Prediction of neuropsychological outcome after resection of temporal and extratemporal seizure foci

Leveraging the resting brain to predict memory decline after temporal lobectomy

OBJECTIVE

Predicting memory morbidity after temporal lobectomy in patients with temporal lobe epilepsy (TLE) relies on indices of preoperative temporal lobe structural and functional integrity. However, epilepsy is increasingly considered a network disorder, and memory a network phenomenon. We assessed the utility of functional network measures to predict postoperative memory changes.

METHODS

Seventy-two adults with TLE (37 left/35 right) underwent preoperative resting-state functional magnetic resonance imaging and pre- and postoperative neuropsychological assessment. We compared functional connectivity throughout the memory network of each patient to a healthy control template (n = 19) to identify differences in global organization. A second metric indicated the degree of integration of the to-be-resected temporal lobe with the rest of the memory network. We included these measures in a linear regression model alongside standard clinical variables as predictors of memory change after surgery.

RESULTS

Left TLE patients with more atypical memory networks, and with greater functional integration of the to-be-resected region with the rest of the memory network preoperatively, experienced the greatest decline in verbal memory after surgery. Together, these two measures explained 44% of variance in verbal memory change, outperforming standard clinical and demographic variables. None of the variables examined was associated with visuospatial memory change in patients with right TLE.

SIGNIFICANCE

Resting-state connectivity provides valuable information concerning both the integrity of to-be-resected tissue and functional reserve across memory-relevant regions outside of the to-be-resected tissue. Intrinsic functional connectivity has the potential to be useful for clinical decision-making regarding memory outcomes in left TLE, and more work is needed to identify the factors responsible for differences seen in right TLE.

Preoperative and postoperative memory in epilepsy patients with 'gliosis only' versus hippocampal sclerosis: a matched case-control study

BACKGROUND

Gliosis only (GO) and hippocampal sclerosis (HS) are distinct histopathological entities in mesial temporal lobe epilepsy. This study explores whether this distinction also exists on a functional level when evaluating pre- and postoperative memory.

METHODS

Using a retrospective matched case-control study design, we analysed verbal and visual memory performance in 49 patients with GO and 49 patients with HS before and one year after elective surgery.

RESULTS

Clinical differences were evident with a later age at seizure onset (18±12 vs 12±9 years) and fewer postoperative seizure-free patients in the GO group (63% vs 82%). Preoperatively, group and individual-level data demonstrated that memory impairments were less frequent, less severe and relatively non-specific in patients with GO compared with HS. Postoperatively, verbal memory declined in both groups, particularly after left-sided resections, with more significant losses in patients with GO. Factoring in floor effects, GO was also associated with more significant visual memory loss, particularly after left resections.

CONCLUSIONS

Compared with HS, GO is characterised by (1) a later onset of epilepsy, (2) less pronounced and more non-specific memory impairments before surgery, (3) a less successful surgical outcome and (4) a more significant memory decline after surgery. Overall, our results regarding cognition provide further evidence that GO and HS are distinct clinical entities. Functional integrity of the hippocampus appears higher in GO, as indicated by a better preoperative memory performance and worse memory outcome after surgery. The different risk-benefit ratios should be considered during presurgical patient counselling.

Cognitive outcomes following pediatric epilepsy surgery

OBJECTIVES

To characterize outcomes following pediatric epilepsy surgery across a broad range of cognitive domains using empirical methods (i.e., reliable change indices: RCIs), compare these outcomes with those based on traditional methods (i.e., standard deviation: SD), and identify factors associated with postoperative cognitive declines and/or improvements.

METHODS

This retrospective cohort study included 186 children who underwent surgical resection for treatment of pharmacoresistant epilepsy and who completed pre- and postoperative neuropsychological assessments. Postoperative testing occurred approximately 6.5 months after surgery and included measures of intelligence, attention/working memory, processing speed, language, executive functioning, visuospatial skills, memory, and academic achievement. Change scores for each patient were classified as decline, no change, or improvement using epilepsy-specific RCIs. Chi-square goodness of fit tests were used to compare the distribution of outcomes as classified with RCIs to those obtained using a traditional one SD cutoff. Multinomial regression analyses were conducted to identify factors associated with cognitive decline and/or improvement.

RESULTS

While 18% of children demonstrated no postoperative declines or improvements in any cognitive domain, the majority demonstrated relatively focal changes (declines and/or improvements in 1-2 cognitive domains). Rates of postoperative decline and improvement across individual cognitive domains were variable and ranged from 4-35% and 2-31%, respectively. Compared to RCIs, SD methodology often overestimated postoperative improvements and varied with respect to declines. Factors associated with RCI decline or improvement included preoperative performance, age at surgery, surgery site, and postoperative seizures.

SIGNIFICANCE

Results suggest substantial variability in individual cognitive outcomes approximately 6.5 months following pediatric epilepsy surgery. The differences in change distributions obtained using epilepsy-specific RCIs versus SDs highlight the need for studies using empiric methodology to study postoperative cognitive change. Variables associated with postoperative cognitive change may be used to develop multivariable prediction models in future studies to aid clinical decision-making and patient counseling.

Mapping of Language-and-Memory Networks in Patients With Temporal Lobe Epilepsy by Using the GE2REC Protocol

Preoperative mapping of language and declarative memory functions in temporal lobe epilepsy (TLE) patients is essential since they frequently encounter deterioration of these functions and show variable degrees of cerebral reorganization. Due to growing evidence on language and declarative memory interdependence at a neural and neuropsychological level, we propose the GE2REC protocol for interactive language-and-memory network (LMN) mapping. GE2REC consists of three inter-related tasks, sentence generation with implicit encoding (GE) and two recollection (2REC) memory tasks: recognition and recall. This protocol has previously been validated in healthy participants, and in this study, we showed that it also maps the LMN in the left TLE (N = 18). Compared to healthy controls (N = 19), left TLE (LTLE) showed widespread inter- and intra-hemispheric reorganization of the LMN through reduced activity of regions engaged in the integration and the coordination of this meta-network. We also illustrated how this protocol could be implemented in clinical practice individually by presenting two case studies of LTLE patients who underwent efficient surgery and became seizure-free but showed different cognitive outcomes. This protocol can be advantageous for clinical practice because it (a) is short and easy to perform; (b) allows brain mapping of essential cognitive functions, even at an individual level; (c) engages language-and-memory interaction allowing to evaluate the integrative processes within the LMN; (d) provides a more comprehensive assessment by including both verbal and visual modalities, as well as various language and memory processes. Based on the available postsurgical data, we presented preliminary results obtained with this protocol in LTLE patients that could potentially inform the clinical practice. This implies the necessity to further validate the potential of GE2REC for neurosurgical planning, along with two directions, guiding resection and describing LMN neuroplasticity at an individual level.

