Is additional mesial temporal resection necessary for intractable epilepsy with cavernous malformations in the temporal neocortex?

PURPOSE: Cavernous malformation (CM) in the temporal neocortex causes intractable epilepsy. Whether to resect additional mesial temporal structures in addition to the lesionectomy is a still controversial issue. To clarify the need for the procedure, we retrospectively analyzed pre- and postoperative clinical data of patients with surgically removed CM. SUBJECTS AND METHODS: We included data from 18 patients with CM in the temporal neocortex who presented with intractable epilepsy. Eleven patients of our early series were treated with extended resection, i.e., lesionectomy and the resection of additional mesial temporal structures. Seven patients underwent lesionectomy, i.e., removal of the CM and of hemosiderin-stained surrounding brain tissue. Pathological assessments of the resected hippocampus were performed. Chronic intracranial electroencephalography (EEG) recordings were obtained in 6 patients. We performed perioperative neuropsychological assessments in all patients. RESULTS: The seizure outcome was recorded as Engel class I in 17 patients (94.4%); Ia = 12 (66.7%) Ib = 2 (11.1%), Ic = 1 (5.6%), Id = 2 (11.1%), and class IIb in one patient (5.6%). Adding resection of the mesial temporal structures to lesionectomy did not alter the seizure outcome. Pathology of hippocampus revealed limited neuronal loss in CA4. Ictal onsets in the ipsilateral lateral cortex were detected in all 6 patients who underwent intracranial EEG. In 4 patients each, we also detected ictal onsets from the ipsilateral mesial temporal structures and from the contralateral temporal lobe. Postoperatively, in the patients where their CM was located in the language-dominant hemisphere (n = 10), the full-scale intelligence quotient (IQ) and the performance IQ increased (p < 0.05), whereas the verbal memory (WMS-R) deteriorated in two of 5 patients. CONCLUSION: Excellent seizure outcomes were obtained even the lesionectomy alone. To confirm appropriate surgical strategy for lateral temporal CM with intractable epilepsy, further studies in large sample size are needed.

Significance of Very-High-Frequency Oscillations (Over 1,000Hz) in Epilepsy.

OBJECTIVE: We previously reported ictal very-high-frequency oscillations (VHFO) of 1,000 to 2,500Hz recorded by subdural macroelectrodes using a 10-kHz sampling rate. The purpose of this study was to clarify the clinical significance of ictal VHFO in neocortical epilepsy. METHODS: This study included 13 patients with neocortical epilepsy who underwent subdural electrode implantation and had at least 1 seizure recorded at a 10-kHz sampling rate and were followed for more than 2 years postoperatively. Extent of resection was determined considering the seizure onset zone (SOZ) and irritative zone, structural lesion, and functional areas. Areas showing VHFO and those with HFO were not taken into consideration. The presence or absence of VHFO (>1,000 Hz), HFO (200-1,000Hz) and SOZ, and completeness of resection of these areas were compared with postoperative seizure outcome. RESULTS: Seven patients had favorable (Engel class Ia) and 6 had unfavorable outcomes (other classes). VHFO was recorded in 6 of 7 patients with a favorable outcome. On the contrary, VHFO was recorded in only 1 of 6 patients with unfavorable outcome. The presence of VHFO was significantly associated with favorable outcome. VHFO was recorded on a limited number of electrodes, and VHFO-generating areas were resected completely, whereas HFO-generating areas and/or SOZ were not always resected completely in both favorable and unfavorable outcome groups. INTERPRETATION: The presence of ictal VHFO may be predictive of favorable outcome. Ictal VHFO may be a more specific marker than ictal HFO or SOZ for identifying the core of epileptogenic zone.

Mesial temporal lobe epilepsy with no specific histological abnormality: a distinct surgically remediable syndrome.

