Is additional mesial temporal resection necessary for intractable epilepsy with cavernous malformations in the temporal neocortex?

Pediatric Neurostimulation and Practice Evolution

Since the late nineteenth century, the prevailing view of epilepsy surgery has been to identify a seizure focus in a medically refractory patient and eradicate it. Sadly, only a select number of the many who suffer from uncontrolled seizures benefit from this approach. With the development of safe, efficient stereotactic methods and targeted surgical therapies that can affect deep structures and modulate broad networks in diverse disorders, epilepsy surgery in children has undergone a paradigmatic evolutionary change. With modern diagnostic techniques such as stereo electroencephalography combined with closed loop neuromodulatory systems, pediatric epilepsy surgery can reach a much broader population of underserved patients.

Kindling in humans: Does secondary epileptogenesis occur?

The relevance of secondary epileptogenesis for human epilepsy remains a controversial subject decades after it was first described in animal models. Whether or not a previously normal brain region can become independently epileptogenic through a kindling-like process has not, and cannot, be definitely proven in humans. Rather than reliance on direct experimental evidence, attempts to answering this question must depend on observational data. In this review, observations based largely upon contemporary surgical series will advance the case for secondary epileptogenesis in humans. As will be argued, hypothalamic hamartoma-related epilepsy provides the strongest case for this process; all the stages of secondary epileptogenesis can be observed. Hippocampal sclerosis (HS) is another pathology where the question of secondary epileptogenesis frequently arises, and observations from bitemporal and dual pathology series are explored. The verdict here is far more difficult to reach, in large part because of the scarcity of longitudinal cohorts; moreover, recent experimental data have challenged the claim that HS is acquired consequent to recurrent seizures. Synaptic plasticity more than seizure-induced neuronal injury is the likely mechanism of secondary epileptogenesis. Postoperative running-down phenomenon provides the best evidence that a kindling-like process occurs in some patients, evidenced by its reversal. Finally, a network perspective of secondary epileptogenesis is considered, as well as the possible role for subcortical surgical interventions.

Anterior temporal lobectomy improved mood status and quality of life in Chinese patients with mesial temporal lobe epilepsy: a single-arm cohort study

BACKGROUND

Many studies have emphasized that selective resection of epileptic lesions in temoral lobe is associated with better preservation of cognition function; whether this applies to patients with refractory mesial temporal lobe epilepsy (MTLE) remains unknown. The objective of this study was to evaluate changes in cognitive functions, mood status, and quality of life after anterior temporal lobectomy in patients with refractory MTLE.

METHODS

This single-arm cohort study assessed cognitive function, mood status, and quality of life, as well as electroencephalography findings, in patients with refractory MTLE who underwent anterior temporal lobectomy at Xuanwu Hospital from January 2018 to March 2019. Pre- and post-operative characteristics were compared to evaluate the effects of surgery.

RESULTS

Anterior temporal lobectomy significantly reduced the frequencies of epileptiform discharges. The overall success rate of surgery was acceptable. Anterior temporal lobectomy did not result in significant changes in overall cognitive functions (P   >  0.05), although changes in certain domains, including visuospatial ability, executive ability, and abstract thinking, were detected. Anterior temporal lobectomy resulted in improvements in anxiety and depression symptoms and quality of life.

CONCLUSIONS

Anterior temporal lobectomy reduced epileptiform discharges and incidence of post-operative seizures as well as resulted in improved mood status and quality of life without causing significant changes in cognitive function.

Is Hippocampal Resection Necessary for Low-Grade Epilepsy-Associated Tumors in the Temporal Lobe?