Surgery procedures in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common cause of refractory epilepsy amenable for surgical treatment and seizure control. Surgery for TLE is a safe and effective strategy. The seizure-free rate after surgical resection in patients with mesial or neocortical TLE is about 70%. Resective surgery has an advantage over stereotactic radiosurgery in terms of seizure outcomes for mesial TLE patients. Both techniques have similar results for safety, cognitive outcomes, and associated costs. Stereotactic radiosurgery should therefore be seen as an alternative to open surgery for patients with contraindications for or with reluctance to undergo open surgery. Laser interstitial thermal therapy (LITT) has also shown promising results as a curative technique in mesial TLE but needs to be more deeply evaluated. Brain-responsive stimulation represents a palliative treatment option for patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior mesial temporal lobe resection. Overall, despite the expansion of innovative techniques in recent years, resective surgery remains the reference treatment for TLE and should be proposed as the first-line surgical modality. In the future, ultrasound therapies could become a credible therapeutic option for refractory TLE patients.

[Surgical treatment of drug-resistant epilepsy following hippocampal sclerosis]

Surgery is an effective approach for drug-resistant temporal lobe epilepsy following hippocampal sclerosis. There is still no clear and unanimous opinion about advantages and disadvantages of certain surgical technique.

MATERIAL AND METHODS

There were 103 surgical interventions in 101 patients. Females prevailed (1.45:1). Age of patients ranged from 16 to 56 years (median 28). Anteromedial temporal lobectomy and selective amygdaloghippocampectomy were performed in 49 (47.6%) and 54 (52.4%) patients, respectively. In the latter group, 30 patients were operated via a 14-mm burr hole-subtemporal approach. Postoperative outcomes were assessed using the Engel grading system. The follow-up period ranged from 2 to 8 years (median 4 years).

RESULTS

By the 2^nd year, Engel class I was observed in 74 (72%) patients, Engel II, III and IV - in 20 (19.4%), 6 (5.8%) and 3 (2.9%) patients, respectively. Engel class I was achieved after anteromedial temporal lobectomy in 68% of cases, selective amygdaloghippocampectomy via standard approaches in 75% of cases, amygdaloghippocampectomy via subtemporal burr hole approach - in 80% of cases. Neurocognitive impairments after anteromedial lobectomy and selective amygdaloghippocampectomy were similar. At the same time, mental disorders de novo prevailed in the group of anteromedial lobectomy (p<0.05). There were no severe visual field disorders after subtemporal burr-hole access. In other cases, these disorders occurred in 36.2% of patients (p<0.05). There were 8 (7.8%) postoperative complications: 5 (10.2%) - after anterior temporal lobectomy, 3 (5.5%) - after selective surgeries via standard approaches. There were no complications after burr-hole surgery.

CONCLUSION

Selective amygdaloghippocampectomy is not inferior to anteromedial lobectomy. Moreover, this procedure is associated with a lower risk of complications and adverse events.

Cognitive outcomes following frontal lobe resection for treatment of epilepsy in children and adolescents

OBJECTIVE

To use reliable change indices (RCIs) developed specifically for pediatric patients with epilepsy to examine cognitive outcomes after frontal lobe resection for pharmacoresistant epilepsy.

METHODS

Forty-one pediatric patients (25 male, Mage = 10 years) completed comprehensive neuropsychological evaluations before and an average of 6.5 months after frontal lobe resections for treatment of epilepsy. Evaluations included tests of intelligence, attention/working memory, processing speed, language, visuospatial skills, executive function, and episodic memory. Practice effect-adjusted RCIs were used to determine clinically significant postoperative cognitive change. Demographic, disease, and surgical variables were examined to identify factors associated with postoperative cognitive decline or improvement.

RESULTS

Within each cognitive domain, there was a large proportion of patients (51-84%) who did not exhibit significant cognitive change. In terms of overall cognitive profile, 44% demonstrated improvement in at least one domain and 69% declined in at least one domain. Postoperative cognitive improvement occurred most commonly in the domain of processing speed, whereas postoperative cognitive decline occurred most frequently in the domain of visuospatial skills. Younger age at surgery was associated with cognitive improvement. Older age at seizure onset and higher baseline cognitive performance were associated with cognitive decline.

SIGNIFICANCE

Approximately 6.5 months after frontal lobe resection, only 15% of our sample showed stable performance across all cognitive domains. Seventeen percent of patients showed improvements without declines, 42% showed declines without improvements, and 27% showed a mix of improvements and declines across different cognitive domains. Age and baseline abilities were associated with postoperative cognitive change on multiple measures. With 1 in 8 children demonstrating postoperative decline across three or more domains, further research is needed to identify factors associated with cognitive decline in order to inform clinical decision-making and patient/family counseling.

Nomograms to Predict Verbal Memory Decline After Temporal Lobe Resection in Adults With Epilepsy

OBJECTIVE

To develop and externally validate models to predict the probability of postoperative verbal memory decline in adults after temporal lobe resection (TLR) for epilepsy using easily accessible preoperative clinical predictors.

METHODS

Multivariable models were developed to predict delayed verbal memory outcome on 3 commonly used measures: Rey Auditory Verbal Learning Test (RAVLT) and Logical Memory (LM) and Verbal Paired Associates (VPA) subtests from Wechsler Memory Scale-Third Edition. With the use of the Harrell step-down procedure for variable selection, models were developed in 359 adults who underwent TLR at the Cleveland Clinic and validated in 290 adults at 1 of 5 epilepsy surgery centers in the United States or Canada.

RESULTS

Twenty-nine percent of the development cohort and 26% of the validation cohort demonstrated significant decline on at least 1 verbal memory measure. Initial models had good to excellent predictive accuracy (calibration [c] statistic range 0.77-0.80) in identifying patients with memory decline; however, models slightly underestimated decline in the validation cohort. Model coefficients were updated with data from both cohorts to improve stability. The model for RAVLT included surgery side, baseline memory score, and hippocampal resection. The models for LM and VPA included surgery side, baseline score, and education. Updated model performance was good to excellent (RAVLT c = 0.81, LM c = 0.76, VPA c = 0.78). Model calibration was very good, indicating no systematic overestimation or underestimation of risk.

CONCLUSIONS

Nomograms are provided in 2 easy-to-use formats to assist clinicians in estimating the probability of verbal memory decline in adults considering TLR for treatment of epilepsy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that multivariable prediction models accurately predict verbal memory decline after TLR for epilepsy in adults.

Does etiology really matter for epilepsy surgery outcome?

