Intracranial EEG-fMRI analysis of focal epileptiform discharges in humans

Purpose: Combining intracranial electroencephalography (iEEG) with functional magnetic resonance imaging (fMRI) is of interest in epilepsy studies as it would allow the detection of much smaller interictal epileptiform discharges than can be recorded using scalp EEG‐fMRI. This may help elucidate the spatiotemporal mechanisms underlying the generation of interictal discharges. To our knowledge, iEEG‐fMRI has never been performed at 3 Tesla (3T) in humans. We report our findings relating to spike‐associated blood oxygen level–dependent (BOLD) signal changes in two subjects. Methods: iEEG‐fMRI at 3T was performed in two subjects. Twelve channels of iEEG were recorded from subdural strips implanted on the left posterior temporal and middle frontal lobes in a 20‐year‐old female with bilateral periventricular gray matter heterotopia. Twenty channels of iEEG were recorded bilaterally from two subdural strips laid anterior–posterior along mesial temporal surfaces in a 29‐year‐old woman with bilateral temporal seizures and mild left amygdalar enlargement on MRI. Functional MRI (fMRI) statistical maps were generated and thresholded at p = 0.01. Key Findings: No adverse events were noted. A total of 105 interictal discharges were recorded in the posterior middle temporal gyrus of Subject 1. In Subject 2, 478 discharges were recorded from both mesial temporal surfaces (n = 194 left, 284 right). The right and left discharges were modeled separately, as they were independent. Subject 1 showed spike‐associated BOLD signal increases in the left superior temporal region, left middle frontal gyrus, and right parietal lobe. BOLD decreases were seen in the right frontal and parietal lobes. In Subject 2, BOLD signal increases were seen in both mesial temporal lobes, which when left and right spikes were modeled independently, were greater on the side of the discharge. In addition, striking BOLD signal decreases were observed in the thalamus and posterior cingulate gyrus. Significance: iEEG‐fMRI can be performed at 3T with low risk. Notably, runs of only 5 or 10 min of EEG‐fMRI were performed as part of our implementation protocol, yet a significant number of epileptiform discharges were recorded, allowing meaningful analyses. With these studies, we have shown that deactivation can be seen in individual subjects with focal epileptiform discharges. These preliminary observations suggest a novel mechanism through which focal interictal discharges may have widespread cortical and subcortical influences.     

Widespread epileptic networks in focal epilepsies: EEG-fMRI study

Purpose: To assess the extent of brain involvement during focal epileptic activity, we studied patterns of cortical and subcortical metabolic changes coinciding with interictal epileptic discharges (IEDs) using group analysis of simultaneous electroencephalography and functional magnetic resonance imaging (EEG‐fMRI) scans in patients with focal epilepsy. Methods: We selected patients with temporal lobe epilepsy (TLE, n = 32), frontal lobe epilepsy (FLE, n = 14), and posterior quadrant epilepsy (PQE, n = 20) from our 3 Tesla EEG‐fMRI database. We applied group analysis upon the blood oxygen–level dependent (BOLD) response associated with focal IEDs. Key Findings: Patients with TLE and FLE showed activations and deactivations, whereas in PQE only deactivations occurred. In TLE and FLE, the largest activation was in the mid–cingulate gyri bilaterally. In FLE, activations were also found in the ipsilateral frontal operculum, thalamus, and internal capsule, and in the contralateral cerebellum, whereas in TLE, we found additional activations in the ipsilateral mesial and neocortical temporal regions, insula, and cerebellar cortex. All three groups showed deactivations in default mode network regions, the most widespread being in the TLE group, and less in PQE and FLE. Significance: These results indicate that different epileptic syndromes result in unique and widespread networks related to focal IEDs. Default mode regions are deactivated in response to focal discharges in all three groups with syndrome specific pattern. We conclude that focal IEDs are associated with specific networks of widespread metabolic changes that may cause more substantial disturbance to brain function than might be appreciated from the focal nature of the scalp EEG discharges.     