Low-grade epilepsy-associated tumors (LEATs) are common in the temporal lobe and can cause drug-resistant epilepsy. Complete resection of LEATs is sufficient for seizure relief. However, hippocampal resection might result in postoperative cognitive impairment. This study aimed to clarify the necessity of hippocampal resection for seizure and cognitive outcomes in patients with temporal lobe LEATs and a normal hippocampus. The study included 32 patients with temporal lobe LEATs and without hippocampal abnormalities. All patients underwent gross total resection as treatment for drug-resistant epilepsy at our tertiary epilepsy center from 2005 to 2020, followed by at least a 12-month follow-up period. Seizure and cognitive outcomes were compared between patients who underwent additional hippocampal resection (Resected group) and those who did not (Preserved group). Among the participants, 14 underwent additional hippocampal resection and 28 (87.5%) achieved seizure freedom irrespective of hippocampal resection. The seizure-free periods were not different between the two groups. Additional hippocampal resection resulted in a significantly negative impact on the postoperative verbal index. In conclusion, additional hippocampal resection in patients with temporal lobe LEATs without hippocampal abnormalities is unnecessary because lesionectomy alone results in good seizure control. Additional hippocampal resection may instead adversely affect the postoperative language function.

Metabolism and Intracranial Epileptogenicity in Temporal Lobe Long-Term Epilepsy-Associated Tumor

Brain tumors are common in epilepsy surgery and frequently occur in the temporal lobe, but the optimal surgical strategies to remove the tumor and epileptogenic zone remain controversial. We aim at illustrating the positron emission tomography (PET) metabolism and the stereoelectroencephalography (SEEG) epileptogenicity of temporal lobe long-term epilepsy-associated tumors (LEAT). In this study, 70 patients and 25 healthy controls were included. Our analysis leveraged group-level analysis to reveal the whole-brain metabolic pattern of temporal lobe LEATs. The SEEG-based epileptogenicity mapping was performed to verify the PET findings in the epileptic network. Compared to controls, patients with a temporal lobe LEAT showed a more widespread epileptic network based on 18FDG-PET in patients with a mesial temporal lobe LEAT than in those with a lateral temporal lobe LEAT. The significant brain clusters mainly involved the paracentral lobule (ANOVA F = 9.731, p < 0.001), caudate nucleus (ANOVA F = 20.749, p < 0.001), putamen (Kruskal−Wallis H = 19.258, p < 0.001), and thalamus (ANOVA F = 4.754, p = 0.011). Subgroup analysis and SEEG-based epileptogenicity mapping are similar to the metabolic pattern. Our findings demonstrate the metabolic and electrophysiological organization of the temporal lobe LEAT epileptic network, which may assist in a patient-specific surgical strategy.

Outcomes of hippocampus-sparing lesionectomy for temporal lobe epilepsy and the significance of intraoperative hippocampography

OBJECTIVES

We investigated hippocampal-sparing lesionectomy (HSL) outcomes in temporal lobe epilepsy (TLE) and the significance of high-frequency oscillations (HFOs) detected by hippocampography in HSL.

METHODS

We retrospectively reviewed data from patients who underwent HSL for lesional TLE. Patients were included when MRI confirmed (i) a lesion limited to the temporal lobe with normal hippocampi preoperatively and (ii) hippocampal integrity postoperatively. Factors possibly related to outcomes were collected. Intraoperative hippocampography was reviewed, and spikes, ripples, and fast ripples were marked. Seizure outcomes were tracked ≥ 2 years. Postoperative neuropsychological tests were performed and analyzed.

RESULTS

We included 67 patients (35 males/32 females, median age at surgery 28 years, 57 seizure-free). Complete resection was significantly associated with being seizure-free without aura, an outcome achieved by 32 (69.6%) patients with complete resection vs 1 (12.5%) with incomplete resection (p = 0.004). Spikes/ripples/fast ripples appeared frequently in the hippocampus, occurring in 86.4%/82.4%/75.0% of cases before resection and 76.7%/78.1%/63.0% after resection. The presence and rate were unconnected to seizure outcome. Postoperative neuropsychological outcomes in intelligence and visual memory improved overall.

CONCLUSIONS

HSL in lesional TLE can produce satisfactory seizure and cognitive outcomes. Intraoperative hippocampography-guided resection of apparently normal hippocampi should be performed cautiously and might not be necessary.

SIGNIFICANCE

This study provided evidence in decision making for patients with lesional TLE with a radiologically normal hippocampus.