Interictal EEG and ictal scalp EEG propagation are highly predictive of surgical outcome in mesial temporal lobe epilepsy

PURPOSE: Surgical outcome in patients with mesial temporal lobe sclerosis (MTS) is worse than that in patients with temporal lobe activity (TLE) with tumors. Previous studies of the ictal EEG focused on ictal EEG onset in scalp EEG or ictal EEG propagation in invasive recordings. Ictal EEG propagation with scalp electrodes has not been reported. METHODS: Ictal scalp EEG propagation patterns were studied in 347 seizures of 58 patients with MTS or nonlesional TLE. Interictal epileptiform discharges (IEDs) and the presence of unilateral mesial temporal lobe atrophy in magnetic resonance imaging (MRI) also were studied in these 58 patients. Forty-nine patients were operated on (minimal follow-up of 1 year). RESULTS: Postoperatively, seizure-free outcome was seen in (a) 82.8% of patients with regionalized EEG seizure without contralateral propagation, but in only 45.5% of patients with contralateral propagation (p = 0.007); (b) 84.6% of patients with 100% IED lateralized to one temporal lobe, but in only 52.2% with <100% unitemporal IED (p = 0.015); (c) 88.9% with 100% unitemporal IED and regionalized ictal EEG combined, 73.7% with one of both variables, and only 33.3% with <100% ipsitemporal IED combined with contralateral ictal EEG propagation (p = 0.007). CONCLUSIONS: Switch of lateralization or bitemporal asynchrony in the ictal scalp EEG and bitemporal IED are most probably an index of bitemporal epileptogenicity in MTS and are associated with a worse outcome.     

Is ‘burned-out hippocampus’ syndrome a distinct electro‐clinical variant of MTLE-HS syndrome?

AimTo study the clinical, electrophysiological and imaging characteristics of patients with unilateral mesial temporal lobe epilepsy (MTLE) with contralateral ictal onset on scalp EEG, viz. ‘burned-out hippocampus’ syndrome (MTLE-BHS).MethodsMTLE-BHS was defined as TLE with unilateral hippocampal sclerosis (HS) without any dual pathology on MRI and contralateral ictal onset on scalp EEG, unlike in classical hippocampal sclerosis (HS). Consecutive “MTLE-BHS” patients evaluated at our Centre for Comprehensive Epilepsy Care from January 2005 to July 2014 were studied. Twenty-five cases of classic MTLE-HS operated during the same period were also analyzed for comparison.ResultsSeventeen patients were diagnosed to have MTLE-BHS. Mean age of seizure onset was 9.5 ± 7.7 years and the mean duration of epilepsy was18.2 ± 7.3 years. Epigastric aura was more common in MTLE-HS and fear, secondary generalized seizures and temporal polar changes on MRI were more prevalent in the MTLE-BHS subgroup. In the latter group, five (29%) exhibited seizure semiology and 2 (12%) had interictal discharges discordant to the side of MTS. Eight (47%) patients in the MTLE-BHS sub-group had normal medial temporal volume on Scheltens scale. Eight patients among MTLE-BHS underwent surgery (4 following intracranial monitoring that localized to the side of HS) with Engel class I outcome at 1 year follow-up in 6 and Engel class II outcome in 2.ConclusionAttenuation of ipsilateral fast ictal rhythms on scalp EEG as well as neocortical changes are likely to be deterministic factors for MTLE-BHS as opposed to the severity of hippocampal atrophy. Considering good post-operative outcomes, intracranial monitoring for surgical selection is not mandatory in MTLE-BHS despite discordant semiology and ictal onset, in the presence of inter-ictal, functional imaging and neuropsychology data concordant to the side of HS.     