Understanding the pathophysiology of reflex epilepsy using simultaneous EEG‐fMRI

Measuring neuro‐haemodynamic correlates in the brain of epilepsy patients using EEG‐fMRI has opened new avenues in clinical neuroscience, as these are two complementary methods for understanding brain function. In this study, we investigated three patients with drug‐resistant reflex epilepsy using EEG‐fMRI. Different types of reflex epilepsy such as eating, startle myoclonus, and hot water epilepsy were included in the study. The analysis of EEG‐fMRI data was based on the visual identi?cation of interictal epileptiform discharges on scalp EEG. The convolution of onset time and duration of these epilepsy spikes was estimated, and using these condition‐specific effects in a general linear model approach, we evaluated activation of fMRI. Patients with startle myoclonus epilepsy experienced epilepsy in response to sudden sound or touch, in association with increased delta and theta activity with a spike‐and‐slow‐wave pattern of interictal epileptiform discharges on EEG and fronto‐parietal network activation pattern on SPECT and EEG‐fMRI. Eating epilepsy was triggered by sight or smell of food and fronto‐temporal discharges were noted on video‐EEG (VEEG). Similarly, fronto‐temporo‐parietal involvement was noted on SPECT and EEG‐fMRI. Hot water epilepsy was triggered by contact with hot water either in the bath or by hand immersion, and VEEG showed fronto‐parietal involvement. SPECT and EEG fMRI revealed a similar fronto‐parietal‐occipital involvement. From these results, we conclude that continuous EEG recording can improve the modelling of BOLD changes related to interictal epileptic activity and this can thus be used to understand the neuro‐haemodynamic substrates involved in reflex epilepsy.     

Combining EEG and fMRI in the study of epileptic discharges

The combining of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) is a unique noninvasive method for investigating the brain regions involved at the time of epileptic discharges. The neuronal discharges taking place during an interictal spike or spike-wave burst result in an increase in metabolism and blood flow, which is reflected in the blood oxygen-level dependent (BOLD) signal measured by fMRI. This increase is most intense in the region generating the discharge but is also present in regions affected by the discharge. On occasion, epileptic discharges result in decreased metabolism, the origin of which is only partially understood. EEG-fMRI applied to focal epilepsy results in maxima of the BOLD signal most often concordant with other methods of localization and has been shown to help in localizing epileptic foci in nonlesional frontal lobe epilepsy. It has also demonstrated the involvement of the thalamus in generalized epileptic discharges. In patients with new-onset epilepsy it could be used to evaluate the source and extent of the brain structures involved during discharges and their evolution as the disease progresses.     

Simultaneous EEG-fMRI in drug-naive children with newly diagnosed absence epilepsy

Purpose: In patients with idiopathic generalized epilepsy (IGE), blood oxygen level dependent (BOLD) EEG during functional MRI (EEG‐fMRI) has been successfully used to link changes in regional neuronal activity to the occurrence of generalized spike‐and‐wave (GSW) discharges. Most EEG‐fMRI studies have been performed on adult patients with long‐standing epilepsy who were on antiepileptic medication. Here, we applied EEG‐fMRI to investigate BOLD signal changes during absence seizures in children with newly diagnosed childhood absence epilepsy (CAE). Methods: Ten drug‐naive children with newly diagnosed CAE underwent simultaneous EEG‐fMRI. BOLD signal changes associated with ictal EEG activity (i.e., periods of three per second GSW) were analyzed in predefined regions‐of‐interests (ROIs), including the thalamus, the precuneus, and caudate nucleus. Results: In 6 out of 10 children, EEG recordings showed periods of three per second GSW during fMRI. Three per second GSW were associated with regional BOLD signal decreases in parietal areas, precuneus, and caudate nucleus along with a bilateral increase in the BOLD signal in the medial thalamus. Taking into account the normal delay in the hemodynamic response, temporal analysis showed that the onset of BOLD signal changes coincided with the onset of GSW. Discussion: In drug‐naive individuals with CAE, ictal three per second GSW are associated with BOLD signal changes in the same striato‐thalamo‐cortical network that changes its regional activity during primary and secondary generalized paroxysms in treated adults. No BOLD signal changes in the striato‐thalamo‐cortical network preceded the onset of three per second GSW in unmediated children with CAE.     

