Posttraumatic epilepsy may be a state in which underlying epileptogenicity involves focal cortical dysplasia

GABAA Receptor-Stabilizing Protein Ubqln1 Affects Hyperexcitability and Epileptogenesis after Traumatic Brain Injury and in a Model of In Vitro Epilepsy in Mice

Posttraumatic epilepsy (PTE) is a major public health concern and strongly contributes to human epilepsy cases worldwide. However, an effective treatment and prevention remains a matter of intense research. The present study provides new insights into the gamma aminobutyric acid A (GABA_A)-stabilizing protein ubiquilin-1 (ubqln1) and its regulation in mouse models of traumatic brain injury (TBI) and in vitro epilepsy. We performed label-free quantification on isolated cortical GABAergic interneurons from GAD67-GFP mice that received unilateral TBI and discovered reduced expression of ubqln1 24 h post-TBI. To investigate the link between this regulation and the development of epileptiform activity, we further studied ubqln1 expression in hippocampal and cortical slices. Epileptiform events were evoked pharmacologically in acute brain slices by administration of picrotoxin (PTX, 50 μM) and kainic acid (KA, 500 nM) and recorded in the hippocampal CA1 subfield using Multi-electrode Arrays (MEA). Interestingly, quantitative Western blots revealed significant decreases in ubqln1 expression 1–7 h after seizure induction that could be restored by application of the non-selective monoamine oxidase inhibitor nialamide (NM, 10 μM). In picrotoxin-dependent dose–response relationships, NM administration alleviated the frequency and peak amplitude of seizure-like events (SLEs). These findings indicate a role of the monoamine transmitter systems and ubqln1 for cortical network activity during posttraumatic epileptogenesis.

Seizing After Freezing: Layer-, Site-, and Cell-Type-Specific Rewiring Mediates Epileptogenesis Following Cortical Freeze Lesion in Mouse

Circuit Mechanisms Underlying Epileptogenesis in a Mouse Model of Focal Cortical Malformation

Yang W, Williams A, Sun QQ. Curr Biol. 2021;31(2):334-345. doi:10.1016/j.cub.2020.10.29

The way in which aberrant neural circuits contribute to epilepsy remains unclear. To elucidate this question, we dissected the circuit mechanisms underlying epileptogenesis using a mouse model of focal cortical malformation with spontaneous epileptiform discharges. We found that spontaneous spike-wave discharges and optogenetically induced hyperexcitable bursts in vivo were present in a cortical region distal to (>0.7 mm) freeze-lesion-induced microgyrus, instead of near the microgyrus. Channelrhodopsin-2-assisted circuit mapping revealed ectopic interlaminar excitatory input from infragranular layers to layers 2/3 pyramidal neurons as the key component of hyperexcitable circuitry. This hyperactivity disrupted the balance between excitation and inhibition and was more prominent in the cortical region distal to the microgyrus. Consistently, the inhibition from both parvalbumin-positive interneurons (PV) and somatostatin-positive interneurons (SOM) to pyramidal neurons were altered in a layer- and site-specific fashion. Finally, closed-loop optogenetic stimulation of SOM, but not PV, terminated spontaneous spike-wave discharges. Together, these results demonstrate the occurrence of highly site- and cell-type-specific synaptic reorganization underlying epileptic cortical circuits and provide new insights into potential treatment strategies.

Non-Ruptured Temporal Lobe Dermoid Cyst Concomitant with Focal Cortical Dysplasia Causing Temporal Lobe Epilepsy-A Case Report and Literature Review

Background: Intracranial dermoid cyst is a rare, benign, nonneoplastic tumor-like lesion that could cause seizures, headache, and hydrocephalus. We hypothesized that the temporal lobe dermoid cyst in combination with other factors were causing the epileptic seizure. Methods: We encountered a 17-year-old girl with anti-seizure medication-resistant epilepsy secondary to dermoid cyst located in the temporal region depicted on magnetic resonance imaging (MRI). She showed neither symptoms of meningitis nor rupture of the cyst according to serial MRI. We hypothesized that temporal lobe dermoid cyst in combination with other factors, such as focal cortical dysplasia (FCD), etc., was causing epileptic seizures in this case. She underwent dermoid cyst removal surgery with resection of the tip of the antero-inferior temporal lobe. Results: Histopathological study showed multiple small intramedullary dermoid cysts in the left antero-inferior temporal lobe in addition to MRI lesions and FCD. Conclusion: A patient with medically intractable epilepsy secondary to left temporal lobe dermoid cyst showed multiple intramedullary dermoid cysts and focal cortical dysplasia that might have interacted to create epileptogenicity. To our knowledge, this is the first case report of dermoid cyst concomitant with FCD.

Epilepsy in patients with focal cortical dysplasia may be associated with autism spectrum disorder

INTRODUCTION

Patients with epilepsy associated with focal cortical dysplasia (FCD) may be associated with autism spectrum disorder (ASD). Therefore, the purpose of this study was to compare surgically treated patients with epilepsy secondary to FCD and normal volunteers without epilepsy and to review the neuropathological findings of patients with FCD.

METHODS

This study involved 38 patients with medically intractable focal onset epileptic seizures who underwent epilepsy surgery (Group 1). All patients had epilepsy associated with FCD. These patients and 38 normal volunteers without epilepsy (Group 2) were administered the autism spectrum quotient (AQ) test, and the groups were compared.

