Relevance of temporal lobe white matter changes in hippocampal sclerosis. Magnetic resonance imaging and histology

Temporal pole blurring in temporal lobe epilepsy revealed by 3D Edge-Enhancing Gradient Echo MRI

While abnormalities of the hippocampus have been well characterized in temporal lobe epilepsy, various additional temporal lobe abnormalities have also been described. One poorly understood entity, the so-called temporal pole blurring (TPB), is one of the more frequently described neocortical abnormalities in TLE and is thought to represent dysmyelination and axonal loss due to chronic electrical perturbations in early age-onset temporal lobe epilepsy. In this study, we describe the first reported cases of TPB diagnosed by a recently described MRI sequence known as 3D Edge-Enhancing Gradient Echo (3D-EDGE), which has an effective "myelin weighting" making it exquisitely sensitive to this temporal pole dysmyelination. The value of detection of TPB lies in lateralizing seizure onset, as well as predicting a lower baseline neuropsychological performance compared to temporal lobe epilepsy without TPB. Additionally, it is critical to not mistake TPB for alternative diagnoses, such as focal cortical dysplasia or neoplasm.

Reduced myelin in patients with isolated hippocampal sclerosis as assessed by SyMRI

Purpose

Synthetic MRI (SyMRI) enables to quantify brain tissue and morphometry. We aimed to investigate the WM and myelin alterations in patients with unilateral hippocampal sclerosis (HS) with SyMRI.

Methods

Adult patients with isolated unilateral HS and age-matched control subjects (CSs) were included in this study. The SyMRI sequence QRAPMASTER in the coronal plane perpendicular to the hippocampi was obtained from the whole brain. Automatic segmentation of the whole brain was processed by SyMRI Diagnostic software (Version 11.2). Two neuroradiologists also performed quantitative analyses independently from symmetrical 14 ROIs placed in temporal and extratemporal WM, hippocampi, and amygdalae in both hemispheres.

Results

Sixteen patients (F/M = 6/10, mean age = 32.5 ± 11.3 years; right/left HS: 8/8) and 10 CSs (F/M = 5/5, mean age = 30.7 ± 7 years) were included. Left HS patients had significantly lower myelin and WM volumes than CSs (p < .05). Myelin was reduced significantly in the ipsilateral temporal lobe of patients than CSs, greater in left HS (p < .05). Histopathological examination including luxol fast blue stain also revealed myelin pallor in all of 6 patients who were operated. Ipsilateral temporal pole and sub-insular WM had significantly reduced myelin than the corresponding contralateral regions in patients (p < .05). No significant difference was found in WM values. GM values were significantly lower in hippocampi in patients than CSs (p < .05).

Conclusion

SyMRI revealed myelin reduction in the ipsilateral temporal lobe and sub-insular WM of patients with HS. Whether this finding correlates with electrophysiological features and SyMRI could serve as lateralization of temporal lobe epilepsy need to be investigated.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00234-021-02824-6.

Gray-White Matter Blurring of the Temporal Pole Associated With Hippocampal Sclerosis: A Microstructural Study Involving 3 T MRI and Ultrastructural Histopathology

Hippocampal sclerosis (HS) is often associated with gray-white matter blurring (GMB) of the anterior temporal lobe. In this study, twenty patients with unilateral temporal lobe epilepsy and HS were studied with 3 T MRI including T1 MP2RAGE and DTI/DMI sequences. Anterior temporal lobe white matter T1 relaxation times and diffusion measures were analyzed on the HS side, on the contralateral side, and in 10 normal controls. Resected brain tissue of three patients without GMB and four patients with GMB was evaluated ultrastructurally regarding axon density and diameter, the relation of the axon diameter to the total fiber diameter (G-ratio), and the thickness of the myelin sheath. Hippocampal sclerosis GMB of the anterior temporal lobe was related to prolonged T1 relaxation and axonal loss. A less pronounced reduction in axonal fraction was also found on imaging in GMB-negative temporal poles compared with normal controls. Contralateral values did not differ significantly between patients and normal controls. Reduced axonal density and axonal diameter were histopathologically confirmed in the temporopolar white matter with GMB compared to temporal poles without. These results confirm that GMB can be considered an imaging correlate for disturbed axonal maturation that can be quantified with advanced diffusion imaging.

Microstructural imaging in temporal lobe epilepsy: Diffusion imaging changes relate to reduced neurite density

PURPOSE

Previous imaging studies in patients with refractory temporal lobe epilepsy (TLE) have examined the spatial distribution of changes in imaging parameters such as diffusion tensor imaging (DTI) metrics and cortical thickness. Multi-compartment models offer greater specificity with parameters more directly related to known changes in TLE such as altered neuronal density and myelination. We studied the spatial distribution of conventional and novel metrics including neurite density derived from NODDI (Neurite Orientation Dispersion and Density Imaging) and myelin water fraction (MWF) derived from mcDESPOT (Multi-Compartment Driven Equilibrium Single Pulse Observation of T1/T2)] to infer the underlying neurobiology of changes in conventional metrics.

METHODS

20 patients with TLE and 20 matched controls underwent magnetic resonance imaging including a volumetric T1-weighted sequence, multi-shell diffusion from which DTI and NODDI metrics were derived and a protocol suitable for mcDESPOT fitting. Models of the grey matter-white matter and grey matter-CSF surfaces were automatically generated from the T1-weighted MRI. Conventional diffusion and novel metrics of neurite density and MWF were sampled from intracortical grey matter and subcortical white matter surfaces and cortical thickness was measured.

RESULTS

In intracortical grey matter, diffusivity was increased in the ipsilateral temporal and frontopolar cortices with more restricted areas of reduced neurite density. Diffusivity increases were largely related to reductions in neurite density, and to a lesser extent CSF partial volume effects, but not MWF. In subcortical white matter, widespread bilateral reductions in fractional anisotropy and increases in radial diffusivity were seen. These were primarily related to reduced neurite density, with an additional relationship to reduced MWF in the temporal pole and anterolateral temporal neocortex. Changes were greater with increasing epilepsy duration. Bilaterally reduced cortical thickness in the mesial temporal lobe and centroparietal cortices was unrelated to neurite density and MWF.

CONCLUSIONS

Diffusivity changes in grey and white matter are primarily related to reduced neurite density with an additional relationship to reduced MWF in the temporal pole. Neurite density may represent a more sensitive and specific biomarker of progressive neuronal damage in refractory TLE that deserves further study.