颞叶癫痫颅内EEG记录定位与海马病理变化的关系

目的探讨颞叶癫痫颅内EEG记录与颞叶海马病变程度的关系。方法视频EEG证实为颞叶癫痫并经MRI检查的病人序贯进入本研究,采用硬膜下电极及深部电极联合纪录,确定领先发作释放(initialictaldischarge,IID)部位。37例病人中,无或轻度海马萎缩(hippocampalatrophy,HA阴性组)27例,中至中度HA(HA阳性组)者10例。海马病理变化依据MRI检查的海马容积测量及术后组织病理学的海马硬化分级。结果本组HA阴性组27例病人中,9例病人IID广泛出现在海马区、内侧旧皮层及外侧新皮层;3例在海马区及内侧古皮层;14例完全出现在海马区以外的颞叶皮层;仅1例局限于海马区。在HA阳性组中,90%的病人IID局限于海马区(P<0.05),在25例低级别海马硬化(HS)中,IID局限于海马区显著低于12例HS高级别病人(P<0.05)。结论颞叶癫痫的抽搐发作放电定位与海马的病理变化存在着密切关系,无HA和低级别HS病人的IID多出现在海马、颞叶内侧皮层、颞叶新皮层的部位,而HA明显者和高级别的HS病人出现的IID往往仅局限于海马(HF)。     

Localization of epileptogenic zone in temporal lobe epilepsy by ictal scalp EEG.

Our aim was to evaluate the ability to localize the epileptogenic zone in temporal lobe epilepsy (TLE) by ictal scalp electroencephalogram (EEG). Using simultaneous video recording, we analysed scalp EEG activity during ictal periods in 38 patients (30 patients with medial TLE (MTLE) and eight with lateral TLE (LTLE)). In 14 patients, intracranial ictal EEGs were recorded with depth electrodes, and simultaneous recordings of scalp and intracranial EEG were performed in 11 patients. Scalp EEG showed that, in all 30 patients with MTLE (71 of 72 seizures), an attenuation of background activity was observed before the appearance of ictal activity. Ictal discharges first appeared in the scalp EEG when the ictal discharges reached the lateral part of the temporal lobe on the intracranial EEG. While, in all eight patients with LTLE (25 of 25 seizures), the attenuation of background activity did not occur before the appearance of ictal activity. When the ictal discharges started in the lateral temporal lobe on intracranial EEG, ictal discharges appeared on the scalp. MTLE and LTLE could be diagnosed by the presence or absence of attenuation of background activity with clinical ictal signs before the appearance of ictal discharges.     

Clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy

ObjectiveTo determine the clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy (TLE).MethodsScalp EEG ictal patterns were retrospectively determined in 27 consecutive patients with medically refractory temporal lobe epilepsy who underwent phase-1 scalp video-EEG and phase-2 simultaneous scalp and intracranial video-EEG recordings for pre-surgical evaluation.ResultsOf the 192 temporal lobe seizures recorded during phase-1 and phase-2 scalp video-EEG studies, 124 (65%) seizures were associated with theta/alpha (5–9 Hz) ictal onset pattern, and 68 (35%) seizures were associated with delta (2–5 Hz) ictal onset pattern. Fourteen (52%) patients had exclusively theta/alpha ictal onset, 3 (11%) patients had exclusively delta ictal onset, and 10 (37%) patients had mixed theta/alpha and delta ictal onsets. MTLE was observed in 26 patients who had 124 seizures with theta/alpha ictal onset and 59 seizures with delta ictal onset. LTLE was observed in one patient who had 9 seizures with delta ictal onset. Scalp ictal EEG pattern was not significantly correlated with postsurgical seizure outcomes.ConclusionsBoth scalp delta and theta/alpha ictal onset patterns can be commonly found in patients with MTLE.SignificanceScalp delta ictal onset is not a unique EEG pattern for LTLE as commonly believed.     

RTTBD‐like activity in association with hippocampal ictal discharges in patients with temporal lobe epilepsy

