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.     

Magnetoencephalographic Analysis of Secondary Bilateral Synchrony

To assess the clinical value of magnetoencephalography (MEG) in investigating the origin of secondary bilateral synchrony (SBS) in patients with partial epilepsy. MEG and simultaneous electroencephalography (EEG) were recorded with a 204-channel whole-head MEG system in 2 patients. The equivalent current dipoles (ECDs) for epileptic discharges on MEG were calculated according to a single dipole model. In patient 1, the ictal EEG showed bursts of bilateral synchronous 3-Hz spike-and-slow-wave complexes. ECDs obtained from the ictal MEG localized to the right medial frontal lobe. On the second patient's MEG recordings, epileptic discharges corresponding to prolonged EEG bursts of bilateral synchronous spike-and-slow-wave complexes were obtained. ECDs calculated from the prolonged bursts were clustered in the left medial frontal lobe. MEG detected the sources of SBS in the medial frontal lobe. MEG is extremely useful for the identification of the source of SBS.     

Efficacy of Thyrotropin-Releasing Hormone in the Treatment of Intractable Epilepsy

Purpose : The ictal EEG and magnetoencephalogram (MEG) for gelastic seizures were recorded in a 4-year-old girl with tuberous sclerosis. The sites of origin for the seizure activities were investigated by using an equivalent current dipole (ECD) with the MEG.
Methods : EEG and MEG were recorded simultaneously under the administration of diazepam (DZP). The MEG recording was performed on a system consisting of an array of 64 sensors uniformly distributed over the patient's whole head (CTF, Canada), and the estimated ECDs were superimposed on the magnetic resonance imaging (MRI) images (Siemens, 1.5 Tesla).
Results : Two laughing attacks lasting 5 s each were documented. The ictal EEG showed gradually increasing 11–Hz rhythmic α activities with dominance over the frontocentral areas bilaterally, followed by irregular spike-and-wave discharges. The ictal MEG detected bilateral frontal rhythmic sharp waves before the appearance of the activities on the EEG. The estimated ECDs were localized in the deep white matter of the right frontal lobe on the MRI. However, those dipoles did not coincide with the locations of her cortical tubers.
Conclusions : Although gelastic seizures accompanied with hypothalamic hamartomas are well known, several reports have suggested a temporal or frontal lobe origin for gelastic seizures. In this patient, the ECD indicated that the seizures originated in the frontal lobe, although ictal scalp EEG recordings could not determine the precise focus. Thus, in cases in which the use of ictal scalp EEG fails to show the sites of origin for the seizures, it is recommended that the origins be estimated by using the non-invasive method of ictal MEG analysis.     

Cephalic auras of supplementary motor area origin: an ictal MEG and SAM(g2) study

Although a nonspecific cephalic sensation, the so-called "cephalic aura," is a common sensory aura, particularly in frontal lobe seizures, but is rarely is the entire sensory seizure event. The unusual presentation of cephalic sensations in isolation representing supplementary motor area (SMA) seizures, which are commonly unaccompanied by ictal electroencephalography (EEG) changes, can easily lead to misdiagnosis of nonepileptic psychogenic seizures. We illustrate the case of a 36-year-old male patient with frontal lobe epilepsy who presented with isolated cephalic auras described as a nonvertiginous sense of head movement without observable clinical signs after his habitual partial motor seizures were controlled with pharmacotherapy. Video/EEG recordings showed no recognizable epileptic discharges time-locked to the onset of the isolated cephalic auras. Ictal magnetoencephalography (MEG) with synthetic aperture magnetometry-kurtosis (SAM(g(2))) analysis demonstrated the SMA onset of the cephalic auras; thus, MEG was essential in differentiating these isolated auras from nonepileptic psychogenic events.     

Frontal lobe epilepsy

About one-quarter of patients with refractory focal epilepsies have frontal lobe epilepsy (FLE). The typical seizure semiology for FLE includes unilateral clonic, tonic asymmetric or hypermotor seizures. Interictal electroencephalograms (EEG) usually reveal interictal epileptiform discharges and rhythmical midline theta, which has localizing value. The usefulness of ictal EEG recordings is limited by frequent muscle artifacts in motor seizures and because a large portion of the frontal lobe cortex is “hidden” to scalp electrodes. Ictal single photon emission CT and positron emission tomography are able to localize FLE in about one-third of patients only. A pre-surgical evaluation should include, whenever possible, a subclassification of FLE as dorsolateral frontal, mesial frontal or basal frontal lobe epilepsy to allow a minimal cortical resection. A review of the typical findings of seizure semiology, interictal and ictal EEG regarding the different FLE subtypes is given. Etiology, medical treatment and surgery are also discussed.     