Increased cortical BOLD signal anticipates generalized spike and wave discharges in adolescents and adults with idiopathic generalized epilepsies

Purpose: Electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) coregistration has recently revealed that several brain structures are involved in generalized spike and wave discharges (GSWDs) in idiopathic generalized epilepsies (IGEs). In particular, deactivations and activations have been observed within the so‐called brain default mode network (DMN) and thalamus, respectively. In the present study we analyzed the dynamic time course of blood oxygen level–dependent (BOLD) changes preceding and following 3 Hz GSWDs in a group of adolescent and adult patients with IGE who presented with absence seizures (AS). Our aim was to evaluate cortical BOLD changes before, during, and after GSWD onset. Methods: Twenty‐one patients with IGE underwent EEG‐fMRI coregistration. EEG‐related analyses were run both at the single‐subject and at group level (random effect). The time‐course analysis was conducted for 3 s time windows before, during, and after GSWDs, and they were included until no further BOLD signal changes were observed. Key Findings: Fifteen patients (nine female, mean age 28 years) had GSWDs during EEG‐fMRI coregistration (262 total events, mean duration 4 s). Time‐course group analysis showed BOLD increments starting approximately 10 s before GSWD onset located in frontal and parietal cortical areas, and especially in the precuneus‐posterior cingulate region. At GSWD onset, BOLD increments were located in thalamus, cerebellum, and anterior cingulate gyrus, whereas BOLD decrements were observed in the DMN regions persisting until 9 s after onset. Significance: Hemodynamic changes (BOLD increments) occurred in specific cortical areas, namely the precuneus/posterior cingulate, lateral parietal, and frontal cortices, several seconds before EEG onset of GSWD. A dysfunction of these brain regions, some of which belongs to the DMN, may be crucial in generating GSWDs in patients with IGE.     

Cluster analysis detection of functional MRI activity in temporal lobe epilepsy

PURPOSE: The objective of this pilot study was to evaluate the ability of a novel method of cluster analysis, 2dTCA, for identifying and characterizing peak fluctuations in fMRI BOLD signals in the temporal lobes and the default-mode network in temporal lobe epilepsy (TLE) without EEG. METHODS: BOLD fMRI images were acquired in 17 TLE patients and compared to EEG. The timing of significant transient BOLD peaks was estimated by 2dTCA, and activation maps were determined. RESULTS: Sixteen subjects (94%) showed apparent temporal lobe activation. Mesial temporal activation was present in 76.4% (13 patients). Temporal lobe or insula activations were detected ipsilateral to the EEG focus in 64.7% (11 patients), bilaterally with no predominance in 29.4% (5 patients), and exclusively contralateral to the EEG focus in none. Eleven subjects showed activation in the so-called default-mode network including posterior cingulate, bilateral posterior parietal cortex, and sometimes anterior cingulate cortex. CONCLUSIONS: These results demonstrate significant positive BOLD fluctuations in the temporal lobes and default-mode regions in a higher percentage of TLE patients than previously reported using other methods. These fluctuations appear physiologically relevant and suggest increased neural activity which may not be detected on scalp EEG, but which may be important in understanding the mechanisms and origins of epileptic discharges.     

The BOLD effect of interictal spike activity in childhood occipital lobe epilepsy

PURPOSE: Occipital lobe epilepsy (OLE) presents in childhood with different manifestations, age of onset and EEG features that form distinct syndromes. The ictal clinical symptoms are difficult to correlate with onset in particular areas in the occipital lobes, and the EEG recordings have not been able to overcome this limitation. The mapping of epileptogenic cortical regions in OLE remains therefore an important goal in our understanding of these syndromes. METHODS: In this work, three patients with two types of idiopathic childhood OLE were studied with EEG source analysis and also with mapping of the BOLD effect associated with spikes in simultaneous EEG/fMRI recordings. RESULTS: Two patients with late onset OLE provided EEG source localizations in the lateral parietal cortex and in the medial occipital areas. The BOLD activations were more consistent and restricted to the medial parietal-occipital cortex in both cases. One patient with photosensitive idiopathic OLE presented with dipole sources in the medial parietal cortex, but the BOLD activations were widespread over inferior and bilateral occipital areas and also posterior temporal ones. There was little spatial overlap between the EEG and BOLD results, but the localizations suggested by the latter are more consistent with the ictal clinical manifestations of each type of epileptic syndrome. CONCLUSIONS: Overall, the BOLD effect associated with interictal spikes maps epileptogenic areas to different localizations than the ones suggested by EEG source analysis. These maps are similar in two patients with late onset idiopathic OLE, but different from a case of photosensitive idiopathic OLE.     

