Functional Deficit Zone Research Articles

Neuropsychology of epilepsy surgery and theory-based practice: an opinion review.

The present review attempts to discuss how some of the central concepts from the Lurian corpus of theories are relevant to the modern neuropsychology of epilepsy and epilepsy surgery. Through the lenses of the main Lurian concepts (such as the qualitative syndrome analysis), we discuss the barriers to clinical reasoning imposed by quadrant-based views of the brain, or even atheoretical, statistically-based and data-driven approaches. We further advice towards a systemic view inspired by Luria's clinical work and theorizing, given their importance towards our clinical practice, by contrasting it to the modular views when appropriate. Luria provided theory-guided methods of assessment and rehabilitation of higher cortical functions. Although his work did not specifically address epilepsy, his theory and clinical approaches actually apply to the whole neuropathology spectrum and accounting for the whole panorama of neurocognition. This holistic and systemic approach to the brain is consistent with the network approach of the neuroimaging era. As to epilepsy, the logic of cognitive functions organized into complex functional systems, contrary to modular views of the brain, heralds current knowledge of epilepsy as a network disease, as well as the concept of the functional deficit zone.

Arousal deregulation in the co-shaping of neuropsychological dysfunction in frontal and mesial temporal lobe epilepsy

ObjectiveOur work aims to investigate the role of physiological arousal in the expression of neuropsychological deficits in frontal lobe epilepsy (FLE) and mesial temporal lobe epilepsy (mTLE), by drawing on the Lurian theory of brain function. MethodsFor this study a total of 43 patients with focal onset epilepsy has been taken; twenty-four patients with FLE, 19 patients with mTLE and 26 healthy controls, all matched for age and education. Participants underwent a comprehensive neuropsychological assessment including various cognitive domains, such as attention, episodic memory, speed of information processing, response inhibition and mental flexibility, working memory, verbal fluency (phonological & semantic). ResultsThere were no significant differences between FLE and mTLE patients in terms of neuropsychological performance. However, both FLE and mTLE patients showed significantly worse performance in several cognitive domains than HCs. The results seem to support our hypothesis that aberrant physiological arousal, as reflected in patients’ worse performance in vigilance and attention, response inhibition, and processing speed, along with other disease-specific variables, may co-determine neuropsychological dysfunction and/or impairment in both FLE and mTLE. ConclusionIdentifying a differential arousal-related neuropsychological affection in FLE and mTLE, among the known deleterious effects of the functional deficit zone and other disease-related variables, may further our understanding of the underlying cognitive-pathophysiological mechanisms in focal epilepsy syndromes.

Understanding frontal lobe function in epilepsy: Juvenile myoclonic epilepsy vs. frontal lobe epilepsy

AimTo compare neuropsychological function in juvenile myoclonic epilepsy (JME) and frontal lobe epilepsy (FLE) since frontal circuitry is involved in both conditions. By drawing on previously theory-guided hypotheses and findings, a particular emphasis is placed on the way different cognitive-pathophysiological mechanisms act upon to produce frontal dysfunction in JME (frontal-executive and attention-related problems: vigilance, reaction times, processing speed, and response inhibition) and in FLE (reflecting the coproduct of the functional deficit zone), respectively. MethodsA total of 16 patients with JME, 34 patients with FLE, and 48 normal controls, all matched for age and education, were administered a comprehensive battery of tests to assess frontal-executive functions, as well as attention, memory, and learning domains. Participants did not take medications other than antiepileptics or have a psychiatric history. ResultsPatients with FLE overall showed worse neuropsychological performance compared to both JME and HCs. With respect to JME, patients with FLE did significantly worse in measures of verbal and nonverbal executive function, short-term-, and long-term- auditory-verbal memory and learning, immediate and delayed episodic recall, visual attention and motor function, visuo-motor coordination and psychomotor speed, speed of visual information processing, and vocabulary. Patients with JME performed significantly worse compared to FLE only in associative semantic processing, while the former outperformed all groups in vocabulary, visuomotor coordination, and psychomotor speed. ConclusionWe suggest that selective impairments of visual- and mostly auditory-speed of information processing, vigilance, and response inhibition may represent a salient neuropsychological feature in JME. These findings suggest the existence of an aberrantly working executive-attention system, secondary to pathological reticulo-thalamo-cortical dynamics. Contrariwise, cortically (frontal and extra-frontal) and subcortically induced malfunction in FLE is determined by the functional deficit zone i.e., the ensemble of cortical and subcortical areas that are functionally abnormal between seizures.

