Epilepsy in Pediatric Patients—Evaluation of Brain Structures’ Volume Using VolBrain Software

Somatostatin interneuron fate-mapping and structure in a Pten knockout model of epilepsy

Disruption of inhibitory interneurons is common in the epileptic brain and is hypothesized to play a pivotal role in epileptogenesis. Abrupt disruption and loss of interneurons is well-characterized in status epilepticus models of epilepsy, however, status epilepticus is a relatively rare cause of epilepsy in humans. How interneuron disruption evolves in other forms of epilepsy is less clear. Here, we explored how somatostatin (SST) interneuron disruption evolves in quadruple transgenic Gli1-CreERT2, Ptenfl/fl, SST-FlpO, and frt-eGFP mice. In these animals, epilepsy develops following deletion of the mammalian target of rapamycin (mTOR) negative regulator phosphatase and tensin homolog (Pten) from a subset of dentate granule cells, while downstream Pten-expressing SST neurons are fate-mapped with green fluorescent protein (GFP). The model captures the genetic complexity of human mTORopathies, in which mutations can be restricted to excitatory neuron lineages, implying that interneuron involvement is later developing and secondary. In dentate granule cell (DGC)-Pten knockouts (KOs), the density of fate-mapped SST neurons was reduced in the hippocampus, but their molecular phenotype was unchanged, with similar percentages of GFP+ cells immunoreactive for SST and parvalbumin (PV). Surviving SST neurons in the dentate gyrus had larger somas, and the density of GFP+ processes in the dentate molecular layer was unchanged despite SST cell loss and expansion of the molecular layer, implying compensatory sprouting of surviving cells. The density of Znt3-immunolabeled puncta, a marker of granule cell presynaptic terminals, apposed to GFP+ processes in the hilus was increased, suggesting enhanced granule cell input to SST neurons. Finally, the percentage of GFP+ cells that were FosB positive was significantly increased, implying that surviving SST neurons are more active. Together, findings suggest that somatostatin-expressing interneurons exhibit a combination of pathological (cell loss) and adaptive (growth) responses to hyperexcitability and seizures driven by upstream Pten KO excitatory granule cells.

A Comparison of Pre- and Post-Treatment Cranial MRI Characteristics in Patients with Pediatric Epilepsy Receiving Levetiracetam

Background and Objectives: This study was performed for the purpose of assessing whether antiepileptic levetiracetam treatment produces a change in brain volumes in children with epilepsy. To that end, we compared the volumes of the basal ganglia (caudate nucleus, putamen, globus, hip-pocampus, and thalamus) at magnetic resonance imaging (MRI) before and after treatment (months 18-24) in pediatric epilepsy patients using levetiracetam. Materials and Methods: This retrospective study involved a volumetric comparison of patients presenting to the Balikesir University Medical Faculty pediatric neurology clinic between 01.08.2019 and 01.11.2023 and diagnosed with epilepsy, and who underwent cranial MRI before and 18-24 months after treatment at the radiology department. The demographic and clinical characteristics (age, sex, family history of epilepsy, type of epilepsy, and EEG features (normal, abnormal, epileptiform)) of the patients included in the study were recorded. Results: The comparison of basal ganglia volumes at cranial MRI before and at months 18-24 of treatment revealed significant differences in the left caudate nucleus, right putamen, left putamen, left globus pallidus, right thalamus, left thalamus, and right hippocampal regions. Conclusions: In conclusion, differing findings are encountered at cranial imaging in patients with epilepsy, depending on the seizure frequency, activity, and the type of antiepileptic drugs used. This study compared basal ganglia volumes on cranial MRIs taken before and 18-24 months after treatment in pediatric epilepsy patients using levetiracetam. A significant increase was observed in the volumes of basal ganglia (caudate nucleus, putamen, globus pallidus, hippocampus, and thalamus) on the MRIs of pediatric epilepsy patients using levetiracetam.

Hippocampal Glutamate Levels and Their Correlation With Subregion Volume in School-Aged Children With MRI-Negative Epilepsy: A Preliminary Study

BACKGROUND

Abnormal levels of glutamate constitute a key pathophysiologic mechanism in epilepsy. The use of glutamate chemical exchange saturation transfer (GluCEST) imaging to measure glutamate levels in pediatric epilepsy is rarely reported in research.

PURPOSE

To investigate hippocampal glutamate level variations in pediatric epilepsy and the correlation between glutamate and hippocampal subregional volumes.

STUDY TYPE

Cross-sectional, prospective.

SUBJECTS

A total of 38 school-aged pediatric epilepsy patients with structurally normal MRI as determined by at least two independent radiologists (60% males; 8.7 ± 2.5 years; including 20 cases of focal pediatric epilepsy [FE] and 18 cases of generalized pediatric epilepsy [GE]) and 17 healthy controls (HC) (41% males; 9.0 ± 2.5 years).

FIELD STRENGTH/SEQUENCE

3.0 T; 3D magnetization prepared rapid gradient echo (MPRAGE) and 2D turbo spin echo GluCEST sequences.

ASSESSMENT

The relative concentration of glutamate was calculated through pixel-wise magnetization transfer ratio asymmetry (MTRasym) analysis of the GluCEST data. Hippocampal subfield volumes were computed from MPRAGE data using FreeSurfer.

