Ictal Behaviors During Nonepileptic Seizures Differ in Patients with Temporal Lobe Interictal Epileptiform EEG Activity and Patients Without Interictal Epileptiform EEG Abnormalities

Summary: Purpose: Ictal behaviors during psychogenic non-epileptic seizures (NES) vary considerably among individuals, and can closely resemble common semiologies of epileptic seizures (ES). We tested the hypothesis that behaviors during NES in patients who have temporal spikes would more closely resemble behaviors during ES in patients with temporal lobe epilepsy than would behaviors during NES in patients who do not have EEG spikes.
Methods: We identified 20 patients who had interictal temporal EEG spikes and EEG-video recorded NES (Study Group), 133 patients with temporal EEG spikes and recorded ES, without NES (Epileptic Group), and 24 patients with recorded NES and no epileptiform EEG abnormalities, without ES (Nonepileptic Group).
Results: The hypothesis was supported with regard to ictal motor behaviors. Motionless staring or complex automatisms occurred mainly during NES in the Study Group and during ES in the Epileptic Group. In contrast, convulsive movements or flaccid falls were most common during NES in the Nonepileptic Group. Duration of unresponsiveness was longer, and there were fewer postictal states in NES both in the Study and Non-epileptic Groups. Unresponsiveness was briefer and postictal states were more consistent in ES in the Epileptic Group, however.
Conclusions: Stereotyped motor activities during NES presumably represent learned behaviors. Processes underlying acquisition of ictal behaviors of NES probably differ in patients with interictal epileptiform EEG abnormalities compared to those without. Prior experiences and temporal lobe dysfunctions that are associated with epilepsy, and psychological characteristics that are unrelated to interictal epileptic dysfunctions, may determine ictal behaviors during NES.     

The Absence of Interictal Spikes with Documented Seizures Suggests Extratemporal Epilepsy

PURPOSE: To determine the demographic and clinical characteristics of patients who have documented epileptic seizures on long-term video-EEG monitoring who do not have interictal spikes. METHODS: The records of 1,223 monitoring studies from 919 patients who underwent noninvasive long-term video-EEG monitoring were reviewed. In 28 patients (3.0% of monitored patients, 4.4% of patients with electrographic evidence of epilepsy), no interictal spikes were found despite the occurrence of at least one recorded electrographic seizure. The demographic, medical, neuropsychological, and EEG data of these patients were compared with those of 28 matched control patients with documented interictal spikes. RESULTS: Extratemporal seizures were significantly more frequent in the patients with at least one recorded epileptic seizure but without interictal spikes compared with patients with epileptic seizures and interictal spikes (p = 0.031). The only other significant difference between the groups (p = 0.016) was a later age at seizure onset (18.3 vs. 10.7 years) for the patients without interictal spikes. Age at evaluation, gender, handedness, clinical seizure type, family history of epilepsy, history of febrile seizures, neuropsychological testing, and neurologic and psychiatric history did not differ between the two groups. CONCLUSIONS: In patients with documented epilepsy without interictal spikes on EEG monitoring, the possibility of an extratemporal focus should be considered.     

Speech During Partial Seizures: Intracranial EEG Correlates

Vocalization during a seizure may help predict the location of seizure onset or identify structures ultimately involved in the seizure. Spontaneous vocalization during seizures was studied retrospectively in 22 patients with refractory complex partial seizures evaluated with bilateral intracranial electrodes. Of 22 patients, 12 vocalized during seizures. Seizures were as likely to originate from language-dominant (6/12) as from language-nondominant mesial temporal cortex (6/12). Fluent speech frequently occurred as seizure activity was recorded from language-dominant temporal lobe neocortex (6/12 seizures). Of the patients with well-localized seizure onsets who did not speak (6/10), seizures arose from both language-dominant and -nondominant mesial temporal cortex. We conclude that the presence or absence of vocalizations during a seizure does not reliably indicate the anatomic regions in which the seizure begins or spreads.     