RESULTS

The 38 patients in Group 1 included 16 females and 22 males (age range 20-60, mean age, 33.0; standard deviation (SD), 11.8 years). The normal volunteers in Group 2 included 22 females and 16 males (age range 20-57, mean age, 30.6 years; SD, 8.8 years). Total AQ scores were significantly higher in Group 1 than Group 2 (p = 0.027). Patients with FCD I showed a higher AQ score than those with FCD II in the AQ test (p ≤ 0.001).

CONCLUSION

Patients with epilepsy secondary to FCD were associated with higher ASD score than normal volunteers. This tendency was seen more strongly in patients with FCD I than FCD II.

Successful Hemispherotomy in a Patient with Encephalopathy with Continuous Spikes and Waves during Sleep Related to Neonatal Thalamic Hemorrhage: A Case Report with Intracranial Electroencephalogram Findings

Neonatal thalamic hemorrhage is a strong risk factor for developing encephalopathy with continuous spikes and waves during sleep (ECSWS), even when not accompanied by widespread cortical destruction. The efficacy and indication of resective epilepsy surgery in such patients has not yet been reported. A 4-year-old boy was diagnosed with ECSWS based on strong epileptiform activation during sleep and neurocognitive deterioration. He had a history of left thalamic hemorrhage related to a straight sinus thrombosis during the newborn period. He presented with daily absence seizures that were refractory to medical treatment. At age 5, he underwent intracranial electroencephalogram (EEG) recording using depth and subdural strip electrodes placed in the left thalamus and over bilateral cortex, respectively. Interictal and ictal epileptiform discharges were observed in the thalamus, always preceded by discharges in the left or right parietal lobe. Left hemispherotomy successfully normalized the EEG of his unaffected hemisphere and extinguished his seizures. This is the first case report documenting resective epilepsy surgery in a patient with ECSWS due to neonatal thalamic injury without widespread cerebral destruction. Based on intracranial EEG findings, his injured thalamus did not directly generate the EEG abnormalities or absence seizures on its own. Patients with ipsilateral neonatal thalamic injury and even mild lateralized cortical changes may be candidates for resective or disconnective surgery for ECSWS.

Excitatory/Inhibitory Synaptic Ratios in Polymicrogyria and Down Syndrome Help Explain Epileptogenesis in Malformations

BACKGROUND

The ratio between excitatory (glutamatergic) and inhibitory (GABAergic) inputs into maturing individual cortical neurons influences their epileptic potential. Structural factors during development that alter synaptic inputs can be demonstrated neuropathologically. Increased mitochondrial activity identifies neurons with excessive discharge rates.

METHODS

This study focuses on the neuropathological examinaion of surgical resections for epilepsy and at autopsy, in fetuses, infants, and children, using immunocytochemical markers, and electron microscopy in selected cases. Polymicrogyria and Down syndrome are highlighted.

RESULTS

Factors influencing afferent synaptic ratios include the following: (1) synaptic short-circuitry in fused molecular zones of adjacent gyri (polymicrogyria); (2) impaired development of dendritic spines decreasing excitation (Down syndrome); (3) extracellular keratan sulfate proteoglycan binding to somatic membranes but not dendritic spines may be focally diminished (cerebral atrophy, schizencephaly, lissencephaly, polymicrogyria) or augmented, ensheathing individual axons (holoprosencephaly), or acting as a barrier to axonal passage in the U-fiber layer. If keratan is diminished, glutamate receptors on the neuronal soma enable ectopic axosomatic excitatory synapses to form; (4) dysplastic, megalocytic neurons and balloon cells in mammalian target of rapamycin disorders; (5) satellitosis of glial cells displacing axosomatic synapses; (6) peri-neuronal inflammation (tuberous sclerosis) and heat-shock proteins.

CONCLUSIONS

Synaptic ratio of excitatory/inhibitory afferents is a major fundamental basis of epileptogenesis at the neuronal level. Neuropathology can demonstrate subcellular changes that help explain either epilepsy or lack of seizures in immature brains. Synaptic ratios in malformations influence postnatal epileptogenesis. Single neurons can be hypermetabolic and potentially epileptogenic.

Case Report: Late-Onset Temporal Lobe Epilepsy Following Subarachnoid Hemorrhage: An Interplay Between Pre-existing Cortical Development Abnormality and Tissue Damage

Epileptogenicity following brain insult depends on various factors including severity of the resulting lesion and extent of brain damage. We report a 54-year-old female patient who developed medically refractory epilepsy resulting from the interplay of pre-existing and post-insult pathologies. She presented with subarachnoid hemorrhage (SAH) due to a ruptured aneurysm and underwent clipping surgery. Seizures started 3 months post-operatively. MRI revealed cerebral ischemia and hemosiderin deposits in the left temporal lobes, and left hippocampal atrophy was suspected. As anti-seizure medications and vagus nerve stimulation failed to control her seizures, she underwent left temporal lobe resection and placement of a ventriculoperitoneal shunt for the post-operative complication of hydrocephalus. She remains seizure-free to date. Neuropathology revealed a previously undiagnosed focal cortical dysplasia (FCD) type 1a. Brain insult likely had a second hit effect in the late onset of epilepsy in this patient with pre-existing mild MCD, in whom secondary epilepsy can be attributed to the interplay of multiple underlying pathologies.