Combined use of sphenoidal electrodes and the dipole localization method for the identification of the mesial temporal focus

We attempted to sub-classify four cases who show temporal spikes on standard scalp electroencephalogram (EEG), using sphenoidal electrodes and the dipole localization METHOD: In a case with mesial temporal epilepsy, spikes showed phase reversal in a sphenoidal electrode, and the spike dipoles were estimated to be in the mesial temporal lobe. In a case with lateral temporal epilepsy, spikes showed no phase reversal in a sphenoidal electrode, and the spike dipoles were estimated to be in the lateral temporal lobe. In two cases out of four, spikes showed phase reversal in sphenoidal electrodes, whilst the dipoles were estimated to be in the frontal lobe. Clinical features also suggested a diagnosis of frontal lobe epilepsy. In one of the two cases in which frontal lobe epilepsy was suspected, ictal dipoles as well as interictal spike dipoles indicated participation of the frontal lobe in the genesis of seizures. Nevertheless, only mesial temporal lobectomy was performed based on results obtained by invasive subdural electrodes. As a result, seizures were not controlled. Although sphenoidal electrodes were useful for differentiating between mesial and lateral temporal lobe foci, it is advisable to use them in combination with the dipole localization method to identify frontal lobe foci.     

Intracranial EEG findings in patients with lesional lateral temporal lobe epilepsy

PURPOSE: Intracranial EEG in patients with lesional lateral temporal lobe epilepsy is rarely reported. Therefore, the number of patients with seizures arising independently from ipsilateral mesial structures or contralateral hemisphere has not been clarified. We analyzed the intracranial EEG of cases with localized lesion in the lateral temporal cortex. METHODS: We studied 15 patients who satisfied the following criteria: (1) MRI depicted a lesion less than 4cm in diameter located lateral to the collateral sulcus and at least 3cm posterior to the temporal pole; (2) intracranial EEG with electrodes placed on bilateral temporal lobes captured at least one complex partial seizure; and (3) postoperative follow-up period of 2 years or longer. The mean age of seizure onset was 16.6 years (range, 11-25) and that at surgery was 26.7 years (range, 16-36). RESULTS: A total of 147 complex partial seizures, 51 simple partial seizures, 16 secondarily generalized seizures, and over 80 subclinical seizures were recorded. On the lesional side, many clinical seizures were recorded from the lateral cortex. Independent of the lateral temporal onset seizures, ictal discharges originating from the mesial temporal structures were recorded in 7 of 15 patients (47%). Moreover, onset of ictal discharges from the contralateral temporal lobe was recorded in 7 of 15 patients (47%). Interictal spikes from ipsilateral mesial structures were recorded in all patients. The presence of ipsilateral mesial onset seizures was not associated with hippocampal neuron losses. CONCLUSION: Intracranial EEG analysis revealed that approximately one-half of the patients with structural lesions in the lateral cortex showed independent epileptogenic areas in ipsilateral mesial structures. Although ictal discharges originating from the contralateral temporal lobe were recorded in a half of these patients, this finding does not constitute a contraindication of resective surgery. Interictal spike is not an indicator of whether mesial structures should be resected.     

Significance of Simple Partial Seizures in Temporal Lobe Epilepsy

Summary: We determined how localization of simple partial seizures (SPS) correlated with localization of complex partial seizure (CPS) in scalp/sphenoidal EEG and assessed prognosis after temporal lobe resective surgery in patients with an ictal correlate of SPS in scalp/sphenoidal EEG recordings. EEGs were recorded with the 10–20 system of electrode placement and supplemented with sphenoidal electrodes. Between 1985 and 1992, 183 patients with temporal lobe epilepsy (TLE) reported an aura (SPS) during inpatient monitoring; all were eligible for inclusion in our study. The EEGs during SPS showed ictal changes in 51 patients (28%, 117 SPS). Forty-four patients had unilateral temporal interictal spikes (IIS), and SPS and CPS always arose from the same region. Seven patients had bitemporal interictal spikes; SPS colocalized with CPS in 4 patients (57%), SPS were contralateral to CPS in 2 patients, and 1 patient had bilateral independent CPS but unilateral SPS. SPS accompanied by EEG ictal changes conveyed a favorable prognosis in patients who underwent epilepsy surgery. Scalp/sphenoidal recorded IIS but were less reliable in identifying the location of CPS onset in patients with bitemporal spikes.     

Musicogenic epilepsy with ictal single photon emission computed tomography (SPECT): could these cases contribute to our knowledge of music processing?