Acute Psychosis During Intracranial EEG Monitoring: Close Relationship Between Psychotic Symptoms and Discharges in Amygdala

PURPOSE: This report examined the underlying mechanism of psychosis associated with epilepsy. METHODS: An adult patient with epilepsy manifesting acute psychosis during long-term EEG monitoring is presented, together with a literature review on this subject. RESULTS: A 25-year-old woman with intractable temporal lobe epilepsy developed acute psychosis while she underwent long-term intracranial EEG monitoring. After a clustering of seizures, she manifested psychotic symptoms including hallucination, stupor, and repeated fear. The transition of psychotic symptoms corresponded to the changes in frequency and morphology of seizure discharges restricted to the left amygdala. Improvement of psychosis coincided with disappearance of seizure discharges. CONCLUSIONS: This case confirmed a close relationship between psychotic symptoms and seizure discharges in the left amygdala. It is suggested that paroxysmal bombardment of the medial temporal lobe structure may be a pathogenetic factor of acute psychosis associated with epilepsy.     

Intracranial EEG substrates of scalp EEG interictal spikes

PURPOSE: To determine the area of cortical generators of scalp EEG interictal spikes, such as those in the temporal lobe epilepsy. METHODS: We recorded simultaneously 26 channels of scalp EEG with subtemporal supplementary electrodes and 46 to 98 channels of intracranial EEG in 16 surgery candidates with temporal lobe epilepsy. Cerebral discharges with and without scalp EEG correlates were identified, and the area of cortical sources was estimated from the number of electrode contacts demonstrating concurrent depolarization. RESULTS: We reviewed approximately 600 interictal spikes recorded with intracranial EEG. Only a very few of these cortical spikes were associated with scalp recognizable potentials; 90% of cortical spikes with a source area of >10 cm(2) produced scalp EEG spikes, whereas only 10% of cortical spikes having <10 cm(2) of source area produced scalp potentials. Intracranial spikes with <6 cm(2) of area were never associated with scalp EEG spikes. CONCLUSIONS: Cerebral sources of scalp EEG spikes are larger than commonly thought. Synchronous or at least temporally overlapping activation of 10-20 cm(2) of gyral cortex is common. The attenuating property of the skull may actually serve a useful role in filtering out all but the most significant interictal discharges that can recruit substantial surrounding cortex.     

Interictal spikes on intracranial recording: behavior, physiology, and implications

Purpose: The physiological, pathological, and clinical meaning of interictal spikes (IISs) remains controversial. We systematically analyzed the frequency, occurrence, and distribution of IISs recorded from multiple intracranial electrodes in 34 refractory epileptic patients with respect to seizures and antiepileptic drug (AED) changes. Methods: Continuous spike counts from all recorded contacts of all implanted electrodes, and also separately for the subset of contacts involved at seizure onset, were tabulated for every hour of every day of recording, and expressed as spikes per hour in six preselected, 24‐h intervals (defined to exclude seizures): (1) on medications; (2) prepreseizure; (3) preseizure; (4) postseizure; (5) off meds; and (6) resumed meds. Mean spike rates were analyzed for differences between designated 24‐h intervals. Results: Spike rate in all recorded contacts consistently and significantly decreased after AED withdrawal, despite variability in initial spike rate, diurnal occurrence, seizure character/number/localization of onset, and type(s) of AED continued or withdrawn (p < 0.0001). A significant increase in spike rate was noted in the 24  h after seizures of medial temporal origin, in the medial temporal lobe contacts; neocortical onset seizures did not show any increase. Conclusions: These observations confirm and extend previous reports, suggesting a general effect of AED withdrawal, and a more specific effect of medial temporal lobe seizures, on IIS rate. AED mechanisms and efficacy might be demonstrated by quantifying IIS with changes in AEDs. Furthermore, variability in IIS rate after seizures distinguishes localization of seizure onset in medial temporal versus neocortical locations.     