Aim. To determine clinical and intracranial EEG correlates of rhythmic temporal theta bursts of drowsiness (RTTBD) and assess its clinical significance in patients with temporal lobe epilepsy (TLE). Methods. A retrospective review of simultaneous scalp and intracranial video‐EEG recordings from 28 patients with TLE was evaluated for epilepsy surgery. Scalp RTTBD patterns were identified and their clinical and intracranial EEG correlates were then determined on video‐EEG recording using depth and subdural electrodes. Results. Thirty‐one RTTBD patterns on scalp EEG were observed in six (21%) of the 28 patients. Five (16%) of the RTTBD patterns occurred during wakefulness and 26 (84%) occurred during drowsiness and light sleep. The mean duration of RTTBD was 10 seconds (range: 3‐28 seconds). RTTDB consistently correlated with hippocampal ictal discharges and was time‐locked to the hippocampal seizures in which the ictal discharges evolved into rhythmic theta frequency (4‐7‐Hz) range. Ictal automatisms were observed during five (16%) RTTBD patterns, while cognitive impairment was observed in four (13%) of the 31 RTTBD patterns. Conclusion. Our findings show that scalp EEG correlates of hippocampal ictal discharges can resemble RTTBD and may be associated with ictal symptoms and cognitive impairment, indicating that RTTBD may rarely be an ictal EEG pattern in patients with TLE.     

Intracranial EEG in temporal lobe epilepsy: location of seizure onset relates to degree of hippocampal pathology

PURPOSE: To determine whether the specific location of electrographic seizure onset in the temporal lobe is related to hippocampal pathology in temporal lobe epilepsy (TLE). METHODS: Consecutive presurgical patients with scalp EEG-video evidence of TLE and no or mild hippocampal atrophy (HA) on magnetic resonance imaging (MRI) were prospectively studied by using depth and subdural strip electrode recordings to identify the site of the initial ictal discharge (IID). Thirty-four patients had either no or mild HA (HA- group). Four additional patients with moderate or marked HA (HA+ group) who required depth and strip electrodes served as a comparison group. Hippocampal pathology was assessed by MRI volumetrics and histopathologic grade of sclerosis (HS). RESULTS: Thirty-eight patients were investigated. In the HA- group, 10 patients had lobar ictal EEG onsets in the hippocampus (HF), medial paleocortex (MPC), and lateral neocortex (LNC); eight cases had regional IIDs in both HF and MPC; 12 persons had IIDs completely outside the HF; three cases lacked depth electrodes, and only one case (3%) had an IID confined to the HF. By contrast, three (75%) of four HA+ cases had IIDs confined to the HF (p = 0.002). Similarly, in 12 patients with low-grade HS, IIDs confined to the HF area were seen significantly less often than in six cases with high-grade HS (p = 0.025). CONCLUSIONS: In this study of a large number of patients with no to mild and a smaller group with moderate to marked HA and HS, the location of seizure onset in the temporal lobe was related to the degree of hippocampal pathology. Absence of HA and low-grade HS was each associated with IIDs in both the hippocampus and medial (with or without lateral) temporal cortex, or only the MPC or LNC. Marked HA and high-grade HS both were associated with IIDs restricted to the HF.     

Is ictal recording mandatory in temporal lobe epilepsy? Not when the interictal electroencephalogram and hippocampal atrophy coincide

OBJECTIVE: To investigate the concordance between scalp electroencephalogram (EEG) lateralization and side of hippocampal atrophy in patients with temporal lobe epilepsy (TLE). METHODS: We studied 184 consecutive patients with TLE without lesions other than those compatible with mesial temporal sclerosis. In this study, we studied specifically hippocampal atrophy and the results of scalp EEG investigation. Patients were classified according to the localization of interictal epileptiform discharges as unilateral, bilateral asymmetric, and bilateral symmetric. The EEG seizure onsets were also classified separately as unilateral, bilateral asymmetric, and bilateral symmetric. The hippocampal atrophy was determined by volumetric measurements using high-resolution magnetic resonance imaging (MRIVol). RESULTS: Only 3% of patients had discordance between the ictal and interictal EEG lateralizations; however, none of these had unilateral interictal EEG abnormalities. Interictal EEGs were considered unilateral in 62.0% of patients, bilateral asymmetric in 31.5%, and bilateral symmetric in 6.5%. Ictal EEGs were considered unilateral in 63.5% of patients, bilateral asymmetric in 30.0%, and bilateral symmetric in 6.5%. The MRIVol showed unilateral hippocampal atrophy in 60.9% of patients, bilateral asymmetric hippocampal atrophy in 19.0%, symmetric hippocampal atrophy in 3.8%, and normal volumes in 16.3%. There was a significant concordance between MRIVol lateralization and both interictal and ictal EEG lateralization (P<.001). All patients with unilateral hippocampal atrophy had concordant interictal and ictal EEG lateralization. Six (18.2%) of the 33 patients with bilateral asymmetric hippocampal atrophy had MRI lateralization discordant with EEG lateralization. CONCLUSIONS: We found a strong concordance between EEG and MRIVol lateralization in patients with TLE. Unilateral hippocampal atrophy predicted ipsilateral interictal epileptiform abnormalities and ipsilateral seizure onsets with no false lateralization. Previous studies in addition to the present series support that a concordant outpatient EEG evaluation in patients with TLE and unilateral hippocampal atrophy would obviate the need for inpatient EEG monitoring.     

