Diffusion tensor imaging abnormalities in focal cortical dysplasia

PURPOSE: Focal cortical dysplasia (FCD) is one of the most common underlying pathologic substrates in patients with medically intractable epilepsy. While magnetic resonance imaging (MRI) evidence of FCD is an important predictor of good surgical outcome, conventional MRI is not sensitive enough to detect all lesions. Previous reports of diffusion tensor imaging (DTI) abnormalities in FCD suggest the potential of DTI in the detection of FCD. The purpose of this study was to study subcortical white matter underlying small lesions of FCD using DTI. METHODS: Five patients with medically intractable epilepsy and FCD were investigated. Diffusion tensor imaging images were acquired (20 contiguous 3 mm thick axial slices) with maps of fractional anisotropy (FA), trace apparent diffusion coefficient (trace/3 ADC), and principal eigenvalues (ADC parallel and ADC perpendicular to white matter tracts) being calculated for each slice. Region of interest analysis was used to compare subcortical white matter ipsilateral and contralateral to the lesion. RESULTS: Three subjects with FCD associated with underlying white matter hyperintensities on T2 weighted MRI were observed to have increased trace/3 ADC, reduced fractional anisotropy and increased perpendicular water diffusivity which was greater than the relative increase in the parallel diffusivity. No DTI abnormalities were identified in two patients with FCD without white matter hyperintensities on conventional T2-weighted MRI. CONCLUSIONS: While DTI abnormalities in FCD with obvious white matter involvement are consistent with micro-structural degradation of the underlying subcortical white matter, DTI changes were not identified in FCD lesions with normal appearing white matter.     

Comparison of MRI features and surgical outcome among the subtypes of focal cortical dysplasia

PurposeFocal cortical dysplasia (FCD) is the most common pathological diagnosis in patients who have undergone surgical treatment for intractable neocortical epilepsy. However, presurgical identification of MRI abnormalities in FCD patients remains difficult, and there are no highly sensitive imaging parameters available that can reliably differentiate among FCD subtypes. The purpose of our study was to investigate the surgical outcome in FCD patients with identifiable MRI abnormalities and to evaluate the prognostic role of the various MRI features and the characteristics of FCD pathology.MethodsWe retrospectively recruited epilepsy patients who had undergone surgical treatment for refractory epilepsy with focal MRI abnormalities and the pathological diagnosis of FCD. We evaluated the surgical outcome according to the pathological subtypes, and studied the prognostic roles of various MRI features. We used recently proposed three-tiered FCD classification system which included FCD type III when FCD occurs in association with other potentially epileptogenic pathologies.ResultsA total of 69 patients were included, and 68.1% of patients became seizure free. Patients with FCD type III had a lower chance for achieving seizure freedom (7/15) than in patients with isolated FCD (FCD types I and II) (40/54, p = 0.044). Cortical thickness and blurring of gray–white matter junction were more common in isolated FCD than in FCD type III, but most MRI features failed to differentiate between FCD types I and II, and only the transmantle sign was specific for FCD type II. We failed to find a prognostic value of specific MRI abnormalities of prognostic value in terms of post-epilepsy surgery outcome in FCD patients.ConclusionsOur study showed that patients with FCD III have poor surgical outcome. Typical MRI features of isolated FCD such as cortical thickness and blurring of gray–white matter junction were less common in FCD type III and only transmantle sign was helpful in differentiating between FCD types I and II.     

脑皮质发育不良继发顽固性癫痫的病理分型及手术治疗

目的 探讨局灶性脑发育不良(FCD)的临床特征、病理学、影像学的特点及手术疗效.方法 42例外科手术切除致痫灶并经病理证实为FCD的患者中,根据Palmini病理学分型进行分类,并对其临床特征、影像学特点及手术疗效进行回顾性分析.结果 42例患者中,按致痫灶部位分类颢叶24例、额叶14例、顶叶6例及枕叶3例,其中多脑叶5例.术前影像学检查阳性率62%.组织学分型FCDⅠA型9例,FCDⅠB型21例,FCDⅡA型5例,FCDⅡB型7例,其中以FCD Ⅰ B型最为常见,多位于颞叶且常伴有海马硬化.所有患者术后至少随访1年以上,癫痫术后治愈率FCD位于颞叶67%,颞叶以外43%(EngleⅠa).结论 FCD是难治性癫痫常见的病理学改变,其病理分型与临床特征和致痫灶部位存在相关性,为制定手术方案和判定手术效果提供了依据.     