PURPOSE: The purposes of the study were twofold: to clarify the clinical features and surgical outcome of mesial temporal lobe epilepsy (MTLE) with no specific histological abnormality and to determine the optimal surgical strategy. METHODS: Twelve patients who met the following criteria were included: (1) normal preoperative MRI; (2) intracranial EEG findings consistent with mesial temporal onset of seizures; (3) selective amygdalohippocampectomy (AHE) was performed, and the patient was followed for more than 2years postoperatively; and (4) hippocampal histopathology was nonspecific. Clinical characteristics, intracranial EEG findings, and postoperative seizure outcome were examined. These twelve patients were compared with twenty-one patients with MTLE with unilateral hippocampal sclerosis (HS) on MRI who underwent intracranial EEG before resection (control group). RESULTS: In patients with MTLE with no specific histological abnormality, the age at onset was significantly higher, the history of febrile seizures was significantly less frequent, and preoperative IQ score was significantly higher than that in the control group. The proportion of patients with bitemporal independent and/or nonlateralizing seizure onset on intracranial EEG was 50% in patients with MTLE with nonspecific histopathology and was significantly higher than that in the control group. Seizure outcome was classified as Engel class I in seven patients, class II in three, class III in one, and class IV in one. Seizure outcome was favorable even in three patients with seizures originating more frequently from the side contralateral to the resected side. CONCLUSIONS: Mesial temporal lobe epilepsy with no specific histological abnormality is a clinical entity distinctly different from MTLE with HS. Bitemporal independent and/or nonlateralizing seizure onset on intracranial EEG is very common. Although the presence of lateral temporal and/or extratemporal epileptogenicity should always be kept in mind, postoperative seizure outcome after AHE is favorable even in cases with bitemporal independent and/or nonlateralizing seizure onset.

Ictal very low frequency oscillation in human epilepsy patients.

Using intracranial electroencephalographic recordings, we identified a distinct brain activity in 3 patients with refractory epilepsy characterized by very early occurrence from 8 minutes 10 seconds to 22 minutes 40 seconds prior to clinical seizure onset, periodical appearance of slow negative baseline shift, long interpeak interval of 40 to 120 seconds, and disappearance after clinical seizure. We named this activity "very low frequency oscillation" (VLFO), which reflected a dynamic process during the preictal state. This observation may render new insight into epileptogenesis and provide additional information concerning the epileptogenic zone as well as prediction of epileptic seizures.

Successful treatment of epilepsy by resection of periventricular nodular heterotopia.

We report on a case of successful surgical treatment of drug-resistant epilepsy associated with a solitary lesion of periventricular nodular heterotopia (PNH). In the reported patient, intracranial ictal electroencephalography disclosed that seizures did not originate from the heterotopic nodules. However, the seizures were completely suppressed by lesionectomy of PNH alone. Epileptogenesis associated with PNH likely involves a very complex network between PNH and the surrounding cortex, and the disruption of this network may be an effective means of curing intractable, PNH-associated epilepsy.

Posterior cortex epilepsy secondary to ulegyria: is it a surgically remediable syndrome?

PURPOSE: To examine whether surgery is indicated for posterior cortex epilepsy secondary to ulegyria. PATIENTS AND METHODS: Ten patients who underwent surgery for posterior cortex epilepsy with ulegyria and were followed for more than 2 years were included. All patients underwent comprehensive presurgical evaluations. Five patients underwent intracranial electroencephalography (EEG) studies. The posterior cortex including the magnetic resonance imaging (MRI) lesion was resected in all patients. Postoperative follow-up period was 2-12 (mean 6) years. RESULTS: Nine patients had a history of perinatal distress including asphyxia and prolonged labor. Age at seizure onset was 5-11 years, except one patient. Three patients had visual field defects preoperatively. Ulegyria was unilateral in four patients and bilateral but unilateral-predominant in six patients. In most of the cases, the lesions were in the posterior cerebral artery area or the watershed area between middle cerebral and posterior cerebral arteries. In four of five patients who underwent intracranial EEG, seizure onset zones extended outside the lesions. Postoperative seizure outcome was Engel's class I in seven cases, and class III in three cases. Three of four patients whose seizure onset zones were not completely resected achieved class I outcome. Four of six patients with bilateral lesions achieved class I outcome. CONCLUSION: Ulegyria due to perinatal distress is considered to be a major cause of posterior cortex epilepsy. Long-term postoperative seizure outcome is favorable. Resection of MRI lesion is important for seizure relief. Bilateral lesions should not be excluded from surgical indication. The usefulness of intracranial EEG may be limited.

