Can Sharp Waves Localized at the Sphenoidal Electrode Accurately Identify a Mesio-temporal Epileptogenic Focus?

In our patient population that had undergone antero-temporal lobectomy, we found 20 patients with a unilateral sphenoidal/antero-temporal interictal focus. All patients had normal computed tomography (CT) scans. Invasive recordings with subdural electrode arrays placed over and under the temporal lobe were used in every patient. We found that the scalp interictal focus predicted for all patients that both the interictal sharp waves and ictal onset would be mesiobasal/anterotemporal in location on the subdural arrays. Seventy-five percent of these patients had an excellent outcome with temporal lobectomy.     

Effect of γ-Vinyl GABA on Interictal Spikes and Sharp Waves in Patients with Intractable Complex Partial Seizures

The effect of gamma-vinyl GABA (GVG) on the interictal electroencephalogram (EEG) was studied in 13 patients with intractable complex partial seizures who participated in a single-blind, add-on, multicenter clinical trial of GVG. Precise operational definitions of epileptiform paroxysms were used to evaluate records before and after 3 months and 1 year of treatment with GVG. After 3 months of treatment, six patients exhibited reduction of both epileptiform paroxysms and seizure frequency, four had no change in seizure frequency nor in the EEG, and three had a reduction in seizure frequency but no concomitant reduction of epileptiform paroxysms in the EEG. Ten patients remained in the study after 1 year of treatment. In 4 patients both seizure frequency and EEG epileptiform paroxysms continued to decrease, in 1 patient both seizure frequency and number of EEG paroxysms increased, and in the remaining 3 there was no correlation between seizure frequency and EEG changes.     

Temporal Lobectomy and Independent Bitemporal Interictal Activity: What Degree of Lateralization Is Sufficient?

We attempted to determine whether the degree of lateralization of independent bitemporal interictal spikes and sharp waves (ISSW) is correlated with good results after temporal lobectomy. Three observers independently counted ISSW in the scalp EEGs of 59 candidates for temporal lobectomy to determine the degree of lateralization of ISSW. Interobserver correlation in percentage of lateralization was excellent (r = 0.92). Thirty-one candidates were also evaluated with depth EEG (DEEG). Operative success was graded by the number of seizures reported in the second postoperative year. There was a significant progressive decrease in the number of good operative results as the degree of lateralization of ISSW lessened (p = 0.0142). Ninety-two percent of patients with greater than 90% lateralization had a good surgical outcome, whereas only 50% with less than 90% lateralization had a good outcome. Even when all DEEG-recorded seizures emerged from the side of the lobectomy, patients with greater than 90% lateralization appeared to have better outcomes than patients with less than 90% lateralization. We conclude that greater than 90% lateralization of temporal ISSW is associated with good surgical outcome, and DEEG may not be necessary in these patients. Less than 90% lateralization is associated with poor surgical outcome and the additional information provided by DEEG may be especially useful in such patients.     

Basal Temporal Subdural Electrodes in the Evaluation of Patients with Intractable Epilepsy

In evaluation of patients with complex partial seizures who are candidates for surgical treatment, exact definition of the epileptogenic focus is essential for a good surgical outcome. We report a new technique which permits detailed mapping of the epileptogenic activity in the basal temporal lobe and the convexity of the temporal lobe. The technique consists of placement of at least 16 basal temporal electrodes and an additional 64 electrodes covering the temporal convexity. This extensive coverage permits accurate definition of the limits of the epileptogenic focus and also of adjacent functional areas and therefore allows more significant determination than have previous techniques of the ideal extent of the surgical resection. This accuracy cannot be achieved with depth electrodes or the limited coverage provided by previously reported epidural or subdural electrode techniques.     