Enhanced visualization of blurred gray-white matter junctions in focal cortical dysplasia by voxel-based 3D MRI analysis

PURPOSE: Focal cortical dysplasia (FCD), a frequent cause of partial epilepsy, is often associated with blurring of the gray-white matter junction in magnetic resonance images (MRI). To improve the recognition and delineation of FCD we developed a novel voxel-based image post-processing method for enhanced visualization of blurred gray-white matter junctions. METHODS: Using standard algorithms of statistical parametric mapping software (SPM99) a T1-weighted MRI volume data set is normalized and segmented. The distribution of gray and white matter is analyzed on a voxelwise basis and compared with a normal database. Based on this analysis, a three-dimensional feature map is created which highlights brain areas with blurred gray-white matter transition. This method was applied to the MRI data of 25 epilepsy patients with histologically proven FCD. RESULTS: In 18/25 patients the new feature maps clearly showed that the dysplastic lesions were accompanied by blurring of the gray-white matter junction. Combined with a formerly published method of voxel-based 3D MRI analysis, 21/25 FCD lesions were shown to be associated with either blurring or abnormal extension of gray matter beyond the normal cortical ribbon, including four cases with lesions not or incompletely recognized on conventional MRI. CONCLUSIONS: The MRI post-processing presented here improves the visualization of FCD and may increase the diagnostic yield of MRI. Thereby, it provides a valuable additional diagnostic tool in the presurgical evaluation of epilepsy patients.     

Neuropathologic measurements in focal cortical dysplasias: validation of the ILAE 2011 classification system and diagnostic implications for MRI

Focal cortical dysplasias (FCD) which represent a composite group of cortical malformations are increasingly recognized as morphological substrate for severe therapy-refractory epilepsy in children and young adults. However, presurgical evaluation remains challenging as not all FCD variants can be reliably detected by high-resolution magnetic resonance imaging (MRI). Here, we studied a cohort of 52 epilepsy patients with neuropathological evidence for FCD using the 2011 classification of the International League against Epilepsy (ILAE) and systematically analysed those histopathologic features applicable also for MRI diagnostics. Histopathologic parameters included quantitative measurements of cellular profiles, cortical thickness, heterotopic neurons in white matter, and myelination that were compared between FCD subtypes and age-/localization-matched controls (n = 36) using multivariate analysis. Dysmorphic neurons in both FCD Type II variants showed significantly increased diameter of their cell bodies and nuclei. Cortical thickness was also increased with a distinct loss of myelin content specifying FCD Type IIb from IIa. The data further suggested that myelination deficits in FCD Type IIb result from compromised oligodendroglial lineage differentiation and we concluded that the "transmantle sign" is a unique finding in FCD Type IIb. In contrast, FCD Type Ia was characterized by a smaller cortical ribbon and higher neuronal densities, but these parameters failed to reach statistical significance (considering age- and location-dependent variability in controls). All FCD variants showed abnormal grey-white matter boundaries with increased numbers of heterotopic neurons. Similar results were obtained also at deep white matter location. Thus, many FCD variants may indeed escape visual MRI inspection, but suspicious areas with increased or decreased cortical thickness as well as grey-white matter blurring may be uncovered using post-processing protocols of neuroimaging data. The systematic analysis of well-specified histopathological features could be helpful to improve sensitivity and specificity in MRI detection during pre-surgical work-up of patients with drug-resistant focal epilepsies.     