Morphological and Advanced Imaging of Epilepsy: Beyond the Basics

The etiology of epilepsy is variable and sometimes multifactorial. Clinical course and response to treatment largely depend on the precise etiology of the seizures. Along with the electroencephalogram (EEG), neuroimaging techniques, in particular, magnetic resonance imaging (MRI), are the most important tools for determining the possible etiology of epilepsy. Over the last few years, there have been many developments in data acquisition and analysis for both morphological and functional neuroimaging of people suffering from this condition. These innovations have increased the detection of underlying structural pathologies, which have till recently been classified as "cryptogenic" epilepsy. Cryptogenic epilepsy is often refractory to anti-epileptic drug treatment. In drug-resistant patients with structural or consistent functional lesions related to the epilepsy syndrome, surgery is the only treatment that can offer a seizure-free outcome. The pre-operative detection of the underlying structural condition increases the odds of successful surgical treatment of pharmacoresistant epilepsy. This article provides a comprehensive overview of neuroimaging techniques in epilepsy, highlighting recent advances and innovations and summarizes frequent etiologies of epilepsy in order to improve the diagnosis and management of patients suffering from seizures, especially young patients and children.

Multimodal computational neocortical anatomy in pediatric hippocampal sclerosis

Objective

In contrast to adult cohorts, neocortical changes in epileptic children with hippocampal damage are not well characterized. Here, we mapped multimodal neocortical markers of epilepsy‐related structural compromise in a pediatric cohort of temporal lobe epilepsy and explored how they relate to clinical factors.

Methods

We measured cortical thickness, gray–white matter intensity contrast and intracortical FLAIR intensity in 22 patients with hippocampal sclerosis (HS) and 30 controls. Surface‐based linear models assessed between‐group differences in morphological and MR signal intensity markers. Structural integrity of the hippocampus was measured by quantifying atrophy and FLAIR patterns. Linear models were used to evaluate the relationships between hippocampal and neocortical MRI markers and clinical factors.

Results

In the hippocampus, patients demonstrated ipsilateral atrophy and bilateral FLAIR hyperintensity. In the neocortex, patients showed FLAIR signal hyperintensities and gray–white matter boundary blurring in the ipsilesional mesial and lateral temporal neocortex. In contrast, cortical thinning was minimal and restricted to a small area of the ipsilesional temporal pole. Furthermore, patients with a history of febrile convulsions demonstrated more pronounced FLAIR hyperintensity in the ipsilesional temporal neocortex.

Interpretation

Pediatric HS patients do not yet demonstrate the widespread cortical thinning present in adult cohorts, which may reflect consequences of a protracted disease process. However, pronounced temporal neocortical FLAIR hyperintensity and blurring of the gray–white matter boundary are already detectable, suggesting that alterations in MR signal intensities may reflect a different underlying pathophysiology that is detectable earlier in the disease and more pervasive in patients with a history of febrile convulsions.

Role of the temporal pole in temporal lobe epilepsy seizure networks: an intracranial electrode investigation

OBJECTIVE A convergence of clinical research suggests that the temporal pole (TP) plays an important and potentially underappreciated role in the genesis and propagation of seizures in temporal lobe epilepsy (TLE). Understanding its role is becoming increasingly important because selective resections for medically intractable TLE spare temporopolar cortex (TPC). The purpose of this study was to characterize the role of the TPC in TLE after using dense electrocorticography (ECoG) recordings in patients undergoing invasive monitoring for medically intractable TLE. METHODS Chronic ECoG recordings were obtained in 10 consecutive patients by using an array customized to provide dense coverage of the TP as part of invasive monitoring to localize the epileptogenic zone. All patients would eventually undergo cortico-amygdalohippocampectomy. A retrospective review of the patient clinical records including ECoG recordings, neuroimaging studies, neuropathology reports, and clinical outcomes was performed. RESULTS In 7 patients (70%), the TP was involved at seizure onset; in 7 patients (70%), there were interictal discharges from the TP; and in 1 case, there was early spread to the TP. Seizure onset in the TP did not necessarily correlate with preoperative neuroimaging abnormalities of the TP. CONCLUSIONS These data demonstrate that TPC commonly plays a crucial role in temporal lobe seizure networks. Seizure onset from the TP would not have been predicted based on available neuroimaging data or interictal discharges. These findings illustrate the importance of thoroughly considering the role of the TP prior to resective surgery for TLE, particularly when selective mesial resection is being considered.

Geschwind Syndrome in frontotemporal lobar degeneration: Neuroanatomical and neuropsychological features over 9 years

Geschwind Syndrome, a characteristic behavioral syndrome frequently described in patients affected by temporal lobe epilepsy (TLE), consists of the following features: hyper-religiosity, hypergraphia, hyposexuality, and irritability. Here we report the 9-year-clinical course of a case of Geschwind Syndrome that developed as a first and salient clinical expression of right temporal lobe variant of frontotemporal lobar degeneration (FTLD). Only one patient affected by frontotemporal dementia has previously been shown to present with Geschwind Syndrome. MS presented at age 73 with 3 years of personality and behavioral symptoms. Her early symptoms primarily included hyper-religiosity, hypergraphia, and poor emotional regulation (irritability, impulsivity, disinhibition, egocentric behavior). Over nine years, other cognitive functions (word retrieval, memory coding and recall, set-shifting, famous face and building recognition) became affected; however, hyper-religiosity, hypergraphia, and scarce emotional control remained her most prominent deficits. Longitudinal cortical thickness and volumetric analyses revealed early atrophy in the right temporal pole, right amygdala, and right hippocampus, which progressively affected homologous regions in the left hemisphere. The present case describes an unusual clinical picture associated with frontotemporal dementia (FTD), in which the most salient symptoms originated and remained consistent with Geschwind Syndrome.

Statistical shape analysis of temporal lobe in mesial temporal sclerosis patients

BACKGROUND

Surgery is regarded as a common treatment option for patients with mesial temporal lobe epilepsy due to hippocampal sclerosis but sometimes deciding this diagnosis can be very difficult. We aim to investigate the shape differences in the temporal lobe of mesial temporal sclerosis epilepsy patients compared with healthy controls, investigating the side difference and, if present, assessing the clinical application of this situation.

METHOD

The MRI scans of mesial TLE patients and controls were retrospectively reviewed. Temporal lobe data were collected from the two-dimensional digital images. Standard anthropometric landmarks were selected and marked on each digital image using TPSDIG 2.04 software. Eight anatomic landmarks were marked on images. A generalized Procrustes analysis was used to evaluate the shape difference. The shape deformation of the temporal lobe from control to patient was evaluated using the TPS method.

RESULTS

There were statistically significant TL shape differences between groups. High level deformations for the left and right side from the control to patient group were seen in the TPS graphic. The highest deformation was determined at the inferior lateral temporal midpoint of the middle temporal gyri and superior temporal landmark points of both the right and left sides.