Improving surgical outcome with electric source imaging and high field magnetic resonance imaging

While most patients with focal epilepsy present with clear structural abnormalities on standard, 1.5 or 3 T MRI, some patients are MRI-negative. For those, quantitative MRI techniques, such as volumetry, voxel-based morphometry, and relaxation time measurements can aid in finding the epileptogenic focus. High-field MRI, just recently approved for clinical use by the FDA, increases the resolution and, in several publications, was shown to improve the detection of focal cortical dysplasias and mild cortical malformations. For those cases without any tissue abnormality in neuroimaging, even at 7 T, scalp EEG alone is insufficient to delimitate the epileptogenic zone. They may benefit from the use of high-density EEG, in which the increased number of electrodes helps improve spatial sampling. The spatial resolution of even low-density EEG can benefit from electric source imaging techniques, which map the source of the recorded abnormal activity, such as interictal epileptiform discharges, focal slowing, and ictal rhythm. These EEG techniques help localize the irritative, functional deficit, and seizure-onset zone, to better estimate the epileptogenic zone. Combining those technologies allows several drug-resistant cases to be submitted to surgery, increasing the odds of seizure freedom and providing a must needed hope for patients with epilepsy.

AS2-1 TREATMENT OF BENIGN INTRA-AXIAL BRAIN TUMORS IN CHILDREN ASSOCIATED WITH EPILEPSY

Low grade neuro-epithelial tumors presenting early-onset epilepsy as the major neurological symptom have recently been categorized as low-grade epilepsy-associated neuro-epithelial tumors, LEAT. Ganglioglioma and dysembryoplastic neuroepithelial tumors consist up to 60% of LEAT. Common characteristics of LEAT being early onset seizure, younger than the age of 15, and temporal lobe localization, its criteria do not include histological or genetic features; LEAT is an independent classification, unrelated to WHO classification.Treatment for epilepsy associated with LEAT includes medication and surgery. As for drug therapy, most tumor-related seizures are controlled well with anti-epileptic drugs for focal epilepsy such as sodium channel blocker. On the other hand, those who are drug-resistant are candidates for surgical therapy. Because epileptogenic zone mostly exists not in tumor itself but in the marginal brain tissue, pure tumor resection without resection of peripheral epileptogenic zone sometimes fails to achieve satisfactory seizure outcome. Concept of epilepsy surgery is indispensable in pre-operative evaluation and in planning surgical strategy. Related association fibers in addition to five zones, epileptogenic zone, seizure onset zone, irritative zone, symptomatogenic zone and functional deficit zone should be taken into consideration.Long-term survival is expected in children who underwent total resection of benign tumors. Therefore, good seizure control is crucial in improving activities of daily lives.

Emotional asymmetries in refractory medial temporal and frontal lobe epilepsy: Their impact on predicting lateralization and localization of seizures

