami. Furthermore, thalamic atrophy was greater ipsilateral to the MTLE origin than on the contralateral side. Here we demonstrate that the thalamic atrophy is most intense in the thalamic nuclei that have strong connections with the limbic hippocampus. This finding suggests that thalamic atrophy reflects this region's anatomical and functional association with the limbic system rather than a general vulnerability to damage.

Hippocampal alterations in children with temporal lobe epilepsy with or without a history of febrile convulsions: evaluations with MR volumetry and proton MR spectroscopy

BACKGROUND AND PURPOSE

The causal effect of early febrile convulsions (FC) on later-onset temporal lobe epilepsy (TLE) remains unclear. In this study, we sought to examine the hippocampal alterations in epileptic children with or without FC history by using MR spectroscopy and volumetry.

METHODS

Fifty-five children ranging in age from 18 months to 15 years were enrolled in this study. Subjects were divided into three groups: the control group without either TLE or history of FC (n = 16), the TLE group with early history of FC (TLE + FC; n = 22), and the TLE group without FC history (n = 17). Measurement of hippocampal volume (HV) was performed on thin section T1-weighted images acquired with a 3D gradient echo MR image and normalized by the intracranial volume. Each individual subject had two measures of lateralization; one gives the smaller side of HV and the other the contralateral larger side of HV, assuming that the side with smaller HV is the possible primary site of seizure focus and the contralateral larger HV the secondary or normal site. Single-voxel proton MR spectroscopy of the hippocampi was performed, with metabolic ratio n-acetylaspartate (NAA)/choline (Cho) + creatine plus phosphocreatine (Cr) calculated and grouped separately as were with volumetry.

RESULTS

The overall mean HV for the control group was 2.61 +/- 0.21 cm(3) at an average intracranial volume of 965 +/- 241 cm(3), and the asymmetry index for hippocampal volume was (2.32 +/- 1.58)%. The overall mean HV was 2.30 +/- 0.33 cm(3) for TLE + FC group and 2.34 +/- 0.33 cm(3) for TLE group. Mean HV differed significantly for the three groups (P < .01). When the small and large sides were analyzed separately, significant differences were found between control and TLE as well as between control and TLE + FC for the smaller side (P < .05), whereas for the larger side significant differences were found only between control and TLE + FC. In MR spectroscopic measurements, the mean NAA/(Cr + Cho) of bilateral hippocampi was 0.77 +/- 0.06 for control group, 0.62 +/- 0.12 for TLE + FC group, and 0.66 +/- 0.11 for TLE group. In terms of statistically significant difference between groups, spectroscopic results were similar to volumetric measurements, except that there was no significant interaction effect between groups and measures of asymmetrical indices (P = .272).

CONCLUSION

Children with TLE and early history of FC tend to have lower hippocampal volumes and NAA/(Cr + Cho) ratios than do TLE children without FC history. The TLE + FC group seems to have increased vulnerability of the contralateral hippocampus as compared with TLE group. MR volumetry and spectroscopy are equally capable of showing the trends of hippocampal alternations in children with TLE with or without FC history.

Non-rigid image registration: theory and practice

Image registration is an important enabling technology in medical image analysis. The current emphasis is on development and validation of application-specific non-rigid techniques, but there is already a plethora of techniques and terminology in use. In this paper we discuss the current state of the art of non-rigid registration to put on-going research in context and to highlight current and future clinical applications that might benefit from this technology. The philosophy and motivation underlying non-rigid registration is discussed and a guide to common terminology is presented. The core components of registration systems are described and outstanding issues of validity and validation are confronted.

Quantitative MR imaging of the neocortex

This article provides an overview of novel MR image analysis methods applied to the quantitative assessment of the neocortex in various forms of epilepsy. Postacquisition processing methods, such as voxel-based morphometry and texture analysis, involve the use of computer software to manipulate, enhance, and classify image information in a digital format. These techniques have the potential to demonstrate subtle abnormalities that are not identified by eye because of anatomic variability. Information provided by quantitative MR imaging of the neocortex may be important for the identification of accurate predictors of surgical outcome and may refine the selection of surgical candidates, particularly those with "nonlesional" neocortical epilepsy.

