Temporal-lobe seizures with additional foci treated by resection

Association Between Quantitative Electroencephalogram Frequency Composition and Post-Surgical Evolution in Pharmacoresistant Temporal Lobe Epilepsy Patients

The purpose of this paper is to estimate the association between quantitative electroencephalogram frequency composition (QEEGC) and post-surgical evolution in patients with pharmacoresistant temporal lobe epilepsy (TLE) and to evaluate the predictive value of QEEGC before and after surgery. A prospective, longitudinal study was made at International Neurological Restoration Center, Havana, Cuba. Twenty-nine patients with TLE submitted to epilepsy surgery were evaluated before surgery, and six months and two years after. They were classified as unsatisfactory and satisfactory post-surgical clinical evolution using the Modified Engels Scale. Eighty-seven electroencephalograms with quantitative narrow- and broad-band measures were analyzed. A Mann Whitney test (p > 0.05) showed that QEEGC before surgery was similar between groups independently of two years post-surgical evolution. A Mann Whitney test (p ˂ 0.05) showed that subjects with two years satisfactory post-surgical evolution had greater alpha power compared to subjects with two years unsatisfactory post-surgical evolution that showed greater theta power. A Wilcoxon test (p ˂ 0.05) showed that alpha and theta power increased for two groups from pre-surgical state to post-surgical state. Logit regression (p ˂ 0.05) showed that six months after surgery, quantitative electroencephalogram frequency value with the greatest power at occipital regions shows predictive value for two years evolution. QEEGC can be a tool to predict the outcome of epilepsy surgery.

Seizure recurrence following epilepsy surgery: is post-operative EEG helpful?

OBJECTIVES

We examined whether the relationship between interictal epileptiform discharges (IED) on post-operative EEG and seizure recurrence after epilepsy surgery was different in patients with neocortical and mesiotemporal resections.

METHODS

We reviewed the records of 93 consecutive patients who underwent epilepsy surgery at our center and who had adequate post-operative follow-up and a post-operative EEG to determine the type of surgery, the recurrence of seizures and the presence of IED on post-operative EEG.

RESULTS

Chi-square test revealed that for the entire group, there was a significant relationship between the presence of IED and seizure recurrence. However, this relationship was significant in neocortical surgery but not in mesiotemporal surgery. Time distribution of seizure recurrence revealed that in more than half the cases, seizures recurred with the first 3 months. Time distribution was not influenced by the presence of IED.

CONCLUSIONS

This study revealed that IED on early post-operative EEG correlate with seizure recurrence in neocortical but not mesiotemporal surgeries and may be used to guide patient counseling in this group of patients.

Language representation in the human brain: evidence from cortical mapping

The manner in which the human brain processes grammatical-syntactic and lexical-semantic functions has been extensively debated in neurolinguistics. The discreteness and selectivity of the representation of syntactic-morphological properties in the dominant frontal cortex and the representation of the lexical-semantics in the temporo-parietal cortex have been questioned. Three right-handed adult male neurosurgical patients undergoing left craniotomy for intractable seizures were evaluated using various grammatical and semantic tasks during cortical mapping. The sampling of language tasks consisted of trials with stimulation (experimental) and without stimulation (control) from sites in the dominant fronto-temporo-parietal cortex The sampling of language implicated a larger cortical area devoted to language (syntactic-morphological and lexical-semantic) tasks. Further, a large part of the fronto-parieto-temporal cortex was involved with syntactic-morphological functions. However, only the parieto-temporal sites were implicated with the ordering of lexicon in sentence construction. These observations suggest that the representation of language in the human brain may be columnar or multilayered.