Prospective magnetic resonance imaging identification of focal cortical dysplasia,including the non—balloon cell subtype

The purpose of this study was to determine the role of high-resolution T2-weighted fast multiplanar inversion-recovery (FMPIR) magnetic resonance (MR) imaging in detecting and delineating microscopic focal cortical dysplasia (FCD). We performed MR scans with FMPIR on 42 patients with suspected neocortical epilepsy. Ten MR studies were read prospectively as showing FCD; these case histories, electroencephalographic studies, and neuroimaging data were reviewed. Eight of these patients subsequently underwent focal cortical resection guided by intraoperative electrocorticography. The MR findings were correlated with pathological findings in these 8 patients. For purposes of radiological-pathological correlation, the FCD lesions were divided into two classes. Radiological classification was based on the absence (type A) or presence (type B) of T2 prolongation of the subcortical white matter. Pathological grading as type I or type II was based on a previously described pathological grading system. Specific MR findings associated with FCD included focal blurring of the gray-white matter interface (n = 9), thickening of the cortical ribbon (n = 7), and T2 prolongation of the subcortical white matter (n = 4). In 3 patients, the only MR finding that suggested FCD was localized blurring of the gray-white matter junction. In 2 of these 3 patients, the MR diagnosis of FCD could be made only by FMPIR. FCD was confirmed histologically in 7 of 8 patients, with insufficient tissue for complete histopathological evaluation in 1 case. Radiological classification of FCD agreed with pathological classification in 5 of 7 cases. Correlation of MR findings with intraoperative electrocorticography results indicated that the MR study localized the epileptogenic lesion correctly in 8 of 8 cases. Scalp ictal electroencephalographic studies localized the epileptogenic lesion in 5 of 8 cases; positron emission tomographic scans were focally abnormal in 3 of 3 cases. FMPIR MR imaging permitted accurate diagnosis and localization of FCD in all patients with pathologically proved FCD. MR identification of FCD aided presurgical planning and intraoperative management of these patients.     

高分辨MRI在Ⅰ型局灶性皮质发育不良患儿术前评估中的应用

目的 探讨高分辨MRI成像在儿童Ⅰ型局灶性皮质发育不良(FCD)术前评估中的价值.方法 回顾性分析52例经病理学证实的FCD Ⅰ型患儿的MRI及相关临床资料,比较高分辨成像与MRI常规序列对Ⅰ型FCD各主要MRI征象(局灶性灰白质分界模糊、局灶性皮质结构异常、白质异常信号灶及局限性脑叶萎缩/发育不全)的检出率,以及对病...     

神经导航结合术中皮质电刺激在局灶性皮质发育不良癫手术中的应用

目的探讨神经导航结合术中皮质电刺激(CES),在局灶性皮质发育不良(FCD)癫手术中的应用。方法对18例FCD癫病人行MRI薄层扫描及血氧水平依赖性功能磁共振成像(BOLD-fMRI)扫描,结合神经导航引导手术入路,CES定位运动区,皮质脑电图定位致灶,行致灶加病灶切除。结果术后病人肢体运动功能均与术前相同,病理结果均为FCD。术后随访1年,Engel分级:Ⅰ级14例,Ⅱ级2例,Ⅲ级1例,Ⅳ级1例。复查脑电图较术前明显改善,棘波、尖波基本消失。结论神经导航结合BOLD-fMRI、CES及皮质脑电图,在FCD癫手术中定位准确,减少运动功能损伤,达到癫灶切除及最大程度保护运动功能的目的。     

Intrinsic epileptogenicity of focal cortical dysplasia as revealed by magnetoencephalography and electrocorticography