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.

Extraoperative functional mapping of motor areas in epileptic patients by high-frequency cortical stimulation.

OBJECT: The aim of this study was to investigate the usefulness of a short train of high-frequency (500 Hz) cortical stimulation to delineate the primary motor cortex (MI), supplementary motor area (SMA), primary somatosensory cortex (SI), supplementary sensory area (SSA), negative motor area (NMA), and supplementary negative motor area (SNMA) in patients with epilepsy who were undergoing functional mapping. METHODS: Seventeen patients were studied, all of whom underwent functional mapping using 50-Hz electrical stimulation. After these clinical evaluations, cortical stimulations with a short train of electrical pulses at 500 Hz were performed through subdural electrodes placed at the MI, SMA, SI, SSA, NMA, and SNMA, which had been identified by 50-Hz stimulation, and surrounding cortical areas, while surface electromyography readings were recorded. RESULTS: Stimulation of the MI elicited motor evoked potentials (MEPs) in contralateral muscles. Stimulation of the SMA also induced MEPs in contralateral muscles but with longer latencies compared with the MI stimulation. Stimulation of the SMA did not elicit MEPs in ipsilateral muscles. Stimulation of the SI, SSA, NMA, and SNMA did not induce MEPs in any muscle. In one patient, MEPs were elicited without seizure induction by 500-Hz stimulation of the electrodes, whereas a 50-Hz stimulation of the same electrodes induced his habitual seizures. CONCLUSIONS: Extraoperative high-frequency stimulation with MEP monitoring is a useful complementary method for cortical mapping without inducing seizure. Stimulation of SMA induces MEPs in contralateral muscles, with longer latencies compared with the stimulation of MI. This finding may be useful for the differentiation between MI and SMA, especially in the foot motor areas.

Early seizure propagation from the occipital lobe to medial temporal structures and its surgical implication.

Intracranial EEG documentation of seizure propagation from the occipital lobe to medial temporal structures is relatively rare. We retrospectively analyzed intracranial EEG recorded with electrodes implanted in the medial temporal lobe in patients who underwent occipital lobe surgery. Four patients with occipital lesions, who underwent intracranial EEG monitoring with intracerebral electrodes implanted in the medial temporal lobe prior to occipital lobe surgery, were studied. Subdural electrodes were placed over the occipital lobe and adjacent areas. Intracerebral electrodes were implanted into bilateral hippocampi and the amygdala in three patients, and in the hippocampus and amygdala ipsilateral to the lesion in one. In light of the intracranial EEG findings, the occipital lobe was resected but the medial temporal lobe was spared in all patients. The follow-up period ranged from six to 16 years, and seizure outcome was Engel Class I in all patients. Sixty six seizures were analyzed. The majority of the seizures originated from the occipital lobe. In complex partial seizures, ictal discharges propagated to the medial temporal lobe. No seizures originating from the temporal lobe were documented. In some seizures, the ictal-onset zone could not be identified. In these seizures, very early propagation to the medial temporal lobe was observed. Interictal spikes were recorded in the medial temporal lobe in all cases. Intracranial EEG revealed very early involvement of the medial temporal lobe in some seizures. Seizure control was achieved without resection of the medial temporal structures.

A classification system for verifying the long-term efficacy of resective surgery for drug-resistant seizures.