Efficacy of temporal lobe surgery for epilepsy in patients with negative MRI for mesial temporal lobe sclerosis

Epilepsy surgery is a successful treatment for refractory temporal lobe epilepsy (TLE). Reports suggest fewer seizure-free outcomes for patients with TLE and who have a negative brain MRI (nMRI) for mesial temporal sclerosis. Data were collected prospectively from patients with nMRI who underwent temporal lobe surgery for TLE characterized by unilateral ictal temporal lobe seizure onset based on a scalp video electroencephalogram or invasive subdural electrode recordings. A total of 86 patients were followed for at least 24 months after surgery. Outcome was evaluated using the Engel classification. Seizure control was obtained by 55% (47/86) of patients (Class [CL]-I), 27% (23/86) showed significant improvement (CL-II) and 19% (16/86) were deemed surgical failures. Shorter duration of epilepsy, later onset of seizures, and ictal theta rhythm (5-7 Hz) were the most significant predictors of postoperative seizure control. Although hypometabolism on positron emission tomography scan and significant memory disparity (>2.5/8) were not significant prognosticators independently, cumulatively they were predictors for favorable outcome.     

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.     

Bilateral Hippocampal Atrophy in Medial Temporal Lobe Epilepsy

Summary: Quantitative evidence of hippocampal atrophy has been correlated with site of seizure onset, hippocampal neuronal loss, and seizure relief after resection. Most studies have quantified hippocampal atrophy using ratios or differences between right and left hippocampal values. However, bilateral hippocampal atrophy may remain undetected by these techniques. To assess the frequency and implications of bilateral hippocampal atrophy, we studied absolute hippocampal volumes in 53 temporal lobectomy patients who had undergone intracranial electroencephalogram recordings preoperatively. Coronal images were constructed perpendicular to the longitudinal axis of the hippocampus. Atrophy was defined as >2 SD below control values in the volume of the posterior. 5 cm of the hippocampus. Five of 53 patients (9%)had bilateral hippocampal atrophy; four of these cases were undetected by ratios. Surgery was performed on the side of ictal onset in all five patients; four have been seizure-free for >2 years. These results suggest that (a) mesial temporal sclerosis can be present bilaterally and may go undetected by hippocampal ratio or difference measures; (b) ab-solute hippocampal volume values as well as ratios are needed to detect all patients with bilateral hippocampal atrophy; and (c) temporal lobectomy is not contraindicated in patients with bilateral hippocampal atrophy, but success depends on electroencephalographic documentation of the side of predominant ictal onset.     

Clinical features of neocoritcal temporal lobe epilepsy

Few Studies have examined the clinical features of neocortical temporal lobe epilepsy (NTLE) in carefully selected patients. We reviewed records from 21 patients wtih NTLE, defined by intracranial electroencephal9ogram (EEG), who have been seizure free for 1 year or more following temporal lobectomy. The mean age of onset at the time of first seizure was 14 years (range, 1–41 years). Febrile seizures were reported in only 2 patients (9.5%). In contrast to prior mesial temporal lobe epilepsy (MTLE) studies, seizure-free intervals between the initial cerebral insult or first seizure and habitual seizures were uncommon. Possible or known risk factors for epilepsy were reported in 13 of 21 patients (62%). Fifteen (71%) patients reproted auras, with experiential phenomena being the most common type. Magnetic resonance imaging was normal or nospecific in 15 patients, revealed mild hippocampal atrophy in 2, tumors in 2, and resonance imaging was normal or nospecifc in 15 patients, revealed mild hippocampal atrophy in 2, tumors in 2, and heterotopic gray matter and hippocampal atrophy in 1, and cortical dysgensis in 1. Neuropsychological testing showed deficits consistent with the seizure focus in 13 patients (62%), and Wada test showed ipsilateral memory deficits in 10 (48%). The most common behavioral manifestatin was a motionless stare at ictal onset (48%). In contrast to prior studies of MTLE, only 1 NTLE patient had frequent independent, contralateral temporal lobe epileptiform spikes on scalp EEG.     