BackgroundEmotional disturbances have been reported in patients with epilepsy. Although conflicting results emanate from relevant studies, depressive symptoms are seen more often in temporal lobe epilepsy (TLE) whereas, hypomanic/manic symptoms usually accompany frontal lobe epilepsy (FLE); the above psychiatric symptoms are especially seen in refractory epilepsy. However, neocortical TLE and medial TLE are considered as distinct epileptic syndromes, and there is limited literature on comparison of affective traits in medial TLE (MTLE) and FLE. AimIn the present study, we sought to investigate affective traits among epilepsy surgery candidates suffering refractory left medial TLE (LMTLE), right medial TLE (RMTLE), left FLE (LFLE), and right FLE (RFLE). ResultsOur results revealed that patients with MTLE scored significantly higher than the ones with FLE in depression, anxiety, asthenia, and melancholia as measured by the Symptoms Rating Scale for Depression and Anxiety (SRSDA), while patients with FLE scored significantly higher in mania than those with MTLE. Moreover, patients with MTLE scored significantly higher than their FLE counterparts on the anxiety scale of the State Trait Personality Inventory (STPI)-trait version. When laterality of the seizure focus was taken into account, no differences were found among both patients with MTLE and patients with FLE, with exception for the Trail Making Test part B (TMT-B) in which patients with RMTLE performed significantly worse than patients with LMTLE. Seizure frequency was higher for FLE. ConclusionsWe provide evidence for an anterior-frontal versus a posterior-medial temporal cerebral functional asymmetry with regard to the manifestation of manic and depressive emotional traits in FLE and MTLE, respectively. Our results are mainly discussed within the frame of their contribution in localizing and to a lesser extent in lateralizing seizures foci in epilepsy surgery candidates. We suggest that this is of great importance in the context of preoperative monitoring of epilepsy surgery, especially when neuropsychologists are called upon to provide anatomical information in defining the functional deficit zone.

Potential implications of Luria's work for the neuropsychology of epilepsy and epilepsy surgery: A perspective for re-examination.

The pioneeristic work of Alexander Romanovic Luria into the field of human neuropsychology offered eminent contributions to clinical praxis by providing theory guided methods and instruments for the study of higher cortical functions. However, lots of this knowledge corpus either remains untranslated and thus inaccessible, or in some cases selectively overlooked by academic authorities and consequently not passed to the future generations of experts. Although Luria was not exclusively devoted to the study of epilepsy, his theories and clinical approaches actually penetrate the whole neuropathology spectrum. His holistic and systemic approach to the brain sounds nowadays more than opportune and consistent with the network approach of the modern neuroimaging era. As to epilepsy, the logic underlying the Lurian approach (cognitive functions organized into complex functional systems with intra- and/or inter-hemispheric distribution, as opposed to the modularistic view of the brain) seems consistent with our current knowledge in epileptology with respect to epileptic networks, as well as the modern construct of the functional deficit zone. These contributions seem to be highly promising for the neuropsychology of epilepsy and epilepsy surgery, since they provide clinicians with valuable methods and theories to assist them in the localization -and lateralization- of cognitive deficits. Consequently they are of great applicability in the context of the preoperative neuropsychological monitoring of patients candidates for epilepsy surgery, where neuropsychologist are called upon to provide surgeons with anatomical data.

Changes in the interictal and early postictal diffusion and perfusion magnetic resonance parameters in familial spontaneous epileptic cats

ObjectiveThe familial spontaneous epileptic cat (FSEC) is thought to be a good genetic model of mesial temporal lobe epilepsy. In the current study, cerebral diffusion and perfusion magnetic resonance imaging (MRI) were used to confirm the functional deficit zone in the FSEC and evaluate the effect of a single seizure on different brain regions. MethodsSix FSECs and six healthy control cats were used in this study. MRI was performed in the interictal state (resting state for control) and postictal state immediately after the vestibular stimulation-induced generalized epileptic seizure (control cats received the same stimulation as the FSECs). The apparent diffusion coefficient (ADC), fractional anisotropy and perfusion parameters (i.e., relative regional cerebral blood volume (rCBV), relative regional cerebral blood flow (rCBF), and relative regional mean transit time (rMTT)) were measured in the hippocampus, amygdala, thalamus, and gray and white matter. ResultsIn the interictal state, the rCBV and rMTT in the hippocampus was significantly decreased in FSECs, compared to the control. In the postictal state, FSECs had a significantly decreased ADC and an increased rCBV, rCBF, and rMTT in the hippocampus, and an increased rMTT in the amygdala, compared to the interictal state. ConclusionThis study showed that FSECs had interictal hypoperfusion in the hippocampus, and postictal hypodiffusion and hyperperfusion in the hippocampus and/or amygdala. These findings suggested that the hippocampus and/or amygdala act as the functional deficit and expanded seizure-onset zones in FSECs.