Focal cortical dysplasia (FCD) is often associated with severe partial epilepsy. In this study, we performed magnetoencephalography (MEG) and electrocorticogrsphy (ECoG) on four patients with FCD-associated epilepsy to confirm the 'intrinsic' epileptogenicity of FCD. In all patients, we determined the three-dimensional locations of the magnetic sources of the interictal paroxysmal activities by a single dipole model, and then the estimated dipole localization was superimposed on the magnetic resonance image. The dipole clusters were located in the T2-prolonged lesions, namely in the FCD lesions themselves. All patients underwent surgery for their medically intractable epilepsy, and the acute and/or chronic ECoG were thereafter recorded. Either frequent or continuous paroxysmal activities were recorded from the ECoG electrodes which were placed over the surface of the FCD lesion, while few paroxysmal activities were observed on the normal appearing adjacent cortex. Intraoperative depth recordings were performed in a patient with the needle electrode inserted into the FCD lesion and they revealed these paroxysmal foci to be located not on the cortical surface but at a depth of 15 mm from the cortical surface where both abnormal giant neurons and bizarre large eosinophilic cells (so-called balloon cells) were also prominently observed on the postoperative histological sections. Following a lesionectomy combined with the removal of the underlying white matter, three patients demonstrated a favorable seizure outcome. Our findings thus suggest the FCD lesions to be highly and intrinsically epileptogenic lesions.     

Epilepsy surgery in children with focal cortical dysplasia (FCD): results of long-term seizure outcome

The purpose of this study was to assess the effect of epilepsy surgery on seizure outcome in children and adolescents under 18 years with intractable epilepsy due to focal cortical dysplasia. We analysed clinical data, such as age at seizure onset, epilepsy course, localisation of focus from presurgical evaluation, MRI, tissue pathology and seizure outcome in 68 patients 6 months to 9 years after epilepsy surgery. Seizure outcome was classified according to the Engel classification. Mean age at seizure onset was 7 months, ranging from the first days of life to 7 years. All patients had medically intractable epilepsy. Localisation of the lesion was predominantly extratemporal: posterior (uni- or multilobar) 43 %, frontal without central region 26 %, multilobar involving central area 19 % and temporal in 12 %. MRI signs typically seen in cortical dysplasia (FCD) such as localised blurring of gray-white matter junction was found in 68 %, dysgyria in 62 %, thickening of the cortical ribbon in 46 % and T2 signal elongation of the subcortical white matter in 40 % of the patients' MRI. Age at surgery ranged from 5 months to 16 years; 14 patients were under 2 years when operated on. In 34 patients (6 patients under 3 years) subdural grid electrode evaluation was performed prior to surgery. Pathology revealed focal cortical dysplasia without balloon cells (type I) in 60 %, FCD of the balloon cell subtype (type II) in 40 % of the specimens. Postoperative complications were subdural hygroma in 5 and an increased motor deficit in 2 patients. Up to two years after epilepsy surgery 50 % of the children were seizure free (Engel class I), 10 % Engel class II, 33 % Engel class III and 7 % unchanged (Engel class IV). Long-term seizure outcome (> 3 years post surgery) in 32 patients showed similar results (class I 50 %, class II 19 %, class III 28 %, class IV 3 %). Complete resection of the dysplastic lesion was significantly correlated with favorable seizure outcome, whereas seizure outcome was not significantly different in patients with mild (type I) or balloon cell (type II) FCD. Children operated after 6 years of age had no better outcome than children operated in infancy or at preschool age. Epilepsy surgery resulted in good (class I and II) seizure control in 60 % of children with intractable epilepsy due to focal cortical dysplasia.     

Different presurgical characteristics and seizure outcomes in children with focal cortical dysplasia type I or II

