Long-Term Neuropsychological Outcomes Following Temporal Lobe Epilepsy Surgery: An Update of the Literature

Association of the cognitive lateralization rating Index with surgical variables of a national cohort of pediatric patients with epilepsy

OBJECTIVE

Surgery is a standard treatment for medically refractory epilepsy, and many factors contribute to determining surgical approaches. The Cognitive Lateralization Rating Index (CLRI) quantifies the degree of dysfunction evident and can suggest atypical neuroanatomical functional organization if dominant skills remain despite left-hemisphere seizure foci (i.e., 'atypically-organized'). We sought to elucidate associations between surgical rate, intent, and procedure type based on CLRI categories.

METHODS

Frequencies and descriptive statistics were run in addition to X2 test of independence and ANOVA evaluating CLRI versus surgical variables. 3-category CLRI included: dominant, non-dominant hemisphere, and non-lateralized dysfunction. 4-catgeory CLRI included the additional 'atypically organized' category.

RESULTS

Of 179 patients with CLRI scores, 139 were offered surgery (78%). Left-hemisphere seizure foci were observed in 51% of patients. There was no relationship between surgery offered and 3-category CLRI (X2 (2, 179) = 0.28, p = 0.88); however, inclusion of atypical organization, was related to surgery offered (X2 (3, 179) = 7.34, p = 0.06). We observed no significant difference between rates of curative or palliative-intent surgery in 3-category (X2 (2, 92) = 0.97, p = 0.62) or 4-category CLRI (X2 (3, 92) = 2.36, p = 0.50). Results trended towards curative procedures (58.7%) with no significant difference between rates of procedures amongst CLRI groups. There was no statistically significant difference between pre- and postoperative cognitive results.

CONCLUSION

Not considering atypical organization may lead to overestimating surgical risk in patients with left-hemisphere seizure foci. While significant differences between surgical offerance, intent, or procedure were not observed, results trended towards significance once consideration of atypical organization was included. Further investigation of these variables in addition to surgical and cognitive outcomes is warranted.

Object naming after epilepsy surgery in the dominant left temporal lobe: risk factors, time course and long-term outcome

BACKGROUND

Deterioration in naming function is a common sequelae after epilepsy surgery in the language-dominant temporal lobe but information on recovery and long-term outcome is scarce. We, therefore, assessed short-term and long-term outcome of object naming in patients undergoing surgery in the temporal lobe and determined factors affecting deterioration and recovery of naming function.

METHOD

Object naming (Boston naming test) before surgery, at early follow-up (FU, 6-12 months) and late FU (≥2 years) was assessed in people with epilepsy (PWE) undergoing resections in the language-dominant left and non-dominant right temporal lobe.

RESULTS

Sixty-six patients with left temporal lobe epilepsy (LTLE) and 87 control patients with right temporal lobe epilepsy (RLTE) were included. At early FU, 28 patients with LTLE (42%) and three patients with RTLE (3%) showed a significant naming decline. In patients with LTLE, risk for deterioration increased with lower verbal memory before surgery, older age at seizure onset and was particularly high with posterior temporal resections (≥40 mm from the temporal pole) and seizure onset >16 years. Of the patients with LTLE with early naming decline, 11 patients (39%) recovered fully in their naming abilities at late FU, averaging almost 10 years. Recovery was associated with the degree of postoperative naming decline at early FU. PWE with a decline of less than 10 items (<20%) had a good prognosis of recovery at late FU. Postoperative seizure control had no significant effect on recovery.

CONCLUSIONS

In our cohort, less than 50% of PWE showed significantly deteriorated naming function after resection of the dominant temporal lobe. If a decline occurred, it appeared to recover to a certain degree and remained as a permanent deficit in 26% of the patients. Long-term outcome of visual object naming can be predicted by the degree of early postoperative decline.

Does epilepsy differentially affect different types of memory?

Despite the recognition that epilepsy can substantially disrupt memory, there are few published accounts of whether and how this disruption varies across different types of memory and/or different types of epilepsy. This review explores four main questions: (1) Are working, episodic and semantic memory differentially affected by epilepsy? (2) Do various types of epilepsy, and their treatment, have different, specifiable effects on memory? (3) Are the usual forms of neuropsychological assessments of memory - many or most designed for other conditions - appropriate for patients with epilepsy? (4) How can research on epilepsy contribute to our understanding of the neuroscience of memory? We conclude that widespread and multifactorial problems are seen in working memory in all patient groups, while patients with temporal lobe epilepsy seem particularly prone to episodic memory deficit, and those with frontal lobe epilepsy to executive function deficits that may in turn impair semantic control. Currently, it is difficult to make individual patient predictions about likely memory deficits based on seizure aetiology and type, but it is possible to guide and tailor neuropsychological assessments in an individualised way. We make recommendations for future directions in validating and optimising neuropsychological assessments, and consider how to approach effective shared decision making about the pros and cons of seizure treatment strategies, especially at crucial educational stages such as adolescence.