Surgical management of pediatric tumor-associated epilepsy

Brain tumors are a common cause of seizures in children. Early surgical treatment can improve seizure outcome, but controversy exists regarding the most appropriate type of surgical intervention. Some studies suggest tumor resection alone is sufficient, while others recommend mapping and resection of the surrounding epileptogenic foci to optimize seizure outcome. To address this issue, we reviewed the charts of 34 pediatric patients aged 18 months to 20 years with medically intractable epilepsy and primary brain tumors. The average age at operation was 12.6 years, and patients had seizures for an average of 6.4 years. The majority of tumors were located in the temporal lobe. Seventeen patients, because of tumor location near an eloquent area, underwent extraoperative mapping using subdural electrode grids prior to definitive tumor resection. Fourteen of these patients had a gross total tumor resection, yet only two had a distinct zone of ictal onset identified and resected. The remaining 17 patients had tumors either in the nondominant hemisphere or far removed from speech-sensitive areas, and therefore did not undergo extraoperative subdural electroencephalograph mapping. Fourteen of these patients also had a gross total tumor resection, while none had intraoperative electrocorticography to guide the resection of additional nontumoral tissue. Overall, of the 28 patients treated with a gross total tumor resection, 24 (86%) are seizure free, while the other four are significantly improved. Of the six patients who had a subtotal tumor removal, five have persistent seizures. The mean follow-up was 3.6 years. We conclude that in children and adolescents, completeness of tumor resection is the most important factor in determining seizure outcome. The routine mapping and resection of epileptogenic foci might not be necessary in the majority of patients. As a corollary, the use of subdural electrode grids in pediatric patients with tumor-associated epilepsy should be limited to cases requiring extraoperative cortical stimulation for localization of nearby eloquent cortex.

Improvement and deterioration of seizure control during the postsurgical course of epilepsy surgery patients

PURPOSE

To determine the factors associated with changes in seizure control during the postsurgical course of epilepsy surgery patients.

METHODS

Evaluation of patients after consecutive temporal and frontal resection whose seizure frequency was scored for each year of postsurgical follow-up. In each cohort, patients with a change in their seizure control after the first postsurgical year were compared with control subjects to determine factors that may be responsible for the change.

RESULTS

Thirty-three (15%) of 214 temporal lobectomy versus 12 (20%) of 59 frontal resection patients experienced a change in seizure control (p>0.05). Ten (5%) of 214 temporal lobectomy versus nine (15%) of 59 frontal resection patients experienced an improvement in seizure control (p = 0.009), but 23 (11%) of 214 temporal lobectomy versus three (5%) of 59 frontal resection patients had a worsening in seizure control (p>0.05). In temporal lobectomy patients, preoperative unilateral temporal epileptiform discharges were associated with improvement (p = 0.03), whereas older age at surgery was associated with worsening of seizure control (p = 0.007). In frontal resection patients, presence of a congenital central nervous system (CNS) anomaly was associated with late improvement in seizure control (p = 0.006).

CONCLUSION

During the postsurgical course, an improvement in seizure control is more common after frontal resection than after temporal lobectomy. Factors associated with improvement are the presence of a congenital CNS abnormality in frontal resection patients, and the occurrence of preoperative unilateral epileptiform discharges in temporal lobectomy patients. Older age at temporal lobectomy may be associated with greater risk of worsening seizure control.

Subtemporal transparahippocampal amygdalohippocampectomy for surgical treatment of mesial temporal lobe epilepsy. Technical note

Amygdalohippocampectomy (AH) is an accepted surgical option for treatment of medically refractory mesial temporal lobe epilepsy. Operative approaches to the amygdala and hippocampus that previously have been reported include: the sylvian fissure, the superior temporal sulcus, the middle temporal gyrus, and the fusiform gyrus. Regardless of the approach, AH permits not only extirpation of an epileptogenic focus in the amygdala and anterior hippocampus, but interruption of pathways of seizure spread via the entorhinal cortex and the parahippocampal gyrus. The authors report a modification of a surgical technique for AH via the parahippocampal gyrus, in which excision is limited to the anterior hippocampus, amygdala and parahippocampal gyrus while preserving the fusiform gyrus and the rest of the temporal lobe. Because transparahippocampal AH avoids injury to the fusiform gyrus and the lateral temporal lobe, it can be performed without intracarotid sodium amobarbital testing of language dominance and language mapping. Thus the operation would be particularly suitable for pediatric patients in whom intraoperative language mapping before resection is difficult.

