Altered seizure patterns after temporal lobectomy

Risk Factors for Seizure Worsening After Epilepsy Surgery in Children and Adults: A Population-Based Register Study

BACKGROUND

Increased seizure frequency and new-onset tonic-clonic seizures (TCS) have been reported after epilepsy surgery.

OBJECTIVE

To analyze potential risk factors for these outcomes in a large cohort.

METHODS

We studied prospectively collected data in the Swedish National Epilepsy Surgery Register on increased seizure frequency and new-onset TCS after epilepsy surgery 1990-2015.

RESULTS

Two-year seizure outcome was available for 1407 procedures, and data on seizure types for 1372. Increased seizure frequency at follow-up compared to baseline occurred in 56 cases (4.0%) and new-onset TCS in 53 (3.9%; 6.6% of the patients without preoperative TCS). Increased frequency was more common in reoperations compared to first surgeries (7.9% vs 3.1%; P = .001) and so too for new-onset TCS (6.7% vs 3.2%; P = .017). For first surgeries, binary logistic regression was used to analyze predictors for each outcome. In univariable analysis, significant predictors for increased seizure frequency were lower age of onset, lower age at surgery, shorter epilepsy duration, preoperative neurological deficit, intellectual disability, high preoperative seizure frequency, and extratemporal procedures. For new-onset TCS, significant predictors were preoperative deficit, intellectual disability, and nonresective procedures. In multivariable analysis, independent predictors for increased seizure frequency were lower age at surgery (odds ratio (OR) 0.70 per increasing 10-yr interval, 95% CI 0.53-0.93), type of surgery (OR 0.42 for temporal lobe resections compared to other procedures, 95% CI 0.19-0.92), and for new-onset TCS preoperative neurological deficit (OR 2.57, 95% CI 1.32-5.01).

CONCLUSION

Seizure worsening is rare but should be discussed when counseling patients. The identified risk factors may assist informed decision-making before surgery.

Abdominal auras in patients with mesial temporal sclerosis

To better clarify abdominal auras and their clinical correlates, we enrolled 331 temporal lobe epilepsy patients who received surgical treatment. Detailed descriptions of their auras were obtained before surgery and reconfirmed during postoperative outpatient follow-ups. Pathology revealed mesial temporal sclerosis (MTS) in 256 patients (77.3%) and 75 non-MTS. Of 214 MTS patients with auras, 78 (36.4%) reported abdominal auras (vs. 30.4% in non-MTS, p=0.439): 42 with left-sided seizure onset, and 36 with right-sided seizure onset. Moreover, 49 of the 78 MTS patients had abdominal auras accompanied by rising sensations (vs. 2 of 14 in non-MTS group, p=0.004). The "rising air" was initially described to locate to the epigastric (47.8%) or periumbilical area (45.7%) and mostly reached the chest (40.4%) or remained in the abdominal region (27.1%). An epigastric location of "rising air" favored a left-sided seizure onset, and non-epigastric areas favored right-sided seizure onset (p=0.018). Finally, we found that abdominal auras with or without rising sensations did not predict postoperative seizure outcomes.

Surgical techniques for the treatment of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of medically intractable epilepsy. Advances in electrophysiology and neuroimaging have led to a more precise localization of the epileptogenic zone within the temporal lobe. Resective surgery is the most effective treatment for TLE. Despite the variability in surgical techniques and in the extent of resection, the overall outcomes of different TLE surgeries are similar. Here, we review different surgical interventions for the management of TLE.

Characteristics of auras in patients undergoing temporal lobectomy

Object

Prior studies suggest that aura semiology may have localizing value. However, temporal lobe aura characteristics and response to surgery have not been studied in large patient series.

Methods

The authors retrospectively analyzed the case records of 182 patients undergoing temporal lobectomy for medically intractable epilepsy at a single institution. They analyzed the frequency and type of auras and seizures preoperatively, and at 3 months and 1 year after temporal lobectomy. Auras were divided into medial semiology (rising epigastric, olfactory/gustatory, experiential, and fear) and lateral semiology (auditory, somatosensory, and visual), or other.