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

The advance of neuroimaging techniques has resulted in a burgeoning of studies reporting abnormalities in brain structure and function in a number of neuropsychiatric disorders. Measurement of hippocampal volume has developed as a useful tool in the study of neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. From this database, the methodology of all original manual tracing protocols were studied. These protocols differed in a number of important factors for accurate hippocampal volume determination including magnetic field strength, the number of slices assessed and the thickness of slices, hippocampal orientation correction, volumetric correction, software used, inter-rater reliability, and anatomical boundaries of the hippocampus. The findings are discussed in relation to optimizing determination of hippocampal volume.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Comparison of standard and optimized voxel-based morphometry for analysis of brain changes associated with temporal lobe epilepsy

We compared statistical parametric maps (SPMs) of group-wise regional gray matter differences between temporal lobe epilepsy (TLE) patients with unilateral hippocampal atrophy (HA) determined by manual volumetric analysis relative to a healthy control population using standard and optimized voxel-based morphometry (VBM). We also investigated the impact of customized neuroanatomical templates on SPMs. Standard and optimized VBM analyses of gray matter concentration (GMC) and gray matter volume (GMV) correctly identified HA, regardless of the template used for normalization. The distribution of hippocampal and extrahippocampal abnormalities differed according to the technique (standard v optimized; GMC v GMV), but was not dependent on template type (default v customized) within each technique. In particular, hippocampal GMC reduction was confined to subregions of hippocampus, whereas GMV reduction was observed in the hippocampal head, body, and tail. Unlike standard and optimized GMC reduction, symmetrical GMV reduction was observed in bilateral thalamus, lenticular nuclei, cerebellum, and ipsilateral entorhinal cortex, perirhinal cortex, and fusiform gyrus in both left and right HA patients. These results show that group-wise SPMs of GMC (i.e., regional distribution of gray matter) and GMV (i.e., volume per se) reduction can identify focal atrophy that has been quantified with manual region of interest techniques, although effects are attenuated in analyses of GMC. Unlike SPMs of GMC, analyses of GMV revealed similar extrahippocampal abnormalities as previous region-of-interest volumetric and histopathological studies of intractable TLE. We suggest that in studies of neurological disorders, optimized VBM analyses of GMV may reveal subtle neuroanatomical changes that are not identified in analyses of GMC.

Whole-brain voxel-based statistical analysis of gray matter and white matter in temporal lobe epilepsy

Volumetric MRI studies based on manual labeling of selected anatomical structures have provided in vivo evidence that brain abnormalities associated with temporal lobe epilepsy (TLE) extend beyond the hippocampus. Voxel-based morphometry (VBM) is a fully automated image analysis technique allowing identification of regional differences in gray matter (GM) and white matter (WM) between groups of subjects without a prior region of interest. The purpose of this study was to determine whole-brain GM and WM changes in TLE and to investigate the relationship between these abnormalities and clinical parameters. We studied 85 patients with pharmacologically intractable TLE and unilateral hippocampal atrophy and 47 age- and sex-matched healthy control subjects. The seizure focus was right sided in 40 patients and left sided in 45. Student's t test statistical maps of differences between patients' and controls' GM and WM concentrations were obtained using a general linear model. A further regression against duration of epilepsy, age of onset, presence of febrile convulsions, and secondary generalized seizures was performed with the TLE population. Voxel-based morphometry revealed that GM pathology in TLE extends beyond the hippocampus involving other limbic areas such as the cingulum and the thalamus, as well as extralimbic areas, particularly the frontal lobe. White matter reduction was found only ipsilateral to the seizure focus, including the temporopolar, entorhinal, and perirhinal areas. This pattern of structural changes is suggestive of disconnection involving preferentially frontolimbic pathways in patients with pharmacologically intractable TLE.

Voxel-based morphometry of unilateral temporal lobe epilepsy reveals abnormalities in cerebral white matter

Voxel-based morphometric (VBM) investigations of temporal lobe epilepsy have focused on the presence and distribution of gray matter abnormalities. VBM studies to date have identified the expected abnormalities in hippocampus and extrahippocampal temporal lobe, as well as more diffuse abnormalities in the thalamus, cerebellum, and extratemporal neocortical areas. To date, there has not been a comprehensive VBM investigation of cerebral white matter in nonlesional temporal lobe epilepsy. This study examined 25 lateralized temporal lobe epilepsy patients (13 left, 12 right) and 62 healthy controls in regard to both temporal and extratemporal lobe gray and white matter. Consistent with prior reports, gray matter abnormalities were evident in ipsilateral hippocampus and ipsilateral thalamus. Temporal and extratemporal white matter was affected ipsilateral to the side of seizure onset, in both left and right temporal lobe epilepsy groups. These findings indicate that chronic temporal lobe epilepsy is associated not only with abnormalities in gray matter, but also with concomitant abnormalities in cerebral white matter regions that may affect connectivity both within and between the cerebral hemispheres.

Psychopathology and Pediatric Complex Partial Seizures: Seizure-related, Cognitive, and Linguistic Variables

PURPOSE

This study examined the role of cognition, language, seizure-related, and demographic variables in the psychopathology of children with complex partial seizure disorder (CPS) of average intelligence.

METHODS

One-hundred one CPS and 102 normal children, aged 5.1 to 16.9 years, had a structured psychiatric interview and cognitive and language testing. Parents provided demographic, perinatal, and seizure-related information, as well as behavioral information through the Child Behavior Checklist (CBCL) and a structured psychiatric interview about the child.