A new trend in operative technique for intracerebral hemorrhage: a comparative study of stereotactic endoscopic removal and stereotactic catheter drainage

The development of less invasive methods to evacuate intracerebral hematomas (ICHs) has improved outcome in patients with traumatic brain injury. Eighteen patients with ICHs underwent surgery via one of two methods: stereotactic endoscopic removal (SER) or stereotactic catheter drainage (SCD). The outcome results were then compared. The patient population was composed of 11 men and seven women with a mean age of 53.3 years (range 33-81 years), all suffering from ICH in the basal ganglia. The mean hematoma volume was 34.4 ml (range 23-105 ml). All patients had major neurological deficits, but showed no sign of transtentorial herniation. Ten patients underwent SCD and eight had SER. All procedures were performed within 24 hours of insult. After local anesthesia was induced in the patient, an intracranial pressure (ICP) monitoring catheter and an Otzuki cannula were placed through separate burr holes in the skull. Using the SER technique, the ICH was removed using suction and forceps through the side window of the cannula until the ICP had decreased significantly. Hemostasis was attained by lesioning with a Nd-YAG laser. In the SCD procedure, we placed a silicone catheter into the hematoma to drain it and then added urokinase. The hematoma was drained for 3 to 5 days in the SER method and 7 to 10 days in the SCD method. Rebleeding occurred in one of the early cases in which we used the SER procedure. At follow-up evaluation, the mortality rate was 13% in the SER group and 10% in the SCD group. The patients in whom outcome was most improved from these treatments were those who had been admitted with an impaired level of consciousness. Stereotactic catheter drainage is a precise, safe, and brief procedure with a very low rebleeding rate, but its outcome effect was more delayed than other procedures. Stereotactic endoscopic removal can easily replace SCD, with a similar mortality rate. Both procedures can be accomplished under direct visualization so as to eliminate any undesirable event or outcome.

Successful epilepsy surgery without intracranial EEG recording: criteria for patient selection

Twenty-two patients with intractable complex partial seizures (CPS) were treated with temporal lobectomy. Eighteen of 22 (82%) are seizure-free while receiving medication, with a mean follow-up time of 4 years. In each case, the clinical seizure pattern, interictal and ictal scalp EEG, magnetic resonance imaging (MRI), neuropsychological testing, and results of the intracarotid amobarbital procedure (IAP) converged to indicate a localized abnormality. None of the patients in this series had mass lesions, vascular malformations, or cortical scars, but 18 of 22 had hippocampal atrophy on MRI and 20 had hippocampal sclerosis (HS) on pathologic examination. We believe it is possible, on the basis of the preoperative evaluation described, to identify a population of epileptic patients who will do very well postoperatively. Such patients do not require invasive EEG monitoring, and they represent approximately 20% of the patients treated surgically in our epilepsy unit in the past several years.

Low-grade gliomas associated with intractable epilepsy: seizure outcome utilizing electrocorticography during tumor resection

Adults and children with low-grade gliomas often present with medically refractory epilepsy. Currently, controversy exists regarding the need for intraoperative electrocorticography (ECoG) to identify and, separately, resect seizure foci versus tumor removal alone to yield maximum seizure control in this patient population. Forty-five patients with low-grade gliomas and intractable epilepsy were retrospectively analyzed with respect to preoperative seizure frequency and duration, number of antiepileptic drugs, intraoperative ECoG data (single versus multiple foci), histology of resected seizure foci, and postoperative control of seizures with or without antiepileptic drugs. Multiple versus single seizure foci were more likely to be associated with a longer preoperative duration of epilepsy. Of the 45 patients studied, 24 were no longer taking antiepileptic drugs and were seizure-free (mean follow-up interval 54 months). Seventeen patients, who all had complete control of their seizures, remained on antiepileptic drugs at lower doses (mean follow-up interval 44 months); seven of these patients were seizure-free postoperatively, yet the referring physician was reluctant to taper the antiepileptic drugs. Four patients continued to have seizures while receiving antiepileptic drugs, although at a reduced frequency and severity. In this series 41% of the adults versus 85% of the children were seizure-free while no longer receiving antiepileptic drugs, with mean postoperative follow-up periods of 50 and 56 months, respectively. This difference was statistically significant (p = 0.016). Therefore, based on this experience and in comparison with numerous retrospective studies involving similar patients, ECoG is advocated, especially in children and in any patient with a long-standing seizure disorder, to maximize seizure control while minimizing or abolishing the need for postoperative antiepileptic drugs.