STATISTICAL TESTS

This study used t tests, one-way analysis of variance, Kruskal-Wallis tests, and Pearson correlation analysis. P < 0.05 was considered statistically significant.

RESULTS

The MTRasym values of both the left and right hippocampi were significantly elevated in GE (left: 2.51 ± 0.23 [GE] vs. 2.31 ± 0.12 [HCs], right: 2.50 ± 0.22 [GE] vs. 2.27 ± 0.22 [HCs]). The MTRasym values of the ipsilateral hippocampus were significantly elevated in FE (2.49 ± 0.28 [ipsilateral] vs. 2.29 ± 0.16 [HCs]). The MTRasym values of the ipsilateral hippocampus were significantly increased compared to the contralateral hippocampus in FE (2.49 ± 0.28 [ipsilateral] vs. 2.35 ± 0.34 [contralateral]). No significant differences in hippocampal volume were found between different groups (left hippocampus, P = 0.87; right hippocampus, P = 0.87).

DATA CONCLUSION

GluCEST imaging have potential for the noninvasive measurement of glutamate levels in the brains of children with epilepsy.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 1.

Valproate associated brain volume-loss in pediatric epilepsy-A case series

Brain atrophy associated with valproate therapy is known from single case reports and is frequently accompanied by cognitive deterioration. We present a case series of incidental findings of brain volume loss in children treated with valproate and employed automatic brain volumetry to assess the effect size of volume loss. 3D T1w datasets were automatically segmented into white matter, gray matter, and cerebrospinal fluid using the SPM-12 algorithm. Respective volumes of cerebrum and cerebellum were read out and normalized to the total intracranial volume. We identified six patients (median age 148.5 [85-178] months) who had received valproate for a median time of 5 (2-23) months prior to MRI in which a loss of brain volume was noted. None had reported the occurrence of new clinical symptoms. Volumetry showed a volume loss of up to 28% for cerebral GM, 25% for cerebellar GM, 10% for cerebral WM, and 20% for cerebellar WM. A volume loss of >5% in at least one of the subvolumes was found in all patients, with the more prominent volume loss in the cerebrum and in gray matter. In one patient, post-valproate MRI was available and showed normalization of brain volume. Our case series indicates that valproate therapy might be associated with an asymptomatic volume loss of brain parenchyma in children with epilepsy and that this volume loss is assessable with automatic volumetry.

Chiari 1 Malformation and Epilepsy in Children: A Missing Relationship

Purpose: Once believed a result of pathophysiological correlations, the association between Chiari 1 malformation (CM1) and epilepsy has since been considered as a coincidence, due to missing etiologic or clinical matching points. At present, the problem is being newly debated because of the increasing number of CM1 diagnoses, often among children with seizures. No specific studies on this topic are available yet. The present study aimed at updating the information on this topic by reporting on a series of children specifically enrolled and retrospectively analyzed for this purpose. Methods: All children admitted between January 2015 and June 2020 for epilepsy and CM1 were considered (Group 1). They were compared with children admitted in the same period for symptoms/signs related to CM1 and/or syringomyelia (Group 2). Syndromic patients were excluded, as well as those with tumoral or other overt intracranial lesions. All patients received a complete preoperative work-up, including MRI and EEG. Symptomatic children with CM1/syringomyelia were operated on. The pertinent literature was reviewed. Results: Group 1 was composed of 29 children (mean age: 6.2 years) showing CM1 and epilepsy with several types of seizures. A share of 27% had CM1-related symptoms and syringomyelia. The mean tonsillar ectopia was 7.5 mm. Surgery was performed in 31% of cases. Overall, 62% of children are currently seizure-free (including 5/9 children who were operated on). Tonsillar herniation and syringomyelia regressed in 4/9 cases and 4/8 cases, improved in 4/9 cases and 3/8 cases, and remained stable in 1/9 and 1/8 cases, respectively. CM1 signs/symptoms regressed completely in 6/8 cases and improved or remained stable in one case in each of the two remaining patients. Group 2 consisted of 77 children (mean age: 8.9 years) showing symptoms of CM1 (75%) and/or syringomyelia (39%). The mean tonsillar ectopia was 11.8 mm. Non-specific EEG anomalies were detected in 13 children (17%). Surgery was performed in 76.5% of cases (18 children were not operated on because of oligosymptomatic). Preoperative symptoms regressed in 26%, improved in 50%, remained stable 22%, and worsened in 2%; CM1 radiologically regressed in 39%, improved in 37%, remained unchanged in 22%, and worsened in 2%; and syringomyelia/hydromyelia regressed in 61%, improved in 30%, and was stable in 9%. No statistically significant differences between the two groups were detected regarding the M/F ratio, presence of syringomyelia/hydromyelia, or CM1/syringomyelia outcome; moreover, no correlation occurred between seizure-free condition and PF decompression in Group 1, or between disappearance of EEG anomalies and PF decompression in Group 2. A significant difference between the two groups was noticed regarding the mean age at admission (p = 0.003), amount of tonsillar herniation (p < 0.00001), and PF decompression (p = 0.0001). Conclusions: These findings do not support clinical correlations between CM1 and epilepsy. Their course depends on surgery and antiepileptic drugs, respectively. The analysis of the literature does not provide evidence of a relationship between seizures and cerebellar anomalies such as CM1. Rather than being linked to a syndrome that could explain such an association, the connection between the two now has to be considered to be random.