CONCLUSION

Our study for the first time demonstrated temporal shape differences in TLE patients using a landmark-based geometrical morphometric method by taking into consideration the topographic distribution of TL.

Temporal pole abnormalities in temporal lobe epilepsy with hippocampal sclerosis: Clinical significance and seizure outcome after surgery

PURPOSE

To assess the clinical significance of temporal pole abnormalities (temporopolar blurring, TB, and temporopolar atrophy, TA) in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS) with a long post-surgical follow-up.

METHODS

We studied 60 consecutive patients with TLE-HS and 1.5 preoperative MRI scans who underwent surgery and were followed up for at least 5 years (mean follow-up 7.3 years). Based on findings of pre-surgical MRI, patients were classified according to the presence of TB or TA. Groups were compared on demographic, clinical, neuropsychological data, and seizure outcome.

RESULTS

TB was found in 37 (62%) patients, while TA was found in 35 (58%) patients, always ipsilateral to HS, with a high degree of overlap (83%) between TB and TA (p<0.001). Patients with TB did not differ from those without TB with regard to history of febrile convulsions, GTCSs, age of epilepsy onset, side of surgery, seizure frequency, seizure outcome, and neuropsychological outcome. On the other hand, they were significantly older, had a longer duration of epilepsy, and displayed lower preoperative scores on several neuropsychological tests. Similar findings were observed for TA. Multivariate analysis corroborated the association between temporopolar abnormalities and age at onset, age at surgery (for TB only), and lower preoperative scores on some neuropsychological tests.

CONCLUSIONS

Temporopolar abnormalities are frequent in patients with TLE-HS. Our data support the hypothesis that TB and TA are caused by seizure-related damages. These abnormalities did not influence seizure outcome, even after a long-term post-surgical follow-up.

White matter in temporal lobe epilepsy: clinico-pathological correlates of water diffusion abnormalities

Using magnetic resonance imaging, it is possible to measure the behavior of diffusing water molecules, and the metrics derived can be used as indirect markers of tissue micro-architectural properties. Numerous reports have demonstrated that patients with temporal lobe epilepsy (TLE) have water diffusion abnormalities in several white matter structures located within and beyond the epileptogenic temporal lobe, showing that TLE is not a focal disorder, but rather a brain network disease. Differences in severity and spatial extent between patients with or without mesial temporal sclerosis (MTS), as well as differences related to hemispheric seizure onset, are suggestive of different pathophysiological mechanisms behind different forms of TLE, which in turn result in specific cognitive disabilities. The biological interpretation of diffusion abnormalities is based on a wealth of information from animal models of white matter damage, and is supported by recent reports that directly correlate diffusion metrics with histological characteristics of surgical specimens of TLE patients. Thus, there is now more evidence showing that the increased mean diffusivity (MD) and concomitant reductions of diffusion anisotropy that are frequently observed in several white matter bundles in TLE patients reflect reduced axonal density (increased extra-axonal space) due to smaller-caliber axons, and abnormalities in the myelin sheaths of the remaining axons. Whether these histological and diffusion features are a predisposing factor for epilepsy or secondary to seizures is still uncertain; some reports suggest the latter. This article summarizes recent findings in this field and provides a synopsis of the histological features seen most frequently in post-surgical specimens of TLE patients in an effort to aid the interpretation of white matter diffusion abnormalities.

Imaging structural and functional brain networks in temporal lobe epilepsy

Early imaging studies in temporal lobe epilepsy (TLE) focused on the search for mesial temporal sclerosis, as its surgical removal results in clinically meaningful improvement in about 70% of patients. Nevertheless, a considerable subgroup of patients continues to suffer from post-operative seizures. Although the reasons for surgical failure are not fully understood, electrophysiological and imaging data suggest that anomalies extending beyond the temporal lobe may have negative impact on outcome. This hypothesis has revived the concept of human epilepsy as a disorder of distributed brain networks. Recent methodological advances in non-invasive neuroimaging have led to quantify structural and functional networks in vivo. While structural networks can be inferred from diffusion MRI tractography and inter-regional covariance patterns of structural measures such as cortical thickness, functional connectivity is generally computed based on statistical dependencies of neurophysiological time-series, measured through functional MRI or electroencephalographic techniques. This review considers the application of advanced analytical methods in structural and functional connectivity analyses in TLE. We will specifically highlight findings from graph-theoretical analysis that allow assessing the topological organization of brain networks. These studies have provided compelling evidence that TLE is a system disorder with profound alterations in local and distributed networks. In addition, there is emerging evidence for the utility of network properties as clinical diagnostic markers. Nowadays, a network perspective is considered to be essential to the understanding of the development, progression, and management of epilepsy.

International consensus classification of hippocampal sclerosis in temporal lobe epilepsy: a Task Force report from the ILAE Commission on Diagnostic Methods

Hippocampal sclerosis (HS) is the most frequent histopathology encountered in patients with drug-resistant temporal lobe epilepsy (TLE). Over the past decades, various attempts have been made to classify specific patterns of hippocampal neuronal cell loss and correlate subtypes with postsurgical outcome. However, no international consensus about definitions and terminology has been achieved. A task force reviewed previous classification schemes and proposes a system based on semiquantitative hippocampal cell loss patterns that can be applied in any histopathology laboratory. Interobserver and intraobserver agreement studies reached consensus to classify three types in anatomically well-preserved hippocampal specimens: HS International League Against Epilepsy (ILAE) type 1 refers always to severe neuronal cell loss and gliosis predominantly in CA1 and CA4 regions, compared to CA1 predominant neuronal cell loss and gliosis (HS ILAE type 2), or CA4 predominant neuronal cell loss and gliosis (HS ILAE type 3). Surgical hippocampus specimens obtained from patients with TLE may also show normal content of neurons with reactive gliosis only (no-HS). HS ILAE type 1 is more often associated with a history of initial precipitating injuries before age 5 years, with early seizure onset, and favorable postsurgical seizure control. CA1 predominant HS ILAE type 2 and CA4 predominant HS ILAE type 3 have been studied less systematically so far, but some reports point to less favorable outcome, and to differences regarding epilepsy history, including age of seizure onset. The proposed international consensus classification will aid in the characterization of specific clinicopathologic syndromes, and explore variability in imaging and electrophysiology findings, and in postsurgical seizure control.