Temporal lobectomy in patients with bitemporal epilepsy defined by depth electroencephalography

Patient selection for temporal lobectomy was reviewed for 23 patients with seizures that arose independently from each temporal lobe as detected by depth electroencephalography (EEG). Although neuropsychological testing, interictal EEG findings, imaging studies, and subclinical seizures were also considered, all patients offered temporal lobectomy had (1) at least 50% of the clinical seizures originating from the lobe to be resected, (2) adequate contralateral memory on testing with amobarbital, and (3) no clear evidence of an extratemporal focus. Eleven patients underwent temporal lobectomy. Pathological findings were considered positive in all nine specimens reviewed. Nine patients had no seizures, one had greater than 75% reduction in seizure frequency, and 1 had 50 to 75% reduction. Pathological features and clinical outcome were similar in the 6 patients with fewer than 80% and the 5 patients with at least 80% of seizures originating from the resected lobe. Thus, having fewer than 80% of seizures originate from one temporal lobe should not be an absolute contraindication for temporal lobectomy.

Comparison of bitemporal and unitemporal epilepsy defined by depth electroencephalography

Of 166 consecutive patients studied with depth electroencephalography (EEG), 87 had seizures arising from one temporal lobe and 23 had seizures arising independently from each temporal lobe. We retrospectively reviewed and compared those patients with unitemporal and those with bitemporal seizures. There was no statistically significant differences between the two groups in terms of age at onset of seizures, duration of epilepsy, localization of scalp EEG abnormalities, surgical results, or pathological findings. The bitemporal group, however, had significantly fewer patients with a history of febrile seizures (p less than 0.025). Two patients with bitemporal seizures were later found to have extratemporal lesions, and one an extrahippocampal temporal lesion, on magnetic resonance scans; one patient's extratemporal lesion was resected and all habitual seizures stopped. These findings suggest that a single pathophysiological process accounts for unitemporal and some bitemporal epilepsy, but that independent onset of seizures from each temporal lobe detected by depth EEG may also indicate extratemporal foci.

Seizures of fronto-orbital origin: a proven case

Distinguishing characteristics of seizures of frontal origin have not been clearly delineated. We describe a case of seizures of proven fronto-orbital origin to provide further definition of characteristics of seizures arising in that lobe. A 36-year-old man had medically intractable seizures since age 8 years. Clinically the seizures were stereotyped, with cessation of activity followed by turning of head and body to the right and then by struggling, kicking, and vocalizations indicating fear. Total seizure duration was approximately 30 s, with an apparent abrupt return of consciousness. The interictal scalp EEGs were similar to those of primary generalized epilepsy, with bisynchronous though asymmetric epileptiform activity anteriorly. Ictal scalp recordings were not localizing. Recordings from bilateral frontal and temporal subdural electrodes showed an electrical focus in the right fronto-orbital region which was confirmed by electrocorticography (ECoG) at the time of craniotomy. The right fronto-orbital cortex was resected and on pathologic examination showed gliotic tissue and intracytoplasmic neuronal inclusions of periodic acid-Schiff (PAS)-positive granules consistent with lipofuscinosis. The patient has remained seizure-free for 6 years after operation.

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.