Musicogenic epilepsy has a strong correlation with the temporal lobe with a right-sided preponderance. We report the case of a 48-year-old woman whose seizures began at the age of 32 years. Her prenatal, natal and childhood histories were unremarkable and her family history was negative for epilepsy. She had typical complex partial seizures with chewing automatisms. Cranial computed tomography, magnetic resonance imaging (MRI) and interictal SPECT showed no abnormality. Interictal EEG showed paroxysmal bitemporal sharp wave discharges predominant on the right side. Ictal EEG showed a combination of high voltage sharp and slow sharp waves and spikes that originated from the right temporal leads and then became generalized. Ictal activity on EEG started 4-5 min after the music stimulus. For the ictal SPECT study, i.v. injection of 20 mCi of HMPAO was administered approximately 30 s after the ictal activity started. Ictal SPECT demonstrated a right anterior and mesial temporal hyperperfusion. These results seem to support the dominant role of the right temporal lobe and the possible relation of mesial temporal structures to the affective content of music in musicogenic epilepsy.     

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.     

Ictal magnetoencephalographic study in a patient with ring 20 syndrome

OBJECTIVE: To report the ictal magnetoencephalography (MEG) in a patient with ring chromosome 20 mosaicism, a rare chromosomal anomaly associated with intractable epilepsy. METHODS: MEG and simultaneous EEG were recorded with a 204 channel whole head MEG system. Ten habitual seizures occurred during the acquisition, which was done twice. The equivalent current dipoles (ECDs) for ictal discharges on MEG were calculated using a single dipole model. The ECDs were superimposed on a magnetic resonance image. RESULTS: During the seizures, EEG showed prolonged bursts of 5-6 Hz high voltage slow waves with spike components, dominantly in the bilateral frontal region. MEG showed epileptiform discharges corresponding to the ictal EEG. Ictal discharges on MEG were dominant in the frontal area in the initial portion, and then spread in the bilateral temporal area in the middle of the seizure. ECDs obtained from the spikes of the initial portion were clustered in the medial frontal lobe. CONCLUSIONS: The source of the ictal MEG was localised in the medial frontal lobe. The findings suggest that the mechanism underlying epilepsy in this case might be similar to medial frontal lobe epilepsy. Ictal MEG is a valuable tool for detecting the site of seizure onset.     

Lack of aura experience correlates with bitemporal dysfunction in mesial temporal lobe epilepsy

The diagnostic value of lack of aura experience in patients with temporal lobe epilepsy (TLE) is unclear. PURPOSE: To evaluate possible factors of bitemporal dysfunction in patients with mesial TLE who did not experience an aura in electroencephalography EEG/video monitoring for epilepsy surgery. METHODS: Ictal scalp EEG propagation patterns of 347 seizures of 58 patients with mesial temporal lobe sclerosis or non-lesional mesial TLE, interictal epileptiform discharges (IED), presence of unilateral mesial temporal lobe sclerosis in visual magnetic resonance imaging (MRI) analysis, prose memory performance, history or not of an aura, and postictal memory or absence of an aura were analyzed. The ictal EEG was categorized as follows. EEG seizure: (a) remaining regionalized, (b) non-lateralized, (c) showing later switch of lateralization or bitemporal asynchronous ictal patterns. RESULTS: Absent aura in monitoring was significantly correlated with absence of unitemporal MRI sclerosis (P=0.004), bitemporal IED (P=0.008), and propagation of the ictal EEG to the contralateral temporal lobe (P=0.001). Other historical data and interictal prose memory performance were not significantly correlated with absent aura. Ten of 11 patients without aura in monitoring also had absent or rare auras in their history. CONCLUSIONS: Lack of aura experience strongly correlates with indicators of bitemporal dysfunction such as bitemporal interictal sharp waves and bitemporal ictal propagation in scalp EEG, and absence of lateralized MRI sclerosis in patients with mesial TLE. The fact that absent auras are not correlated with episodic memory suggests a transient memory deficit, probably because of rapid propagation to the contralateral mesial temporal lobe.     