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

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

Interictal Epileptiform Discharges in Temporal Lobe Epilepsy Due to Hippocampal Sclerosis Versus Medial Temporal Lobe Tumors

PURPOSE: It remains controversial whether a specific pattern of interictal epileptiform activity exists that may help to differentiate temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) from other forms of TLE. In this study, we characterized the distribution of interictal epileptiform discharges in TLE due to HS as compared with those in patients with tumors restricted to the medial temporal lobe structures. METHODS: The study included 21 adult patients with unilateral HS who remained seizure free (>1 year) after anterior temporal lobectomy with amygdalohippocampectomy. Patients with "dual pathology" were excluded. The comparison group consisted of nine patients with tumors restricted to the amygdala and hippocampus. All patients underwent video-EEG monitoring preoperatively by using 39 scalp electrodes (including the 10-10 system over both temporal regions) and bilateral sphenoidal electrodes. RESULTS: The HS patient group showed a significantly higher percentage of ipsilateral epileptiform discharges maximal at anterior temporal electrodes (median, 97.0%; sphenoidal electrode alone, 88.1%), as compared with the tumor group (median, 72.1%; p<0.001; sphenoidal electrode alone, 24.8%; p<0.001). The HS group had significantly fewer extratemporal spikes/sharp waves (median, 0.0), as compared with the tumor group (10.0%; p<0.001). At least 90% of the interictal discharges were located in the anterior temporal region in 20 (95.2%) of 21 HS patients, but in none of the tumor patients (p<0.001). Bilateral temporal discharges were found in nine (42.9%) of 21 patients with HS and in two (22.2%) of nine tumor patients (p = 0.42). CONCLUSIONS: We conclude that ipsilateral interictal epileptiform discharges outside the anterior temporal region are rare (<10%) in adults with intractable TLE due to unilateral HS. Frequent posterior or extratemporal sharp waves may detract from the certainty of this diagnosis in complicated cases. These restricted epileptiform discharges suggest a smaller irritative zone in HS as compared with medial tumors, or a more organized activity associated with intrinsic hippocampal disease. Bilateral epileptiform discharges were not uncommon in both groups.     

Interictal, unifocal spikes in refractory extratemporal epilepsy predict ictal origin and postsurgical outcome.

OBJECTIVES: To evaluate the significance of exclusively unifocal, unilateral, interictal epileptiform patterns on scalp electroencephalography (EEG) in surgical candidates with medically intractable extratemporal epilepsy. METHODS: We reviewed 126 patients with refractory extratemporal partial seizures who underwent epilepsy surgery at our center. All were followed for at least 2 years after resections. Surgery was based on ictal EEG recordings. We examined ictal onsets and surgical outcome in subjects whose preoperative, interictal scalp EEGs during long-term monitoring (LTM) demonstrated only unilateral, well-defined focal discharges, and outcome in patients whose interictal EEGs during LTM showed bilateral, non-localized, or multifocal epileptiform patterns. RESULTS: We found that 26 subjects exhibited only unilateral, unifocal, interictal epileptiform patterns. In all 26 cases (100%) clinical seizures arose from the regions expected by the interictal findings (P<0.0001, Sign test). At last follow-up 77% (20/26) of these patients were seizure-free, while 23% (6/26) had >75% reduction in seizures. This compares to the remaining patients, of whom 34% (34/100) were seizure-free, 41% (41/100) had >75% reduction in seizures, and 25% (25/100) had <75% reduction in seizures (P=0.0001, Fisher's Exact test). CONCLUSIONS: Strictly unifocal, interictal epileptiform patterns on scalp EEG, though seen in a minority of subjects, may be an important, independent factor in evaluating subjects with intractable extratemporal, localization-related epilepsy for surgical therapy. This finding is highly predictive of both ictal onsets and successful postsurgical outcome.     