Ictal magnetoencephalography in temporal and extratemporal lobe epilepsy

PURPOSE: We evaluated visual patterns and source localization of ictal magnetoencephalography (MEG) in patients with intractable temporal lobe epilepsy (TLE) and extratemporal epilepsy (ETE). METHODS: We performed spike and seizure recording simultaneously with EEG and MEG on two patients with TLE and five patients with ETE. Scalp EEG was recorded from 21 channels (10-20 international system), whereas MEG was recorded from two 37-channel sensors. We compared ictal EEG and MEG onset, frequency, and evolution and performed MEG dipole source localization of interictal spikes and early ictal discharges and co-registered dipoles to brain magnetic resonance imaging (MRI). We correlated dipole characteristics with intracranial EEG, surgical resection, and outcome. RESULTS: Ictal MEG lateralized seizure onset in both TLE patients and demonstrated ictal onset, frequency, and evolution in accordance with EEG. Ictal MEG source analysis revealed tangential vertical dipoles in the anterolateral angle in one patient, and anterior dipoles with anteroposterior orientation in the other. Intracranial EEG revealed regional entorhinal seizure onset in the first patient. Both patients became seizure free after temporal lobectomy. In ETE, ictal MEG demonstrated visual patterns similar to ictal EEG and had concordant localization with interictal MEG in all five patients. Two patients underwent surgery. Ictal MEG localization was concordant with intracranial EEG in both cases. One patient had successful outcome after surgery. The second patient did not improve after limited resection and multiple subpial transections. CONCLUSIONS: Ictal MEG can demonstrate ictal onset frequency and evolution and provide useful localizing information before epilepsy surgery.     

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。     

A magnetoencephalographic study of patients with Panayiotopoulos syndrome

Summary:  Purpose: Panayiotopoulos syndrome (PS) is a newly identified type of benign childhood epilepsy characterized by ictal vomiting and eye deviation. It is usually accompanied by occipital spike discharges; however, its classification as an early-onset benign childhood occipital epilepsy is controversial. To characterize this condition further, we examined the localization of equivalent current dipoles (ECDs) of spike discharges by magnetoencephalography (MEG) in patients with PS.
Methods: We studied 13 patients with a mean age at time of examination of 5 years (range, 3–14 years). MEG was measured by using a whole-head 204-channel neuromagnetometer with simultaneous EEG recordings. The estimated locations of ECDs of each peak of the spike discharges were overlaid on magnetic resonance images of the brain.
Results: Eleven (84.6%) patients showed clustered ECDs in the areas alongside the parietooccipital sulcus (eight of 13; 61.5%) and/or the calcarine sulcus (four of 13; 30.8%). Despite Fp-O synchronization of the spike discharges in the scalp EEG of five patients, no frontal locations of ECDs were found. All five (38.5%) boys with sylvian seizures, who also showed clustered ECDs in rolandic areas, had an earlier age at onset and higher seizure frequency than did other patients. ECD orientations were regular in all but one patient, who showed irregular and dispersed ECDs alongside bilateral calcarine sulci.
Conclusions: Our results demonstrate localized cortical hyperexcitability in the areas alongside major cortical sulci in PS and indicate that PS is closely related to benign childhood epilepsy with centrotemporal spikes.     

Brain connectivity changes during ictal aggression (a strangulation attempt)

Ictal aggressive behaviour is a rare manifestation of focal seizures. We report an episode of ictal aggression occurring during an intracerebrally recorded seizure (using stereoelectroencephalography) in a patient with drug‐resistant temporal lobe epilepsy. Aggression occurred during the last part of the seizure and was coincident with marked EEG slowing of the frontal regions and persistent ictal activity in the medial temporal lobe. A functional connectivity study (h² estimation of interdependencies) showed a bilateral massive hypersynchronization between frontal and temporal regions. This case illustrates the occurrence of aggression during imbalance between the electrical activity in the temporal limbic cortex and prefrontal cortex, in agreement with the current neurobiological theories of aggression.     