Multiple factors influence the outcomes of epilepsy surgery. Prognostic indicators varying from clinical characteristics, imaging findings, ictal, and interictal electrophysiological activity have been linked to surgical outcomes. In this review, we focus on the relatively under‐studied role of the underlying epilepsy histopathology in driving post‐surgical outcomes, specifically focusing on the broad categories of seizure outcomes and cognitive outcomes. For each of these two outcomes of interest, we answer two questions: 1)‐ does etiology matter? and 2)‐ how could it matter? The goal is to review the existing literature on the relationship between etiology and surgical outcomes to provide the best possible judgment as to whether a causal relationship exists between histopathology and the ultimate surgical outcome as an initial step. Then, we delve into the possible mechanisms via which such relationships can be explained. We conclude with a call to action to the epilepsy surgery and histopathology research community to push the mechanistic understanding of the pathology‐outcome interaction and identify actionable knowledge and biomarkers that could inform patient care in a timely fashion.

In this review, we focus on the relatively under‐studied role of the underlying epilepsy histopathology in driving post‐surgical outcomes, specifically focusing on the broad categories of seizure outcomes and cognitive outcomes. For each of these two outcomes of interest, we answer two questions: (1) does etiology matter? and (2) how could it matter? We then delve into the mechanisms of these answers.

Anatomical Subpial Resection of Tumors in the Amygdala and Hippocampus

OBJECTIVE

Surgical techniques to achieve complete resection of mesial-basal temporal tumors should be pursued by neurosurgical oncologists. We describe the anatomical subpial amygdalohippocampectomy (SpAH) technique for tumor resection.

METHODS

The key anatomical landmarks and critical steps of the SpAH technique were outlined and emphasized with medical illustrations and intraoperative photographs. The senior author's 90-day surgical outcomes with this approach were reviewed.

RESULTS

Twenty-five patients (men, 17 [68%]; women, 8 [32%]; median [range] age, 59 [23-80] years) with temporal tumors involving the amygdalohippocampal region were included. SpAH was performed selectively in 8 [32%] patients, whereas 17 [68%] patients underwent SpAH in conjunction with an anterior temporal lobectomy due to tumor involvement of the anterolateral temporal cortex. The subpial resection of the amygdala protected the critical structures of the suprasellar cistern and sylvian fissure. Identifying the choroidal fissure as the superior-most aspect of hippocampal resection protected the optic tract and the thalamus. Subpial resection of the parahippocampal gyrus inferiorly protected the brainstem and critical structures of the ambient cistern. Tumors in the amygdalohippocampal region were anatomically and completely resected in all 25 patients. Of the 15 patients who presented with seizures, 13 (87%) were seizure-free at the 90-day postsurgical follow-up. Permanent neurologic deficits occurred in 3 patients (12%).

CONCLUSIONS

The SpAH technique permits complete resection of mesial-basal temporal tumors with an acceptable morbidity profile. An in-depth understanding of temporal lobe anatomy combined with a refined microsurgical technique allows for reproducible resection of tumor in the amygdalohippocampal region while protecting critical neurovascular structures.

Transsylvian amygdalohippocampectomy for mesial temporal lobe epilepsy: Comparison of three different approaches

OBJECTIVE

This study's objective was to compare the transinsular (TI-AH), transuncus (TU-AH), and temporopolar (TP-AH) amygdalohippocampectomy approaches regarding seizure control, temporal stem (TS) damage, and neurocognitive decline.

METHODS

We included 114 consecutive patients with unilateral hippocampal sclerosis (HS) who underwent TI-AH, TU-AH, or TP-AH between 2002 and 2017. We evaluated seizure control using Engel classification. We used diffusion tensor imaging and postoperative Humphrey perimetry to assess the damage of the TS. We also performed pre- and postoperative memory performance and intelligence quotient (IQ).

RESULTS

There were no significant differences in the proportion of patients free of disabling seizures (Engel IA+IB) among the three surgical approaches in the survival analysis. However, more patients were free of disabling seizures (Engel IA+IB) at 2 years of postsurgical follow-up with TP-AH (69.5%) and TI-AH (76.7%) as compared to the TU-AH (43.5%) approach (p = .03). The number of fibers of the inferior fronto-occipital fasciculus postoperatively was reduced in the TI-AH group compared with the TU-AH and TP-AH groups (p = .001). The rate of visual field defects was significantly higher with TI-AH (14/19, 74%) in comparison to the TU-AH (5/15, 33%) and TP-AH (13/40, 32.5%) approaches (p = .008). Finally, there was a significant postoperative decline in verbal memory in left-sided surgeries (p = .019) and delayed recall for both sides (p < .001) regardless of the surgical approach. However, TP-AH was the only group that showed a significant improvement in visual memory (p < .001) and IQ (p < .001) for both right- and left-sided surgeries.

SIGNIFICANCE

The TP-AH group had better short-term seizure control than TU-AH, a lower rate of visual field defects than TI-AH, and improved visual memory and IQ compared to the other groups. Our findings suggest that TP-AH is a better surgical approach for temporal lobe epilepsy with HS than TI-AH and TU-AH.

Outcomes of resections that spare vs remove an MRI-normal hippocampus

OBJECTIVE

To characterize seizure and cognitive outcomes of sparing vs removing an magnetic resonance imaging (MRI)-normal hippocampus in patients with temporal lobe epilepsy.

METHODS

In this retrospective cohort study, we reviewed clinical, imaging, surgical, and histopathological data on 152 individuals with temporal lobe epilepsy and nonlesional hippocampi categorized into hippocampus-spared (n = 74) or hippocampus-resected (n = 78). Extra-hippocampal lesions were allowed. Pre- and postoperative cognitive data were available on 86 patients. Predictors of seizure and cognitive outcomes were identified using Cox-proportional hazard modeling followed by treatment-specific model reduction according to Akaike information criterion, and built into an online risk calculator.

RESULTS

Seizures recurred in 40% within one postoperative year, and in 63% within six postoperative years. Male gender (P = .03), longer epilepsy duration (P < .01), normal MRI (P = .04), invasive evaluation (P = .02), and acute postoperative seizures (P < .01) were associated with a higher risk of recurrence. We found no significant difference in postoperative seizure freedom rates at 5 years between those whose hippocampus was spared and those whose hippocampus was resected (P = .17). Seizure outcome models built with pre- and postoperative data had bootstrap validated concordance indices of 0.65 and 0.72. The dominant hippocampus-spared group had lower rates of decline in verbal memory (39% vs 70%; P = .03) and naming (41% vs 79%; P = .01) compared to the hippocampus-resected group. Partial hippocampus sparing had the same risk of verbal memory decline as for complete removal.