Bilateral mesial temporal lobe epilepsy: comparison of scalp EEG and hippocampal MRI-T2 relaxometry

OBJECTIVE: Bilateral hippocampal abnormality is frequent in mesial temporal lobe sclerosis and might affect outcome in epilepsy surgery. The objective of this study was to compare the lateralization of interictal and ictal scalp EEG with MRI T2 relaxometry. MATERIAL AND METHODS: Forty-nine consecutive patients with intractable mesial temporal lobe epilepsy (MTLE) were studied with scalp EEG/video monitoring and MRI T2 relaxometry. RESULTS: Bilateral prolongation of hippocampal T2 time was significantly associated with following bitemporal scalp EEG changes: (i) in ictal EEG left and right temporal EEG seizure onsets in different seizures, or, after regionalized EEG onset, evolution of an independent ictal EEG over the contralateral temporal lobe (left and right temporal asynchronous frequencies or lateralization switch; P = 0.002); (ii) in interictal EEG both left and right temporal interictal slowing (P = 0.007). Bitemporal T2 changes were not, however, associated with bitemporal interictal epileptiform discharges (IED). Lateralization of bilateral asymmetric or unilateral abnormal T2 findings were associated with initial regionalization of the ictal EEG in all but one patient (P < 0.005), with lateralization of IED in all patients (P < 0.005), and with scalp EEG slowing in 28 (82,4%) of 34 patients (P = 0.007). CONCLUSION: Our data suggest that EEG seizure propagation is more closely related to hippocampal T2 abnormalities than IED. Interictal and ictal scalp EEG, including the recognition of ictal propagation patterns, and MRI T2 relaxometry can help to identify patients with bitemporal damage in MTLE. Further studies are needed to estimate the impact of bilateral EEG and MRI abnormal findings on the surgical outcome.     

Localizing value of scalp EEG spikes: a simultaneous scalp and intracranial study.

OBJECTIVE: To determine the relationship between cortical origins of interictal and ictal EEG discharges in patients with temporal lobe epilepsy. METHODS: Simultaneous cortical and scalp EEG recordings were obtained from six patients with temporal lobe epilepsy. Subdural electrode contacts active at seizure onset and when scalp ictal rhythms became evident were identified. Similarly, cortical substrates of scalp EEG spikes were identified at spike peak and at the initial rising phase of the potential. RESULTS: Intracranial seizure onsets were commonly focal and involved only a few electrode contacts, as opposed to scalp ictal rhythms, which required synchronous activation of multiple electrode contacts. At the peak of scalp spikes, multiple electrode contacts were similarly active. However, at spike onset, cortical substrates were more discrete and commonly involved electrodes similar to that of seizure onsets. CONCLUSIONS: Scalp EEG ictal rhythms and the peak of a scalp spike may poorly localize the epileptogenic focus because of propagation. Cortical source area at scalp spike onset is more discrete, however, and the seizure onset zone often lies within this area. SIGNIFICANCE: Analysis of scalp spikes, such as source modeling, at their initial rising phase might provide useful localizing information about seizure origins in the same patient.     

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.     

Surgically proven coexistence of focal and generalized epilepsy: A case report

The coexistence of focal and idiopathic generalized epilepsy (IGE) is rarely observed, and the mechanism underlying this situation remains unknown. We report a 13-year-old girl with well-controlled generalized epilepsy and medically-refractory left temporal lobe epilepsy.She underwent intracranial EEG recording, which demonstrated two characteristic seizure patterns of generalized ictal onset and left mesial temporal onset. In addition, two types of interictal spike distribution, including the left mesial temporal region and generalized spikes, were also supportive of the coexistence of left mesial temporal lobe epilepsy and IGE. Thereafter, a left anterior temporal lobectomy and post-surgical medication significantly improved her seizure outcome. This case illustrates the importance of considering surgical management for patients with medically-intractable focal epilepsy coexisting with generalized epilepsy.     

枕叶癫痫的临床特征分析及手术治疗

目的：癖结枕叶癫痫的临床特征及手术效果,方法：对病人进行电生理学,CT,MRI及ECT检查,手术中行皮层脑电监测,结果,枕叶癫痫病人31例,年龄3至34岁,临床主要表现有视觉异常发作,头偏转,颞叶样或（及）额顶样发作,头皮脑电显示31例病人中30例枕叶或枕叶及周围脑叶出现棘波,CT检查27例中24例异常,MRI检查9例中8例异常,ECT检查13例中11例术区皮层血流减少,所有病人均在皮层脑电监测下切除病灶,术后随访到22例（时间1至4年）,11列无痫发作,其余明显好转,结论,枕叶癫痫的临床特点包括,视觉异常发作,癫痫发作形式多样,枕叶区域异常脑电及影像学改变,手术切除病灶能获得好效果。     

New-onset mesial temporal lobe epilepsy in a 90-year-old: clinical and EEG features

Although there is a peak in the incidence of epilepsy in the elderly compared with the general population, complex partial seizures represent less than 15% of the seizure types reported. We report on a 92-year-old woman with a 2-year history of daily complex partial seizures. Prolonged video/EEG recording showed bilateral anterior mesial temporal interictal spikes, which predominated on the left, and two typical seizures arising from the left temporal area. Cranial MRI scanning showed multiple lacunar infarcts without temporal lobe involvement or mesial temporal atrophy. Our case appears to be oldest patient in the literature with newly diagnosed mesial temporal lobe epilepsy confirmed by video/EEG recording.     