Association of Combined MRI, Interictal EEG, and Ictal EEG Results with Outcome and Pathology After Temporal Lobectomy

Summary: Purpose: Magnetic resonance imaging, interictal scalp EEG, and ictal scalp EEG each have been shown to localize the primaly epileptic region in most patients with mesial-basal temporal lobe epilepsy (MBTLE), but the association of surgical outcome and pathology with each combination of these test results is not known. Methods: We reviewed the MRI, interictal scalp EEG, and ictal scalp EEG results of 90 consecutive patients with MBTLE. Twelve patients were excluded from the analysis because inconclusive bitemporal intracranial EEG results precluded anterior temporal lobectomy (ATL); none had concordant MRI and interictal scalp EEG results. We compared all combinations of presurgical MRI, interictal EEG, and ictal EEG results to seizure outcome and tissue pathology in the 78 patients who underwent an ATL. Results: Forty-eight (61%) patients had concordant lateral-ized MRI and interictal EEG temporal lobe abnormalities, with no discordant ictal EEG results; 77% of these patients were seizure-free after ATL. Concordance of MRI and interictal EEG abnormalities correlated with seizure cessation (p < 0.05), compared to all combinations with discordant or nonlateralizing MRI and interictal EEG results. Mesial temporal sclerosis (MTS) was confirmed pathologically in about 80% of both groups (p = 0.5). Outcome in patients with concordant MRI and ictal EEG with nonlateralizing interictal EEG was significantly worse than combinations with concordant MRI and interictal EEG (p < 0.02). Conclusions: Compared to other combinations of test results, concordance of MRI and interictal EEG is most closely associated with surgical outcome in MBTLE. However, most selected patients have pathologic confirmation of MTS regardless of test results or outcome. This information may be useful for planning the presurgical evaluation of patients with medically intractable MBTLE.     

Interictal temporal delta activity in temporal lobe epilepsy: correlations with pathology and outcome

PURPOSE: To determine the characteristics and the clinical significance of focal slow activity and its association with focal epileptogenesis in patients with temporal lobe epilepsy (TLE). METHODS: We analyzed the interictal EEGs of 141 patients who had temporal lobe resections for intractable focal seizures and correlated the findings with pathologic changes and outcome. The pathologic changes were categorized into medial temporal sclerosis, tumors, and nonspecific changes. RESULTS: Lateralized slow activity was found in 66% of the patients, and it was mainly temporal, of delta frequency and irregular morphology. None of its characteristics, including quantity and reactivity to eye opening, was substrate specific. It was highly concordant with temporal spiking (60%), without any difference across the three groups, but provided additional information in 19 (15%) patients who had no lateralizing spikes. The effect of sleep also was similar in all three groups and included transition of slow waves into spikes. Lateralized slow activity to the side of the operation was significantly associated with favorable outcome only in the group with nonspecific pathology (p = 0.008), regardless of the presence, laterality, or topography of spikes. CONCLUSIONS: Our findings suggest that in patients with TLE whose brain magnetic resonance imaging (MRI) is either normal or suggestive of medial temporal sclerosis, interictal temporal slow activity has a lateralizing value similar to that of temporal spiking. Its association with a favorable outcome in patients with nonspecific pathology also suggests that candidates with lateralizing temporal delta and normal MRI should not be barred from further preoperative assessment.     

Predictive Value of Interictal Epileptiform Discharges During Non-REM Sleep on Scalp EEG Recordings for the Lateralization of Epileptogenesis

Summary: Purpose: EEG recording during sleep is widely used in the assessment of epilepsy, particularly in candidates for surgery, yet the diagnostic value of this procedure is not well established. We evaluated the predictive reliability of interictal epileptiform discharges (IEDs) for localization in pre-surgical patients with temporal lobe epilepsy (TLE) during non-REM sleep.
Methods: Preoperative scalp EEG recordings with waking and sleep states were assessed in 83 patients with TLE in whom localization of the epileptogenic zone was subsequently confirmed by successful surgical treatment (patient seizure-free >1 year).
Results: The accuracy of EEG recordings for prediction of lateralization significantly changed from 51.8% during waking to 78.3% during sleep. After exclusion of patients who showed no discharges, the predictive value changed from 74.1 to 86.7%. However, in patients in whom the waking scalp EEG lateralized incorrectly, no improvement in reliability was achieved by sleep recording.
Conclusions: Our results suggest that IEDs occurring in non-REM sleep provide more accurate information for lateralization of epileptogenesis than do those occurring during waking. This gain of diagnostic information was obtained in patients who showed either bilateral or no discharges in waking records, because unilateral discharges arising de novo in sleep were always correctly lateralizing. On the other hand, in patients who showed unilateral discharges in the awake state, whether ipsilateral or contralateral to the epileptogenic zone, the findings were generally unchanged during sleep.     