SIGNIFICANCE

Sparing or removing an MRI-normal hippocampus yielded similar long-term seizure outcome. A more conservative approach, sparing the hippocampus, only partially shields patients from postoperative cognitive deficits. Risk calculators are provided to facilitate clinical counseling.

High frequency oscillations relate to cognitive improvement after epilepsy surgery in children

OBJECTIVE

To investigate how high frequency oscillations (HFOs; ripples 80-250 Hz, fast ripples (FRs) 250-500 Hz) and spikes in intra-operative electrocorticography (ioECoG) relate to cognitive outcome after epilepsy surgery in children.

METHODS

We retrospectively included 20 children who were seizure free after epilepsy surgery using ioECoG and determined their intelligence quotients (IQ) pre- and two years postoperatively. We analyzed whether the number of HFOs and spikes in pre- and postresection ioECoGs, and their change in the non-resected areas relate to cognitive improvement (with ≥ 5 IQ points increase considered to be clinically relevant (=IQ+ group) and < 5 IQ points as irrelevant (=IQ- group)).

RESULTS

The IQ+ group showed significantly more FRs in the resected tissue (p = 0.01) and less FRs in the postresection ioECoG (p = 0.045) compared to the IQ- group. Postresection decrease of ripples on spikes was correlated with postoperative cognitive improvement (correlation coefficient = -0.62 with p = 0.01).

CONCLUSIONS

Postoperative cognitive improvement was related to reduction of pathological HFOs signified by removing FR generating areas with subsequently less residual FRs, and decrease of ripples on spikes in the resection edge of the non-resected area.

SIGNIFICANCE

HFOs recorded in ioECoG could play a role as biomarkers in the prediction and understanding of cognitive outcome after epilepsy surgery.

Memory Decline Following Epilepsy Surgery: Can We Predict Who Will Pay the Price?

Postoperative Memory Prognosis in Temporal Lobe Epilepsy Surgery: The Contribution of Postictal Memory

Sveikata L, Kavan N, Pegna AJ, et al. Epilepsia. 2019;60(8):1639-1649. doi:10.1111/epi.16281. Epub July 22, 2019. PMID: 31329286.

Objective:

The prediction of verbal memory decline after temporal lobe epilepsy (TLE) surgery remains difficult at an individual level. We evaluated the prognostic value of postictal memory testing in predicting the postoperative verbal memory function.

Methods:

Sixty-three consecutive patients were included in the analysis who underwent TLE surgery at our center with preoperative interictal/postictal and postoperative memory testing. Verbal memory was evaluated using the Rey Auditory Verbal Learning Test (RAVLT). We used reliable change indices with 90% confidence interval (90% RCIs) to evaluate a significant postoperative memory decline. The sensitivity (Sn), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy (ACC) were calculated. The analysis was performed for all patients with TLE and for the subgroup with hippocampal sclerosis (HS).

Results:

Patients with left TLE (n = 31) had lower verbal memory scores on RAVLT than right TLE at 3 months (57% vs 78%) and 12 months (53% vs 78%) after surgery. The 90% RCI was estimated to be a loss of 4 out of 15 items. The predictive value was Sn = 42%, Sp = 84%, PPV = 39%, NPV = 86%, AUC = 0.630, and ACC = 76% to predict a verbal memory decline in the whole group (n = 63). In patients with HS (n = 41), the postictal verbal memory test had Sn = 50%, Sp = 88%, PPV = 50%, NPV = 88%, AUC = 0.689, and ACC = 81% to predict a significant postoperative decline.

Significance:

Postictal memory is a noninvasive bedside memory test that can help predict the postoperative verbal memory decline in patients with HS with an overall ACC of 81%.

Identification and Treatment of Drug-Resistant Epilepsy

PURPOSE OF REVIEW

Drug-resistant epilepsy is a potentially life-threatening condition affecting one-third of people living with epilepsy. Despite existing evidence of improved outcomes in patients who received surgical treatment compared to continued medical treatment, epilepsy surgery remains underused in patients with drug-resistant epilepsy. This article discusses the gap between evidence and practice and common misconceptions about epilepsy surgery and reviews the current diagnostic and therapeutic surgical options.

RECENT FINDINGS

Three randomized controlled trials comparing the medical versus surgical treatment for patients with drug-resistant epilepsy have shown the superiority of surgery in controlling seizures and improving patients' quality of life. In addition to resective surgery, neuromodulation through devices such as responsive neurostimulation and vagal nerve stimulation have also shown efficacy in seizure control that increases over time. Diagnostic and therapeutic surgical tools are tailored to the needs of each patient.

SUMMARY

Appropriate patients with drug-resistant epilepsy benefit more from epilepsy surgery than from continuing medical treatment. These patients should be referred to comprehensive epilepsy centers where a thorough presurgical workup and surgical options can be provided. The gap between evidence and practice can be bridged by education, community outreach, and providers' earnest efforts to improve the quality of life of patients with epilepsy.

Predicting verbal memory decline following temporal lobe resection for epilepsy

OBJECTIVES

The aim of the study was to develop a prediction model for verbal memory decline after temporal lobe resection (TLR) for epilepsy. The model will be used in the preoperative counselling of patients to give individualized information about risk for verbal memory decline.

MATERIALS AND METHODS

A sample of 110 consecutive patients who underwent TLR for epilepsy at Sahlgrenska University Hospital between 1987 and 2011 constituted the basis for the prediction model. They had all gone through a formal neuropsychological assessment before surgery and 2 years after. Penalized regression and 20 × 10-fold cross-validation were used in order to build a reliable model for predicting individual risks.

RESULTS

The final model included four predictors: side of surgery; inclusion or not of the hippocampus in the resection; preoperative verbal memory function; and presence/absence of focal to bilateral tonic-clonic seizures (TCS) the last year prior to the presurgical investigation. The impact of a history of TCS is a new finding which we interpret as a sign of a more widespread network disease which influences neuropsychological function and the cognitive reserve. The model correctly identified 82% of patients with post-operative decline in verbal memory, and the overall accuracy was 70%-85% depending on choice of risk thresholds.

CONCLUSIONS

The model makes it possible to provide patients with individualized prediction regarding the risk of verbal memory decline following TLR. This will help them make more informed decisions regarding treatment, and it will also enable the epilepsy surgery team to prepare them better for the rehabilitation process.

Seizures and Epilepsy

Epilepsy affects 65 million people worldwide, and is a leading neurologic cause of loss of quality-adjusted life years. The diagnosis of seizures and epilepsy often depends on a careful history, and is supported with electroencephalogram and imaging. First-line treatment of epilepsy includes medical management. Antiepileptic drugs must be chosen with the patient's particular comorbidities in mind. Drug-resistant epilepsy cases should be referred to an epilepsy specialist and may be evaluated for additional medications, epilepsy surgery, neurostimulation, or dietary therapy. When caring for women, providers must take into account needs for contraception or pregnancy safety where applicable.