Ictal MEG in two children with partial seizures

We report on the successful identification of epileptic foci in two children with partial epilepsy using ictal magnetoencephalography (MEG). Case 1 is a 12-year-old male suffering with simple partial seizures with leftwards nystagmus. Ictal SPECT revealed a hyperperfusion area in the right lateral occipital area, and MRI revealed cortical dysplasia in the same area. Interictal EEG dipoles were concentrated in the right mesial occipital lobe. Both interictal and ictal MEG dipoles were concentrated in the right mesial occipital lobe, which corresponded well with neuroimaging data and his clinical features. Case 2 is a 5-year-old female suffering with simple partial seizures with left-side facial twitching. Interictal EEG dipoles were located in her left motor area, the pre-sylvian fissure, close to the location of the interictal MEG-estimated dipoles. Ictal EEGs showed no remarkable changes associated with her clinical manifestations. However, ictal MEG showed high-voltage slow waves over her left hemisphere, and ictal MEG iso-contour maps revealed a clear dipolar pattern, which suggested that the MEG dipole was located in the area of the sylvian fissure. Ictal SPECT revealed hyperperfusion areas around the left sylvian fissure. Conclusion: Ictal MEG is useful for determining the precise location of epileptic focus in patients with motionless seizures, including children.     

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。     

Speech preservation during language-dominant, left temporal lobe seizures: report of a rare, potentially misleading finding

PURPOSE: To evaluate the prevalence and mechanism of ictal speech in patients with language-dominant, left temporal lobe seizures. METHODS: We retrospectively reviewed the video-EEG telemetry records for the presence of ictal speech in 96 patients with surgically proven left temporal lobe epilepsy and studied the seizure-propagation patterns in three patients who required intracranial EEG recordings for seizure localization. RESULTS: Ictal speech preservation was observed in five patients. One patient's seizures demonstrated rapid propagation of the ictal discharges to the contralateral temporal area where the seizure evolved, resembling a nondominant temporal lobe seizure. The other two patients had ictal discharges that remained confined to the inferomesial temporal areas, sparing language cortex. CONCLUSIONS: Preservation of speech in complex partial seizures of language-dominant, left temporal lobe origin is rare. Based on intracranial EEG recordings, the likely mechanism underlying this potentially misleading clinical finding is the preservation of language areas due to limited seizure-propagation patterns.     

Two magneto-encephalographic epileptic foci did not coincide with the electrocorticographic ictal onset zone in a patient with temporal lobe epilepsy.

To evaluate the usefulness and limitations of magneto-encephalography (MEG) for epilepsy surgery, we compared 'interictal' epileptic spike fields on MEG with ictal electrocorticography (ECoG) using invasive chronic subdural electrodes in a patient with intractable medial temporal lobe epilepsy (MTLE) associated with vitamin K deficiency intracerebral hemorrhage. A 19-year-old male with an 8-year history of refractory complex partial seizures, secondarily generalized, and right hemispheric atrophy and porencephaly in the right frontal lobe on MRI, was studied with MEG to define the interictal paroxysmal sources based on the single-dipole model. This was followed by invasive ECoG monitoring to delineate the epileptogenic zone. MEG demonstrated two paroxysmal foci, one each on the right lateral temporal and frontal lobes. Ictal ECoG recordings revealed an ictal onset zone on the right medial temporal lobe, which was different from that defined by MEG. Anterior temporal lobectomy with hippocampectomy was performed and the patient has been seizure free for two years. Our results indicate that interictal MEG does not always define the epileptogenic zone in patients with MTLE.     

Clinical and Electroencephalographic Evidence for Sites of Origin of Seizures with Diffuse Electrodecremental Pattern

Summary: A diffuse electrodecremental ictal pattern with other forms of epilepsy and has been considered to reflect a generalized seizure disorder of diffuse cortical or subcortical (brainstem) origin. In some seizures associated with DEP, however, focal ictal manifestations have been observed. We reviewed the records of all patients admitted to our seizure monitoring unit for 3 years and detected 39 patients with seizures associated with DEP. In 23 of 39 patients, clinical ictal behaviors resembled seizures of unilateral supero/mesiofrontal lobe origin and interictal EEG showed a prominent unilateral frontal component. Nine of 39 had complex absences (CA)/complex partial seizures (CPS); 4 of them were of unilateral frontal lobe origin. Seven of 39 patients had tonic or atonic seizures. Seven patients were studied further with subdural electrodes. Ictal onsets showed a highfrequency frontal lobe discharge. We conclude that in a subgroup of patients a generalized electrodecremental pattern on scalp EEG results from a regional cortical high-frequency ictal discharge originating in a single frontal lobe.     