Intracranial EEG seizure-onset patterns in neocortical epilepsy

PURPOSE: We investigated neocortical seizure-onset patterns recorded by intracranial EEG with regard to anatomic location, pathologic substrate, and prognostic value for surgical outcome. METHODS: Seizure onset was analyzed in 53 neocortical resective epilepsy surgery patients. Anatomic location was divided into temporal and extratemporal. Pathologic substrate was classified as developmental, mature, and negative or non-specific gliosis. Onset frequency was categorized by visual analysis into tradition EEG frequency bands. Spatial extent was divided into focal (fewer than four contacts) and regional (more than five contacts). Waveform at seizure onset was divided into several types based on their morphology. Onset features were examined with respect to anatomic location, pathologic substrate, and surgical outcome. RESULTS: Seizure-onset frequency was significantly related to spatial distribution and to anatomic location. Extratemporal and regional onset were more commonly in the gamma range, and temporal and focal onset in the beta frequency range or slower. Waveform could be categorized into five different patterns, of which low voltage fast activity (LVFA) was the most common form (57%). LVFA and rhythmic alpha-theta spike activity were more common in developmental than in mature pathology, whereas rhythmic sinusoidal waves at onset were found in only mature substrates. Waveform pattern showed a possible correlation with surgical outcome (p = 0.097): LVFA and rhythmic sinusoidal waves onset patterns were associated with favorable outcome more often (40.4%) than the other three patterns (6.3%). Slow onset suggested poor outcome in the subgroup of developmental pathology (p = 0.062). CONCLUSIONS: Certain electrographic seizure-onset features are associated with specific substrates and outcomes, whereas others reflect the anatomic location and its connections independent of the pathology.     

Spike EEG Abnormalities in Patients without Epileptic Seizures: A Clinical and Long-Term Follow-Up Study

Abstract: A study was conducted on a total of 850 patients who had not previously manifested any epileptic seizures but exhibited at least one spike EEG abnormality. They accounted for 7.2% of the total number of patients without epileptic seizures (850/11,773). Among the 850 patients, 564 were followed up for 1–24 years. Nine boys and one girl, 1.e. 1.8% of the 564 patients, had manifested epileptic seizures during the observation period. They expressed the following six characteristics: males, first EEG examination at 0–4 years of age, onset of initial chief complaints at 04 yeurs of age, mental retardation, spike and wave EEG abnormalities and past history of perinatal birth injuries. These factors are considered to be efficient in detecting patients liable to manifest epileptic seizures later.     

Does Physical Exercise Influence the Occurrence of Epileptiform EEG Discharges in Children?

Summary: Purpose: To determine if, and how, epileptiform EEG discharges in children were influenced by physical exercise.
Methods: Twenty-six children with intractable partial and generalized epilepsy exercised during video-telemetry recording, aiming at exhaustion after ∼10 min.
Results: During the exercise, epileptiform discharges decreased in 20 of 26 children (17 children had at least 25% reduction) and showed a rebound increase after the exercise (17 of 26 children) compared to baseline conditions. This exercise-induced reduction in epileptiform discharges reached statistical significance only in the 16 patients with localization-related epilepsy. Five patients showed an atypical EEG response to exercise with either unchanged or increased epileptiform activity while exercising. As compared to the other patients, these 5 children had experienced frequent clinical seizures during or immediately after exercise in their leisure time.
Conclusions: In the majority of the tested children, epileptiform EEG discharges decreased during exercise. "Exercise-EEG" may be a helpful diagnostic tool to identify patients who are disposed to have exercise-induced seizures.     