Improvement in cognitive function after surgery for low-grade glioma

OBJECTIVE

Cognition is a key component in health-related quality of life (HRQoL) and is currently incorporated as a major parameter of outcome assessment in patients treated for brain tumors. The effect of surgery on cognition and HRQoL remains debatable. The authors investigated the impact of resection of low-grade gliomas (LGGs) on cognition and the correlation with various histopathological markers.

METHODS

A retrospective analysis of patients with LGG who underwent craniotomy for tumor resection at a single institution between 2010 and 2014 was conducted. Of 192 who underwent resective surgery for LGG during this period, 49 had complete pre- and postoperative neurocognitive evaluations and were included in the analysis. These patients completed a full battery of neurocognitive tests (memory, language, attention and working memory, visuomotor organization, and executive functions) pre- and postoperatively. Tumor and surgical characteristics were analyzed, including volumetric measurements and histopathological markers (IDH, p53, GFAP).

RESULTS

Postoperatively, significant improvement was found in memory and executive functions. A subgroup analysis of patients with dominant-side tumors, most of whom underwent intraoperative awake mapping, revealed significant improvement in the same domains. Patients whose tumors were on the nondominant side displayed significant improvement only in memory functions. Positive staining for p53 testing was associated with improved language function and greater extent of resection in dominant-side tumors. GFAP positivity was associated with improved memory in patients whose tumors were on the nondominant side. No correlation was found between cognitive outcome and preoperative tumor volume, residual volume, extent of resection, or IDH1 status.

CONCLUSIONS

Resection of LGG significantly improves memory and executive function and thus is likely to improve functional outcome in addition to providing oncological benefit. GFAP and pP53 positivity could possibly be associated with improved cognitive outcome. These data support early, aggressive, surgical treatment of LGG.

Tailored suprainsular partial hemispherotomy: a new functional disconnection technique for stroke-induced refractory epilepsy

OBJECTIVEHemispherotomy is currently the most frequently performed surgical option for refractory epilepsy associated with large perinatal or childhood ischemic events. Such an approach may lead to good seizure control, but it has inherent functional consequences linked to the disconnection of functional cortices. The authors report on 6 consecutive patients who presented with severe epilepsy associated with hemiplegia due to stroke and who benefitted from a new, stereoelectroencephalography-guided partial disconnection technique.METHODSThe authors developed a new disconnection technique termed "tailored suprainsular partial hemispherotomy" (TSIPH). Disconnection always included premotor and motor cortex with variable anterior and posterior extent.RESULTSAt a mean follow-up of 28 months, there were no deaths and no patient had hydrocephalus. Motor degradation was observed in all patients in the 2 weeks after surgery, but all patients completely recovered. The 6 patients were seizure free (Engel class IA) at the last follow-up. No neuropsychological aggravation was observed.CONCLUSIONSTSIPH appears to be a conservative alternative to classic hemispherotomy, leading to favorable outcome in this series.

Test-specific differences in verbal memory assessments used prior to surgery in temporal lobe epilepsy

OBJECTIVE

To study the relationship between two commonly used verbal memory tests in presurgical evaluation for temporal lobe epilepsy (TLE) in Sweden, the Claeson-Dahl Test for verbal learning and retention (CDT) and the Swedish version of the Rey Auditory Verbal Learning Test (RAVLT).

METHODS

Fifty-nine patients with TLE (male: 41%, mean: age 41.7 ± 12.3 years; epilepsy onset at mean age: 18.3 ± 13.1 years) previously tested with the CDT, the RAVLT, and three nonverbal memory tests on the same occasion were included. We performed (1) a principal component analysis (PCA) on test performances in the CDT and the RAVLT as well as in nonverbal memory tests; (2) a Pearson's correlation analysis for memory components, biological age, education, age at epilepsy onset, and self-rating scores for depression and anxiety; and (3) an estimation of clinically significant verbal memory impairment in patients with left TLE and left-sided hippocampal sclerosis.

RESULTS

The PCAs showed coherence between the learning variables of the CDT and the RAVLT and divergence between the recall variables of the two tests. The RAVLT delayed recall variable was correlated to four out of five nonverbal memory measures. Both tests showed 70-80% clinically significant impairment of verbal memory in patients with left TLE, with or without hippocampal sclerosis, similar to other cohorts with resistant TLE.

CONCLUSIONS

The construct structure of the two verbal memory differs. It was shown that the RAVLT correlated with visuospatial memory, whereas the CDT did not. The study highlights that there are important nonoverlapping features regarding verbal recall of the two tests, indicating that these tests cannot fully replace one another.

Cognition, health-related quality of life, and mood in children and young adults diagnosed with a glioneuronal tumor in childhood

AIMS

The aim of this study was to investigate long-term cognitive outcome, health-related quality of life (HRQoL), and psychiatric symptoms in children and young adults diagnosed with a glioneuronal tumor in childhood.

METHODS

Twenty-eight children and adolescents (0-17.99years) with a minimum postoperative follow-up time of five years were eligible for the study; four persons declined participation. A cross-sectional long-term follow-up evaluation was performed using the following study measures: Wechsler Intelligence Scale for Children (WISC-IV) or Wechsler Adult Intelligence Scale (WAIS-IV), Reys Complex Figure Test (RCFT), Short Form 36 version 2 (SF-36v2), Short Form 10 (SF-10), Quality of Life in Epilepsy 31 (QOLIE-31), Hospital Anxiety Depression Scale (HADS) or Beck Youth Inventory Scales (BYI), and Rosenberg Self-Esteem Scale. Historical WISC-III and RCFT data were used to compare cognitive longitudinal data.

RESULTS

Mean follow-up time after surgery was 12.1years. Sixty-three percent (15/24) were seizure-free. Despite a successive postoperative gain in cognitive function, a significant reduction relative to norms was seen in the seizure-free group with respect to perceptual reasoning index (PRI), working memory index (WMI), and full-scale intelligence quotient (FSIQ). Seizure freedom resulted in acceptable HRQoL. Thirty-two percent and 16% exceeded the threshold level of possible anxiety and depression, respectively, despite seizure freedom.

CONCLUSION

Although lower than in corresponding reference groups, cognitive outcome and HRQoL are good provided that seizure freedom or at least a low seizure severity can be achieved. There is a risk of elevated levels of psychiatric symptoms. Long-term clinical follow-up is advisable.

Psychosocial outcome in epilepsy after extratemporal surgery

OBJECTIVE

Only limited data exist on psychosocial long-term outcome after epilepsy surgery in patients with extratemporal epilepsy. The aim of this study was to investigate psychosocial outcome after extratemporal epilepsy surgery and to assess factors predicting favorable outcome.