Ictal Speech Manifestations in Temporal Lobe Epilepsy: A Video-EEG Study

Summary: To evaluate ictal speech manifestations in complex partial seizures (CPS), we reviewed videotapes of 68 consecutive patients who underwent anterior temporal lobectomy (ATL) for treatment of intractable epilepsy in Taiwan. In all, 261 CPS were collected from their video-EEG (VEEG) recordings. Cerebral speech dominance was determined by intracarotid injection of sodium amobarbital (Wada test) in all cases. Ictal speech manifestations, classified as verbalization or vocalization, occurred in 32 patients (47.1%) with 96 seizures (36.8%). Ictal verbalization occurred in 10 patients (14.7%). Ictal vocalization was observed in 28 patients (41.2%); including 6 patients who also had ictal verbalization. Thirty-six patients (52.9%) had no seizure with ictal speech manifestations. Ictal verbalization had significant lateralization value: 90% of patients with this manifestation had seizure focus in the nondominant temporal lobe (p = 0.049). Seizures of patients with ictal vocalization were not more likely to arise from either temporal lobe. We also observed bilingual patients who exclusively spoke in their mother tongue (Taiwanese) rather than the acquired language (Mandarin) in 72.2% of seizures with verbalization. This finding is significant and contrary to a commonly held notion that the acquired language is used in seizures associated with speech behaviors.     

Interictal Spiking Increases with Sleep Depth in Temporal Lobe Epilepsy

Summary: Purpose : To test the hypothesis that deepening sleep activates focal interictal epileptiform discharges (IEDs), we performed EEG-polysomnography in 21 subjects with medically refractory temporal lobe epilepsy.
Methods: At the time of study, subjects were seizure-free for 224 h and were taking stable doses of antiepileptic medications (AEDs). Sleep depth was measured by log delta power (LDP). Visual sleep scoring and visual detection of IEDs also were performed. Logistic-regression analyses of IED occurrence in relation to LDP were carried out for two groups of subjects, nine with frequent IEDs (group 1) and 12 with rare IEDs (group 2).
Results: The LDP differentiated visually scored non-rapid eye movement (NREM) sleep stages (p = 0.0001). The IEDs were most frequent in NREM stages 3/4 and least frequent in REM sleep. Within NREM sleep, in both groups, IEDs were more frequent at higher levels of LDP (p < 0.05). In group 1, after accounting for the level of LDP, IEDs were more frequent (a) on the ascending limb of LDP and with more rapid increases in LDP (p = 0.007), (b) in NREM than in REM sleep (p = 0.002), and (c) closer to sleep onset (p < 0.0001). Fewer than 1% of IEDs occurred within 10 s of an EEG arousal.
Conclusions: Processes underlying the deepening of NREM sleep, including progressive hyperpolarization in thalamocortical projection neurons, may contribute to IED activation in partial epilepsy. Time from sleep onset and NREM versus REM sleep also influence IED occurrence.     

Correlative Study of Interictal Electroencephalogram and Aura in Complex Partial Seizures

To understand further relationships of the interictal electroencephalogram to the aura in complex partial seizures (CPS), we studied the interictal EEG and aura in 144 patients with CPS. The ages of the patients studied ranged from 31 to 80 years (average 52.44 years). The duration of seizures ranged from 1 to 60 years (average 15.69 years). Seventy patients (49%) reported auras which were classified according to the guidelines recommended by the Commission of the International League Against Epilepsy. Statistical analysis revealed no relationship between presence, laterality, or localization of EEG abnormality and the number or type of aura. The results emphasize that more factors than electrophysiologic localization alone participate in the determination of aura in CPS. Our data support the position that aura has, at most, a limited relationship to lateralization or localization of interictal cerebral dysfunction in CPS.     

Clinical and EEG Features of Complex Partial Seizures of Temporal Lobe Origin

Summary: The electrographic and clinical behavioural manifestations of 96 temporal lobe seizures are reviewed from recordings in 19 patients who were submitted to stereotaxic depth electrode implantation in temporal and frontal lobes. Focal onset in hippocampus was recorded in 40% of the seizures. Sixty percent of temporal lobe seizures exhibited a regional seizure onset but in two-thirds of these ictal changes were restricted to amygdaloid and hippocampal structures. Thus, in approximately 80% of seizures, the onset of ictal EEG changes resided in the mesial temporal structures. The main behavioral manifestations observed during seizure discharge restricted to one temporal lobe included warning (67%), motionless stare (24%), automatism (22%), and head-body turning (24%). The predominant ictal behavioural manifestations observed during seizure spread to contralateral temporal and extratemporal structures included warning (3%), motionless stare (36%), automatism (77%), and head-body turning (81%). The direction of head turning did not provide reliable lateralization as to the side of seizure onset.     