Defining clinico-neuropathological subtypes of mesial temporal lobe epilepsy with hippocampal sclerosis

Hippocampal sclerosis (HS) is the most frequent cause of drug-resistant focal epilepsies (ie, mesial temporal lobe epilepsy with hippocampal sclerosis; mTLE-HS), and presents a broad spectrum of electroclinical, structural and molecular pathology patterns. Many patients become drug resistant during the course of the disease, and surgical treatment was proven helpful to achieve seizure control. Hence, up to 40% of patients suffer from early or late surgical failures. Different patterns of hippocampal cell loss, involvement of other mesial temporal structures, as well as temporal neocortex including focal cortical dysplasia, may contribute to the extent of the epileptogenic network and will be discussed. An international consensus is mandatory to clarify terminology use and to reliably distinguish mTLE-HS subtypes. High-resolution imaging with confirmed histopathologic diagnosis, as well as advanced neurophysiologic and molecular genetic measures, will be a powerful tool in the future to address these issues and help to predict each patient's probability to control their epilepsy in mTLE-HS conditions.

Anterior temporal lobe white matter abnormal signal (ATLAS) as an indicator of seizure focus laterality in temporal lobe epilepsy: comparison of double inversion recovery, FLAIR and T2W MR imaging

OBJECTIVES

To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences.

METHODS

This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using κ statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons.

RESULTS

Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P ≤ 0.031 for each evaluator).

CONCLUSIONS

The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE.

Voxel-based relaxometry for cases of an unresolved epilepsy diagnosis

PURPOSE

Voxel-based relaxometry (VBR) is a technique in which a voxel-level statistical comparison of quantitative MR T2 maps is performed to identify regions with significantly elevated T2 relaxation time. Our objective was to assess the performance of single-subject VBR at 3T as a diagnostic tool for patients whose diagnosis of epilepsy or seizure focus location is uncertain.

METHODS

Fifty-nine patients with possible epilepsy or known epilepsy, but an unknown focus and forty-five healthy controls were studied. All subjects were scanned at 3T using a Carr-Purcell-Meiboom-Gill MR sequence. Single-subject VBR was performed at a significance level of α=0.001. Patients were classified based on whether the diagnosis of epilepsy was in question and whether there was a suspected focus. A VBR score was determined based on the presence of VBR abnormalities in any of 13 predefined regions per hemisphere.

RESULTS

All patients exhibited significantly more median VBR abnormalities than controls (p<0.05). VBR abnormalities were seen in 69% and 89% of patients with a normal or questionably abnormal MR scan, respectively. Nineteen of the 27 patients with a suspected focus (70%) had VBR abnormalities in the suspected focus, with additional regions of involvement being elucidated. VBR also correctly predicted the seizure focus in 50% of patients whose seizure foci were confirmed based on follow-up history or clinical investigations.

CONCLUSIONS

Single subject VBR can help identify potential seizure foci in patients whose seizure foci are uncertain.

[Structural magnetic resonance imaging in epilepsy]

Magnetic resonance imaging is the main structural imaging in epilepsy. In patients with focal seizures, detection (and characterization) of a structural lesion consistent with electroclinical data allows therapeutic decisions without having to resort to other more expensive or invasive diagnostic procedures. The identification of some lesions may provide prognostic value, as in the case of Mesial Temporal Sclerosis (MTS) or may contribute to genetic counseling, as in the case of some Malformations of Cortical Development (MCD). The aim of this paper is to review the current state of structural MRI techniques, propose a basic protocol of epilepsy and mention the indications for structural MRI. Also, review the semiology of the main causes of epilepsy, with emphasis on MTS and MCD, by its highest frequency and by the special impact that MRI has shown in dealing with these entities.

Magnetic resonance imaging in epilepsy

With a major role in revealing epileptogenic lesions, magnetic resonance imaging (MRI) has also been very helpful in surgical planning and postoperative follow-up of drug-resistant focal epilepsies. In this article, in addition to discussing the most common epileptogenic lesions, advanced quantitative and functional MRI techniques in detecting abnormalities and revealing hemodynamic and microstructural changes are emphasized.

Presence of Temporal Gray-White Matter Abnormalities Does Not Influence Epilepsy Surgery Outcome in Temporal Lobe Epilepsy With Hippocampal Sclerosis

BACKGROUND:

Temporal lobe gray-white matter abnormalities (GWMA) are frequent morphological aberrances observed on MRI in patients with temporal lobe epilepsy (TLE) in addition to hippocampal sclerosis (HS).

OBJECTIVE:

To study the influence of temporal pole GWMA on clinical characteristics and seizure outcome in patients with HS operated on for TLE.

METHODS:

A cohort of 370 patients undergoing surgery for intractable TLE was prospectively collected in an epilepsy surgery data base. Clinical characteristics and seizure outcome of all 58 TLE patients with identified HS and GWMA (group 1) were compared with those of a matched control group of 58 HS patients without GWMA (group 2). Both groups were further subdivided into patients undergoing transsylvian selective amygdalohippocampectomy (sAH) and anterior temporal lobectomy with amygdalohippocampectomy (ATL).

RESULTS:

The HS plus GWMA patients were significantly younger at epilepsy onset than those without GWMA. In the HS plus GWMA group, 41% of patients were younger than 2 years when they experienced their first seizure in contrast to only 17% of patients with pure HS (P = .004). Seizure outcome was not statistically different between the 2 groups: 75.9% of the patients in group 1 were seizure free (Engel class I) compared with 81% of patients in group 2. Seizure outcome in both groups was about equally successful with selective amygdalohippocampectomy and anterior temporal lobectomy (ns).

CONCLUSION:

Limited and standard resections in TLE patients with HS are equally successful regardless of the presence of GWMA.

Temporal lobe sclerosis associated with hippocampal sclerosis in temporal lobe epilepsy: neuropathological features

Widespread changes involving neocortical and mesial temporal lobe structures can be present in patients with temporal lobe epilepsy and hippocampal sclerosis. The incidence, pathology, and clinical significance of neocortical temporal lobe sclerosis (TLS) are not well characterized. We identified TLS in 30 of 272 surgically treated cases of hippocampal sclerosis. Temporal lobe sclerosis was defined by variable reduction of neurons from cortical layers II/III and laminar gliosis; it was typically accompanied by additional architectural abnormalities of layer II, that is, abnormal neuronal orientation and aggregation. Quantitative analysis including tessellation methods for the distribution of layer II neurons supported these observations. In 40% of cases, there was a gradient of TLS with more severe involvement toward the temporal pole, possibly signifying involvement of hippocampal projection pathways. There was a history of a febrile seizure as an initial precipitating injury in 73% of patients with TLS compared with 36% without TLS; no other clinical differences between TLS and non-TLS cases were identified. Temporal lobe sclerosis was not evident preoperatively by neuroimaging. No obvious effect of TLS on seizure outcome was noted after temporal lobe resection; 73% became seizure-free at 2-year follow-up. In conclusion, approximately 11% of surgically treated hippocampal sclerosis is accompanied by TLS. Temporal lobe sclerosis is likely an acquired process with accompanying reorganizational dysplasia and an extension of mesial temporal sclerosis rather than a separate pathological entity.