METHOD

Sixty-five out of 104 eligible patients who had undergone extratemporal epilepsy surgery at our epilepsy center between 1990 and 2015 (mean age: 42.2. years; 75% of the resections in the frontal lobe) completed a questionnaire asking about seizure status, employment status, marital and living situation, driving status, depressive symptoms, and quality of life (QOL). Follow-up was on average 9.2years after surgery (range: 1-26years).

RESULTS

Thirty-eight (58%) patients were free of disabling seizures (Engel class I), and 28 (43%) have not experienced any seizures after surgery (Engel class IA). Employment rate in the primary labor market remained at 45%, but more patients lost employment (14%) than gained employment (8%). Postoperative employment was predicted by preoperative employment (p=.007), seizure freedom (p=.025), older age at seizure onset (p=.018), younger age at follow-up (p=.035), and female gender (p=.048). Seizure-free patients were more likely to be driving; have a partner, particularly in males; and have lower depressive scores. Quality of life at follow-up was best predicted by employment (p=.012), partnership (p=.025), and seizure freedom (p=.025). In contrast, recurrence of seizures and early seizure onset were associated with poor psychosocial outcome, particularly in men.

CONCLUSION

The study provides support that extratemporal surgery can lead to improved QOL and favorable psychosocial outcome. Seizure freedom is important but not the only determinant of good psychosocial outcome.

Verbal memory decline from hippocampal depth electrodes in temporal lobe surgery for epilepsy

OBJECTIVE

To explore whether patients with refractory mesial temporal lobe epilepsy risk aggravated verbal memory loss from intracranial electroencephalography (EEG) recording with longitudinal hippocampal electrodes in the language-dominant hemisphere.

METHODS

A long-term neuropsychological follow-up (mean 61.5 months, range 22-111 months) was performed in 40 patients after ictal registration with left hippocampal depth electrodes (study group, n = 16) or no invasive EEG, only extracranial registration (reference group, n = 24). The groups were equal with respect to education, age at seizure onset, epilepsy duration, and prevalence of pharmacoresistant temporal lobe epilepsy (TLE; 75%) versus seizure freedom (25%). Retrospective neuropsychological data from preoperative surgical workup (T1) and prospective follow-up neuropsychological data (T2) were compared. A ≥1 SD intrapatient decline was considered as clinically relevant deterioration of verbal memory.

RESULTS

Significant decline in verbal memory was seen in 56% of the patients in the study group compared to 21% in the reference group. At T1, there were no statistical between-group differences in memory performance. At T2, between-group comparison showed significantly greater verbal memory decline for the study group (Claeson Dahl Learning and Retention Test, Verbal Learning: p = 0.05; Rey Auditory Verbal Learning Test, Total Learning: p = 0.04; Claeson Dahl Learning and Retention Test, Verbal Retention: p = 0.04). An odds ratio (OR) of 7.1 (90% confidence interval [CI] 1.3-37.7) for verbal memory decline was seen if right temporal lobe resection (R TLR) had been performed between T1 and T2. The difference between groups remained unchanged when patients who had undergone R TLR were excluded from the analysis, with a remaining aggravated significant decline in verbal memory performance for the study group compared to the reference group.

SIGNIFICANCE

Our results suggest a risk of verbal memory deterioration after the use of depth electrodes along the longitudinal axis of the hippocampus. Until this issue is further investigated, caution regarding depth electrodes in the language-dominant hemisphere hippocampus seems advisable.

Neuropsychological outcome following frontal lobectomy for pharmacoresistant epilepsy in adults

OBJECTIVE

This retrospective cohort study characterized cognitive and motor outcomes in a large sample of adults who underwent frontal lobe resections for treatment of pharmacoresistant epilepsy.

METHODS

Ninety patients who underwent unilateral frontal lobe resection for epilepsy (42 language-dominant hemisphere/48 nondominant hemisphere) between 1989 and 2014 completed comprehensive preoperative and postoperative neuropsychological evaluations that included measures of verbal and nonverbal intellectual functioning, attention/working memory, processing speed, language, executive functioning, verbal and visual memory, and motor functioning. Objective methods were used to assess meaningful change across a wide range of abilities and to identify factors associated with neuropsychological decline following frontal lobectomy. Detailed postoperative neuroimaging analysis was conducted to characterize region, extent, and volume of resection.

RESULTS

Forty-eight percent of patients did not demonstrate meaningful postoperative declines in cognition and an additional 42% demonstrated decline in 1 or 2 cognitive domains. When cognitive decline was observed, it usually occurred on measures of intelligence, visuomotor processing speed, or executive functioning. Side and site of resection were unrelated to cognitive outcome, but played a role in decline of contralateral manual dexterity following supplementary motor area resection. Higher preoperative ability, older age at surgery, absence of a malformation of cortical development on MRI, and poor seizure outcome were related to cognitive decline on some measures, but had poor sensitivity in identifying at-risk patients.

CONCLUSIONS

The vast majority of patients who undergo frontal lobectomy for treatment of pharmacoresistant epilepsy demonstrate good cognitive and motor outcomes.

Parahippocampal and Entorhinal Resection Extent Predicts Verbal Memory Decline in an Epilepsy Surgery Cohort

The differential contribution of medial-temporal lobe regions to verbal declarative memory is debated within the neuroscience, neuropsychology, and cognitive psychology communities. We evaluate whether the extent of surgical resection within medial-temporal regions predicts longitudinal verbal learning and memory outcomes. This single-center retrospective observational study involved patients with refractory temporal lobe epilepsy undergoing unilateral anterior temporal lobe resection from 2007 to 2015. Thirty-two participants with Engel Class 1 and 2 outcomes were included (14 left, 18 right) and followed for a mean of 2.3 years after surgery (±1.5 years). Participants had baseline and postsurgical neuropsychological testing and high-resolution T1-weighted MRI scans. Postsurgical lesions were manually traced and coregistered to presurgical scans to precisely quantify resection extent of medial-temporal regions. Verbal learning and memory change scores were regressed on hippocampal, entorhinal, and parahippocampal resection volume after accounting for baseline performance. Overall, there were no significant differences in learning and memory change between patients who received left and right anterior temporal lobe resection. After controlling for baseline performance, the extent of left parahippocampal resection accounted for 27% (p = .021) of the variance in verbal short delay free recall. The extent of left entorhinal resection accounted for 37% (p = .004) of the variance in verbal short delay free recall. Our findings highlight the critical role that the left parahippocampal and entorhinal regions play in recall for verbal material.