Sensitivity of recordings at sphenoidal electrode site for detecting seizure onset: evidence from scalp, superficial and deep foramen ovale recordings.

OBJECTIVES: Some authors have recently stressed that the position of the tip of sphenoidal electrodes plays a crucial role in their efficacy in detecting ictal onset. An opportunity to test this hypothesis is provided by recordings from the most superficial contacts of foramen ovale (FO) electrode bundles because these contacts are located at the FO, in a position equivalent to that of optimally located sphenoidal electrodes. To simplify wording, recordings obtained by superficial FO electrodes will hereafter be called sphenoidal recordings, although they have not been obtained with standard sphenoidal electrodes. The sensitivities of simultaneous scalp and sphenoidal recordings for detecting ictal onset have been compared with each other, and with a 'gold standard' provided by simultaneous deep intracranial FO recordings from the mesial aspect of the temporal lobe. METHODS: Three hundred and fourteen seizures obtained from 110 patients under telemetric presurgical assessment for temporal lobe epilepsy have been studied. Scalp electrodes included anterior temporal placements. All scalp electrodes were considered when identifying seizure onset but the anterior temporal electrodes were most frequently involved. RESULTS: Ictal onset time at sphenoidal and scalp recordings: initial ictal changes appeared simultaneously in scalp and sphenoidal recordings in 123 seizures (39.2%). Initial changes occurred earlier in sphenoidal recordings in 63 seizures (20.1%), whereas they were seen earlier on the scalp in 76 seizures (24.2%). Artefacts prevented the comparison between sphenoidal and scalp recordings in 16 seizures (5.1%) and no ictal changes were seen on the scalp and/or sphenoidal recordings in 36 seizures (11.5%). In most of the 63 seizures where ictal changes appeared earlier in sphenoidal recordings, a delayed ipsilateral scalp onset was seen as the signal amplitude increased or scalp changes could be identified retrospectively on the scalp with an onset which appeared simultaneous and ipsilateral to the initial sphenoidal changes. Sphenoidal recordings supplied additional information when compared to scalp recordings in only 22 seizures (7%): in 5 seizures with artefacts on the scalp, in 6 seizures with no changes on the scalp and in 11 seizures with discrepant laterality at onset. Congruence in laterality with respect to deep intracraneal FO recordings: of the 61 seizures with unilateral onset on the scalp, onsets at sphenoidal recordings and deep FO electrodes were ipsilateral in most cases. In only 3 of these 61 seizures (4.9%), sphenoidal recordings lateralized ipsilateral to the deep FO electrodes in the presence of a contralateral onset on the scalp. In 14 among the 122 seizures (11.5%) with bilateral asymmetrical onset on the scalp, sphenoidal recordings lateralized seizure onset ipsilateral to the deep FO electrodes in the presence of a contralateral scalp onset. Thus, when compared with scalp EEG, sphenoidal recordings increased laterality congruence with respect to deep FO electrodes in 17 seizures (5.4%). CONCLUSIONS: Extracranial electrodes located next to the FO at the sphenoidal electrode site yield an improvement over suitable surface electrodes in the identification of ictal onset in only 5.4-7% of seizures. Such improvement derives from the fact that the low amplitude signals often seen at seizure onset may show higher amplitude on sphenoidal than on scalp recordings.     

Role of immediate postictal diffusion-weighted MRI in localizing epileptogenic foci of mesial temporal lobe epilepsy and non-lesional neocortical epilepsy.