Results

Of 182 patients, 150 were included in this study. The preoperative prevalence of auras was 77%. Multiple types of auras were present in 20% of patients. The most common aura was rising epigastric (26% of all auras). Postoperatively, auras were eliminated in 63% of patients at 3 months and in 64% at 1 year. Seventy-seven patients (51%) were seizure-free and aura-free, 22 (15%) were seizure-free with auras, 26 (17%) had seizures but no auras, and 25 (17%) had seizures with auras. Despite having their auras eliminated, 6.7% of patients continued to have complex partial seizures. Lateral temporal auras were more than twice as likely as medial temporal auras to persist after surgery (p < 0.002).

Conclusions

While the majority of patients in the authors' series became seizure- and aura-free, a significant minority still had persistent auras. Patients with lateral temporal auras appear to be at increased risk for having persistent postoperative auras. The discrepancy between aura and seizure outcomes results in a small group of patients having persistent seizures but losing their auras postoperatively.

Synchronous recording of intracranial and extracranial EEG in temporal lobe epilepsy

PURPOSE

To explore the diagnostic value of intracranial electrodes in highly suspected temporal lobe epilepsy (TLE) and the value of sphenoid electrodes (PG) and the propagation patterns of ictal discharges in focus lateralization.

METHODS

Intracranial electrodes were implanted in 22 probable TLE patients through bilateral temporal burr holes. Extracranial electrodes included the 10-20 international EEG system and bilateral PGs. Intracranial and extracranial EEGs (IEEG, EEEG) were synchronously recorded. The interictal epileptic discharges (IEDs) were counted for 3h of interictal preoperative long-playing video EEG. Time intervals between electrodes recording the ictus and ictus occurring were measured and the propagation patterns were deduced.

RESULTS

By IEEG, 18 patients with confirmed TLE had surgery; 14 were seizure-free. 3 had FLE, and 1, uncertain localization. Of the 14 TLE and postoperative seizure-free patients, the ratio (left:right) of IEDs in the 3h interictal EEG was 483:211 in the 6 left TLE and 263:654 in the 8 right TLE. In 12 of the 14 cases, the side with more IEDs at PG was the epileptic focus side. In 11 of the 14 cases the earlier PG recording side was focus side. We found that the propagation sequence of ictus followed certain rules in most attacks.

CONCLUSIONS

The results indicated that IEEG was useful for final diagnosis of highly suspected TLE and that PG was helpful in focus lateralization. The propagation patterns of ictus might provide a new tool in focus lateralization and localization.

The occurrence and characteristics of auras in a large epilepsy cohort

OBJECTIVES

Despite several studies, estimates of the frequency with which auras occur in conjunction with epilepsy continue to be imprecise. The aim of this study was to assess the occurrence and characteristics of auras in a large population-based epilepsy cohort.

MATERIALS AND METHODS

Subjects with verified epilepsy were recruited from population-based twin registries in the USA, Denmark and Norway. Using a structured interview in which a list of auras was provided, subjects were asked about the warning symptoms preceding their epileptic attacks.

RESULTS

31% of the total sample (n = 1897) and 39% of those with active epilepsy (n = 765) had experienced an aura. Six percent reported more than one type. Non-specified auras were most frequently reported (35%), followed by somatosensory (11%) and vertiginous (11%). While the majority of those reporting auras (59%) had focal epilepsies, auras of a mostly non-specific nature were experienced by 13% of those with generalized epilepsies.

CONCLUSION

Auras serve an important purpose in that they may prevent seizure-related injuries and could provide an indication as to where the seizures originate. The occurrence of auras often is underestimated, especially in children and those with learning disabilities.

Long-term seizure outcomes following epilepsy surgery: a systematic review and meta-analysis