OBJECTIVE: To verify the long-term efficacy of resective surgery, we created a classification system in which strictly defined patterns of postoperative seizure emergence are incorporated as basic components and the seizure states throughout the entire follow-up period are assessed comprehensively. METHODS: In our system, Class I has three subclasses (A-C); subclasses A and B are identical to Engel I-A and I-B, respectively. Subclass C comprises patients whose disabling seizures remit within the first 2 years postoperatively. Patients in Class II have only 1-3 days with disabling seizures throughout follow-up after the first 2 years. Patients in Class III have a maximum of 3 seizure days annually, and those in Class IV have ≥4 seizure days annually after the first 2 years. Classes II-IV each have 2 subclasses (A and B): subclass A, late recurrence (i.e., the first seizure occurs after 2 years postoperatively); and subclass B, early recurrence (i.e., first seizure within 2 years). In 646 patients who underwent resective surgery (temporal lobe resection, 74.6%) and were followed for at least 8 years (mean, 14.6 years), we analyzed three patterns of postoperative seizures: early remission, late recurrence, and occasional seizures. In addition, we investigated the differences between the long-term seizure outcomes of the cohort as determined according to our system and the Engel scale. RESULTS: Overall, 52.9% of the cohort experienced at least one disabling seizure postoperatively throughout the follow-up period; in 1/3 of these patients, the first seizure occurred after 2 years. In 73.8% of the 80 patients who manifested the running-down phenomenon, seizure remission occurred within the first 2 years. In addition, 36.7% of the 283 patients who had disabling seizures after 2 years experienced only 1-3 seizure days. Engel Class I-C included about 30% of the patients who had ≥4 seizure days after 2 years. The long-term seizure outcomes, determined according to our system, were: Class I, 56.2% (C, 9.1%) of the overall cohort; Class II, 16.1% (A, 11.0%); and Class III/IV, 27.7% (A, 6.6%). CONCLUSION: Our system clarifies the actual effect of resective surgery more precisely than the Engel scale and thus may be useful for comparing outcomes between different surgical procedures or for identifying potential risk factors predicting unfavorable outcome.

Usefulness of 123I-iomazenil single-photon emission computed tomography in discriminating between mesial and lateral temporal lobe epilepsy in patients in whom magnetic resonance imaging demonstrates normal findings.

OBJECT: To provide greater accuracy in determining the epileptogenic zone during preoperative evaluation, the authors retrospectively examined 123I-iomazenil single-photon emission computed tomography (IMZ SPECT) studies obtained in patients with temporal lobe epilepsy (TLE) in whom there was no evidence of an abnormality on magnetic resonance (MR) images. METHODS: Twelve patients, seven with mesial TLE (MTLE) and five with lateral TLE (LTLE), satisfied the criteria for inclusion in the study. The IMZ SPECT findings in these patients were reviewed retrospectively, and a comparison was made between findings in patients with MTLE and those in patients with LTLE. RESULTS: The IMZ SPECT studies demonstrated decreased IMZ uptake in the ipsilateral mesial temporal region and the anterobasal temporal lobe in all patients who had MTLE on only one side. On the other hand, IMZ SPECT examinations revealed low IMZ uptake in the ipsilateral lateral temporal lobe in four of five patients with LTLE in whom abnormal findings were restricted to the lateral neocortex. In the remaining patient with LTLE, abnormally low IMZ uptake was found in both mesial and lateral temporal lobes, although pure LTLE was diagnosed by an invasive electroencephalographic evaluation; this patient's habitual seizures continued even after temporal lobectomy, although his mesial structures were spared. CONCLUSIONS: The authors report characteristics of IMZ SPECT findings that differed between patients with MTLE and those with LTLE. The IMZ SPECT examinations proved useful for preoperative evaluation and, to a certain extent, for discrimination between MTLE and LTLE in cases in which MR imaging demonstrated normal findings. The results of this study suggest that IMZ SPECT findings may reflect localization of the epileptogenic zone.

Bilateral symmetric tonic posturing suggesting propagation to the supplementary motor area in a patient with precuneate cortical dysplasia.