Purpose:   Cortical dysplasia (FCD) is a frequent cause of epilepsy in childhood. Two major pathological variants are distinguished, FCD type I and II. The aim of the study was to characterize differences between FCD type I and II with respect to imaging and EEG findings, clinical and neuropsychological presentations, and surgical outcome.
Methods:   Forty children with refractory epilepsy and histopathologically confirmed FCD were retrospectively analyzed. FCD type I was identified in 24 and FCD type II in 16 patients.
Results:   Characteristic MRI abnormalities in FCD type I included subtle white matter signal changes and regional reduction of the white matter volume. Typical MRI findings in FCD type II were increased cortical thickness, transmantle sign, gray-white matter junction blurring, fluid-attenuated inversion recovery (FLAIR) and proton density (PD) gray matter signal changes as well as T1w, and PD white matter signal changes. Continuous EEG slowing was significantly more common in patients with FCD type I. Children with FCD type I presented with lower levels of intelligence and were suffering more often from maladaptive behavior and behavioral disorders. Surgical outcome was significantly worse in the FCD type I group (seizure freedom was achieved in 21% FCD type I patients and in 75% FCD type II subjects, p < 0.001).
Conclusions:   Clinically important differences were found in children with distinct histopathological subtypes of FCD. Due to prominent neuropsychological deficits and worse seizure outcome, treatment strategies in FCD type I are more challenging than previously reported and these children should be recognized and specifically addressed within the incoherent group of patients with malformative brain disorders.     

Focal cortical dysplasia type IIb: completeness of cortical, not subcortical, resection is necessary for seizure freedom

Purpose: Focal cortical dysplasia type IIb (FCD IIb) lesions are highly epileptogenic and frequently cause pharmacoresistant epilepsy. Complete surgical resection leads to seizure freedom in most cases. However, the term “complete” resection is controversial with regard to the necessity of performing resections of the subcortical zone, which is frequently seen in these lesions on magnetic resonance imaging (MRI). Methods: We retrospectively analyzed 50 epilepsy patients with histologically proven FCD IIb. The extent of surgical resection was determined by SPM5‐based coregistration of the preoperative and postoperative MRI scans. Postoperative outcome was analyzed with regard to (1) the completeness of the resection of the cortical abnormality and (2) the completeness of the resection of the subcortical abnormality. Key Findings: Complete resection of the cortical abnormality led to postoperative seizure freedom (Engel class Ia) in 34 of 37 patients (92%), whereas incomplete cortical resection achieved this in only one of 13 patients (8%, p < 0.001). Among the patients with complete cortical resection, 36 had FCDs with a subcortical hyperintensity according to MRI. In this group, complete resection of the subcortical abnormality did not result in a better postoperative outcome than incomplete resection (90% vs. 93% for Engel class Ia, n.s.). Significance: Complete resection of the MRI‐documented cortical abnormality in FCD IIb is crucial for a favorable postoperative outcome. However, resection of the subcortical hyperintense zone is not essential for seizure freedom. Therefore, sparing of the subcortical white matter may reduce the surgical risk of encroaching on relevant fiber tracts. In addition, these findings give an interesting insight into the epileptogenic propensity of different parts of these lesions.     

Appearance of focal cortical dysplasia on serial MRI after maturation of myelination

Case report It is well known that magnetic resonance imaging (MRI) findings of focal cortical dysplasia (FCD) can change with maturation of myelination. In this paper, we report a patient with intractable epilepsy and negative MRI at the age of 2.5 years, after completion of myelination. Follow-up MRI at the age of 6 years revealed typical FCD findings in the right frontal lobe. During these 3.5 years, electroencephalogram (EEG) consistently depicted an area of irritation in accordance with de novo MRI findings. Intraoperative electrocorticogram showed frequent paroxysmal activity in the right frontal lobe; excision of the epileptogenic cortex resulted in a reduction in seizures. Conclusion It is possible that FCD becomes apparent on MRI even after maturation of myelination; thus, repeated MRI is recommended while EEG continues to demonstrate focal findings.     

