Neural networks underlying hyperkinetic seizures: A quantitative PET and SEEG study

Ictal semiology in temporo-frontal epilepsy: A systematic review and meta-analysis

We performed a systematic review of the ictal semiology of temporo-frontal seizures with the aim to summarize the state-of-the-art anatomo-clinical correlations in the field, and help guide the interpretation of ictal semiology within the framework of presurgical evaluation. We conducted the systematic review and meta-analysis, and reported its results according to the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. We searched electronic databases (Scopus, PUBMED, Web of Science, and EMBASE) using relevant keywords related to temporal, frontal and sublobar structures, semiology, and electroencephalography/stereoelectroencephalography exploration. The risk of bias was evaluated using the QUADAS2. We included articles in English, reporting the seizure semiology of patients with temporal lobe epilepsy with temporal-frontal involvement and patients with frontal lobe epilepsy and fronto-temporal network involved. We performed hierarchical cluster analysis to determine signs and symptoms associated with the temporo-frontal epileptogenic network for all patients and for each subgroup (frontal/temporal seizure onset). Fisher exact test was performed to evaluate the difference in seizure freedom and clinical sign/symptom occurrence in patients that underwent unilobar versus bilobar resection. Meta-analysis on the prevalence of temporo-frontal/fronto-temporal involvement applying a random-effect model was used. We included 40 articles and we extracted data from 109 patients. The meta-analysis showed the total prevalence of temporo-frontal/fronto-temporal network involvement was 19.75%, CI 12.02-27.47, high heterogeneity (82.71%). For the whole group and subgroups, the main cluster of clinical manifestations is emotional, autonomic, cognitive, grimace, hyperkinetic (association coefficient higher than .6). Elementary motor semiology is significantly associated with multilobar resection (p = .022 whole group and p = .0012 fronto-temporal subgroup). Fifty-eight patients were seizure-free after surgery. There was no significant difference between seizure freedom in uni versus bilobar resections (p = .28). Seizures involving temporo-frontal/fronto-temporal network usually manifest with a cluster of signs and symptoms: emotional, autonomic, grimace, cognitive and hyperkinetic behavior. Based on semiology, one cannot distinguish between fronto-temporal and temporo-frontal cases at individual patient level. In those patients undergoing a surgical procedure, elementary motor seizure semiology is significantly associated with multilobar resection.

Deep brain stimulation of the nucleus basalis of Meynert modulates hippocampal-frontoparietal networks in patients with advanced Alzheimer's disease

BACKGROUND

Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) has shown potential for the treatment of mild-to-moderate Alzheimer's disease (AD). However, there is little evidence of whether NBM-DBS can improve cognitive functioning in patients with advanced AD. In addition, the mechanisms underlying the modulation of brain networks remain unclear. This study was aimed to assess the cognitive function and the resting-state connectivity following NBM-DBS in patients with advanced AD.

METHODS

Eight patients with advanced AD underwent bilateral NBM-DBS and were followed up for 12 months. Clinical outcomes were assessed by neuropsychological examinations using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale. Resting-state functional magnetic resonance imaging and positron emission tomography data were also collected.

RESULTS

The cognitive functioning of AD patients did not change from baseline to the 12-month follow-up. Interestingly, the MMSE score indicated clinical efficacy at 1 month of follow-up. At this time point, the connectivity between the hippocampal network and frontoparietal network tended to increase in the DBS-on state compared to the DBS-off state. Additionally, the increased functional connectivity between the parahippocampal gyrus (PHG) and the parietal cortex was associated with cognitive improvement. Further dynamic functional network analysis showed that NBM-DBS increased the proportion of the PHG-related connections, which was related to improved cognitive performance.

CONCLUSION

The results indicated that NBM-DBS improves short-term cognitive performance in patients with advanced AD, which may be related to the modulation of multi-network connectivity patterns, and the hippocampus plays an important role within these networks.

TRIAL REGISTRATION

ChiCTR, ChiCTR1900022324. Registered 5 April 2019-Prospective registration. https://www.chictr.org.cn/showproj.aspx?proj=37712.

Patterns of hypometabolism in frontal lobe epilepsy originating in different frontal regions

Objectives

Analysis of FDG‐PET imaging commonly shows that hypometabolism extends into extra‐epileptogenic zones (extra‐EZ). This study investigates the distribution patterns of hypometabolism in frontal lobe epilepsy (FLE) originating in different frontal regions.

Methods

Sixty‐four patients with FLE were grouped by EZ localization according to Brodmann areas (BAs): Group 1 (the frontal motor and premotor area), BAs 4, 6, and 8; Group 2 (the inferior frontal gyrus and opercular area), BAs 44, 45, and 47; Group 3 (the dorsal prefrontal area), BAs 9, 10, 11, and 46; and Group 4 (the medial frontal and anterior cingulate gyrus), BAs 32 and 24. Regions of extra‐EZ hypometabolism were statistically analyzed between FLE groups and healthy controls. Correlation analysis was performed to identify relationships between the intensity of hypometabolism and clinical characteristics.

Results

Significant hypometabolism in the ipsilateral (Groups 1 and 4) or bilateral (Groups 2 and 3) anterior insulae was found. Groups 1 and 4 presented with limited distribution of extra‐EZ hypometabolism, whereas Groups 2 and 3 showed widely distributed extra‐EZ hypometabolism in the rectus gyrus, cingulate gyrus, and other regions. Additionally, the intensity of hypometabolism was correlated with epilepsy duration in Groups 2 and 3.

Conclusions

All FLE groups showed hypometabolism in the anterior insula. In addition, distinct patterns of extra‐EZ hypometabolism were identified for each FLE group. This quantitative FDG‐PET analysis expanded our understanding of the topography of epileptic networks and can guide EZ localization in the future.

Cortical regions and networks of hyperkinetic seizures: Electrocorticography and diffusion tensor imaging study

OBJECTIVE

The present study investigated the cortical areas and networks responsible for hyperkinetic seizures by analyzing invasive recordings and diffusion tensor imaging (DTI) tractography.

METHODS

Seven patients with intractable focal epilepsy in whom hyperkinetic seizures were recorded during an invasive evaluation at Sapporo Medical University between January 2012 and March 2020 were enrolled in the present study. Intracranial recordings were analyzed to localize seizure-onset zones (SOZs) and symptomatogenic zones (spread areas at clinical onset). DTI was used to identify the subcortical fibers originating from SOZs.

RESULTS

Ten SOZs were located in four areas: (1) the inferior parietal lobule (two SOZs in two patients), (2) temporo-occipital junction (three SOZs in two patients), (3) medial temporal area (three SOZs in three patients) and (4) medial/lateral frontal lobe (two SOZs in two patients). Symptomatogenic zones appeared to be the premotor area, basal temporal area, temporo-occipital junction, and the postcentral gyrus/supramarginal gyrus. The tractographic analysis revealed that the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), middle longitudinal fasciculus (MLF), arcuate fasciculus (AF)/superior longitudinal fasciculus (SLF) II, III, and cingulum bundle may be associated with hyperkinetic seizures.

CONCLUSION

The present results suggest the cortical areas (the inferior parietal lobule, temporo-occipital junction, medial temporal area, and medial/lateral frontal lobe) and subcortical fibers (IFOF, ILF, MLF, AF/SLFII, III, and the cingulum bundle) responsible for generating hyperkinetic seizures.