We report a patient manifesting seizures with bilateral symmetric tonic posturing, which were markedly reduced after resection of the left precuneus. A 16-year-old man had sudden onset, complex partial seizures with bilateral symmetric tonic posturing since the age of eight years. Magnetic resonance fluid-attenuated inversion-recovery imaging revealed a hyperintense lesion in left precuneus. In almost all focal seizures recorded during an invasive EEG evaluation, ictal onset was detected from the inferomesial aspect of the lesion, but fast paroxysmal discharges from the ipsilateral supplementary motor area (SMA) were observed just before the clinical onset. After surgical excision of the EEG onset zone, including the lesion, seizure frequency was markedly (> 95%) reduced. By the 20th month after surgery, there were only brief nocturnal seizures involving slight elevation of both shoulders and slight abduction of both arms, with preservation of consciousness occurring once every few days. Invasive EEG findings and surgical outcome suggested that the epileptic activity originating from the epileptogenic zone may have propagated to the symptomatogenic zone including mainly the ipsilateral SMA. In summary, we report an interesting case of bilateral symmetric tonic posturing suggesting propagation to the SMA. MRI and invasive EEG confirmed the epileptogenic focus as a precuneate cortical dysplasia lesion.[Published with video sequences].

Long-term outcomes of epilepsy surgery in 85 pediatric patients followed up for over 10 years: a retrospective survey.

OBJECTIVE The aim of this study was to investigate the treatment outcomes and social engagement of patients who had undergone pediatric epilepsy surgery more than 10 years earlier. METHODS Between 1983 and 2005, 110 patients younger than 16 years underwent epilepsy surgery at the National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders. The authors sent a questionnaire to 103 patients who had undergone follow-up for more than 10 years after surgery; 85 patients (82.5%) responded. The survey contained 4 categories: seizure outcome, use of antiepileptic drugs, social participation, and general satisfaction with the surgical treatment (resection of the epileptic focus, including 4 hemispherectomies). The mean patient age at the time of surgery was 9.8 ± 4.2 (SD) years, and the mean duration of postoperative follow-up was 15.4 ± 5.0 years. Of the 85 patients, 79 (92.9%) presented with a lesional pathology, such as medial temporal sclerosis, developmental/neoplastic lesions, focal cortical dysplasia, and gliosis in a single lobe. RESULTS For 65 of the 85 responders (76.5%), the outcome was recorded as Engel Class I (including 15 [93.8%] of 16 patients with medial temporal sclerosis, 20 [80.0%] of 25 with developmental/neoplastic lesions, and 27 [73.0%] of 37 with focal cortical dysplasia). Of these, 29 (44.6%) were not taking antiepileptic drugs at the time of our survey, 29 (44.6%) held full-time jobs, and 33 of 59 patients (55.9%) eligible to drive had a driver's license. Among 73 patients who reported their degree of satisfaction, 58 (79.5%) were very satisfied with the treatment outcome. CONCLUSIONS The seizure outcome in patients who underwent resective surgery in childhood and underwent followup for more than 10 years was good. Of 85 respondents, 65 (76.5%) were classified in Engel Class I. The degree of social engagement was relatively high, and the satisfaction level with the treatment outcome was also high. From the perspective of seizure control and social adaptation, resective surgery yielded longitudinal benefits in children with intractable epilepsy, especially those with a lesional pathology in a single lobe.

Bereitschaftspotentials recorded from the lateral part of the superior frontal gyrus in humans.

To demonstrate the Bereitschaftspotentials (BPs) over the high lateral convexity in the superior frontal gyrus, movement-related cortical potentials with respect to the middle finger extension were recorded in seven patients with refractory epilepsy who underwent subdural implantation of platinum electrode grids and/or strips covering the high lateral frontal convexity. In two out of the seven patients, BPs were recorded from the electrodes placed on the superior frontal gyrus in the vicinity of the border between the medial and lateral frontal lobes, which were distinct from those recorded from the primary sensorimotor cortex. The results suggest the possible contribution of either the lateral dorsal non-primary motor area or the SMA to the generation of the BPs.