Focal Cortical Dysplasias: clinical implication of neuropathological classification systems

Focal Cortical Dysplasias (FCDs) are highly epileptogenic brain lesions and are a frequent cause for drug-resistant focal epilepsies in humans. FCDs present with variable histopathological patterns, including architectural, cytoarchitectural or white matter abnormalities. Pathomechanisms compromising neuroblast proliferation, migration, or differentiation are likely to play a role in the etiology of FCD variants. FCDs were subsumed, therefore, into the broad spectrum of malformations of cortical development. The most frequent subtype comprises FCD Type II, which in general occurs as isolated lesion in extratemporal location and is histopathologically characterized by dysmorphic neurons (Type IIA) and balloon cells (Type IIB). Neuroimaging hallmarks include hyperintense T2-signaling and a “transmantle sign”. Electrophysiological recordings show peculiar interictal spike patterns and complete surgical resection results in favorable seizure control. In contrast, FCD Type I can be identified in young children with severe epilepsy and psychomotor retardation. Parietal, temporal, and occipital lobes may be involved in seizure generation, although neuroimaging often reveals normal contrast intensities. Surgical resection strategies ameliorate seizure frequencies in many children, whereas complete seizure relief can be achieved only in rare cases. According to the currently used FCD classification system, the same histopathological FCD Type I variant can be diagnosed as associated lesion in the large cohort of epilepsy patients with hippocampal sclerosis, low-grade glio-neuronal tumors, vascular malformations, or glial scarring. MRI is often not helpful to detect the dysplastic cortical areas. In addition, there is no specific electrophysiological pattern for an associated dysplastic lesion. Surgical resection of the epileptogenic area results, however, in favorable seizure control. These findings argue for a revised neuropathological classification system that distinguishes isolated versus associated FCD variants to obtain a better correlation with electro-clinical findings and prediction of postsurgical seizure control.     

Intraoperative ultrasound to define focal cortical dysplasia in epilepsy surgery

Focal cortical dyplasia (FCD) is a frequent cause of medication-resistant focal epilepsy. Patients with FCD may benefit from epilepsy surgery. However, it is difficult to intraoperatively define lesion boundaries. In this case report we present a novel tool to identify FCD intraoperatively. A patient with frontal lobe epilepsy underwent resection of a left frontomesial FCD. Image guidance was achieved by intraoperative ultrasound, which depicted the lesion with a higher resolution than preoperative MRI. Postoperatively the patient remained seizure free. Intraoperative ultrasound may be helpful in identifying and targeting subtle epileptogenic lesions, which are difficult to visualize.     

Taylor-type focal cortical dysplasia in infants: some MRI lesions almost disappear with maturation of myelination

Identification of focal cortical dysplasia (FCD) on magnetic resonance (MR) images of young children with refractory focal epilepsy is important, as surgical resection may offer improvement of seizure control and subsequent developmental progress. However, the MR appearances of malformations of cortical development may change during brain maturation. We report 4 children with refractory focal epilepsy, whose MR images in infancy showed localized cortical and subcortical signal abnormalities (hypointense on T(2)-weighted and hyperintense on T(1)-weighted images), suggestive of abnormal cortical development. The visibility of these lesions was significantly reduced on later MR images. Subtle blurring of the gray-white matter junction in these areas was the only indicator of cortical abnormality in 3 patients, which was recognized only after comparison with earlier images. Taylor-type FCD was subsequently confirmed in all patients, following surgical cortical resection of the lesions. MR images performed early within the first year of life in children with epilepsy are important to identify areas of FCD. The appearances of FCD on later scans can be very subtle escaping recognition, and conclusions may be misleading with respect to diagnosis and appropriateness of surgical treatment.     