Interictal spike detection comparing subdural and depth electrodes during electrocorticography

We compared the ability of subdural and depth electrodes to detect and localize interictal epileptiform discharges (IEDs) in the temporal lobe. Sixteen patients had simultaneous intraoperative recordings with depth and subdural electrodes while undergoing anterior temporal lobe resections under local anesthesia for medically intractable seizures. IEDs that were focal (detected at just 1 or 2 electrode contacts) typically registered at the nearest contact, regardless of type. IEDs that were regional (engaging more than 2 electrode contacts) typically appeared simultaneously at both electrode types. Neither method was better able to indicate whether an IED was mesial or lateral, posterior or anterior. Subdural and depth electrodes seem to provide complementary information on the location of IEDs within the temporal lobe.

Depth electrode investigations in patients with bitemporal epileptiform abnormalities

Fifty-seven patients showing bitemporal independent epileptiform abnormalities on extracranial electroencephalograms (EEGs) in whom the epileptogenic zone could not be localized or lateralized by extracranial EEG and other noninvasive tests were investigated with stereotactic depth electrode recordings. In a majority of 44 patients (77%), seizures originated exclusively or with a strong predominance in one temporal lobe only. Of the remaining 13 patients (23%), 8 had seizures originating independently in either temporal lobe without significant lateralized predominance, and 5 had multiple seizure patterns, which were often diffuse. The patterns of seizure onset as recorded by depth electrodes tended to vary even in the same patient. Electrical stimulation studies and the determination of afterdischarge thresholds were of limited utility for lateralization of seizure onset.

Results of surgical treatment in patients with bitemporal epileptiform abnormalities

Fifty-three of 57 patients who had evidence of bitemporal epileptiform abnormalities and who required investigation with stereotactic depth electroencephalography (SDEEG) recordings to determine the site of origin of seizures underwent surgical resection for the treatment of their epilepsy. A minimum of 2 years' follow-up was available in 48 patients who underwent a temporal lobe resection. In this group, 19 patients (40%) were greatly improved, and of these 14 (29%) became seizure free and 5 (10%) had no more than 3 seizures each year. Another 22 patients (46%) showed a worthwhile reduction in seizure frequency of at least 50%. Seven patients (15%) were not significantly improved. An etiological factor of early convulsions before age 3 (usually febrile) was associated with a better outcome. Both the lack of a strong predominance for SDEEG-recorded seizures to arise in the resected temporal lobe and the presence of residual epileptiform abnormalities in the postexcision electrocorticogram were correlated with poorer results.

Pediatric epilepsy surgery

The use of implantable arrays of epidural electrodes has made it possible to carry out extraoperative electrocorticography (ECoG) and functional localization in the awake child. This has permitted cortical excisions that are determined by criteria similar to those obtained during surgical procedures performed under local anesthesia in adults. In addition, the method also permits simultaneous ECoG and video monitoring during the child's symptomatic seizures, providing additional important localizing information that is impractical to obtain in operations under local anesthesia. We report our experience with 75 children, ages 5 months to 15 years, whom we have managed with epidural electrode arrays. The method of extraoperative ECoG is described and illustrative cases are presented to demonstrate its feasibility and utility in children. In addition, we call attention to gliomas as a common cause of chronic focal seizures in children. Of 49 children undergoing resection and followed for from 1 to 14 years (mean of 5.8 years), 32 (65%) are either seizure free or have had a significant reduction in seizure frequency that has unambiguously improved their quality of life. The results are analyzed further by relating the surgical outcome to each of the pathologic entities that caused the seizures. This analysis reveals the variety of neurological conditions that commonly cause intractable focal seizure disorder in children and distinguishes those pathologic entities in which the seizure disorder is apt to respond to surgical intervention from those that will not.