Altered functional connectivity in default mode network in absence epilepsy: a resting-state fMRI study

Dysfunctional default mode network (DMN) has been observed in various mental disorders, including epilepsy (see review Broyd et al. [2009]: Neurosci Biobehav Rev 33:279–296). Because interictal epileptic discharges may affect DMN, resting-state fMRI was used in this study to determine DMN functional connectivity in 14 healthy controls and 12 absence epilepsy patients. To avoid interictal epileptic discharge effects, testing was performed within interictal durations when there were no interictal epileptic discharges. Cross-correlation functional connectivity analysis with seed at posterior cingulate cortex, as well as region-wise calculation in DMN, revealed decreased integration within DMN in the absence epilepsy patients. Region-wise functional connectivity among the frontal, parietal, and temporal lobe was significantly decreased in the patient group. Moreover, functional connectivity between the frontal and parietal lobe revealed a significant negative correlation with epilepsy duration. These findings indicated DMN abnormalities in patients with absence epilepsy, even during resting interictal durations without interictal epileptic discharges. Abnormal functional connectivity in absence epilepsy may reflect abnormal anatomo-functional architectural integration in DMN, as a result of cognitive mental impairment and unconsciousness during absence seizure.     

额叶癫痫发作录像脑电图特点分析

目的通过录像脑电图观察额叶癫痫的临床特征、发作期及发作间歇期的脑电图特点。方法使用录像脑电图（ｖｉｄｅｏＥＥＧ,ＶＥＥＧ）对５０例确诊为额叶癫痫的患者进行常规及长时间记录,对其中１７例（２０次）癫痫发作的临床表现及脑电图所见进行分析。结果额叶癫痫常见的发作形式有：姿势性发作,具有额叶癫痫特点的自动症;复杂部分性发作时伴发声、偏转或表情的变化,有时出现发作性情绪改变或强迫思维等少见症状。其发作特点为：持续时间短,发作相对较频繁,无明显发作后意识障碍。发作间歇期脑电图有时可无阳性所见,典型的临床发作及发作时ＶＥＥＧ记录到的额部爆发性节律有助于诊断。本组９例儿童期起病的额叶癫痫患者,以夜间频繁的躯体自动症发作为主,检查均未发现相应的脑器质性病变。脑电图睡眠描记可见频繁的额部导联癫痫样放电。临床治疗观察预后良好,提示可能为一组儿童原发性部分发作型癫痫综合征。结论额叶癫痫是一组较为特征性的癫痫综合征,临床并不少见,及时而正确的诊断有助于治疗。     

Interictal regional delta slowing is an EEG marker of epileptic network in temporal lobe epilepsy

Purpose: Several studies have suggested that interictal regional delta slowing (IRDS) carries a lateralizing and localizing value similar to interictal spikes and is associated with favorable surgical outcomes in patients with temporal lobe epilepsy (TLE). However, whether IRDS reflects structural dysfunction or underlying epileptic activity remains controversial. The objective of this study is to determine the cortical electroencephalography (EEG) correlates of scalp‐recorded IRDS, in so doing, to further understand its clinical and biologic significances. Methods: We examined the cortical EEG substrates of IRDS with electrocorticography (ECoG‐IRDS) and delineated the spatiotemporal relationship between ECoG‐IRDS and both interictal and ictal discharges by recording simultaneously scalp and intracranial EEG in 18 presurgical candidates with TLE. Key Findings: Our results demonstrated that ECoG‐IRDS is typically a mixture of delta/theta slowing and spike‐wave potentials. ECoG‐IRDS was predominantly recorded from basal and anterolateral temporal cortex, occasionally in mesial, posterior temporal, and extratemporal regions. Abundant IRDS was most commonly observed in patients with neocortical temporal lobe epilepsy (NTLE), whereas infrequent to moderate IRDS was usually observed in patients with mesial temporal lobe epilepsy (MTLE). The anatomic distribution of ECoG‐IRDS was highly correlated with the irritative and seizure‐onset zones in 10 patients with NTLE. However, it was poorly correlated with the irritative and seizure‐onset zones in the 8 patients with MTLE. Significance: These findings demonstrate that IRDS is an EEG marker of epileptic network in patients with TLE. Although IRDS and interictal/ictal discharges likely arise from the same neocortical generator in patients with NTLE, IRDS in patients with MTLE may reflect a network disease that involves temporal neocortex.     