Mesial temporal sclerosis and epilepsy: a narrative review

Mesial temporal sclerosis (MTS) stands out as a prevalent etiology of medically intractable temporal lobe epilepsy. Understanding the pathological alterations, clinical manifestations and risk factors of MTS is crucial for the recognition and suspicion of this condition. In this paper, we provide a comprehensive narrative review on the pathophysiology, clinical manifestations, and treatment options for MTS. By doing so, we aim to provide an up-to-date understanding of this condition.

Predictors of long-term memory and network connectivity 10 years after anterior temporal lobe resection

OBJECTIVE

Anterior temporal lobe resection (ATLR) effectively controls seizures in medically refractory temporal lobe epilepsy but risks significant episodic memory decline. Beyond 1 year postoperatively, the influence of preoperative clinical factors on episodic memory and long-term network plasticity remain underexplored. Ten years post-ATLR, we aimed to determine biomarkers of successful memory network reorganization and establish presurgical features' lasting impact on memory function.

METHODS

Twenty-five ATLR patients (12 left-sided) and 10 healthy controls underwent a memory-encoding functional magnetic resonance imaging paradigm alongside neuropsychometry 10 years postsurgery. Generalized psychophysiological interaction analyses modeled network functional connectivity of words/faces remembered, seeding from the medial temporal lobes (MTLs). Differences in successful memory connectivity were assessed between controls and left/right ATLR. Multivariate regressions and mixed-effect models probed preoperative phenotypes' effects on long-term memory outcomes.

RESULTS

Ten years post-ATLR, lower baseline functioning (verbal and performance intelligence quotient) and a focal memory impairment preoperatively predicted worse long-term memory outcomes. Poorer verbal memory was significantly associated with longer epilepsy duration and earlier onset age. Relative to controls, successful word and face encoding involved increased functional connectivity from both or remnant MTL seeds and contralesional parahippocampus/hippocampus after left/right ATLR. Irrespective of surgical laterality, successful memory encoding correlated with increased MTL-seeded connectivity to frontal (bilateral insula, right anterior cingulate), right parahippocampal, and bilateral fusiform gyri. Ten years postsurgery, better memory performance was correlated with contralateral frontal plasticity, which was disrupted with longer epilepsy duration.

SIGNIFICANCE

Our findings underscore the enduring nature of functional network reorganizations to provide long-term cognitive support. Ten years post-ATLR, successful memory formation featured stronger connections near resected areas and contralateral regions. Preoperative network disruption possibly influenced effectiveness of postoperative plasticity. These findings are crucial for enhancing long-term memory prediction and strategies for lasting memory rehabilitation.

An exploratory computational analysis in mice brain networks of widespread epileptic seizure onset locations along with potential strategies for effective intervention and propagation control

Mean-field models have been developed to replicate key features of epileptic seizure dynamics. However, the precise mechanisms and the role of the brain area responsible for seizure onset and propagation remain incompletely understood. In this study, we employ computational methods within The Virtual Brain framework and the Epileptor model to explore how the location and connectivity of an Epileptogenic Zone (EZ) in a mouse brain are related to focal seizures (seizures that start in one brain area and may or may not remain localized), with a specific focus on the hippocampal region known for its association with epileptic seizures. We then devise computational strategies to confine seizures (prevent widespread propagation), simulating medical-like treatments such as tissue resection and the application of an anti-seizure drugs or neurostimulation to suppress hyperexcitability. Through selectively removing (blocking) specific connections informed by the structural connectome and graph network measurements or by locally reducing outgoing connection weights of EZ areas, we demonstrate that seizures can be kept constrained around the EZ region. We successfully identified the minimal connections necessary to prevent widespread seizures, with a particular focus on minimizing surgical or medical intervention while simultaneously preserving the original structural connectivity and maximizing brain functionality.

Neurorehabilitation: Looking Back and Moving Forward, 1st Edition

Rehabilitation is "a set of interventions designed to optimize functioning and reduce disability in individuals with health conditions in interaction with their environment", according to the recent report from the World Health Organization (WHO), released in January 2023 [...].