Scalp and Limbic P3 Event-Related Potentials in the Assessment of Patients with Temporal Lobe Epilepsy

Auditory oddball scalp and limbic P3s were recorded from 18 patients with unilateral temporal lobe epilepsy (TLE) prior to seizure surgery. Limbic P3s were unilaterally absent ipsilateral to the seizure focus and were present in the nonepileptogenic temporal lobe in all 18 cases studied. Scalp P3s, recorded from C3 and C4, on the other hand, were elicited bilaterally and there was no significant difference in amplitude or latency between the epileptogenic and nonepileptogenic sides. These data concur with studies of scalp P3 performed following surgery and suggest that the assessment of the contribution of limbic P3 to scalp P3 may be masked by volume conduction effects and other generators of P3. We conclude that the P3 recorded from central scalp sites, unlike its limbic counterpart, offers little clinical information in the presurgical assessment of patients with TLE.     

Magnetic Resonance Imaging in Localization of EEG Depth Electrodes for Seizure Monitoring

Preoperative evaluation of patients with medically refractory complex partial seizures requires intensive EEG monitoring. Part of this process may include insertion of depth electrodes into temporal lobe structures. Although many imaging methods have been used for stereotactic placement of the electrodes, only computed tomography (CT) has been used to verify position after implantation. We studied 30 patients in whom magnetic resonance imaging (MRI) was used to visualize the position of stainless-steel electrodes stereotactically implanted in the temporal lobes. The procedure is noninvasive, does not utilize radiation, and has the additional advantages of multiplanar capability, increased soft tissue contrast, and lack of bony artifacts commonly associated with CT.     

Prognostic Significance of Ictal and Interictal Epileptiform Activity in Temporal Lobe Epilepsy

Summary: Long-term electrocorticograms (ECoG), recorded by chronically implanted subdural electrodes during preoperative evaluation of 59 patients with temporal lobe epilepsy (TLE) were analyzed retrospectively to assess the prognostic relevance of distribution of interictal epileptiform potentials (IEP) and seizure origin (SO) and to investigate factors affecting their lateralization. Subsequent to preoperative evaluation, a standardized two thirds anterotemporal lobectomy including subtotal hippocampectomy had been performed in all patients. The following results were obtained: (a) Only patients with 100% lateralization of SO and IEP had excellent seizure outcome (= 89% seizure-free); (b) patients with bitemporal SO were unlikely to benefit from surgical treatment (=12.5% seizure-free); (c) 40–56% patients with unilateral temporal SO and bitemporal IEP, became seizure-free irrespective of the degree of lateralization of IEP; and (d) multidimensional analysis of variance showed that lateralization of SO, presence of a magnetic resonance imaging (MRI)-detectable lesion, presence of hippocampal sclerosis, presence of febrile seizures and seizures at age ≥6 years are the five most important variables indicating abolition of seizures. Combined analysis of ECoG-recorded SO and IEP allows prediction of postoperative seizure control within close boundaries.     

Mirror Focus: Function of Seizure Frequency and Influence on Outcome After Surgery

Summary: The concept of the mirror focus (MF) implies that an actively discharging epileptiform region may induce similar paroxysmal behavior in a homologous site. In a group of patients with complex partial seizures (CPS) we investigated whether occurrence of a MF was influenced by certain clinical factors and whether surgical out-come was influenced by the presence of an MF. Factors studied included age at onset, duration, and total number of seizures. Patients had had CPS for >3 years and had pathologically proven temporal lobe neoplasms. Seizure frequency was estimated by the history-taking physician. We estimated total seizure number by multiplying frequency by duration. Seven patients had MF, and 15 did not. Mean age at onset of seizures, duration of seizure disorder, and total seizure number did not vary statistically between the two groups of patients. All patients with an MF except 1 were seizure-free at follow-up. Ten of the 15 patients without MF were seizure-free. Three patients who were not seizure-free had had subtotal resection owing to tumor overlap with eloquent cortex. We conclude that an MF is not a contraindication to operation even when the preponderance of interictal spike activity is contralateral to the tumor or when seizures appear to arise from the MF on scalp EEG.     