Interictal and ictal EEG activity in the basal ganglia: an SEEG study in patients with temporal lobe epilepsy

PURPOSE: The interictal and ictal EEG activity in the basal ganglia in patients with temporal lobe epilepsy were studied during invasive EEG monitoring. METHODS: Eight epilepsy surgery candidates, each with a proven mesiotemporal seizure-onset zone, participated in the study. We used two invasive EEG methods to determine the seizure-onset zone. In both methods, diagonal electrodes were targeted into the amygdalohippocampal complex via a frontal approach and were passed through the basal ganglia with several leads. We analyzed 16 partial epileptic seizures, four of which became secondarily generalized. RESULTS: No epileptic interictal or ictal discharges were noticed in the basal ganglia. The interictal activity in the basal ganglia was a mixture of low-voltage beta activity and medium-voltage alpha-theta activity. When the ictal paroxysmal activity remained localized to the seizure-onset zone, the activity of the basal ganglia did not change. The spread of epileptic activity to other cortical structures was associated with the basal ganglia EEG slowing to a theta-delta range of 3-7 Hz. This slowing was dependent on the spread of ictal discharge within the ipsilateral temporal lobe (related to the investigated basal ganglia structures); alternatively, the slowing occurred in association with the regional spread of ictal activity from the mesiotemporal region to the temporal neocortex contralaterally to the investigated basal ganglia. Secondary generalization was associated with a further slowing of basal ganglia activity. CONCLUSIONS: The basal ganglia do not generate specific epileptic EEG activity. Despite the absence of spikes, the basal ganglia participate in changing or reflect changes in the distribution of the ictal epileptic activity.     

额叶癫痫的特点及手术治疗

目的 :分析额叶癫痫的临床特征、发作期及发作间期脑电图特点 ,探讨额叶癫痫手术治疗。方法 :应用视频脑电图对 9例额叶癫痫患者进行长程监测 ,并对其中 6例记录颅内脑电图。分析癫痫发作的临床表现及脑电图特点 ,定位致痫灶 ,行手术切除。结果 :额叶癫痫的发作特点为 :发作频繁而短暂 ,以睡眠期发作为主 ,常见过度运动 ,姿势性强直 ,发声等发作症状。发作期可见棘波节律 ,广泛低幅快活动 ,节律性慢波等特征性脑电活动。颅内电极记录可清晰显示异常脑电活动的发作起源及扩散情况 ,有助于定位致痫灶。手术切除病灶及致痫灶 ,效果满意。结论 :额叶癫痫是一组具有特征性的癫痫综合征 ,颅内电极记录有助于揭示其脑电活动变化。对于难治疗性额叶癫痫 ,准确定位致痫灶是手术成功的关键。     

A case of MELAS presenting complex partial status epilepticus]

We reported a 37-year-old man who presented complex partial status epilepticus as the initial symptom of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). He showed fluctuating consciousness disturbance, left homonymous hemianopsia, and paroxysmal conjugated eye deviation to the left. The lactic acid level was elevated in blood and CSF, and ragged-red fibers were observed in the biopsied muscle. MRI demonstrated T2-prolonged lesions in the right occipito-parieto-temporal lobes. Since a mutation of mitochondrial DNA (A3243G) was identified, he was diagnosed as having MELAS. On an ictal record, high amplitude, rhythmic sharp waves were observed at right parieto-temporo-occipital region. High amplitude slow waves were also observed on the right hemisphere, especially in the right frontal lobe. These ictal discharges gradually decreased at their amplitude and in frequency, and then ictal EEG turned to the interictal EEG. During an ictal period, conjugated eye deviation to the left side and consciousness loss were observed. These seizures were observed once every several minutes. During the interictal period, sharp waves and sharp-wave complexes were observed frequently at right parietal and posterior temporal lobes. The venous injection of diazepam (10 mg) normalized EEG quickly. When consciousness loss, especially fluctuating, was observed in the patients of MELAS, complex partial status epilepticus should be considered.     

Ictal EEG Changes with Corpus Callosum Section

Summary: Corpus collosum section diminishes but does not completely abolish secondary bilaterally synchronous interictal EEG discharges, yet often causes cessation of generalized seizures. The effects of corpus callosum section on ictal EEG patterns have not been described. We contrasted ictal EEG patterns before and after anterior callosotomy in 18 patients and before and after total callosotomy in 10 patients. Bilaterally synchronous seizure onset was disrupted in 5 of 11 anterior section patients and 5 of 5 total section patients. Seven of 18 anterior section patients and 5 of 10 total section patients had more localized seizure onset after the procedure; localization to the frontal lobe was observed after anterior or total section, but only total section patients had newly demonstrated posterior locations of seizure onset. These data suggest that the mechanisms by which bilaterally synchronous interictal and ictal discharges are generated differ. Although brainstem or diencephalic structures may contribute to formation of interictal bilateral synchrony, the corpus callosum may be the only pathway used in producing apparent bilateral synchronous seizure onset in patients with secondarily generalized seizures.     