Clinical MRI in children and adults with focal epilepsy: a critical review

Hippocampal sclerosis in adults and focal cortical dysplasia in children with epilepsy are frequent lesions, but they are overlooked on standard MRI. Errors in the interpretation of MRI in epilepsy can be attributed mainly to poor technique and perceptual misses, but incomplete knowledge and poor judgment are also possible sources. This review covers what to expect in structural MRI of an adult patient with mesial temporal lobe epilepsy (TLE) and how to find hippocampal sclerosis (HS). It also covers the clinical MRI-based detection of focal cortical dysplasia (FCD) in extratemporal lobe epilepsy, mainly in children. In a stepwise approach, first, a typical epilepsy MRI protocol at 1.5 T includes axial and coronal fluid-attenuated inversion recovery (FLAIR) imaging, T2- and T2 *-weighted images, and a T1-weighted, three-dimensional volume acquisition. Advanced MR techniques (quantitation, new contrasts like diffusion, MR spectroscopy, high-contrast high-resolution imaging on high-field MR scanners > or = 3 T) are used to increase the method's sensitivity to detect a lesion in an individual patient. Exploiting increased sensitivity, we can avoid false-positive results in the light of a clinical hypothesis, possibly isolating a localized brain area by seizure semiology and EEG prior to MR reading.

Temporal lobe epilepsy: differential pattern of damage in temporopolar cortex and white matter

Our purpose was to quantify structural changes of the temporopolar cortex (TPC) and its white matter (TPWM) in temporal lobe epilepsy (TLE) using MRI volumetry and texture analysis. We studied 23 patients with hippocampal atrophy, and 20 healthy controls. Gradient magnitude and entropy were calculated to model signal intensity blurring on T1-MRI. Two observers assessed signal changes and atrophy visually. Compared to controls, TLE patients had a decrease in TPC and TPWM volume ipsilateral to the seizure focus. The gradient magnitude and entropy were decreased ipsilateral to the focus only in TPWM, indicating blurring of this compartment. Eighty-seven percent of TLE patients had at least one volumetric or textural abnormality. Although sensitivity of visual and quantitative assessment of TPC atrophy was comparable (43 and 39%), specificity was higher for volumetry (54% vs. 95%). Compared to visual analysis of signal changes in TPWM on T1-MRI, texture metrics had higher sensitivity (65% vs. 17%) and specificity (100% vs. 69%). The proportion of patients with blurring of TPWM as determined by texture analysis was higher than that seen on visual inspection of T2 images (78% vs. 43%). We found no clear association between volumetric or textural changes of TPC and TPWM and outcome after surgery. Structural changes of the anatomically distinct TPC and TPWM are found ipsilateral to the seizure focus in the majority of TLE patients with hippocampal sclerosis. MRI post-processing allows dissociating different pathological tissue characteristics and shows that atrophy involves gray and white matter, whereas blurring is confined to white matter.

Temporal pole signal abnormality on MR imaging in temporal lobe epilepsy with hippocampal sclerosis: a fluid-attenuated inversion-recovery study

OBJECTIVE: To determine the frequency and regional involvement of temporal pole signal abnormality (TPA) in patients with hippocampal sclerosis (HS) using fluid-attenuated inversion-recovery (FLAIR) MR imaging, and to correlate this feature with history. METHOD: Coronal FLAIR images of the temporal pole were assessed in 120 patients with HS and in 30 normal subjects, to evaluate gray-white matter demarcation. RESULTS: Ninety (75%) of 120 patients had associated TPA. The HS side made difference regarding the presence of TPA, with a left side prevalence (p=0.04, chi2 test). The anteromedial zone of temporal pole was affected in 27 (30%) out of 90 patients. In 63 (70%) patients the lateral zone were also affected. Patients with TPA were younger at seizure onset (p=0.018), but without association with duration of epilepsy. CONCLUSION: Our FLAIR study show temporal pole signal abnormality in 3/4 of patients with HS, mainly seen on the anteromedial region, with a larger prevalence when the left hippocampus was involved.

Correlation between temporal pole MRI abnormalities and surface ictal EEG patterns in patients with unilateral mesial temporal lobe epilepsy

OBJECTIVE

The objective of this retrospective study is to analyze ictal patterns observed during continuous Video-EEG monitoring in patients with temporal lobe epilepsy (TLE) due to unilateral hippocampal sclerosis (HS), and to correlate these EEG patterns to temporal pole abnormalities observed on magnetic resonance imaging exams.

METHODS

We analyzed 147 seizures from 35 patients with TLE and unilateral HS. Ictal patterns were classified and correlated to signal abnormalities and volumetric measures of the temporal poles. Volume differences over 10% were considered abnormal.

RESULTS

The most frequent type of ictal pattern was rhythmic theta activity (RTA), encountered in 65.5% of the seizures. Rhythmic beta activity (RBA) was observed in 11% of the seizures, localized attenuation in 8%, interruption of epileptiform discharges in 6%, repetitive discharges in 5.5%, and rhythmic delta activity (RDA) in 4%. Sixty-six percent of the patients presented signal abnormalities in the temporal pole that were always ipsilateral to the HS. Sixty percent presented significant asymmetry of the temporal poles consisting of reduced volume that was also always ipsilateral to HS. Although patients with RTA as the predominant ictal pattern tended to present asymmetry of temporal poles (p=0.305), the ictal EEG pattern did not correlate with temporal pole asymmetry or signal abnormalities.

CONCLUSIONS

RTA is the most frequent initial ictal pattern in patients with TLE due to unilateral HS. Temporal pole signal changes and volumetric reduction were commonly found in this group of patients, both abnormalities appearing always ipsilateral to the HS. However, neither temporal pole volume reduction nor signal abnormalities correlated with the predominant ictal pattern, suggesting that the temporal poles are not crucially involved in the process of epileptogenesis.

Proton magnetic resonance spectroscopy of mesial temporal sclerosis: Analysis of voxel shape and position to improve diagnostic accuracy

OBJECTIVE

To determine if change in voxel shape and position improves the lateralization of magnetic resonance (MR) spectroscopy to the side of the MR imaging and/or electroencephalography (EEG) abnormality in mesial temporal sclerosis.

METHODS

In 10 patients with unilateral mesial temporal sclerosis and 5 controls, MR spectroscopy was performed. Long echo time single-voxel spectroscopy was obtained in the right and left hippocampus. First, the standard 2-cm x 2-cm x 2-cm cubic voxels were placed bilaterally. Then, 1-cm x 2-cm x 4-cm rectangular voxels were used. With this rectangular voxel shape, more of the hippocampus and less of the adjacent medial temporal lobe were included in the interrogation voxel. N-acetylaspartate-to-creatine (NAA/Cr) ratios and choline-to-creatine (Cho/Cr) ratios were obtained. The difference between the affected and unaffected sides in the patients was calculated and compared with the controls. Additionally, the mean difference and standard deviation were determined. Predictive values and Student t tests were also performed.