Anterior Temporal Artery-to-Anterior Cerebral Artery Bypass: Anatomic Feasibility of a Novel Intracranial-Intracranial Revascularization Technique

BACKGROUND

Complex aneurysms of the anterior cerebral artery (ACA) may require a bypass procedure as part of their surgical management. Most current bypass paradigms recommend technically demanding side-to-side anastomosis of pericallosal arteries or use of interposition grafts, which involve longer ischemia times. The purpose of this study is to assess the feasibility of an anterior temporal artery (ATA) to ACA end-to-side bypass.

METHODS

Fourteen cadaveric specimens (17 ATAs) were prepared for surgical simulation. The cisternal course of the ATA was freed from perforating branches and arachnoid. The M3-M4 junction of the ATA was cut, and the artery was mobilized to the interhemispheric fissure. The feasibility of ATA bypass to the precommunicating and postcommunicating ACA was assessed in relation to the cisternal length and branching pattern of the middle cerebral artery.

RESULTS

Successful anastomosis was feasible in 14 ATAs (82%). Three ATAs did not reach the ACA. These ATAs were branching distally and originated from the M3 (opercular) middle cerebral artery. In specimens where bypass was not feasible, the average cisternal length of the ATA was significantly shorter than the rest.

CONCLUSIONS

ATA-ACA bypass is anatomically feasible and may be a useful alternative to other revascularization techniques in selected patients. It is technically simpler than A3-A3 in situ bypass. ATA-ACA bypass can be performed through the same pterional exposure used for the ACA aneurysms, sparing the patient an additional interhemispheric approach, required for the A3-A3 anastomosis.

Cognitive eloquence in neurosurgery: Insight from graph theoretical analysis of complex brain networks

The structure and function of the brain can be described by complex network models, and the topological properties of these models can be quantified by graph theoretical analysis. This has given insight into brain regions, known as hubs, which are critical for integrative functioning and information transfer, both fundamental aspects of cognition. In this manuscript a hypothesis is put forward for the concept of cognitive eloquence in neurosurgery; that is regions (cortical, subcortical and white matter) of the brain which may not necessarily have readily identifiable neurological function, but if injured may result in disproportionate cognitive morbidity. To this end, the effects of neurosurgical resection on cognition is reviewed and an overview of the role of complex network analysis in the understanding of brain structure and function is provided. The literature describing network, behavioral, and cognitive effects resulting from lesions to, and disconnections of, centralized hub regions will be emphasized as evidence for the espousal of the concept of cognitive eloquence.

Outcome after epilepsy surgery at the University Hospitals Leuven 1998-2012

We performed a retrospective outcome study of 199 patients who underwent resective epilepsy surgery from 1998 to 2012 and had a minimum of one-year follow-up at the University Hospitals Leuven. Our aim was to assess seizure outcome, prognostic factors for seizure outcome and complication rate. Good seizure outcome after surgery was 38 % at 5 years and 34 % at 10 years follow-up. Good seizure outcome over the previous year at last follow-up, however, was 77 %, which could be explained by the 'running-down phenomenon', i.e. seizure freedom after initial recurrent epilepsy in 32 % of the patients, mainly after temporal lobe surgery. Good seizure outcome for at least 1 year at the last visit was 82 % for temporal and 62 % for extra-temporal lobe interventions. Other variables predictive of a good seizure outcome were not identified. Permanent complications of epilepsy surgery were observed in 31 %. The most important were word finding difficulties (22 %), depression (18 %) and memory deficits (12 %). In conclusion, epilepsy surgery is an excellent treatment option for selected patients, with a good seizure outcome in around 80 % of patients and complications in about 30 %.

Contextual modulation of hippocampal activity during picture naming

Picture naming is a standard task used to probe language processes in healthy and impaired speakers. It recruits a broad neural network of language related areas, among which the hippocampus is rarely included. However, the hippocampus could play a role during picture naming, subtending, for example, implicit learning of the links between pictured objects and their names. To test this hypothesis, we recorded hippocampal activity during plain picture naming, without memorization requirement; we further assessed whether this activity was modulated by contextual factors such as repetition priming and semantic interference. Local field potentials recorded from intracerebral electrodes implanted in the healthy hippocampi of epileptic patients revealed a specific and reliable pattern of activity, markedly modulated by repetition priming and semantic context. These results indicate that the hippocampus is recruited during picture naming, presumably in relation to implicit learning, with contextual factors promoting differential hippocampal processes, possibly subtended by different sub-circuitries.

Resting-state functional connectivity in epilepsy: growing relevance for clinical decision making

PURPOSE OF REVIEW

Seizures produce dysfunctional, maladaptive networks, making functional connectivity an ideal technique for identifying complex brain effects of epilepsy. We review the current status of resting-state functional connectivity (rsFC) research, highlighting its potential added value to epilepsy surgery programs.

RECENT FINDINGS

RsFC research has demonstrated that the brain impact of seizures goes beyond the epileptogenic zone, changing connectivity patterns in widespread cortical regions. There is evidence for abnormal connectivity, but the degree to which these represent adaptive or maladaptive plasticity responses is unclear. Empirical associations with cognitive performance and psychiatric symptoms have helped understand deleterious impacts of seizures outside the epileptogenic zone. Studies in the prediction of outcome suggest that there are identifiable presurgical patterns of functional connectivity associated with a greater likelihood of positive cognitive or seizure outcomes.

SUMMARY

The role of rsFC remains limited in most clinical settings, but shows great promise for identifying epileptic circuits and foci, predicting outcomes following surgery, and explaining cognitive deficits and psychiatric symptoms of epilepsy. RsFC has demonstrated that even focal epilepsies constitute a network and brain systems disorder. By providing a tool to both identify and characterize the brain network impact of epileptiform activity, rsFC can make a strong contribution to presurgical algorithms in epilepsy.

The corpus callosum and recovery of working memory after epilepsy surgery

OBJECTIVE

For patients with medically intractable focal epilepsy, the benefit of epilepsy surgery must be weighed against the risk of cognitive decline. Clinical factors such as age and presurgical cognitive level partially predict cognitive outcome; yet, little is known about the role of cross-hemispheric white matter pathways in supporting postsurgical recovery of cognitive function. The purpose of this study is to determine whether the presurgical corpus callosum (CC) midsagittal area is associated with pre- to postsurgical change following epilepsy surgery.

METHODS

In this observational study, we retrospectively identified 24 adult patients from an epilepsy resection series who completed preoperative high-resolution T1 -weighted magnetic resonance imaging (MRI) scans, as well as pre- and postsurgical neuropsychological testing. The total area and seven subregional areas of the CC were measured on the midsagittal MRI slice using an automated method. Standardized indices of auditory-verbal working memory and delayed memory were used to probe cognitive change from pre- to postsurgery. CC total and subregional areas were regressed on memory-change scores, after controlling for overall brain volume, age, presurgical memory scores, and duration of epilepsy.

