Voxel-based morphometry in patients with idiopathic generalized epilepsies.
ABSTRACT Idiopathic generalized epilepsies (IGE) are a group of frequent age-related epilepsy syndromes. IGE are clinically characterized by generalized tonic-clonic, myoclonic and absence seizures. According to predominant seizure type and age of onset, IGE are divided in subsyndromes: childhood absence and juvenile absence epilepsy (AE), juvenile myoclonic epilepsy (JME) and generalized tonic-clonic seizures on awakening (GTCS). The limits between these subsyndromes are not well defined, supporting the existence of only one major syndrome. Visual assessment of routine magnetic resonance imaging (MRI) in patients with IGE is normal. MRI voxel-based morphometry (VBM) uses automatically segmented gray and white matter for comparisons, eliminating the investigator bias. We used VBM to study 120 individuals (47 controls, 44 with JME, 24 with AE and 15 with GTCS) to investigate the presence of subtle structural abnormalities in IGE subsyndromes. VBM was performed searching for abnormalities on gray matter concentration (GMC) between patients groups and controls. Compared to controls, JME presented increased GMC in frontobasal region and AE showed increased GMC in the superior mesiofrontal region. The GTCS group did not differ from controls. There were no areas of reduced GMC with the statistical level selected. Region of interest analysis showed increased GMC in the anterior portion of the thalamus in patients with absence seizures. Our results support subtle GMC abnormalities in patients with JME and AE when compared to controls. These findings suggest the existence of different patterns of cortical abnormalities in IGE subsyndromes.
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ABSTRACT: Traditionally lesion location has been reported using standard templates, text based descriptions or representative raw slices from the patient's CT or MRI scan. Each of these methods has drawbacks for the display of neuroanatomical data. One solution is to display MRI scans in the same stereotaxic space popular with researchers working in functional neuroimaging. Presenting brains in this format is useful as the slices correspond to the standard anatomical atlases used by neuroimagers. In addition, lesion position and volume are directly comparable across patients. This article describes freely available software for presenting stereotaxically aligned patient scans. This article focuses on MRI scans, but many of these tools are also applicable to other modalities (e.g. CT, PET and SPECT). We suggest that this technique of presenting lesions in terms of images normalized to standard stereotaxic space should become the standard for neuropsychological studies.Behavioural neurology 02/2000; 12(4):191-200. · 1.25 Impact Factor
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ABSTRACT: Absence seizures are the most pure form of generalized epilepsy. They are characterized in the electroencephalogram by widespread bilaterally synchronous spike-wave discharges (SWDs), which are the reflections of highly synchronized oscillations in thalamocortical networks. To reveal network mechanisms responsible for the initiation and generalization of the discharges, we studied the interrelationships between multisite cortical and thalamic field potentials recorded during spontaneous SWDs in the freely moving WAG/Rij rat, a genetic model of absence epilepsy. Nonlinear association analysis revealed a consistent cortical "focus" within the peri-oral region of the somatosensory cortex. The SWDs recorded at other cortical sites consistently lagged this focal site, with time delays that increased with electrode distance (corresponding to a mean propagation velocity of 1.4 m/sec). Intra-thalamic relationships were more complex and could not account for the observed cortical propagation pattern. Cortical and thalamic sites interacted bi-directionally, whereas the direction of this coupling could vary throughout one seizure. However, during the first 500 msec, the cortical focus was consistently found to lead the thalamus. These findings argue against the existence of one common subcortical pacemaker for the generation of generalized spike-wave discharges characteristic for absence seizures in the rat. Instead, the results suggest that a cortical focus is the dominant factor in initiating the paroxysmal oscillation within the corticothalamic loops, and that the large-scale synchronization is mediated by ways of an extremely fast intracortical spread of seizure activity. Analogous mechanisms may underlie the pathophysiology of human absence epilepsy.Journal of Neuroscience 03/2002; 22(4):1480-95. · 6.91 Impact Factor
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ABSTRACT: Grey matter heterotopias, demonstrated by MRI, may present with a broad spectrum of clinical severity. We have studied 33 patients with periventricular nodular heterotopias (PNH); 19 (58%) had unilateral and 14 (42%) bilateral lesions. Thirteen of the 19 patients (68%) with unilateral subependymal nodules of grey matter had, in addition, unilateral focal subcortical heterotopias (SNH), comprising 39% of the entire group. Most had normal intellectual and motor function but some presented with mild mental retardation and neurological deficits. Recurrent seizures were described in 82%, mainly partial attacks with temporo-parieto-occipital auras. Nodular heterotopias led to unilateral or bilateral independent temporal epileptic discharges in 47% of epileptic patients with PNH alone and in 61% of those who had SNH in addition. Extratemporal or multilobar, unilateral or bilateral interictal spiking was present in 10 other patients (36%). Two first degree relatives of patients with seizures were affected but had no seizures, three were investigated for other apparently unrelated neurological symptoms: memory impairment, vertigo or transient ischaemic attacks in one person each. Contiguous ovoid nodules of grey matter, symmetrically lining both lateral ventricles, were described in nine patients. Seven of them were female, including four with familial incidence of PNH. Such lesions may explain the familial occurrence of epilepsy in some families. Seven patients underwent anterior temporal resection: two patients with unilateral subependymal and focal subcortical heterotopias were seizure free or significantly improved. Four patients, three with PNH alone and one with additional subcortical nodules, did not improve significantly after surgery. The remaining patient was followed for less than 6 months.Brain 11/1995; 118 ( Pt 5):1273-87. · 9.92 Impact Factor