RESULTS

In all 10 patients, using the NAA/Cr ratios, the rectangular voxel correctly identified the abnormal side. The cubic voxel only identified the abnormal side in 6 of the 10 patients, however. Additionally, the mean difference between the affected and unaffected sides was 0.30 for the rectangular voxel but only 0.003 for the cubic voxel; that is, there was no overall significant difference when using the cubic voxel (P = 0.007). No significant correlation between the affected and unaffected sides was found using the Cho/Cr ratios. No significant difference between the right and left sides was found in the controls.

CONCLUSION

Use of a 1-cm x 2-cm x 4-cm rectangular voxel places more of the hippocampus in the region of interrogation with less partial volume artifact from the adjacent brain parenchyma, which occurs with use of the standard 2-cm x 2-cm x 2-cm cubic voxel, resulting in improved correct lateralization of MR spectroscopy to the side of the MR imaging and/or EEG abnormality.

MR Imaging of Epilepsy: Strategies for Successful Interpretation

MR imaging plays a pivotal role in the evaluation of patients with epilepsy. With its high spatial resolution, excellent inherent soft tissue contrast, multiplanar imaging capability, and lack of ionizing radiation, MR imaging has emerged as a versatile diagnostic tool in the evaluation of patients with epilepsy. MR imaging not only identifies specific epileptogenic substrates but also determines specific treatment and predicts prognosis. Employing appropriate imaging protocols and reviewing the images in a systematic manner helps in the identification of subtle epileptogenic structural abnormalities. With future improvements in software, hardware, and post-processing methods, MR imaging should be able to throw more light on epileptogenesis and help physicians to better understand its structural basis.

White matter abnormalities in the anterior temporal lobe suggest the side of the seizure foci in temporal lobe epilepsy

INTRODUCTION

White matter abnormalities in the anterior temporal lobe (WAATL) are sometimes observed on magnetic resonance (MR) images of patients with temporal lobe epilepsy (TLE). Our purpose was to determine whether WAATL could indicate if the seizure foci are ipsilateral on electroencephalograms (EEG) in TLE patients.

METHODS

We reviewed 112 consecutive patients with medically intractable TLE. We compared the side of seizure foci on EEG (preoperative and intraoperative) and MR images.

RESULTS

Both loss of gray-white matter demarcation and increased signal intensity changes in the anterior white matter (positive WAATL) were observed in 54 of 112 patients (48.2%) with TLE. WAATL were present on the same side as the seizure foci on preoperative intracranial EEG with subdural electrodes (iEEG) and on intraoperative electrocorticography (ECG) in all the patients. In 47 patients, MR images showed WAATL and focal lesions that were possibly epileptogenic for TLE. In 2 of the 47 patients, the seizure foci on iEEG and ECG were contralateral to the focal lesion; in the remaining 45 patients, the seizure foci on surface EEG (sEEG) and ECG and the focal lesion were on the same side. In three patients, no focal lesions were seen but WAATL were present on the same side as the seizure foci on sEEG and ECG. In four patients, MR images showed focal lesions for which epileptogenicity was questionable, and WAATL on the same side as the seizure foci on EEG.

CONCLUSION

WAATL are clinically useful because they indicate the side of the seizure foci.

Imaging the neocortex in epilepsy with double inversion recovery imaging

The neocortices of 10 patients with partial seizures and acquired lesions, 14 patients with malformations of cortical development (MCD) and 33 patients with partial seizures and normal conventional MRI were quantitatively evaluated using whole brain double inversion recovery imaging (DIR) and Statistical Parametric Mapping (SPM). Compared to a group of 30 control subjects, DIR and objective voxel-by-voxel statistical comparison identified regions of significantly abnormal DIR signal intensity (DSI) in 9 out of 10 patients with acquired nonprogressive cerebral lesions and partial seizures. In all 9 patients, the areas of abnormal DSI concurred with abnormalities identified on visual inspection of conventional MRI. In all 14 patients with MCD, SPM detected regions of significantly abnormal DSI; all of which corresponded to abnormalities identified on visual inspection of conventional MRI. In addition, in both groups, there were areas that were normal on conventional imaging, which demonstrated abnormal DSI. Voxel-by-voxel statistical analysis identified significantly abnormal DSI in 15 of the 33 patients with cryptogenic focal epilepsy. In 10 of these, the areas of abnormal DSI concurred with epileptic EEG abnormality and clinical seizure semiology. Group analysis of MRI-negative patients with electroclinical seizure onset localising to the left temporal and left and right frontal regions revealed significantly abnormal DSI within the white matter of each respective lobe. DIR analysed using SPM was sensitive in patients with MCDs and acquired cerebral damage. Significant abnormalities in DSI in individual and grouped MRI-negative patients suggest that occult epileptogenic cerebral lesions are associated with subtle structural abnormalities. DIR is, therefore, a useful quantitative MRI technique for characterising epileptic foci and may contribute to presurgical evaluation.

Dysmorphic neurons in patients with temporal lobe epilepsy

We studied morphologic characteristics of dysmorphic neurons in the hippocampus of seven patients with medically intractable TLE and compare histological, clinical, and imaging features with ten TLE patients with classical hippocampal sclerosis without abnormal cells. Such dysmorphic neurons were observed in the hilus of the dentate gyrus and were characterized by giant or misshapen cells with abnormal cytoskeletal structure and atypical dendritic processes that resembled the dysmorphic neurons from cortical dysplasias. Specimens with dysmorphic cells also contained other cytoarchitectural abnormalities including bilamination of the dentate granular cell layer (four out seven cases), and the presence of Cajal-Retzius cells in the dentate gyrus or Ammon's horn (five out seven cases). There were no statistically significant differences regarding the age at onset, duration of epilepsy, and hippocampal asymmetry ratio between patients with or without dysmorphic cells. Nevertheless, it is interesting to note that a higher proportion of patients with dysmorphic neurons continued to present auras after surgery, when compared with patients without those cells.

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.

Structural abnormalities remote from the seizure focus: a study using T2 relaxometry at 3 T

OBJECTIVE

To determine the extent and severity of mesial temporal and subcortical signal abnormalities in patients with partial epilepsy.

METHODS

T2 relaxation time maps were acquired in 50 consecutive patients and 55 control subjects on a 3 T MRI scanner. Twenty-two patients had hippocampal sclerosis (HS), 16 had malformations of cortical development (MCD), and 12 had no obvious MR abnormalities (normal MR). The following eight regions were measured bilaterally: hippocampus, anterior temporal lobe (ATL) white matter, amygdala, frontal lobe white matter, caudate, putamen, pallidum, and thalamus.