Surgical management of epilepsy using epidural recordings to localize the seizure focus. Review of 100 cases

One hundred patients with focal epilepsy (44 were children) were evaluated with extraoperative electrocorticography via epidural electrode arrays. Localization of the epileptogenic focus was derived predominantly from recordings made during spontaneously occurring seizures. All resection procedures were carried out under general anesthesia. During anesthesia, the recording of sensory evoked responses made it possible to readily identify the sensorimotor region. Of the 100 patients, 72 underwent resection of an epileptogenic focus, and 33 of these were children. Those who did not have a resection either exhibited a diffuse seizure focus, failed to show an electrical seizure discharge in association with the clinical seizure, failed to have a seizure during the period of monitoring, or failed to exhibit conclusive changes for identifying a focus in the interictal record. Fifty-seven patients (29 children and 28 adults) who had a resection have been followed for between 1 and 12 years. Eighteen (62%) of the 29 children and 18 (64%) of the 28 adults enjoyed a good result. Twenty of the 100 patients reported here had temporal lobe epilepsy. They were candidates for recordings with depth electrodes to identify their focus, but they were evaluated instead with epidural recordings; the method is described. In 15 of them, a unilateral focus was identified and they underwent an anterior temporal lobectomy. Pathological changes were found in every case and, in 11 patients, the epidural recordings distinguished between a medial and a lateral focus. Ten of these patients have been followed for 9 months to 3 1/2 years, and seven have had a good result. The observations suggest that epidural electrodes may be used in lieu of depth electrodes for identifying the symptomatic temporal lobe.

The localizing value of depth electroencephalography in 32 patients with refractory epilepsy

Clinical seizure manifestations, physical examination, radiological studies, neuropsychological tests, and scalp and depth electroencephalographic (EEG) studies were done to localize seizure foci in 32 patients, 23 of whom have undergone surgery with more than one year of follow-up. Of 16 patients with unlocalized scalp EEGs, depth EEG detected a consistent focal seizure onset in 3. Of 15 patients with localized scalp EEGS, depth EEG revealed multiple foci in 3 and inaccurate localization of the focus by scalp EEG in 4. Therefore, localization by scalp EEG was inaccurate in 10 of 31 patients. When depth EEG revealed a consistent focal seizure onset and this localization was used to determine to surgical resection site, good to excellent results were obtained in 12 of 13 patients. When depth EEG revealed additional foci of seizure origin, surgical results were fair or poor in all patients. No other localizing criteria predicted depth EEG results or surgical success with such accuracy. Furthermore, some criteria, including neuropsychological tests and radiological abnormalities, were falsely localizing at times. Therefore, of the presently available localizing criteria, depth EEG appears to be the most accurate.

Ictal effects of anticonvulsant medication withdrawal in epileptic patients

Medication withdrawal is used in selected instances to precipitate seizures during evaluation of epileptic patients. Whether such medication manipulation can alter electrical seizure onset or clinical seizure type is not known. Information regarding the effects of anticonvulsant withdrawal on depth EEG onset and clinical manifestations of seizures was reviewed in 25 patients with partial complex seizures in whom intracranial electrodes were implanted. For the purposes of this study, the withdrawal period was defined as the time after abrupt cessation of medication between one and five half-lives of the drug and the base-line state as all other times. Ten patients were withdrawn from carbamazepine, 6 from phenobarbital, 2 from phenytoin, and 3 from primidone. Overall effects of anticonvulsant withdrawal in 18 patients and 21 instances of withdrawal with a total of 89 withdrawal and 71 base-line seizures were notable. Focal electrical onset and typical clinical seizure type during withdrawal were entirely consistent with electrical and/or clinical characteristics of seizures occurring during the base-line state in 13 instances. "New" clinical and/or electrical seizure types occurred during withdrawal only in a number of patients in whom bilateral or multifocal seizure onset was confirmed electrographically outside of the withdrawal period. In only 1 patient did withdrawal produce atypical clinical and electrical seizures when the base-line state showed a clinically typical seizure of clear-cut localized onset. After surgery this patient was shown to have unequivocal multifocal seizure onset. Thus, for purposes of localizing single epileptic foci, information obtained during the anticonvulsant withdrawal period provided no misleading information in this group of patients, while condensing the time needed for evaluation.