Interictal diffusion and perfusion magnetic resonance imaging features of cats with familial spontaneous epilepsy.

OBJECTIVE To evaluate the usefulness of diffusion and perfusion MRI of the cerebrum in cats with familial spontaneous epilepsy (FSECs) and identify microstructural and functional deficit zones in affected cats. ANIMALS 19 FSECs and 12 healthy cats. PROCEDURES Diffusion-weighted, diffusion tensor, and perfusion-weighted MRI of the cerebrum were performed during interictal periods in FSECs. Imaging findings were compared between FSECs and control cats. Diffusion (apparent diffusion coefficient and fractional anisotropy) and perfusion (relative cerebral blood volume [rCBV], relative cerebral blood flow [rCBF], and mean transit time) variables were measured bilaterally in the hippocampus, amygdala, thalamus, parietal cortex gray matter, and subcortical white matter. Asymmetry of these variables in each region was also evaluated and compared between FSECs and control cats. RESULTS The apparent diffusion coefficient of the total amygdala of FSECs was significantly higher, compared with that of control cats. The fractional anisotropy of the right side and total hippocampus of FSECs was significantly lower, compared with that of control cats. The left and right sides and total hippocampal rCBV and rCBF were significantly lower in FSECs than in control cats. The rCBV and rCBF of the parietal cortex gray matter in FSECs were significantly lower than in control cats. CONCLUSIONS AND CLINICAL RELEVANCE In FSECs, diffusion and perfusion MRI detected microstructural changes and hypoperfusion (lowered function) in the cerebrum during interictal periods from that of healthy cats. These findings indicated that diffusion and perfusion MRI may be useful for noninvasive evaluation of epileptogenic foci in cats.

Presurgical diagnosis of epilepsies – concepts and diagnostic tools

SummaryIntroduction.Numerous reviews of the currently established concepts, strategies and diagnostic tools used in epilepsy surgery have been published. The focus concept which was initially developed by Forster, Penfield and Jasper and popularised and enriched by Lüders, is still fundamental for epilepsy surgery.Aim.To present different conceptual views of the focus concept and to discuss more recent network hypothesis, emphasizing so-called “critical modes of an epileptogenic circuit”.Method.A literature search was conducted using keywords: presurgical evaluation, epileptic focus concepts, cortical zones, diagnostic tools.Review and remarks.The theoretical concepts of the epileptic focus are opposed to the network hypothesis. The definitions of the various cortical zones have been conceptualized in the presurgical evaluation of candidates for epilepsy surgery: the seizure onset zone versus the epileptogenic zone, the symptomatogenic zone, the irritative and functional deficit zones are characterized. The epileptogenic lesion, the “eloquent cortex” and secondary epileptogenesis (mirror focus) are dealt with. The current diagnostic techniques used in the definition of these cortical zones, such as video-EEG monitoring, non-invasive and invasive EEG recording techniques, magnetic resonance imaging, ictal single photon emission computed tomography, and positron emission tomography, are discussed and illustrated. Potential modern surrogate markers of epileptogenicity, such asHigh frequency oscillations, Ictal slow waves/DC shifts, Magnetic resonance spectroscopy, Functional MRI,the use ofMagnetized nanoparticlesin MRI,Transcranial magnetic stimulation,Optical intrinsic signalimaging, andSeizure predictionare discussed. Particular emphasis is put on the EEG: Scalp EEG, semi-invasive and invasive EEG (Stereoelectroencephalography) and intraoperative electrocorticography are illustrated. Ictal SPECT and18F-FDG PET are very helpful and several other procedures, such as dipole source localization and spike-triggered functional MRI are already widely used. The most important lateralizing and localizing ictal signs and symptoms are summarized. It is anticipated that the other clinically valid surrogate markers of epileptogenesis and epileptogenicity will be further developed in the near future. Until then the concordance of the results of seizure semiology, localization of epileptogenicity by EEG and MRI remains the most important prerequisite for successful epilepsy surgery.Conclusions and future perspectives.Resective epilepsy surgery is a widely accepted and successful therapeutic approach, rendering up to 80% of selected patients seizure free. Although other therapies, such as radiosurgery, and responsive neurostimulation will increasingly play a role in patients with an unresectable lesion, it is unlikely that they will replace selective resective surgery. The hope is that new diagnostic techniques will be developed that permit more direct definition and measurement of the epileptogenic zone.