RESULTS

In patients with HS, increased T2 relaxation times were found in the ipsilateral hippocampus and ATL but not in subcortical nuclei. In patients with MCD, increased T2 relaxation times were found in the temporal lobe (hippocampus, ATL) and in subcortical areas (caudate, putamen, and pallidum); in patients with normal MR, increased T2 relaxation times were found in the hippocampus and putamen. The degree of abnormality did not correlate with the duration of epilepsy or the estimated seizure load.

CONCLUSIONS

Mesial temporal structures show increased T2 relaxation times not only in patients with hippocampal sclerosis but also in patients with a seizure focus remote from the hippocampus. Patients with normal MR and focal malformations of cortical development have increased T2 relaxation times in subcortical structures. Therefore, abnormalities in T2 relaxation time can be found remote from the seizure focus. They cannot be simply attributed to secondary seizure effects.

The temporopolar cortex plays a pivotal role in temporal lobe seizures

We investigated the role of the temporal pole (TP) in 48 consecutive patients with drug-refractory temporal lobe epilepsy (TLE). Chronic depth recordings of TP cortex activity were used in association with video recording of ictal symptoms during 48 spontaneous seizures. In 23 cases (48%, group 1) the TP was involved at the onset of the seizure, before or concurrently with the hippocampus. In the remaining 25 patients (52%, group 2) the TP was involved 16.4 +/- 13.8 s after the hippocampus. A past history of febrile seizures was found in both groups, with no statistical difference. Ictal symptoms did not differentiate TP seizures from seizures originating in the hippocampus but the first clinical sign occurred sooner in group 1 compared with group 2 (respectively 10.56 +/- 9 and 25.7 +/- 19 s, respectively, P = 0.005). Loss of awareness also occurred sooner in the case of TP seizures compared with mesiotemporal lobe (MTL) seizures (22.9 +/- 22.6 versus 42.2 +/- 18.6 s, P = 0.0002). MRI data analysis showed that hippocampal sclerosis was present in both groups of patients, although it was more frequent in patients with MTL onset. Anterior temporal white matter changes were found ipsilateral to the epileptogenic area and tended to be more frequent in patients with TP seizures. All the patients underwent tailored anterior temporal lobectomy that included the TP, the hippocampus, the parahippocampal gyrus and the anterior part of the lateral temporal cortex. A better postoperative outcome was achieved in group 1 compared with group 2 (Engel class 1, 95 and 72% respectively, P = 0.04). We conclude that the frequent TP involvement at the onset of seizures could be a supplementary explanation for some failures of selective amygdalohippocampectomy, which should be addressed preferentially to well-selected patients. Moreover, the involvement of the TP cortex at the onset of the seizures is a good predicting factor for postoperative seizure outcome.

Limbic System Abnormalities Associated with Ammon's Horn Sclerosis Do Not Alter Seizure Outcome after Amygdalohippocampectomy

PURPOSE

To evaluate whether limbic system abnormalities associated with Ammon's horn sclerosis alter seizure outcome after selective amgydalohippocampectomy.

METHODS

In 45 patients with unilateral mesial temporal lobe epilepsy, histologically proven Ammon's horn sclerosis, and uneventful postoperative course, volumes of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix were measured by using a T(1)-weighted 3-D gradient-echo sequence with roughly isotropic (1.17 x 1.17 x 1-mm) voxels. In addition, signal intensity of the hippocampus and of the temporal lobe white matter was visually assessed and graded on a coronal T(2)-weighted fast-spin-echo sequence with 2-mm-thick slices. Volumetric measurements and visual analysis were compared between seizure-free and non-seizure-free patients examined 12 months after surgery.

RESULTS

Hippocampal, hemispheric, entorhinal cortex, mamillary body, and fornix volumes, but not amygdalar volumes, were significantly smaller on the operated-on than on the non-operated-on side and significantly smaller in patients compared with controls. No volume differences of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix existed between seizure-free (Engel class IA) and non-seizure-free patients (Engel class IB-IV). Increased temporal lobe white matter signal was observed in 15 patients but did not alter seizure outcome.

CONCLUSIONS

Limbic system abnormalities are not a surrogate marker to predict postsurgical seizure outcome in patients with unilateral Ammon's horn sclerosis.

Novel MR contrasts to reveal more about the brain

Twenty percent of patients with refractory focal epilepsy have an undetermined etiologic basis for their epilepsy despite extensive investigation, including optimal MR imaging. Surgical treatment of this group is associated with a less favorable postoperative outcome. Even with improvements in imaging techniques, a proportion of these patients will remain "MR imaging-negative." It is likely, however, that some of the discrete macroscopic focal lesions that are currently occult will be identified by imaging techniques interrogating different microstructural characteristics. Furthermore, these methods may provide pathologic specificity when used in combination. The description and application of these techniques in epilepsy are the focus of this article.

MR imaging of epilepsy: strategies for successful interpretation

MR imaging plays a pivotal role in the evaluation of patients with epilepsy. With its high spatial resolution, excellent inherent soft tissue contrast,multiplanar imaging capability, and lack of ionizing radiation, MR imaging has emerged as a versatile diagnostic tool in the evaluation of patients with epilepsy. MR imaging not only identifies specific epileptogenic substrates but also determines specific treatment and predicts prognosis. Employing appropriate imaging protocols and reviewing the images ina systematic manner helps in the identification of subtle epileptogenic structural abnormalities. With future improvements in software, hardware, and post-processing methods, MR imaging should be able to throw more light on epileptogenesis and help physicians to better understand its structural basis.

Qualitative and quantitative imaging of the hippocampus in mesial temporal lobe epilepsy with hippocampal sclerosis

MR imaging allows the in vivo detection of hippocampal sclerosis (HS) and has been instrumental in the delineation of the syndrome of mesial temporal lobe epilepsy with HS (mTLE-HS). MR features of HS include hippocampal atrophy with an increased T2 signal. Quantitative MR imaging accurately reflects the degree of hippocampal damage.Ictal single photon emission computed tomography (SPECT) in mTLE-HS shows typical perfusion patterns of ipsilateral temporal lobe hyperperfusion, and ipsilateral frontoparietal and contralateral cerebellar hypoperfusion. Interictal 18fluoro-2-deoxyglucose positron emission tomography (PET) shows multiregional hypometabolism, involving predominantly the ipsilateral temporal lobe. 11C-flumazenil PET shows hippocampal decreases in central benzodiazepine receptor density. Future strategies to study the etiology and pathogenesis of HS should include longitudinal MR imaging studies,MR studies in families with epilepsy and febrile seizures, stratification for genetic background, coregistration with SPECT and PET, partial volume correction and statistical parametric mapping analysis of SPECT and PET images.