Assessment of long-term outcomes is essential in brain surgery for epilepsy, which is an irreversible intervention for a chronic condition. Excellent short-term results of resective epilepsy surgery have been established, but less is known about long-term outcomes. We performed a systematic review and meta-analysis of the evidence on this topic. To provide evidence-based estimates of long-term results of various types of epilepsy surgery and to identify sources of variation in results of published studies, we searched Medline, Index Medicus, the Cochrane database, bibliographies of reviews, original articles and book chapters to identify articles published since 1991 that contained > or =20 patients of any age, undergoing resective or non-resective epilepsy surgery, and followed for a mean/median of > or =5 years. Two reviewers independently assessed study eligibility and extracted data, resolving disagreements through discussion. Seventy-six articles fulfilled our eligibility criteria, of which 71 reported on resective surgery (93%) and five (7%) on non-resective surgery. There were no randomized trials and only six studies had a control group. Some articles contributed more than one study, yielding 83 studies of which 78 dealt with resective surgery and five with non-resective surgery. Forty studies (51%) of resective surgery referred to temporal lobe surgery, 25 (32%) to grouped temporal and extratemporal surgery, seven (9%) to frontal surgery, two (3%) to grouped extratemporal surgery, two (3%) to hemispherectomy, and one (1%) each to parietal and occipital surgery. In the non-resective category, three studies reported outcomes after callosotomy and two after multiple subpial transections. The median proportion of long-term seizure-free patients was 66% with temporal lobe resections, 46% with occipital and parietal resections, and 27% with frontal lobe resections. In the long term, only 35% of patients with callosotomy were free of most disabling seizures, and 16% with multiple subpial transections remained free of all seizures. The year of operation, duration of follow-up and outcome classification system were most strongly associated with outcomes. Almost all long-term outcome studies describe patient cohorts without controls. Although there is substantial variation in outcome definition and methodology among the studies, consistent patterns of results emerge for various surgical interventions after adjusting for sources of heterogeneity. The long-term (> or =5 years) seizure free rate following temporal lobe resective surgery was similar to that reported in short-term controlled studies. On the other hand, long-term seizure freedom was consistently lower after extratemporal surgery and palliative procedures.

The chance of cure following surgery for drug-resistant temporal lobe epilepsy. What do we know and do we need to revise our expectations?

Although surgery is often seen as a curative treatment for patients with drug-resistant temporal lobe epilepsy, little information is available how many cases can be considered cured after surgery, i.e. are seizure-free for several years without taking antiepileptic drugs (AEDs). In our review, 13 retrospective and five prospective clinical observations published since 1980 provided data on long-term seizure control off AEDs in a total of 1658 patients. No randomized studies were found. Following temporal lobe surgery, approximately one in four adult patients and approximately one in three children or adolescents can currently shown to be seizure-free for 5 years without AEDs (25%, mean of eight studies in adults, 95% CI: 21-30%, and 31%, mean of three studies in children, 95% CI: 20-41%). The rate of seizure control off AEDs seemed to be stable after 2 years of follow-up. However, as 55% of patients free of disabling seizures preferred not to discontinue their medication completely as late as 5 years after surgery, it is impossible to know if they are cured or not. No features predictive of surgical cure were detected except for better cure outcome in children versus adults with hippocampal sclerosis and in patients with typical versus atypical Ammonshorn's sclerosis or tumor in one small study each. In conclusion, the available evidence on seizure outcome off AEDs after temporal lobe surgery is based on non-randomized studies and, in part, data were collected retrospectively. A randomized controlled trial is needed to determine if, in fact only one in three to four patients with temporal lobe epilepsy undergoing surgery can be considered cured.

Seizures after epilepsy surgery

This article reviews types and prognostic significance of seizures that occur after epilepsy surgery, so-called postsurgical seizures.

Practice parameter: temporal lobe and localized neocortical resections for epilepsy

PURPOSE

To examine evidence for effectiveness of anteromesial temporal lobe and localized neocortical resections for disabling complex partial seizures.

METHODS

Systemic review and analysis of the literature since 1990.

RESULTS

One intention-to-treat Class I randomized controlled trial of surgery for mesial temporal lobe epilepsy found that 58% of patients randomized to be evaluated for surgical therapy (64% of those who received surgery) were free of disabling seizures and 10 to 15% were unimproved at the end of 1 year, compared with 8% free of disabling seizures in the group randomized to continued medical therapy. There was a significant improvement in quantitative quality-of-life scores and a trend toward better social function at the end of 1 year for patients in the surgical group, no surgical mortality, and infrequent morbidity. Twenty-four Class IV series of temporal lobe resections yielded essentially identical results. There are similar Class IV results for localized neocortical resections; no Class I or II studies are available.

CONCLUSIONS

A single Class I study and 24 Class IV studies indicate that the benefits of anteromesial temporal lobe resection for disabling complex partial seizures is greater than continued treatment with antiepileptic drugs, and the risks are at least comparable. For patients who are compromised by such seizures, referral to an epilepsy surgery center should be strongly considered. Further studies are needed to determine if neocortical seizures benefit from surgery, and whether early surgical intervention should be the treatment of choice for certain surgically remediable epileptic syndromes.