Localization of interictal spikes and high frequency oscillations (HFO) using magnetoencephalography (MEG)

Event Abstract Back to Event Localization of interictal spikes and high frequency oscillations (HFO) using magnetoencephalography (MEG) Vahe Poghosyan1* 1 King Fahad Medical City, Department of Neurophysiology, National Neuroscience Institute, Saudi Arabia Epidemiological data show that about 40% of the patients with epilepsy are refractory to pharmacological treatment. In many such patients with focal epilepsy, an alternative therapeutic option of choice is the surgical resection of the epileptogenic zone. At present, a variety of diagnostic tools (e.g. analysis of seizure semiology, electrophysiological and neuroimaging tools, functional testing etc.) are used to define the different epilepsy-related cortical zones (symptomatogenic, irritative, seizure onset and functional deficit zones, and epileptogenic lesion), each of which indexes to a certain extent the location and boundaries of the epileptogenic zone. Recently, high frequency oscillations (HFO, 80 – 500 Hz) have been proposed as accurate biomarkers of the epileptogenic zone in intracranial electroencephalography recordings (Jacobs et al. 2012). Magnetoencephalography (MEG) substantially contributes to the pre-surgical evaluation of patients with focal epilepsy. Currently, its primary application is to localize the cortical sources of interictal spikes (irritative zone) as an estimate for the epileptogenic zone. Recent studies have shown that MEG can also be used to identify and localize sources of HFOs (Papadelis et al., 2009; Rampp et al., 2010). Accurate identification and localization of MEG HFOs can provide an important non-invasive biomarker for epileptogenicity. We have used several source localization methods to estimate and compare the sources of MEG interictal spikes and HFOs, and correlate them with the clinical information and post-surgical outcome. In this presentation, I will describe the results of this analysis and provide relevant recommendations. References Jacobs J., Staba R., Asano E., Otsubo H., Wu J.Y., Zijlmans M., Mohamed I., Kahane P., Dubeau F., Navarro V., and Gotman J. (2012). High-frequency oscillations (HFOs) in clinical epilepsy. Progress in neurobiology, 98: 302–315 Papadelis C., Poghosyan V., Fenwick P.B.C., and Ioannides A.A. (2009). MEG’s ability to localize accurately weak transient neural sources. Clinical Neurophysiology, 120: 1958–1970 Rampp S., Kaltenhäuser M., Weigel D., Buchfelder M., Blümcke I., Dörfler A., and Stefan, H. (2010). MEG correlates of epileptic high gamma oscillations in invasive EEG. Epilepsia, 51: 1638–1642. Keywords: Epilepsy, interictal epileptiform discharges, interictal spikes, Magnetoencephalography (MEG), high frequency oscillation Conference: SAN2016 Meeting, Corfu, Greece, 6 Oct - 9 Oct, 2016. Presentation Type: Oral Presentation in the Symposium Epilepsy and Sleep Topic: Symposium Epilepsy and Sleep Citation: Poghosyan V (2016). Localization of interictal spikes and high frequency oscillations (HFO) using magnetoencephalography (MEG). Conference Abstract: SAN2016 Meeting. doi: 10.3389/conf.fnhum.2016.220.00122 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 Aug 2016; Published Online: 01 Aug 2016. * Correspondence: Dr. Vahe Poghosyan, King Fahad Medical City, Department of Neurophysiology, National Neuroscience Institute, Riyadh, Saudi Arabia, vpoghosyan@kfmc.med.sa Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vahe Poghosyan Google Vahe Poghosyan Google Scholar Vahe Poghosyan PubMed Vahe Poghosyan Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Network specific change in white matter integrity in mesial temporal lobe epilepsy