Analysis of different types of resection for pediatric patients with temporal lobe epilepsy

OBJECTIVE

Resection strategies for the treatment of temporal lobe epilepsy (TLE) are a matter of discussion. Few data on the significance of resection type are available for pediatric patients with TLE.

METHODS

Data for a series of 89 children who were surgically treated for TLE were analyzed. A first cohort of patients were mainly surgically treated with anterior temporal lobectomies. For a second cohort, resections were preoperatively "tailored" to the lesion and presumed epileptogenic area.

RESULTS

The follow-up period was 46 months (range, 14-118 mo). Seventy-seven patients (87%) attained satisfactory seizure control (82% Engel Class I and 5% Class II). For 12 patients (13%), seizure control was unsatisfactory (8% Class III and 5% Class IV). Anterior temporal lobectomies resulted in 94% satisfactory seizure control (33 patients), whereas the success rates were only 74% (20 patients) for amygdalohippocampectomy (AH) (P = 0.023) and 77% (13 patients) for lesionectomy plus hippocampectomy (not significant). All patients who underwent purely lateral temporal lesionectomies became seizure-free (14 patients). Logistic regression revealed the factors of AH (P = 0.021) and left-side surgery (P = 0.017) as significant predictors of unsatisfactory seizure control. Satisfactory seizure control was not dependent on the histopathological diagnoses. There was a low rate of verbal memory deterioration after left-side operations. Neuropsychological deterioration was rare after right temporal resections. Attentional and contralateral functions improved after surgery.

CONCLUSION

Surgery for the treatment of juvenile TLE is successful and safe, but the resection type may influence outcomes. Results after AHs were disappointing, probably because of difficulties in precise localization of the epileptogenic focus among children. Neuropsychological results demonstrated minimal rates of deterioration and significant improvements in contralateral functions. Surgical treatment of juvenile TLE should be encouraged, but the use of especially left AH should possibly be restricted.

Analysis of parahippocampal gyrus in 115 patients with hippocampal sclerosis

PURPOSE: Analysis of the parahippocampal gyrus (PHG) involvement in 115 patients with hippocampal sclerosis (HS) by MR imaging. The simultaneous occurrence of ipsilateral fornix (F) and mamillary body (MB) volume loss was checked also. These findings were correlated with the side of hippocampal involvement, the sex, patient´s age, and the symptoms onset. METHOD: The MR images of 115 patients with HS were studied retrospectively. All the examinations were performed on 1.5 T units (SIGNA, GE, Milwaukee, WI) and included high resolution coronal T2-weighted images (3 mm thickness, 0.6 mm gap). RESULTS: The patient's age ranged between 3.5 and 80 years (mean 34.1); 62 (53.9%) were female and 53 (46.1%) were male. There were HS on the left side in 53 (46.0%), on the right side in 51 (44.3%), and bilateral in 11 (9.7%). In 43 (37.3%) cases there were ipsilateral PHG volume loss and signal hyper intensity on T2-weighted imaging. In 29 (25.2%) cases there were ipsilateral fornix volume loss and in 10 (34.5%) of this there were also ipsilateral MB changes. In abnormal PHG, 23 (53.4%) were on the left side, 17 (39.5%) were on the right side, and 3 (7.1%) were bilateral. There were fornix changes in 15 (34.8%) cases and MB volume loss in 5 (11.6%) cases. Pertinent clinical data were obtained in only 18 (41.8%) of the PHG lesion cases and 11 (61.1%) of these patients had epileptic attacks for more than 20 years before the examination. CONCLUSION: PHG involvement must be investigated in patients with HS and we suggest that the term mesial temporal sclerosis should be used only if there are also changes at this anatomical site.

Role of white matter lesions, cerebral atrophy, and APOE on cognition in older persons with and without dementia: the Cache County, Utah, study of memory and aging

Neuropsychological, qualitative, and quantitative magnetic resonance imaging findings were examined in subjects with Alzheimer's disease (AD), non-AD dementia or mixed neuropsychiatric disorder, subjects characterized as mild/ambiguous, and controls, all with known apolipoprotein E (APOE) genotype. Neuropsychological tasks included an expanded Consortium to Establish a Registery for Alzheimer's Disease (J. T. Tschanz et al., 2000; K. A. Welsh, J. M. Hoffman, N. L. Earl, & M. W. Hanson 1994) battery and the Mini-Mental Status Examination (M. F. Folstein, S. E. Folstein, & P. R. McHugh, 1975). Periventricular white matter lesions were the most clinically salient, and generalized measures of cerebral atrophy were the most significant quantitative indicators. APOE genotype was unrelated to imaging or neuropsychological performance. Neuropsychological relationships with neuroimaging findings depend on the qualitative or quantitative method used.

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

OBJECTIVES

To investigate the use of whole brain voxel based morphometry (VBM) and stereological analysis to study brain morphology in patients with medically intractable temporal lobe epilepsy; and to determine the relation between side, duration, and age of onset of temporal lobe epilepsy, history of childhood febrile convulsions, and grey matter structure.

METHODS

Three dimensional magnetic resonance images were obtained from 58 patients with left sided seizure onset (LSSO) and 58 patients with right sided seizure onset (RSSO), defined using EEG and foramen ovale recordings in the course of presurgical evaluation for temporal lobectomy. Fifty eight normal controls formed a comparison group. VBM was used to characterise whole brain grey matter concentration, while the Cavalieri method of modern design stereology in conjunction with point counting was used to estimate hippocampal and amygdala volume. Age and sex were used as confounding covariates in analyses.

RESULTS

LSSO and RSSO patients showed significant reductions in volume (using stereology) and grey matter concentration (using VBM) of the hippocampus, but not of the amygdala, in the presumed epileptogenic zone when compared with controls, but hippocampal (and amygdala) volume and grey matter concentration were not related to duration or age of onset of epilepsy. LSSO and RSSO patients with a history of childhood febrile convulsions had reduced hippocampal volumes in the presumed epileptogenic zone compared with patients without such a history. Left amygdala volume was also reduced in LSSO patients with a history of childhood convulsions. VBM results indicated bilateral thalamic, prefrontal, and cerebellar GMC reduction in patients, which correlated with duration and age of onset of epilepsy.

CONCLUSIONS

Hippocampal sclerosis is not necessarily the consequence of recurrent temporal lobe seizures. A major cause of hippocampal sclerosis appears to be an early aberrant neurological insult, such as childhood febrile seizures. Secondary brain abnormalities exist in regions outside the presumed epileptogenic zone and may result from recurrent seizures.