Cortical and Hippocampal Volume Deficits in Temporal Lobe Epilepsy

Summary: Purpose : To use quantitative magnetic resonance imaging (MRI) methods to examine the extent of volume abnormalities in the hippocampus and in extrahippocampal brain regions in localization-related epilepsy of temporal lobe origin (TLE).
Methods : Hippocampal, temporal lobe, and extratemporal lobe volumes were examined with 3–mm spin-echo coronal MRI scans in patients with unilateral TLE who were candidates for temporal lobe resection. Measures were adjusted for normal variation due to intracranial volume and age based on 72 healthy male controls. Group differences between 14 male TLE [7 left TLE (LTLE), 7 right TLE (RTLE)] patients and a subset of 49 age range-matched controls were examined with analysis of variance (ANOVA).
Results : As compared with controls, patients with TLE had smaller temporal lobe and frontoparietal region gray matter volumes, bilaterally, smaller temporal lobe white matter volumes bilaterally, and larger ventricular volumes. In contrast to these bilateral tissue volume deficits, hippocampal volume deficits in TLE were ipsilateral to the epileptogenic temporal lobe.
Conclusions : Extrahippocampal volume abnormalities were bilateral and occurred in both temporal and extra-temporal cortical regions in TLE, whereas hippocampal deficits were related to the side of the epileptogenic focus. These data suggest that brain abnormalities in TLE are not limited to the epileptogenic region.     

Advances in neuroimaging: Non-substrate-directed partial epilepsy

Contemporary neuroimaging studies using structural and functional techniques are critical in the evaluation of patients with localization-related epilepsy. Imaging procedures may be used to localize the epileptic brain tissue or determine the likely pathologic findings underlying the epileptogenic zone, or both. The diagnostic yield of magnetic resonance imaging (MRI) has been demonstrated in patients with partial epilepsy. The identification of an MRI epileptogenic lesion is almost invariably a reliable indicator of the site of seizure onset. Peri-ictal single photon emission computed tomography (SPECT) may be of particular benefit in patients with normal MRI studies. The use of neuroimaging in the care and management of patients with partial epilepsy is discussed here.     

Contribution of magnetic resonance imaging in 100 cases of refractory partial epilepsy with normal CT scans

One hundred epileptic patients were included in this study according to the following criteria: intractable partial epilepsy, normal CT scan and focal EEG abnormalities. Eighty-nine patients were suffering from complex partial seizures of temporal or frontal origin, 55 and 34 cases respectively. Eleven patients presented with only simple partial seizures. MRI was abnormal in 31 patients. The abnormalities were: focal T2 increased signal intensity (13 cases) most often temporal (10 cases), cryptic arteriovenous malformation (4 cases), focal T1 and T2 signal abnormality (4 cases), focal atrophy (2 cases) and multiple abnormal T2 signals scattered in the white matter (8 cases). The site of MRI abnormalities was consistent with electroclinical data in 22 patients, of whom 20 had a temporal lobe epilepsy. Thus MRI proved to be more often abnormal in temporal than in frontal lobe epilepsy (36 p. 100 and 5.9 p. 100 respectively) when the CT scan is normal. However MRI data, particularly focal T2 hypersignals should be confronted to electroclinical and metabolic findings whenever functional surgery is considered.     

Ictal SPECT is useful in localizing the epileptogenic zone in infants with cortical dysplasia

Aims. To assess the localizing value of ictal SPECT in very young epilepsy surgery candidates when cerebral haemodynamic responses are known to be immature. Methods. We retrospectively studied 13 infants with intractable focal epilepsy caused by focal cortical dysplasia (FCD). Completeness of resection of the (1) ictal SPECT hyperperfusion zone and (2) cerebral cortex with prominent ictal and interictal abnormalities on intracranial EEG (ECoG or long‐term invasive monitoring) and the MRI lesion, when present, were correlated with postoperative seizure outcome. Results. All five patients with complete resection of the ictal SPECT hyperperfusion zone were seizure‐free compared to only one of eight patients with incomplete or no excision of hyperperfusion zones (p=0.00843). Similar results were noted for the MRI/iEEG‐defined epileptogenic region; five of six patients with complete removal were seizure‐free, whereas only one of seven incompletely resected patients was seizure‐free (p=0.02914). All four patients who underwent complete resection of both regions were seizure‐free compared to none of the six with incomplete resection (p=0.01179). Conclusion. Despite age‐related differences in cerebral perfusion, ictal SPECT provides useful localization data in infants with FCD. Complete resection of the hyperperfused regions is a strong predictor of favourable outcome. The added information may alleviate the need for invasive EEG evaluations in some patients.