ObjectivesTo identify the specific change of white matter integrity that occurs in the brain network related to epileptic activity in patients with mesial temporal lobe epilepsy (MTLE). MethodsWe recruited 18 patients with MTLE and 18 healthy subjects. In MTLE patients, the remote functional-deficit zone was delineated using fluorodeoxyglucose positron emission tomography as an extratemporal region showing glucose hypometabolism. Using diffusion magnetic resonance imaging tractography, we defined a seizure propagation tract (PT) as a white matter pathway that connects the focus with a remote functional deficit zone. We also used the corticospinal tract (CST) and inferior longitudinal fasciculus (ILF) as control tracts in the hemisphere ipsilateral to the focus. Fractional anisotropy (FA), mean diffusivity (MD), and volume of the tracts were compared among PT, CST, and ILF. ResultsTractographic analysis identified the uncinate fasciculus, arcuate fasciculus, and fornix as PTs. A decrease in FA was found in MTLE patients compared with healthy subjects in all tracts, but PTs showed a more significant decrease in FA than did the two control tracts. Although the change in MD was also found in MTLE patients compared with healthy controls, a tract-specific change was not observed. Although white-matter damage was observed in all candidate tracts examined, the integrity of white matter was most significantly decreased in PTs in MTLE. ConclusionThe change in white matter integrity occurs specifically in the pathways that connect the focus and remote functional deficit zones in patients with MTLE, i.e., the pathways that are assume to be associated with seizure propagation.

Professor Hans Otto Lüders

Professor Lüders has made significant contributions to Clinical Neurology and particularly to Epilepsy and Clinical Neurophysiology. Some of his most important contributions include the following: 1.He pioneered the use of chronically implanted, large plates of subdural electrodes in the presurgical evaluation of patient who were candidates for epilepsy surgery. These electrodes were used to record epileptic seizures and by electrical stimulation to establish the location of eloquent cortex. Lately he has also advocated the use in the USA of stereotactically implanted depth electrodes for presurgical evaluation of epilepsy patients who had deep seated epileptic foci which were impossible to assess with subdural electrodes. These techniques were imported from Europe. 2.Mapping studies with subdural electrodes led to the discovery of a number of cortical eloquent areas that had not been described before: a. The basal temporal language area located in the dominant fusiform gyrus. b. The "negative motor areas" located in the caudal region of the inferior frontal gyrus (bilaterally) and immediately in mesial frontal pre-SMA region (also bilaterally). He concluded that these "negative motor areas" most likely correspond to praxis regions. c. The dominant posterior fusiform gyrus which plays a crucial role in processing reading material. Stimulation of that area produces "alexia without agraphia". 3.He developed a new classification of epileptic seizures based exclusively on semiological ictal characteristics. With the development of the semiological seizure classification he also defined several new seizure types: a. Dialeptic seizures, b. Hypnopompic seizures, c. Hypomotor seizures. 4.Working with general epilepsy principles, he established the existence of 6 zones that characterize the epilepsies: the epileptogenic zone, the irritative zone, the seizure onset zone, the epileptogenic lesion, the symptomatogenic zone and functional deficit zone. 5.He described the ictal DC (direct current) shift seen at the beginning of focal seizures and its value for localization of the seizure onset zone.