New Topographic Mapping of Temporal Lobe Seizures

A unique topographic map has been developed based on EEG data of ictal events originating from the basal/mesiotemporal lobe regions. This technique involves a new mapping method of temporal lobe seizures as opposed to the interictal activity maps of most commercially available software. The map integrates data from sphenoidal electrodes as well as the standard 10–20 surface electrodes recorded with bipolar montages. A basal view is ideal for visualization of onset of temporal lobe ictal discharges recorded with chronic sphenoidal electrodes. We used the last 150 ictal events from 40 patients with basal/mediotemporal lobe epilepsy to develop this technique. Results indicate that a topographic view incorporating sphenoidal and scalp electrodes may provide a useful adjunct for interpretation of EEG recordings and a basis for comparison between and among patient groups for both ictal and interictal epileptic discharges.     

Musicogenic seizures can arise from multiple temporal lobe foci: intracranial EEG analyses of three patients

PURPOSE: To determine the ictal-onset zone of musicogenic seizures by using intracranial EEG monitoring. METHODS: Musicogenic seizures in three patients with medically intractable musicogenic epilepsy were first localized by using noninvasive methods including, in one patient, ictal magnetoencephalography (MEG) and magnetic resonance spectroscopy (MRS). The ictal-onset zones in these patients were then further localized using by intracranial EEG monitoring, and the outcomes of the two patients who underwent epilepsy surgery were determined. RESULTS: Patient 1's musicogenic seizures localized to the right lateral temporal lobe, patient 2's originated in the right mesial temporal lobe, and patient 3's arose independently from both mesial temporal lobes. Patients 1 and 2 underwent resective epilepsy surgery and are seizure free (Engel class I). CONCLUSIONS: Musicogenic epilepsy is a heterogeneous syndrome with seizures that can arise from multiple temporal lobe foci. Patients with medically intractable musicogenic epilepsy and with unilateral ictal onset zones may be considered candidates for resective epilepsy surgery.     

Conditions for Omitting Invasive Long-Term Monitoring before Surgical Resection in Patients with Temporal Lobe Epilepsy

Abstract: The omission of invasive long-term monitoring before surgical resection in patients with epilepsy should be permitted only for those in whom the epileptogenic focus is presumed to localize unilaterally in the mesial aspect of the temporal lobe. The localization may well be confirmed through noninvasive measures. Retrospective analyses of data obtained from noninvasive investigations (scalp-recorded and sphenoidal EEG, neu-rolmages, and electroclinical seizure manifestations) were carried out in 58 :patients. The localization of their epileptogenic focus was subsequently confirmed by the implantation of both intracerebral and subdural electrodes; the focus had an amygdalohippocampal origin in 41 :patients and a lateral temporal origin in 17 :patients. From the comparison of noninvasive Andings between these two groups, we propose the following indispensable conditions for omitting an invasive evaluation: 1. Appearance of focal epileptic discharges unilaterally in the sphenoidal lead observed during the simple phase of partial seizures, or unilateral discharges with predominancy in the sphenoidal lead during the early phase of complex partial seizures. 2. Interictal spikes on scalp-recorded EECs localizing unilaterally in the anterior region of the temporal lobe, and if bilaterally independent, presenting with unilateral predominancy in a ratio of greater than 41. 3. Presence of autonomic signs in the initial phase of signal symptoms. 4. Neuroimaging Andings in the mesial temporal region: elongated T2 on MRI and hippocampal atrophy, or a tumorous lesion. The lateralhation conforms to interictal and ictal paroxysmal EEC findings. There were 8 :patients with seizures of amygdalohippocampal origin who satisfied all the indispensable condition, but not a single patient with seizures of lateral temporal origin. Thus, the conditions we propose are surely useful for determining whether patienta with lateral temporal seizures should be excluded from invasive long-term monitoring before surgical resection.     