Complex Partial Seizures of Temporal Lobe Origin in Children of Different Age Groups

Summary: The semiology of complex partial seizures(CPS) of temporal lobe origin in adults is well known and is important in establishing seizure localization in patients considered for epilepsy surgery. In contrast, the behavioral features of temporal lobe seizures (TLS) in children described in the literature have not been consistent. In the present study, we investigated children with TLS to compare their attacks to TLS occurring in adults. The study was based on video recordings of 29 children with TLS aged 18 months to 16 years. Children were included, if they became seizure-free after temporal lobectomy (except 4 children with a marked reduction in seizure frequency and 1 with isolated auras), and if clear unitemporal seizure onset in ictal EEG-recordings, unilateral radiological lesions, and corresponding histopathological findings were detected. Children aged >6 years had TLS with features similar to those of adults. In younger children, typical semiology included symmetric motor phenomena of the limbs, postures similar to frontal lobe seizures in adults, and head nodding as in infantile spasms. We concluded that the clinical features of TLS in younger children can be misleading and should therefore be considered with caution in selecting patients for surgical procedures on the temporal lobe.     

Anterior Temporal Lobectomy and Medically Refractory Temporal Lobe Epilepsy of Childhood

The evaluation and outcome of 22 patients who had onset of complex partial seizures (CPS) of temporal lobe origin in childhood and subsequently underwent anterior temporal lobectomy are described. All patients showed improved seizure control; 81.8% had a reduction greater than or equal to 95% in seizure frequency. However, many patients had difficulty adjusting to a seizure-free life. Psychosocial, behavioral, and educational problems occurred more frequently in patients whose surgery was delayed until adult life. We conclude that attempts should be made early in the course of CPS of childhood to determine whether the seizures are truly intractable to medical management so that surgical intervention can be expedited.     

Focal Medial Temporal Lobe Spike-Wave Complexes Evoked by a Memory Task

Several factors are known to modulate the occurrence of interictal spike-wave complexes (SWC). During performance of a recent memory task by a patient with uncontrolled complex partial seizures and implanted electrodes, visually presented stimuli consistently evoked focal medial temporal lobe interictal SWC with an average latency of 228 +/- 29 ms. The SWC were more often lateralized to the left medial temporal lobe. No consistent change in interictal spike rate was observed during performance of several other cognitive tasks during which visual or auditory stimuli were presented. This suggests that performance of specific cognitive tasks--in this case, recognition memory of words--can trigger interictal SWC.     

Bicycling Movements as a Manifestation of Complex Partial Seizures of Temporal Lobe Origin

Alternating movements of the limbs during a seizure, especially bicycling movements of the legs, are often taken as strong evidence for the psychogenic origin of seizure activity in an adult population. A recent review of pseudoseizure manifestations concluded that alternating limb movements were "highly characteristic of pseudoseizures." We report two adult patients with complex partial seizures of temporal lobe origin, confirmed by ictal video EEG recording, in whom bicycling movements were the prominent ictal manifestation. Bicycling occurred 5-30 s after ictal onset and lasted 15-30 s. Use of video EEG recording continues to increase our understanding of the wide range of behaviors which may occur in the course of an epileptic seizure, particularly complex partial seizures. Few absolute clinical criteria remain to distinguish epileptic seizures from pseudoseizures. These two cases and one other reported case clearly remove bicycling movements from that category.     