Late results of operation in temporal lobe epilepsy in adults and children

In our clinic at the Medical Academy in Warsaw 282 patients with temporal lobe epilepsy were treated surgically. The causes of the illness were trauma in 43.2%, including birth trauma in 19.5%, infections diseases in early life in 19.8%, and microtumours in 6.8%. In 30% the aetiology was unknown. Fifty per cent had fits before 10 years and 75% before 20 years of age. The period of conservative treatment was on average nine years. Serial and stereo-EEG recordings including activation by ketamine, as well as intracarotid sodium amytal tests were performed routinely. The interictal EEG epileptiform abnormalities were found most frequently in both temporal lobes (154 cases). The operation was carried out according to Penfield's technique, with electrocorticography and resection of the temporal lobe extending for 6 to 10 cm in the nondominant hemisphere and for 4 to 5 cm in the dominant hemisphere using suction technique. In 75% microscopical changes in the hippocampus were found, in 20% so-called hamartomas and in 6.8% small gliomas. Two patients died and in 13 patients there was a hemiparesis which was transient in 10. The authors present the analysis of late results of 262 cases with a follow-up from 2 to 22 years after operation. Very good results were obtained in 127 cases (48.5%) - no attacks since leaving the clinic. Good results were observed in 42 patients (16%) - not more than 1-2 attacks a year. Thus, the operation resulted in freedom from attacks, or nearly so, in 169 cases (64.5%). In an additional 47 patients (18%) there was a significant reduction (at least 50%) in seizures without complete freedom from attacks, and in 44 cases (16.8%) no improvement was observed. The analysis of our series suggests that the best results may be obtained in patients with unilateral temporal EEG changes. The existence of an additional focus in parts of the other temporal lobe does not impair the operative results when the dominant epileptic focus has been removed. Among 24 cases with equally pronounced bitemporal EEG abnormalities the stereo-EEG studies allowed detection of the epileptic focus in 13 patients (54%). Detailed analysis of the results, obtained in 51 children below 15 years of age, led to the conclusion that temporal lobe epilepsy should be operated upon even in young children, provided that the epileptic focus can be clearly identified.

Depth electroencephalography in selection of refractory epilepsy for surgery

Depth electroencephalography (EEG) is sometimes used to evaluate medically refractory epileptic patients for surgical treatment. Surgical excision of well-defined epileptogenic foci has been shown repeatedly to cause a substantial reduction of seizure frequency in 60 to 80% of these patients; however, because surgical success is no better at centers that employ depth EEG in patient evaluation, the procedure remains controversial. Review of the available literature shows that depth EEG results reported to date, when compared to scalp EEG results in 178 patients, could have enabled selection of 36% more patients for surgery by defining otherwise unidentifiable single epileptogenic foci. Furthermore, depth EEG could have prevented surgery in another 18% by demonstrating different or additional epileptogenic foci in patients otherwise thought to have a single discharging focus amenable to resection. Thus depth EEG had the potential to alter the surgical decision in more than 50% of patients reported. Centers that employ depth EEG may evaluate a different population of patients, which could account for their lack of increased surgical success.

A method for surgical management of focal epilepsy, especially as it relates to children

A method of surgical management for intractable epilepsy is described. The essential features are: 1) all surgical manipulation is carried out under general, rather than local, anesthesia; 2) the sensorimotor region is readily identified in the anesthetized patient by recording cortical sensory evoked responses; and 3) the epileptogenic focus is localized by extraoperative electrocorticography via indwelling epidural electrode arrays, localization deriving from recordings made during spontaneously occuring clinical seizures. Cases are presented to demonstrate that: 1) in some instances, recording of sensory evoked responses is the only means of sensorimotor localization in both the awake and anesthetized patient, and 2) spontaneous and electrically induced electroencephalographic seizure activity may provide false localization of the focus, the correct localization requiring recordings made during spontaneous clinical seizures. The outcome of surgery and the various epileptogenic lesions encountered are described. A good result has been achieved in 61% of patients followed 1 to 10 years. When the results obtained in children are analyzed alone, 70% have benefited from surgery.