[Surgical treatment for extratemporal lobe epilepsy].

We analyzed the seizure outcome of 140 patients who underwent resective surgeries of extratemporal lobes including multilobar resection and hemispherectomy. The patients were followed for 2.0 to 16.7 years after surgery (mean, 6.2 years). The overall seizure outcome was Engel's class I in 87 patients (62%), class II in 14 (10%), class III in 13 (9%), and class IV in 26 (19%). The proportion of class I cases was 76% in 71 patients with discrete lesions under 5 cm in diameter on MRI, whereas the proportion was 52% in 46 patients with widespread lesions over 5 cm, and 39% in 23 patients with no MRI-detectable lesion. The seizure-free rates of extratemporal lobe resection was slightly lower compared with temporal lobe resection. Even in patients with extratemporal lobe epilepsies, clinicians should consider the option of surgical intervention from the early stage of disease.

Motor-related functional subdivisions of human lateral premotor cortex: epicortical recording in conditional visuomotor task.

OBJECTIVE: To clarify the functional subdivisions of the human lateral premotor cortex (PM) in the visuomotor control. METHODS: Event-related potentials (ERPs) were epicortically recorded from PM in 5 epilepsy patients. S1-Go/NoGo choice delayed reaction time (RT), S1-warned S2-Go simple RT and control fixation paradigms were compared using paired visual stimuli (S1, S2). RESULTS: Signal-related activity peaked at 176-194 ms after S1 in the ventrorostral PM (PMvr) in all 3 paradigms, indicating its role in signal perception. Early set-related activity was recorded with its peak <810 ms after S1 in the dorsorostral PM (PMdr) and was larger in the choice than in the simple RT paradigm, suggesting its role in signal selection. Its cognitive component was recorded as surface-positive transients at PMdr, while its motoric aspect, seen as negative transients, extended to the caudal PM. Late sustained set-related activity was observed in preparation for hand movement in the caudal PM at the hand and face positive motor areas. After presentation of S2, movement-related activity was observed at the hand sensorimotor area for motor execution, following the signal-related activity at PMvr. CONCLUSIONS: The present ERP study suggests the temporally sequential representation of predominantly 'cognitive' function in the rostral PM and 'motor' function in the caudal PM. SIGNIFICANCE: The rostrocaudal cognitive-motor gradient was demonstrated in the lateral premotor cortex in humans by means of an epicortical ERP approach.

Statistical parametric mapping of interictal 123I-iomazenil SPECT in temporal lobe epilepsy surgery.

Brain single photon emission computed tomography (SPECT) for epilepsy is divided into two types (using three radionuclide tracers)-perfusion SPECT (123I-IMP or 99 mTc-ECD), identifying epileptogenic foci by detecting abnormality in regional cerebral blood flow, and 123I-iomazenil SPECT, identifying epileptogenic foci based on distribution of central benzodiazepine receptors. This study aimed to statistically evaluate and compare the SPECT effectiveness for the three tracers. Statistical parametric mapping (SPM) analysis was performed on 30 mesial temporal lobe epilepsy (mTLE) patients. The radionuclide and patient data were categorized as follows: abnormality in the medial temporal lobe on the operated hemisphere (AAA), in the entire temporal lobe on the operated hemisphere (AA), in the dominantly affected temporal lobe on the operated hemisphere (A), in bilateral temporal lobes (B), with no abnormalities in bilateral temporal lobes (C), and with abnormality in the temporal lobe on the nonoperated hemisphere (D). For analyses of (AAA), (AA), and (A), examining the hemisphere containing epileptogenic foci, IMP-SPECT was significantly superior to ECD-SPECT (P<0.05). For (AAA), indicating localization, IMZ-SPECT was significantly superior to the other two (P<0.05). IMP-SPECT was superior for lateralizing and IMZ-SPECT was useful for localizing epileptogenic foci in mTLE patients though the applicability of the results in extratemporal lobe epilepsy is unknown.