Dipole Modeling in Epilepsy Surgery Candidates

Summary: Purpose : The validity and clinical significance of dipole modeling in epilepsy surgery candidates is not fully established.
Patients and Methods : Interictal and ictal dipole modeling was performed in 43 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum magnetic resonance imaging (MRI: space–occupying, n = 15; atrophic, n = 26; dysplastic, n = 2). Video–EEG monitoring showed CPS in all patients. In 12 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 11 patients and medial occipital ictal onset in 1.
Results : Spatiotemporal dipole mapping of averaged interictal spikes and epochs of early ictal discharges revealed two distinct dipole patterns. Patients with lesions located in the medial (± lateral) temporal lobe (n = 34) and medial occipital lobe (n = 1) uniformly presented a combined interictal dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Eight of 9 patients with extratemporal lesions had a less stable dipole with a predominant radial component. Ictal dipole modeling identified the ictal onset zone correctly as compared with intracranial EEG recordings from bilateral hippocampal depth electrodes. Ictal dipoles showed a striking correspondence with the interictal dipoles in individual patients.
Conclusions : Interictal and ictal dipole mapping provided additional, reliable, and relevant localizing information in surgical candidates for refractory CPS. Ictal dipole analysis may limit the number of patients who require intracranial electrodes.     

Hyperorality in epileptic seizures: periictal incomplete Klüver-Bucy syndrome

PURPOSE: To analyze systematically hyperorality associated with epileptic seizures and its relation to the localization of epileptic activity. METHODS: To identify patients with periictal hyperorality, we reviewed video-recordings of 269 patients (aged 6-59 years) who had consecutively undergone presurgical evaluations including ictal video-EEG recordings and high-resolution magnetic resonance imaging (MRI) and had had epilepsy surgery because of intractable frontal (FLE) or temporal lobe epilepsy (TLE). Periictal hyperorality was defined if patients put or unambiguously intended to put nonfood items into their mouths during or after at least one of the reviewed seizures. For the further analysis, we included only patients with periictal hyperorality. We reviewed their medical records and reexamined their ictal video-EEG recordings. RESULTS: We identified eight patients (six women) aged 8-59 years who had hyperorality during or after seizures. Seven patients had TLE, and one patient had frontal lobe epilepsy (FLE). Three of these patients underwent right-sided surgery, whereas five patients had surgery on the left. Three patients exhibited ictal and five showed postictal hyperorality. Interictal EEG suggested bilateral interictal epileptiform discharges (IEDs) in three patients; in two other patients, no IEDs were detected. Ictal EEG suggested bilateral involvement in six cases. Patients with unilateral epileptiform activity had left TLE. CONCLUSIONS: Periictal hyperorality is a rare phenomenon occurring in 3% of the investigated epilepsy population. We suggest that periictal hyperorality is an ictal-postictal mental disturbance, an incomplete Klüver-Bucy syndrome. In most patients, bilateral seizure activity plays an important role in the pathomechanism, but it would appear that left-sided epileptic activity without contralateral involvement also can cause periictal hyperorality.     

Usefulness of near-infrared spectroscopy for identification of epileptic foci in two localization-related epilepsy patients]

We monitored cerebral blood volume (CBV) using near-infrared spectroscopy (NIRS) of two patients with symptomatic localization-related epilepsy who had no epileptic discharges in ictal scalp EEG. Case 1 was a 9-month-old boy who was suspected to have frontal lobe epilepsy. Although epileptic discharges were not identified on his ictal EEG due to motion artifacts, NIRS demonstrated an increase of CBV of the left brain during the seizure. Ictal single photon emission CT (SPECT) was dominant at the left side. Case 2 was a 3-year-old girl who was suspected to have temporal lobe epilepsy. Ictal EEG tracings, theta waves revealed prominent but did not enable identification of the focus. She had cortical dysplasia in the right cerebral hemisphere. NIRS monitoring demonstrated an increase in CBV in the right frontal region, which began 10 minutes before the seizure onset and lasted for 3 hours. Thus NIRS is a sensitive and non-invasive procedure for monitoring CBV changes during the seizure, and is useful in identification of the epileptic focus.     