Spatial distribution of intracranially recorded spikes in medial and lateral temporal epilepsies

Purpose: Although seizures and interictal spikes are not always colocalized, there may be valuable localizing information in the spatial distribution of spikes. To test this hypothesis, we studied the spatial distribution of intracranially recorded interictal spikes in patients with medial temporal (MT) and lateral temporal (LT) neocortical seizure onset. Methods: A total of 21 patients (MT n = 12, LT n = 9) who completed intracranial monitoring were selected for this study. Two 4‐h intracranial electroencephalography (icEEG) epochs were analyzed, one during wake and one during sleep, both at least 6 h removed from seizures. Spikes detected automatically in medial temporal structures [hippocampal formation (H) and entorhinal cortex (EC)], and in five cortical areas (occipital, frontal, parietal, lateral temporal, and inferior temporal) were tabulated. Results: Interictal spikes occurred broadly over medial temporal structures and cortical areas in MT and LT patients. The patients differed with a greater number of spikes in medial temporal structures in the MT group (p < 0.05 for H and p < 0.001 for EC) and a greater number of spikes in parietal (p < 0.01) and frontal (p < 0.001) areas in the LT group. There were sleep‐related increases in spike rates in inferomedial temporal structures in both groups. The two groups could be separated with a classifier based on medial temporal and parietal and frontal spikes (p < 0.0001). Discussion: MT and LT patients have different spatial distributions of interictal spikes and can be distinguished by the relative spike rates in medial temporal and extratemporal areas during sleep and wake.     

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.     

Effect of Interictal Epileptiform Discharges on Nocturnal Plasma Prolactin Concentrations in Epileptic Patients with Complex Partial Seizures

To investigate the effect of interictal epileptiform discharges (IEDs) on plasma prolactin (PRL) level, we studied 18 epileptic patients with complex partial seizures (CPS) who did not experience clinical or subclinical ictal events during all-night monitoring with polygraphic recording and video imaging. The density of IEDs peaked during non-REM stages and was significantly reduced during REM stage. Mean plasma PRL concentrations in epileptic patients, when sampled at 30-min intervals, showed a moderate but significant elevation during non-REM (p less than 0.001) and awake stages (p less than 0.005), but not during REM stage, when compared with 10 nonepileptic control subjects studied in a similar fashion. The data obtained in this physiologically controlled environment indicate that the cumulative effect of IEDs may modify PRL regulatory mechanisms, resulting in a modest elevation of plasma concentrations independent of ictal discharges.     

Extent of neocortical resection and surgical outcome of epilepsy: Intracranial EEG analysis

Purpose: Intracranial electroencephalography (EEG) monitoring is an important process in the presurgical evaluation for epilepsy surgery. The objective of this study was to identify the ideal resection margin in neocortical epilepsy guided by subdural electrodes. For this purpose, we investigated the relationship between the extent of resection guided by subdural electrodes and the outcome of epilepsy surgery. Methods: Intracranial EEG studies were analyzed in 177 consecutive patients who had undergone resective epilepsy surgery. We reviewed various intracranial EEG findings and resection extent. We analyzed the relationships between the surgical outcomes and intracranial EEG factors: the frequency, morphology, and distribution of ictal‐onset discharges, the propagation speed, and the time lag between clinical and intracranial ictal onset. We also investigated whether the extent of resection, including the area showing ictal rhythm and various interictal abnormalities—such as frequent interictal spikes, pathologic delta waves, and paroxysmal fast activity—influenced the surgical outcome. Results: Seventy‐five patients (42%) were seizure free. A seizure‐free outcome was significantly associated with a resection that included the area showing ictal spreading rhythm during the first 3 s or included all the electrodes showing pathologic delta waves or frequent interictal spikes. However, subgroup analysis revealed that the extent of resection did not affect the surgical outcome in lateral temporal lobe epilepsy. Conclusions: The extent of resection is closely associated with surgical outcome, especially in extratemporal lobe epilepsy. Resection that includes the area with total pathologic delta waves and frequent interictal spikes predicts a good surgical outcome.