OBJECTIVE: To determine whether meaningful changes in signal intensity or in the apparent diffusion coefficient of water (ADC) in the ictal onset zone can be detected through immediate postictal and interictal diffusion-weighted magnetic resonance imaging (DWMRI) in patients with localization-related epilepsy. METHOD: In randomly selected 10 medial and lateral temporal lobe epilepsy (TLE) and four extratemporal epilepsy patients, DWMRI was performed immediately after a seizure and during the interictal period. All 14 patients were non-lesional except for hippocampal sclerosis detected on MRI. The mean time interval from seizure onset to postictal DWMRI was 81 min. Regions of interest (ROI) were selected in both the cortex, which was believed to be the ictal onset zone, and the corresponding anatomical region of the contralateral hemisphere in the postictal and interictal DWMRI. The mean ADC measured from all ROIs was compared. Ictal onset zones were determined by ictal electroencephalography (EEG) and seizure semiology. RESULTS: On visual inspection of postictal and interictal DWMRI, signal changes in the ictal onset zone could be identified in only one patient with medial TLE. The mean ADC values from the ictal onset zones were not significantly different from those of the corresponding contralateral regions of the cortices in both postictal and interictal DWMRI. However, the postictal ADC values of the epileptogenic foci of neocortical epilepsy or neocortical temporal portion of TLE without hippocampal sclerosis were decreased compared with interictal ones in whom both interictal and postictal DWMRIs were obtained (P = 0.028). CONCLUSION: Our results demonstrate that water diffusion can change even after a single seizure in non-lesional neocortical epilepsy.     

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.     

Hypersalivation in temporal lobe epilepsy

PURPOSE: We sought to determine whether hypersalivation helps lateralize seizure onset during complex partial seizures of temporal lobe origin. Several clinical signs, which help lateralize seizure onset, have been reported in temporal lobe epilepsy (TLE). Increased salivation only occasionally has been reported as a manifestation of partial epilepsy. METHODS: Of 590 consecutive patients admitted for video-EEG monitoring, either as a part of a presurgical evaluation of medically intractable epilepsy or for diagnosis and clarification of their paroxysmal symptoms, we identified 10 patients with ictal hypersalivation as a prominent manifestation of complex partial seizures. We reviewed the clinical features, scalp-sphenoidal video-EEG monitoring, intracarotid amytal (Wada) testing, hippocampal volumetric magnetic resonance imaging (MRI), and fluorodeoxyglucose-positron emission tomography (FDG-PET) scans of these patients. RESULTS: Of the 10 patients with ictal hypersalivation, seven patients had nondominant/right TLE, and three patients had dominant/left TLE. All patients had hippocampal atrophy on volumetric MRI. Eight of the 10 patients underwent standard temporal lobectomy with amygdalohippocampectomy (six right, two left). All of the operated-on patients had a seizure-free (Engel class I) outcome, and their increased salivation resolved. Two patients, who did not undergo surgical treatment, continue to have complex partial seizures with increased salivation. CONCLUSIONS: We conclude that increased salivation as a prominent ictal finding in complex partial seizures of temporal lobe origin is more likely to be of nondominant temporal lobe origin. Further studies with larger numbers of patients are needed to replicate this finding.     

Electroencephalographic Correlations of Extracranial and Epidural Electrodes in Temporal Lobe Epilepsy

Thirty patients with medically intractable complex partial seizures of temporal lobe origin, but no structural abnormalities on neuroradiologic investigations, had both extracranial (scalp) and epidural EEG recordings. Fifteen patients (50%) had localized, unilateral, ictal, scalp EEGs, but one of these had bilateral independent temporal seizure onset according to epidural recordings. Of the 15 patients in whom scalp EEGs were non-localizing, 12 had well-localized epidural ictal EEGs, and 3 had multifocal or bilateral independent temporal ictal recordings. Epidural recordings provide information for determination of site of onset of temporal lobe seizures in selected patients.     