Ictal automatisms with preserved responsiveness in a patient with left mesial temporal lobe epilepsy

PURPOSE: To describe the possible mechanism of ictal automatisms with preserved responsiveness (APRs) in a patient with left mesial temporal lobe epilepsy, which had not been reported previously. METHODS: Ictal EEGs recorded from bilateral foramen ovale electrodes with scalp-sphenoidal electrodes were analyzed in respect to the ictal semiology. RESULTS: The patient had a right hemispheric language dominance in the dextral. Electroclinical analysis revealed that the onset of oroalimentary automatisms coincided with the involvement of the left mesial and lateral temporal structures by spreading ictal discharges. The ictal discharge spreading was limited to the ipsilateral hemisphere throughout the seizure, which explained the intact consciousness and preserved responsiveness of the patient. CONCLUSIONS: This case suggests that APRs take place in seizures originating from the nondominant temporal lobe, during which ipsilateral mesial and lateral temporal structures are diffusely involved without spreading to the contralateral side.     

The impact of cerebral source area and synchrony on recording scalp electroencephalography ictal patterns

PURPOSE: To determine the cerebral electroencephalography (EEG) substrates of scalp EEG seizure patterns, such as source area and synchrony, and in so doing assess the limitations of scalp seizure recording in the localization of seizure onset zones in patients with temporal lobe epilepsy. METHODS: We recorded simultaneously 26 channels of scalp EEG with subtemporal supplementary electrodes and 46-98 channels of intracranial EEG in presurgical candidates with temporal lobe epilepsy. We correlated intracranial EEG source area and synchrony at seizure onset with the corresponding scalp EEG. Eighty-six simultaneous intracranial- and scalp-recorded seizures from 23 patients were evaluated. RESULTS: Thirty-four intracranial ictal discharges (40%) from 9 patients (39%) had sufficient cortical source area (namely > 10 cm(2)) and synchrony at seizure onset to produce a simultaneous or nearly simultaneous focal scalp EEG ictal pattern. Forty-one intracranial ictal discharges (48%) from 10 patients (43%) gradually achieved the necessary source area and synchrony over several seconds to generate a scalp EEG ictal pattern. These scalp rhythms were lateralized, but not localizable as to seizure origin. Eleven intracranial ictal discharges (13%) from 4 patients (17%) recruited the necessary source area, but lacked sufficient synchrony to result in a clearly localized or lateralized scalp ictal pattern. CONCLUSIONS: Sufficient source area and synchrony are mandatory cerebral EEG requirements for generating scalp-recordable ictal EEG patterns. The dynamic interaction of cortical source area and synchrony at the onset and during a seizure is a primary reason for heterogeneous scalp ictal EEG patterns.     

Ictal urinary urge indicates seizure onset in the nondominant temporal lobe

ARTICLE ABSTRACT: The authors describe six patients with medically refractory temporal lobe epilepsy whose seizures were characterized by an aura of ictal urinary urge. All seizures originated in the nondominant temporal lobe as evidenced from interictal spikes, ictal EEG, and MRI. Ictal SPECT, which was obtained in two patients, showed a hyperperfusion of the insular cortex, indicating a critical role of the insula for the generation of this symptom. Ictal urinary urge represents a new lateralizing sign indicating a seizure onset in the nondominant temporal lobe.     

Contralateral temporal hypometabolism on positron emission tomography in temporal lobe epilepsy

Introduction — No detailed case studies report lateralised hypometabolism on positron emission tomography (PET) contralateral to the epileptogenic focus in temporal lobe epilepsy (TLE). Material and methods — We performed ¹⁸F fluorodeoxyglucose (FDG) PET in two intractable TLE patients. Results — One had right temporal interictal spikes on electroencephalography (EEG) and a right medial temporal lobe lesion on magnetic resonance imaging (MRI). FDG-PET showed decreased uptake in the left temporal lobe. Right temporal ictal onset, with bilateral interictal epileptiform activity, occurred on intracranial EEG. He is seizure free after right temporal lobectomy and ganglioglioma resection. The second had right temporal lobe interictal and ictal EEG activity. MRI demonstrated right anteriomedial temporal increased T2 signal. Neuropsychology revealed bilateral cognitive dysfunction. FDG-PET showed left anterior temporal and lateral frontal hypometabolism. He is seizure free after right temporal lobectomy. Conclusion — These findings suggest that regional uptake asymmetry on FDG-PET may be give misleading lateralising information in TLE.