Visual hallucinations of autobiographic memory and asomatognosia: a case of epilepsy due to brain cysticercosis

The current study describes the case of a woman with symptomatic epilepsy due to brain cysticercosis acquired during childhood. During her adolescence, she developed seizures characterized by metamorphopsia, hallucinations of autobiographic memory and, finally, asomatognosia. Magnetic brain imaging showed a calcified lesion in the right occipitotemporal cortex, and positron emission tomography imaging confirmed the presence of interictal hypometabolism in two regions: the right parietal cortex and the right lateral and posterior temporal cortex. We discuss the link between these brain areas and the symptoms described under the concepts of epileptogenic lesion, epileptogenic zone, functional deficit zone, and symptomatogenic zone.

Chapter Ten - Modern Techniques of Epileptic Focus Localization

A clear concept of epileptic zones remains of high clinical relevance in presurgical evaluation of refractory epilepsy patients and in resection planning. Recent advances in understanding how each of the epileptic zones is functionally organized strengthened the importance of the network concept. It has been shown that neuronal networks underlying the individual epileptic zone may involve multiple brain structures with complex interactions between them. The network concept has impact not only for better understanding of pathophysiology of partial epilepsy but also for clinical practice, particularly for epilepsy surgery. This review examines recent reports on the use of advanced imaging techniques which enable to map the epileptic zones and their structural and functional organization. Magnetic resonance postprocessing substantially improved the accuracy in detection of the epileptogenic lesions. The seizure-onset zone is primarily determined by electrophysiology but can also be localized using single photon emission computed tomography. The functional deficit zone is commonly assessed by a number of tests including methods of functional neuroimaging (positron emission tomography) which can delineate hypometabolic cortical areas and subcortical structures. Hemodynamic fluctuations associated with interictal epileptiform discharges can be detected by novel functional magnetic resonance technique which is nowadays widely used for the irritative zone localization. These techniques open new prospect for epilepsy surgery in patients who were previously considered as not suitable candidates of surgical treatment.

Visuo-spatial memory tests in right temporal lobe epilepsy foci: Clinical validity

ObjectiveTo examine the appropriateness of visual memory tests as an identification method for right mesial temporal lobe dysfunctions in an epilepsy patient group and to study the relationship and possible overlap with non-memory cognitive domains and demographic variables. MethodsEighty preoperative candidates with mesial temporal lobe epilepsy (TLE) were examined using the “Corsi Block-Tapping Test”, “Diagnosticum für Cerebralschädigung” (DCS), the path subtest of the “Verbaler und Visueller Merkfähigkeitstest” (VVM), and the Rey-Osterrieth Complex Figure Test (ROCF). Factorial analyses were performed on raw scores to determine the effect of epilepsy–related variables, interictal epileptiform discharges (IEDs) and presence of cortical dysgenesis, on visual and verbal memory parameters. Sensitivity, specificity and Receiver Operating Characteristic (ROC) curves were calculated based on normative data. Furthermore, Spearman correlations between memory and non-memory cognitive tasks were performed. ResultsThe scores for test sensitivity and specificity and the ROC curves illustrate the tests' poor capacity to lateralize the functional deficit zone even when epilepsy–related factors, such as cortical dysgenesis or presence of contralateral IEDs were controlled. Significant correlations were found between the visual memory measures and nonverbal reasoning, processing speed, attentional flexibility, and visual planning. ConclusionThese neuropsychological tests are not sensitive enough to lateralize the epileptogenic focus in temporal lobe epilepsy patients since in addition to learning and consolidation processes, they measure additional cognitive domains. These results have implications for clinical neuropsychologists, in terms of test choice and the interpretation in the context of presurgical diagnostics.