RESULTS

Significantly more CPS patients had psychopathology, cognitive deficits, and linguistic deficits than did those in the normal group. Among the patients, Verbal IQ predicted the presence of a psychiatric diagnosis, as well as CBCL scores in the borderline/clinical range. Seizure, linguistic, and demographic variables were unrelated to psychopathology. The cognitive and linguistic deficits of the CPS group, however, were predicted by seizure factors (e.g., prolonged seizures/febrile convulsions; seizure frequency/number of antiepileptic drugs) and demographic factors (e.g., minority status).

CONCLUSIONS

Because subtle verbal cognitive deficits predict behavioral disturbances in pediatric CPSs, the study's findings highlight the importance of assessing behavior, cognition, and language in these children. They also underscore the negative impact of prolonged seizures, febrile convulsions, seizure frequency, and antiepileptic drug polytherapy on cognition and language in pediatric CPSs.

Neuroanatomy of adult strabismus: a voxel-based morphometric analysis of magnetic resonance structural scans

Cerebral deficit has been implicated in the genesis of strabismus and in the mechanisms adopted to compensate for the visual disorder. Voxel-based morphometry (VBM) was applied to magnetic resonance images of strabismic adults to detect any abnormal brain anatomy, which could not be easily identified by simple inspection. The gray matter volume in strabismic adults was smaller than that in normal subjects at the areas consistent with the occipital eye field (OEF) and parietal eye field (PEF). However, greater gray matter volume was found in strabismic adults relative to normal controls at the areas consistent with the frontal eye field (FEF), the supplementary eye field (SEF), the prefrontal cortex (PFC), and subcortical regions such as the thalamus and the basal ganglia. These opposite gray matter changes in the visual and the oculomotor processing areas are compatible with a hypothesis of plasticity in the oculomotor regions to compensate for the cortical deficits in the visual processing areas.

Multimodality imaging in partial epilepsies

PURPOSE OF REVIEW

The rapid expansion of novel applications and the development of new techniques in structural and functional imaging modalities present a troubling challenge to keep up with and harness potential valuable information created in this critical field of epilepsy localization and non-invasive in-vivo research.

RECENT FINDINGS

Recent advances in epilepsy imaging have centered on: (1) improving the localization of epileptogenic tissue beyond that of state-of-the-art structural magnetic resonance imaging; (2) monitoring the development and progression of epileptogenic pathology, particularly mesial temporal sclerosis; and (3) an investigation of the in-vivo structural and functional disturbances underlying and revealing mechanisms of partial epilepsy pathophysiology.

SUMMARY

The main impact of the progress in epilepsy localization with multimodality imaging is to allow more effective presurgical evaluation and the selection of patients with intractable seizures. By combining serial imaging findings and genetic studies, the major questions surrounding the development and progression of mesial temporal sclerosis with regard to the cause and consequence of epilepsy will soon be answered. Long-standing questions concerning in-vivo metabolic and neurotransmitter disturbances associated with partial epilepsy, detected and depicted (but not understood) with magnetic resonance spectroscopy and positron emission tomography, are finally being addressed.

Detection of human herpesvirus-6 in mesial temporal lobe epilepsy surgical brain resections

BACKGROUND

Human herpesvirus-6 (HHV-6), a ubiquitous beta-herpesvirus, is the causative agent of roseola infantum and has been associated with a number of neurologic disorders including seizures, encephalitis/meningitis, and multiple sclerosis. Although the role of HHV-6 in human CNS disease remains to be fully defined, a number of studies have suggested that the CNS can be a site for persistent HHV-6 infection.

OBJECTIVE

To characterize the extent and distribution of HHV-6 in human glial cells from surgical brain resections of patients with mesial temporal lobe epilepsy (MTLE).

METHOD

Brain samples from eight patients with MTLE and seven patients with neocortical epilepsy (NE) undergoing surgical resection were quantitatively analyzed for the presence of HHV-6 DNA using a virus-specific real-time PCR assay. HHV-6 expression was also characterized by western blot analysis and in situ immunohistochemistry (IHC). In addition, HHV-6-reactive cells were analyzed for expression of glial fibrillary acidic protein (GFAP) by double immunofluorescence.

RESULTS

DNA obtained from four of eight patients with MTLE had significantly elevated levels of HHV-6 as quantified by real-time PCR. HHV-6 was not amplified in any of the seven patients with NE undergoing surgery. The highest levels of HHV-6 were demonstrated in hippocampal sections (up to 23,079 copies/10(6) cells) and subtyped as HHV-6B. Expression of HHV-6 was confirmed by western blot analysis and IHC. HHV-6 was co-localized to GFAP-positive cells that morphologically appeared to be astrocytes.

CONCLUSIONS

HHV-6B is present in brain specimens from a subset of patients with MTLE and localized to astrocytes in the absence of inflammation. The amplification of HHV-6 from hippocampal and temporal lobe astrocytes of MTLE warrants further investigation into the possible role of HHV-6 in the development of MTLE.