KCC2 was downregulated in small neurons localized in epileptogenic human focal cortical dysplasia.

Focal cortical dysplasia (FCD), which is characterized histologically by disorganized cortical lamination and large abnormal cells, is one of the major causes of intractable epilepsies. γ-aminobutyric acid (GABA)(A) receptor-mediated synchronous depolarizing potentials have been observed in FCD tissue. Since alterations in Cl(-) homeostasis might underlie these depolarizing actions of GABA, cation-Cl(-) cotransporters could play critical roles in the generation of these abnormal actions. We examined the expression patterns of NKCC1 and KCC2 by in situ hybridization histochemistry and immunohistochemistry in FCD tissue obtained by surgery from patients with intractable epilepsy. KCC2 mRNA and protein were expressed not only in non-dysplastic neurons in histologically normal portions located in the periphery of the excised cortex, but also in dysplastic cells in FCD tissue. The levels of KCC2 mRNA and protein were significantly decreased in the neurons around large abnormal neurons (giant neurons), but not in giant neurons, compared with non-dysplastic neurons. The neurons localized only around giant neurons significantly smaller than non-dysplastic neurons. However NKCC1 expression did not differ among these cell types. These results suggest that the intracellular Cl(-) concentration ([Cl(-)](i)) of small neurons might increase, so that depolarizing GABA actions could occur in the FCD tissue of epileptic foci.

Clinical significance of ictal high frequency oscillations in medial temporal lobe epilepsy.

OBJECTIVE: To clarify the clinical significance of ictal high frequency oscillations (HFO) in the medial temporal lobe. METHODS: This study included 19 patients who underwent intracranial electrode implantation in bilateral temporal lobes and had at least one seizure recorded at 1kHz sampling rate. The characteristics of ictal HFO in the medial temporal lobe, and the relations between the presence of HFO, pathology, and postoperative seizure outcome were analyzed. RESULTS: Ictal HFO were detected from medial temporal structures in 11 patients with medial temporal lobe epilepsy (MTLE). Among eight patients without HFO, only three were diagnosed with MTLE. Ictal HFO were detected from unilateral medial temporal structures ipsilateral to the side of hippocampal sclerosis (HS). In one patient with bitemporal independent seizure onset, ictal HFO were detected only on the side of HS. HS was detected in all 11 patients with HFO, but in only one of four patients without HFO. Seizure outcome did not differ between patients with and without HFO. CONCLUSIONS: Ictal HFO in the medial temporal lobe may be a specific marker for MTLE with HS. SIGNIFICANCE: Recording of ictal HFO in the medial temporal lobe may be useful for presurgical evaluation of MTLE.

Versive seizures in occipital lobe epilepsy: lateralizing value and pathophysiology.

To clarify the value of versive seizures in lateralizing and localizing the epileptogenic zone in patients with occipital lobe epilepsy, we studied 13 occipital lobe epilepsy patients with at least one versive seizure recorded during preoperative noninvasive video-EEG monitoring, who underwent occipital lobe resection, and were followed postoperatively for more than 2 years with Engel's class I outcome. The videotaped versive seizures were analyzed to compare the direction of version and the side of surgical resection in each patient. Moreover, we examined other motor symptoms (partial somatomotor manifestations such as tonic and/or clonic movements of face and/or limbs, automatisms, and eyelid blinking) associated with version. Forty-nine versive seizures were analyzed. The direction of version was always contralateral to the side of resection except in one patient. Among accompanying motor symptoms, partial somatomotor manifestations were observed in only five patients. In conclusion, versive seizure is a reliable lateralizing sign indicating contralateral epileptogenic zone in occipital lobe epilepsy. Since versive seizures were accompanied by partial somatomotor manifestations in less than half of the patients, it is suggested that the mechanism of version in occipital lobe epilepsy is different from that in frontal lobe epilepsy.