Anatomy-based reconstruction of FDG-PET images with implicit partial volume correction improves detection of hypometabolic regions in patients with epilepsy due to focal cortical dysplasia diagnosed on MRI

Detection of hypometabolic areas on interictal FDG-PET images for assessing the epileptogenic zone is hampered by partial volume effects. We evaluated the performance of an anatomy-based maximum a-posteriori (A-MAP) reconstruction algorithm which combined noise suppression with correction for the partial volume effect in the detection of hypometabolic areas in patients with focal cortical dysplasia (FCD). FDG-PET images from 14 patients with refractory partial epilepsy were reconstructed using A-MAP and maximum likelihood (ML) reconstruction. In all patients, presurgical evaluation showed that FCD represented the epileptic lesion. Correspondence between the FCD location and regional metabolism on a predefined atlas was evaluated. An asymmetry index of FCD to normal cortex was calculated. Hypometabolism at the FCD location was detected in 9/14 patients (64%) using ML and in 10/14 patients (71%) using A-MAP reconstruction. Hypometabolic areas outside the FCD location were detected in 12/14 patients (86%) using ML and in 11/14 patients (79%) using A-MAP reconstruction. The asymmetry index was higher using A-MAP reconstruction (0.61, ML 0.49, p=0.03). The A-MAP reconstruction algorithm improved visual detection of epileptic FCD on brain FDG-PET images compared to ML reconstruction, due to higher contrast and better delineation of the lesion. This improvement failed to reach significance in our small sample. Hypometabolism outside the lesion is often present, consistent with the observation that the functional deficit zone tends to be larger than the epileptogenic zone.

Medial temporal lobe epilepsy associated with cortical dysplasia extending from the medial temporal lobe to the fornix: a case report

We report a case of lesional medial temporal lobe epilepsy (TLE) associated with cortical dysplasia extending from the right medial temporal lobe to the fornix via the basal and medial aspects of the frontal lobe and septum pellucidum. A 23-year-old man had had medically intractable psychomotor seizures since 11 years of age. Interictal EEG demonstrated paroxysmal activities in the right temporal region, and functional imaging by positron emission tomography with [18F] fluorodeoxyglucose revealed a functional deficit zone in the apex and medial part of the right temporal lobe. An intraoperative electrocorticogram demonstrated frequent paroxysmal activities in the medial temporal lobe. An anterior temporal lobectomy was performed, with an additional hippocampectomy including the focus of the paroxysmal activities on the intraoperative hippocampal EEG. Postoperatively, he became seizure-free. The surgical strategies for intractable TLE with widely distributed cortical dysplasia lesion are discussed.

THE SURGERY OF EPILEPSY

The idea of surgical treatment for epilepsy is not new. However, widespread use and general acceptance of this treatment has only been achieved during the past three decades. A crucial step in this direction was the development of video electroencephalographic monitoring. Improvements in imaging resulted in an increased ability for preoperative identification of intracerebral and potentially epileptogenic lesions. High resolution magnetic resonance imaging plays a major role in structural and functional imaging; other functional imaging techniques (e.g., positron emission tomography and single-photon emission computed tomography) provide complementary data and, together with corresponding electroencephalographic findings, result in a hypothesis of the epileptogenic lesion, epileptogenic zone, and the functional deficit zone. The development of microneurosurgical techniques was a prerequisite for the general acceptance of elective intracranial surgery. New less invasive and safer resection techniques have been developed, and new palliative and augmentative techniques have been introduced. Today, epilepsy surgery is more effective and conveys a better seizure control rate. It has become safer and less invasive, with lower morbidity and mortality rates. This article summarizes the various developments of the past three decades and describes the present tools for presurgical evaluation and surgical strategy, as well as ideas and future perspectives for epilepsy surgery.

Presurgical evaluation of epilepsy

The objective of the multimodality presurgical evaluation in patients with refractory epilepsy is to establish sufficient concordance among the various investigations. There should be maximum overlap in the epileptogenic zone, the irritative zone, the ictal onset zone, the functional deficit zone and the symptomatogenic zone. The ictal and interictal electroencephalogram measures the localization of epileptiform discharges, which should be concordant with structural abnormalities noted on MRI brain and functional abnormalities in the form of a zone of hypometabolism on fluorodeoxyglucose positron emission tomography, interictal single photon emission computerized tomography (SPECT) or hyperperfusion of the epileptogenic zone on ictal SPECT for a good surgical outcome. There should be no conflicting data from any of these studies, neuropsychological evaluation or seizure semiology.