Epileptic-network-based prediction and control of seizures in humans

Epilepsy is now conceptualized as a network disease. The epileptic brain network comprises structurally and functionally connected cortical and subcortical brain regions - spanning lobes and hemispheres -, whose connections and dynamics evolve in time. With this concept, focal and generalized seizures as well as other related pathophysiological phenomena are thought to emerge from, spread via, and be terminated by network vertices and edges that also generate and sustain normal, physiological brain dynamics. Research over the last years has advanced concepts and techniques to identify and characterize the evolving epileptic brain network and its constituents on various spatial and temporal scales. Network-based approaches further our understanding of how seizures emerge from the evolving epileptic brain network, and they provide both novel insights into pre-seizure dynamics and important clues for success or failure of measures for network-based seizure control and prevention. In this review, we summarize the current state of knowledge and address several important challenges that would need to be addressed to move network-based prediction and control of seizures closer to clinical translation.

Predictors of surgical outcomes in patients with drug-resistant temporal lobe epilepsy

Aim. To identify predictors of surgical outcomes in patients with drug-resistant temporal lobe epilepsy in a multivariate model.

Materials and methods. Aretrospective study included 69 patients with drug-resistant temporal lobe epilepsy who underwent microsurgical anterior temporal lobectomy. The study included 31 (45%) men and 38 (55%) women. The median age was 28 (21; 36). Surgical treatment outcomes were assessed at 6, 12, 36, and 60 months after surgical intervention according to the Engel Epilepsy Surgery Outcome Scale. Logistic regression equations were calculated, a ROC curve was constructed, and odds ratio (OR) with 95% confidence interval (CI), sensitivity, specificity, area under the ROC curve (AUC) were calculated.

Results. In all assessed time periods, 88.3–93.0% of patients had outcomes consistent with Engel classes I and II. The distribution of patients by outcome classes did not change statistically significantly over the entire follow-up period. There were the following predictors of high efficacy of surgical treatment at 6 months after surgery: relatively shorter duration of active disease course (OR 0.719, 95%, CI: 0.437–0.966, p < 0.05), absence of status epilepticus (OR 0.048, 95% CI: 0.002–0.472, p < 0.05), absence of subdominant foci of irritative activity (OR 0.123, 95% CI: 0.012–0.845, p < 0.01), presence of mesial temporal sclerosis (OR 1008, 95% CI: 21.59–1310851, p < 0.01), a relatively longer resection margin on the temporal lobe (OR 637.32, 95% CI: 5.43–1960062, p < 0.05), lateralization of epileptogenic zone in subdominant hemisphere (OR 0.103, 95% CI 0.004–0.937, p = 0.0532). AUC was 0.957 (0.917–0.997), p < 0.0001; sensitivity 87.5%, and specificity 82.8%.

Conclusion. Independent predictors of the efficacy of microsurgical anterior temporal lobectomy in patients with drug-resistant temporal lobe epilepsy are the following: shorter duration of active disease course, absence of status epilepticus in the history, absence of subdominant foci, presence of mesial temporal sclerosis, a relatively longer resection margin on the temporal lobe, and lateralization of the epileptogenic zone in the temporal lobe of the subdominant hemisphere.

Changes in the Brain in Temporal Lobe Epilepsy with Unilateral Hippocampal Sclerosis: An Initial Case Series

Temporal lobe epilepsy (TLE) is a network disorder of the brain. Network disorders predominately involve dysregulation of hippocampal function caused by neuronal hyperexcitability. However, the relationship between the macro- and microscopic changes in specific brain regions is uncertain. In this study, the pattern of brain atrophy in patients with TLE and hippocampal sclerosis (HS) was investigated using volumetry, and microscopic changes in specific lesions were observed to examine the anatomical correspondence with specific target lesions using diffusion tensor imaging (DTI) with statistical parametric mapping (SPM). This retrospective cross-sectional study enrolled 17 patients with TLE and HS. We manually measured the volumes of the hippocampus (HC), amygdala (AMG), entorhinal cortex, fornix, and thalamus (TH) bilaterally. The mean diffusivity and fractional anisotropy of each patient were then quantified and analyzed by a voxel-based statistical correlation method using SPM8. In right TLE with HS, there was no evidence of any abnormal diffusion properties associated with the volume reduction in specific brain regions. In left TLE with HS, there were significant changes in the volumes of the AMG, HC, and TH. Despite the small sample size, these differences in conditions were considered meaningful. Chronic left TLE with HS might cause structural changes in the AMG, HC, and TH, unlike right TLE with HS.