Ictal kissing in a patient with right frontal lobe epilepsy

When performing pre‐surgical evaluation of patients with refractory epilepsy, the analysis of seizure semiology is one of the key elements used to generate a hypothesis about the location of the epileptogenic zone. Ictal kissing is a very rarely observed ictal automatism described in patients with temporal lobe epilepsy. We present a 62‐year‐old man who was referred to our epilepsy centre for comprehensive evaluation. During prolonged video‐EEG monitoring, six focal‐onset hyperkinetic seizures were registered. In five seizures, the patient repeatedly produced sonorous kisses “into the air”. Initial ictal EEG pattern consisted of rhythmic theta or alpha activity at the right fronto‐polar and fronto‐medial electrodes. MRI depicted focal cortical dysplasia located in the right prefrontal medial cortex. This case suggests that ictal kissing can also occur in the setting of right frontal lobe epilepsy; we therefore believe that this observation expands the anatomo‐clinical correlation for this rare ictal automatism. [Published with video sequences].     

Role of the frontal lobes in the propagation of mesial temporal lobe seizures.

The depth ictal electroencephalographic (EEG) propagation sequence accompanying 78 complex partial seizures of mesial temporal origin was reviewed in 24 patients (15 from the University of Pittsburgh Epilepsy Center and 9 from UCLA). All patients were monitored with bilateral mesial frontal and mesial temporal depth electrodes and later received anterior temporal lobectomy. Ictal EEG records were categorized according to sequence of spread from the temporal focus to the other regions. Although propagation patterns varied both within and between patients, certain features were notable: (a) It was very common for seizure activity to spread initially to the ipsilateral frontal lobe (observed in 22 of 24 patients). (b) The most common mode of spread (15 of 24 patients) was initiating temporal lobe----ipsilateral frontal lobe----contralateral frontal lobe----contralateral temporal lobe. (c) Occasionally, seizure discharges invaded the frontal lobes but failed to invade the contralateral temporal lobe (2 of 24 patients). (d) Seizure activity occasionally invaded the contralateral temporal lobe prior to invading the frontal lobes (2 of 24 patients). Other notable features included (i) a clear tendency for mesial temporal seizure discharges initially to invade orbitofrontal (as opposed to anterior cingulate) cortex and (ii) the emergence of a period of clear asymmetry in the frontal lobes during which high-amplitude, rapid discharges were present on the side ipsilateral to the initiating temporal lobe. These results suggest that the prefrontal region, especially the orbitofrontal cortex, is strongly influenced by mesial temporal ictal activity. This region appears to be frequently involved in the propagation of seizures initiated in the mesial temporal lobe and may play a role in the interhemispheric propagation of mesial temporal seizures.     

Two magneto-encephalographic epileptic foci did not coincide with the electrocorticographic ictal onset zone in a patient with temporal lobe epilepsy

Abstract

To evaluate the usefulness and limitations of magneto-encephalography (MEG) for epilepsy surgery, we compared 'interictal' epileptic spike fields on MEG with ictal electrocorticography (ECoG) using invasive chronic subdural electrodes in a patient with intractable medial temporal lobe epilepsy (MTLE) associated with vitamin K deficiency intracerebral hemorrhage. A 19-year-old male with an 8-year history of refractory complex partial seizures, secondarily generalized, and right hemispheric atrophy and porencephaly in the right frontal lobe on MRI, was studied with MEG to define the interictal paroxysmal sources based on the single-dipole model. This was followed by invasive ECoG monitoring to delineate the epileptogenic zone. MEG demonstrated two paroxysmal foci, one each on the right lateral temporal and frontal lobes. Ictal ECoG recordings revealed an ictal onset zone on the right medial temporal lobe, which was different from that defined by MEG. Anterior temporal lobectomy with hippocampectomy was performed and the patient has been seizure free for two years. Our results indicate that interictal MEG does not always define the epileptogenic zone in patients with MTLE. [Neurol Res 2001; 23: 830-834]