Practice parameter: temporal lobe and localized neocortical resections for epilepsy: report of the Quality Standards Subcommittee of the American Academy of Neurology, in association with the American Epilepsy Society and the American Association of Neurological Surgeons

OBJECTIVES/METHODS

To examine evidence for effectiveness of anteromesial temporal lobe and localized neocortical resections for disabling complex partial seizures by systematic review and analysis of the literature since 1990.

RESULTS

One intention-to-treat Class I randomized, controlled trial of surgery for mesial temporal lobe epilepsy found that 58% of patients randomized to be evaluated for surgical therapy (64% of those who received surgery) were free of disabling seizures and 10 to 15% were unimproved at the end of 1 year, compared with 8% free of disabling seizures in the group randomized to continued medical therapy. There was a significant improvement in quantitative quality-of-life scores and a trend toward better social function at the end of 1 year for patients in the surgical group, no surgical mortality, and infrequent morbidity. Twenty-four Class IV series of temporal lobe resections yielded essentially identical results. There are similar Class IV results for localized neocortical resections; no Class I or II studies are available.

CONCLUSIONS

A single Class I study and 24 Class IV studies indicate that the benefits of anteromesial temporal lobe resection for disabling complex partial seizures is greater than continued treatment with antiepileptic drugs, and the risks are at least comparable. For patients who are compromised by such seizures, referral to an epilepsy surgery center should be strongly considered. Further studies are needed to determine if neocortical seizures benefit from surgery, and whether early surgical intervention should be the treatment of choice for certain surgically remediable epileptic syndromes.

Semiology of temporal lobe epilepsy in children and adolescents. Value in lateralizing the seizure onset zone [corrected]

PURPOSE

To determine the frequency and lateralizing value of clinical seizure symptoms in children and adolescents with drug-resistant temporal lobe epilepsy (TLE).

METHODS

Patients enrolled had to be <18 years of age and seizure free at follow-up for at least 12 months after epilepsy surgery. Patients were assigned to two age groups, children (age<12 years) and adolescents (age>12 and <18 years). Video-tapes were reviewed blinded to patients' demographic data and results of additional investigations by two independent raters. Clinical signs of known lateralizing significance in adults and additional clinical signs without lateralizing value were assessed.

RESULTS

14 patients (eight boys; 2-18 years) fulfilled the inclusion criteria. Inter-observer agreement was excellent (kappa coefficient: 0.82). Compared with adult series, no differences were found concerning overall occurrence of lateralizing signs and lateralizing accuracy. There were age-related differences, however, concerning the occurrence of individual signs: secondary generalization, complex automatisms and version were less frequent in children than in adolescents.

CONCLUSIONS

Clinical signs of lateralizing value can also be found in children and adolescents, provided that the evaluation protocols used consider developmental aspects.

Seizure outcome after temporal lobectomy: current research practice and findings

PURPOSE

The literature regarding seizure outcome and prognostic factors for outcome after temporal lobectomy is often contradictory. This is problematic, as these data are the basis on which surgical decisions and counseling are founded. We sought to clarify inconsistencies in the literature by critically examining the methods and findings of recent research.

METHODS

A systematic review of the 126 articles concerning temporal lobectomy outcome published from 1991 was conducted.

RESULTS

Major methodologic issues in the literature were heterogeneous definitions of seizure outcome, a predominance of cross-sectional analyses (83% of studies), and relatively short follow-up in many studies. The range of seizure freedom was wide (33-93%; median, 70%); there was a tendency for better outcome in more recent studies. Of 63 factors analyzed, good outcome appeared to be associated with several factors including preoperative hippocampal sclerosis, anterior temporal localization of interictal epileptiform activity, absence of preoperative generalized seizures, and absence of seizures in the first postoperative week. A number of factors had no association with outcome (e.g., age at onset, preoperative seizure frequency, and extent of lateral resection).

CONCLUSIONS

Apparently conflicting results in the literature may be explained by the methodologic issues identified here (e.g., sample size, selection criteria and method of analysis). To obtain a better understanding of patterns of long-term outcome, increased emphasis on longitudinal analytic methods is required. The systematic review of possible risk factors for seizure recurrence provides a basis for planning further research.