Ictal and Interictal Activity in Partial Epilepsy Recorded with Multichannel Magnetoelectroencephalography: Correlation of Electroencephalography/Electrocorticography, Magnetic Resonance Imaging, Single Photon Emission Computed Tomography, and Positron Emission Tomography Findings

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity. Main zones of ictal activity were shown to evolve from the tissue at the centers of interictal activity. Pre- and intra-operative electrocorticography (ECoG) as well as postoperative outcome confirmed localization in the temporal and frontal lobe. Results also correlated with findings from scalp EEG, interictal and ictal single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Combined multichannel MEG/EEG recording permitted dipole localization of interictal and ictal activity.     

Impact of interictal epileptic activity on normal brain function in epileptic encephalopathy: an electroencephalography-functional magnetic resonance imaging study

Using electroencephalography (EEG) in combination with functional magnetic resonance imaging (fMRI), we studied a 9.5-year-old girl who developed cognitive and behavioral regression in association with intense interictal bilaterally synchronous epileptic discharges (IBSEDs) both during the awake state and during sleep. During runs of IBSEDs, EEG-fMRI demonstrated deactivations in the lateral and medial frontoparietal cortices, posterior cingulate gyrus, and cerebellum together with focal relative activations in the right frontal, parietal, and temporal cortices. The deactivations probably reflect the repercussion of the interictal epileptic activity on normal brain function which might cause the neuropsychological regression by inducing repetitive interruptions of neurophysiological function resulting in a chronic state of specific psychomotor impairment. The relative activations could possibly indicate the source of epileptic activity rapidly spreading to other brain regions.     

Interictal and ictal magnetoencephalographic study in patients with medial frontal lobe epilepsy

PURPOSE: To determine whether magnetoencephalography (MEG) has any clinical value for the analysis of seizure discharges in patients with medial frontal lobe epilepsy (FLE). METHODS: Four patients were studied with 74-channel MEG. Interictal and ictal electroencephalographic (EEG) and MEG recordings were obtained. The equivalent current dipoles (ECDs) of the MEG spikes were calculated. RESULTS: In two patients with postural seizures, interictal EEG spikes occurred at Cz or Fz. The ECDs of interictal MEG spikes were localized around the supplementary motor area. In the other two patients with focal motor or oculomotor seizures, interictal EEG spikes occurred at Fz or Cz. The ECDs of interictal MEG spikes were localized at the top of the medial frontal region. The ECDs detected at MEG ictal onset were also localized in the same area as those of the interictal discharges. CONCLUSIONS: In medial FLE patients, interictal and ictal MEG indicated consistent ECD localization that corresponded to the semiology of clinical seizures. Our findings demonstrate that MEG is a useful tool for detecting epileptogenic focus.     

Focal akinetic seizures as documented by electroencephalography and video recordings.

In three patients with focal epilepsies, focal akinetic seizures that were characterized by ictal paresis of the contralateral arm during preserved consciousness were recorded with EEG and video. MRI and ictal/interictal EEG revealed a frontal or central focus in all patients. Focal akinetic seizures are probably due to epileptic activation of negative motor areas.     

Coexistence of symptomatic focal and absence seizures: Video-EEG and EEG-fMRI evidence of overlapping but independent epileptogenic networks

The distinction between typical absences and hypomotor seizures in patients having frontal lesions is difficult. In focal epilepsy, generalized-like interictal discharges can reflect either a coexistent generalized epileptic trait or a secondary bilateral synchrony. Using combined measures of the EEG and blood oxygenation level dependent (BOLD) activity, we studied a 50-year-old patient with both absence-like and symptomatic focal motor seizures. Focal activity induced activation in the lesional area and deactivation in the contralateral central cortex. Generalized spike-and-wave discharges (GSWDs) resulted also in perilesional activation, and multifocal symmetrical cortical and thalamic activations, and deactivation in associative cortical areas. Although the central cortex was involved during both types of epileptic activity, electroencephalography (EEG)–functional magnetic resonance imaging (fMRI) revealed distinct neuronal networks at the time of the focal or generalized discharges, allowing a clear-cut differentiation of the generators. Whether the patient had distinct epileptic syndromes or distinct electrographic patterns from the lesional trigger remains debatable.