RESULTS

Patients had significantly reduced CC area relative to healthy controls. We found a positive relationship between CC area and change in working memory, but not delayed memory; specifically, the larger the CC, the greater the postsurgical improvement in working memory (β = 0.523; p = 0.009). Effects were strongest in posterior CC subregions. There was no relationship between CC area and presurgical memory scores.

SIGNIFICANCE

Findings indicate that larger CC area, measured presurgically, is related to improvement in working memory abilities following epilepsy surgery. This suggests that transcallosal pathways may play an important, yet little understood, role in postsurgical recovery of cognitive functions.

MRI-guided stereotactic amygdalohippocampectomy: a single center experience

BACKGROUND

This paper presents our experience of stereotactic radiofrequency amygdalohippocampectomy performed for intractable mesial temporal lobe epilepsy.

METHODS

The article describes the cases of 61 patients who were treated during the period from 2004 to 2010. Mean postoperative follow-up was 5.3 years. Neuropsychological results were obtained for a subset of 31 patients.

RESULTS

At their last postsurgical visit, 43 (70.5%) patients were Engel class I, six (9.8%) class II, nine (14.8%) class III, and three (4.9%) class IV. The surgery was complicated by four intracranial hematomas. One of them caused acute hydrocephalus and was treated by shunting and resolved without sequelae, while another caused transitory aphasia. The remaining hematomas were asymptomatic. There were two cases of meningitis which required antibiotic treatment. One patient committed suicide due to postoperative depression. After the procedure, we performed open epilepsy surgery and rethermolesions in three and two patients, respectively (8.2%). Patients showed increases in their mean full scale, verbal, and performance intelligence quotient (IQ) scores of 4, 3, and 4 IQ points, respectively (P<0.05). Five (17.2%), four (13.8%), and four (13.3%) patients improved their full scale, verbal, and performance IQ scores, respectively. No significant changes were found in memory performance, with a mean increase of 1, 3, and 0 memory quotient points in global, verbal, and visual memory, respectively (P<0.05). Global memory improved in three (10.3%) patients, verbal memory in one (3.4%), and one patient (3.3%) showed deterioration in visual memory.

CONCLUSION

Stereotactic radiofrequency amygdalohippocampectomy offers a safe, effective, and less aggressive treatment modality in cases of well-defined mesial temporal lobe epilepsy. Seizure outcome is comparable with the results of conventional epilepsy surgery and cognitive results could be even better.

Verbal memory after epilepsy surgery in childhood

PURPOSE

To investigate verbal memory after epilepsy surgery both group-wise and at the level of individual children, and to assess associations with side of surgery and removal of the temporal lobe.

METHODS

A prospective controlled study in a consecutive sample of 21 children undergoing epilepsy surgery, with comprehensive assessments of verbal memory before surgery and six, 12 and 24 months after surgery. For each patient, two age- and gender-matched controls were tested at similar intervals. Standardized regression-based (SRB) analysis was applied to compare post-surgical change in individual patients with change in controls.

RESULTS

Group-wise, average normed scores on verbal memory tests were higher after epilepsy surgery than before, corroborating earlier reports. By dint of empirically based SRB analysis, however, considerable individual differences in post-surgical change were revealed. Children with resections that included the left temporal lobe functioned significantly poorer than predicted on the basis of their pre-surgical performance. In contrast, verbal memory performance after surgery was consistent with pre-surgical baseline in the majority of children with resections that spared the left temporal lobe.

CONCLUSIONS

Despite cessation of epileptic seizures, verbal memory remains vulnerable in children who required surgery including the left temporal lobe. In most - but not all - children with other types of surgery, post-surgical verbal memory is consistent with their individual pre-surgical base level.

Effects of dual pathology on cognitive outcome following left anterior temporal lobectomy for treatment of epilepsy

The objective of this retrospective study was to determine if dual pathology [DUAL - focal cortical dysplasia (FCD) and mesial temporal sclerosis (MTS)] in patients with left temporal lobe epilepsy is associated with greater risk for cognitive decline following temporal lobectomy than single pathology (MTS only). Sixty-three adults (Mage=36.5years, female: 52.4%) who underwent left anterior temporal lobectomy for treatment of epilepsy (MTS=28; DUAL=35) completed preoperative and postoperative neuropsychological evaluations. The base rate of dual pathology was 55.5%. Repeated measures ANOVAs yielded significant 2-way interactions (group×time) on most measures of language and memory with generally moderate effect sizes. Specifically, patients with MTS only demonstrated postoperative declines, while those with dual pathology remained unchanged or improved. Results suggest that dual pathology may be associated with better cognitive outcome following epilepsy surgery than MTS alone, possibly reflecting limited functionality of the resected tissue or intrahemispheric reorganization of function in the context of a developmental lesion.

Executive functioning and depressed mood before and after unilateral frontal lobe resection for intractable epilepsy

Executive dysfunction occurs in a variety of patients who have sustained damage to the frontal lobes. In individuals with frontal lobe epilepsy (FLE) or after unilateral frontal lobe resection (FLR), a unique neuropsychological profile linking executive functions (EF) with the frontal lobe has been elusive, with conflicting findings in the literature. Some studies show greater risk of executive impairment with left-sided FLE or FLR, while others report greater risk for right-sided patients. Some studies report no relationship between FLE and EF impairment, while others show EF impairment regardless of side of seizure foci or surgery. In patients with temporal lobe epilepsy, executive dysfunction is associated with depressed mood possibly reflecting disruption of cortical-limbic pathways and/or frontal-striatal circuitry. Although not previously examined, depression level may affect executive functioning in those with FLE or FLR. We hypothesized that FLE patients with poor mood state would show greater executive dysfunction than FLE patients without poor mood state. The relationship among EF, side of surgery and depressed mood before and 8 months after unilateral FLR was evaluated in 64 patients using validated measures of EF and mood state (Beck Depression Inventory-II). Results indicated that individuals with depressed mood before surgery had greater difficulty on a task of mental flexibility compared to patients without preoperative depressed mood. Further, individuals with depressed mood before surgery had significant increases in perseverative responding and completed fewer categories on a card-sorting task after surgery compared to patients without preoperative depressed mood. Regression analyses showed that among side of surgery, seizure freedom status after surgery and depression status, only pre-surgical depression status explained a significant amount of variance in executive functioning performance after surgery. Results suggest that clinically elevated depressive symptoms before surgery are a risk factor for moderate declines in EF after surgery. Results may be attributable to reduced cognitive reserve in patients with depressive symptoms, or may reflect a common cause attributable to damage to unilateral dorsal and ventral lateral frontal lobe.