Influence of Epilepsy and Temporal Lobe Resection on Olfactory Function

Summary: Olfactory auras accompany some cases of epilepsy. Several aspects of olfactory function, including sensitivity, also may be altered. We reviewed the literature on these topics, as well as studies evaluating the influences of temporal lobe resection and other seizure management procedures on olfactory function. We concluded that: (a) despite several studies, the prevalence of olfactory auras in epilepsy is unknown, with estimates ranging from <1% to >30%; (b) epilepsy appears to cause a generalized decrease in olfactory functioning, although increased sensitivity may occur in some epileptic patients at some time in the preictal period; (c) other sensory modalities are also affected by the epileptic process which, in some cases, involve limbic-related temporal lobe structures; (d) many of the olfactory deficits previously attrib-uted to temporal lobe resection actually exist preoperatively; (e) a tastehlavor confusion exists in the reporting of taste auras; (0 unpleasant auras are associated with hyperresponsiveness of neurons, which may explain why most epilepsy-related olfactory auras are described as "bad"; and (g) interesting parallels exist between the effects of the neuroendocrine system on seizure activity and olfactory function.     

Pre- and Postoperative Auditory Event-Related Potentials in Temporal Lobe Epilepsy

We studied auditory event-related potentials (ERPs) in 11 surgically treated patients with intractable temporal lobe epilepsy (TLE) pre- and postoperatively. ERPs through sphenoidal electrodes (Sp1-T3, Sp2-T4) provided clinically relevant and correctly lateralizing electrophysiologic evidence of temporal lobe dysfunction in 9 of 11 patients, confirmed by EEGs, electrocorticograms, neuroradiologic, and neuropsychological results, and clinical follow-up. Lateralizing asymmetries were noted in P300 amplitude, but latencies were prolonged bilaterally. Sphenoidal ERPs might serve as a new functional indicator of temporal lobe dysfunction in patients evaluated for epilepsy surgery.     

Significance of Sharp Waves in Routine EEGs After Epilepsy Surgery

We retrospectively analyzed the presence of sharp waves in 2-h EEGs performed 6 months after epilepsy surgery in 59 patients. To study the significance of the postoperative interictal epileptiform activity in the tissue remaining after resection, we included only patients with a single epileptic focus (as defined preoperatively by prolonged video/EEG recordings and subdural electrode arrays studies) and no progressive structural lesions. Temporal lobectomy was performed in 51 patients (86%); extratemporal resections were performed in the remainder. The epileptogenic focus was completely resected in 26 patients (44%). The immediate postoperative electrocorticograms (EcoG) showed spikes in 13 patients (22%). At 6-month follow-up, 43 patients (73%) were seizure-free or had auras only and 12 patients (20%) had epileptiform activity on EEG. A significant correlation was noted between presence of sharp waves in the 6-month postoperative EEG and recurrence of seizures (Fisher's exact test p = 0.011) and also with the extent of the resection (complete vs. incomplete p = 0.042). We noted no correlation between postoperative epileptiform activity and location of the resection (temporal vs. extratemporal), presence of spikes in immediate postoperative EcoG, or occurrence of auras only at 6-month follow-up.     

Memory Function and Verbal Learning Ability in Patients with Complex Partial Seizures of Temporal Lobe Origin

A variety of experimental paradigms have been utilized to study verbal learning and memory ability in patients with epilepsy. One commonly used paradigm, the free recall of a list(s) of related or unrelated words, has revealed a variety of performance anomalies in patients with complex partial seizures (CPS) of temporal lobe origin, but published studies have varied markedly in important methodological details, making it difficult to interpret discrepant findings as well as to assess the generalizability of results. The purpose of this investigation was to simultaneously inquire into several aspects of verbal learning and memory function that have been reported or hypothesized to be compromised in individuals with CPS of left temporal lobe origin. Thirty patients with CPS of lateralized temporal lobe onset [15 left temporal (LT) and 15 right temporal (RT)] were compared with 15 matched controls (NC) on several measures derived from the California Verbal Learning Test (CVLT), i.e., verbal learning ability, immediate free recall, presence of retroactive interference effects, semantic organization, retrieval efficiency, and recognition memory. Compared to RT and NC groups, the LT patients manifested poorer verbal learning ability, impaired immediate memory, and increased difficulty in the retrieval of verbal material from memory store. Compared to NC subjects, the LT group showed poorer semantic organization in their verbal learning and recall. The RT and NC groups were essentially similar in all respects. Finally, the clinical utility of these findings were investigated, and a series of decision rules designed to separate LT from RT patients was derived.