Scalp EEG in temporal lobe epilepsy surgery

Electroencephalography (EEG) with standard scalp and additional noninvasive electrodes plays a major role in the selection of patients for temporal lobe epilepsy surgery. Recent studies have provided data supporting the value of interictal and postictal EEG in assessing the site of ictal onset. Scalp ictal rhythms are morphologically complex but at least one pattern (a five cycles/second rhythm maximum at the sphenoidal or anterior temporal electrode) occurs in >50% of patients and has a high predictive value and interobserver reliability for temporal lobe originating seizures. Thorough interictal and ictal scalp EEG evaluation, in conjunction with modern neuroimaging, is sufficient for proceeding to surgery without invasive recordings in some patients. Further studies are required to define the scalp ictal characteristics of mesial vs. lateral temporal lobe epilepsy.     

Intracranial EEG Substrates of Scalp Ictal Patterns from Temporal Lobe Foci

Summary: Purpose: To determine the intracranial EEG features responsible for producing the various ictal scalp rhythms, which we previously identified in a new EEG classification for temporal lobe seizures. Methods: In 24 patients, we analyzed simultaneous intracranial and surface ictal EEG recordings (64 total channels) obtained from a combination of intracerebral depth, subd-ural strip, and scalp electrodes. Results: Four of four patients with Type 1 scalp seizure patterns had mesial temporal seizure onsets. However, discharges confined to the hippocampus produced no scalp EEG rhythms. The regular 5- to 9-Hz subtemporal and temporal EEG pattern of Type 1a seizures required the synchronous recruitment of adjacent inferolateral temporal neocortex. Seizure discharges confined to the mesiobasal temporal cortex produced a vertex dominant rhythm (Type 1c) due to the net vertical orientation of dipolar sources located there. Ten of 13 patients with Type 2 seizures had inferolateral or lateral, temporal neocortical seizure onsets. Initial cerebral ictal activity was typically a focal or regional, low voltage, fast rhythm (20–40 Hz) that was often associated with widespread background flattening. Only an attenuation of normal rhythms was reflected in scalp electrodes. Irregular 2- to 4-Hz cortical ictal rhythms that commonly followed resulted in a comparably slow and irregular scalp EEG pattern (Type 2a). Type 2C seizures showed regional, periodic, 1– to 4-Hz sharp waves following intracranial seizure onset. Seven patients had Type 3 scalp seizures, which were characterized by diffuse slowing or attenuation of background scalp EEG activity. This resulted when seizure activity was confined to the hippocampus, when there was rapid seizure propagation to the contralateral temporal lobe, or when cortical ictal activity failed to achieve widespread synchrony. Conclusions: Type 1, 2, and 3 scalp EEG patterns of temporal lobe seizures are not a reflection of cortical activity at seizure onset. Differences in the subsequent development, propagation, and synchrony of cortical ictal discharges produce the characteristic scalp EEG rhythms.     

Temporal lobe epilepsy associated with cystic lesion in the temporal lobe and middle cranial fossa]

Four patients out of 52 patients with temporal lobe epilepsy (TLE), who underwent epilepsy surgery in our hospital since September of 1994, had cystic lesions in the temporal lobe and middle cranial fossa. Case 1 had old hematoma cavity in the inferior temporal gyrus and chronic subdural electrode recording revealed the ictal onset zone to be localized in the ipsilateral medial temporal region. Case 2 had cystic ganglioglioma in the temporal tip, and intraoperative electrocorticography demonstrated independent paroxysmal activities from medial temporal region and temporal tip near the cyst. Both area were resected and the patients became seizure free. Case 3 and 4 had arachnoid cysts in the middle cranial fossa. Chronic subdural electrode recording revealed that the ictal onset zone was localized in the ipsilateral inferior temporal gyrus (that had microdysgenesis) in Case 3 and contralateral medial temporal region (that had hippocampal sclerosis) in Case 4, respectively. These finding suggest that co-existence of extra-axial cyst such as Case 3 and 4 is incidental and that arachnoid cyst is less epileptogenic. However, intra-axial cyst such as Case 1 and 2 is epileptogenic and complicated physiological mechanism such as kindling phenomenon or secondary epileptogenesis may effect on the hippocampus. Comprehensive presurgical evaluation including electrocorticography is needed in the surgical treatment of TLE with cystic lesion.