Epilepsy

Introduction

Epilepsy is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Epilepsy is a chronic neurological disorder characterized by an enduring predisposition to generate epileptic seizures — sudden, abnormal electrical discharges in the brain that cause changes in awareness, behavior, sensation, or movement. Defined by the occurrence of at least two unprovoked seizures more than 24 hours apart, epilepsy affects approximately 52 million people worldwide, with a global prevalence of ~658 per 100,000 population (GBD Epilepsy Collaborators, 2024). Approximately 5 million new diagnoses occur annually, with incidence reaching 139 per 100,000/year in low- and middle-income countries. Premature death risk is up to 3 times higher in people with epilepsy compared to the general population (WHO, 2024). ^{1Nature Reviews Neurology - Epilepsy (2024)2024Open reference}

Epilepsy is increasingly recognized as deeply intertwined with neurodegeneration. People with late-onset epilepsy have a 2- to 3-fold higher risk of developing dementia, while Alzheimer’s disease patients show subclinical epileptiform activity in up to 31% of cases (Vossel et al., 2024). Shared mechanisms including excitotoxicity, tau] hyperphosphorylation, neuroinflammation, blood-brain barrier disruption, and mTOR pathway dysregulation link epilepsy to neurodegenerative diseases at the molecular level. ^{2Epilepsia - Seizure Classification (2024)2024Open reference}

Classification

The International League Against Epilepsy (ILAE) classifies epilepsy at three levels: seizure type, epilepsy type, and epilepsy syndrome. The 2025 updated classification identifies four main seizure classes — Focal, Generalized, Unknown, and Unclassified — comprising 21 seizure types (Beniczky et al., 2025). Epilepsy types include focal epilepsy, generalized epilepsy, combined generalized and focal epilepsy, and unknown epilepsy. ^{3CitationPMID 39254353Open reference}

Relationship to Neurodegeneration

Bidirectional Link with Dementia

Strong evidence supports a bidirectional relationship between epilepsy and neurodegeneration: ^{4CitationPMID 27497924Open reference}

• Late-onset epilepsy (LOE) is associated with increased risk of all-cause dementia (adjusted relative risk: 1.34; 95% CI: 1.13–1.59) and Alzheimer’s disease specifically (aRR: 2.49; 95% CI: 1.16–5.32)

• Early-onset AD carries the highest risk of 5-year epilepsy (pooled hazard ratio: 4.06; 95% CI: 3.25–5.08)

• Prevalence of dementia in epilepsy patients reaches 17%

• amyloid-beta demonstrates epileptogenic potential even in early stages of the amyloid cascade, inducing neuronal hyperexcitability

• Subclinical epileptiform activity (SEA) prevalence: 50% in dementia, 27% in MCI, 25% in preclinical AD; patients with SEA show accelerated cognitive decline (Vossel et al., 2024; Epilepsy & Behavior, 2024)

Post-Stroke Epilepsy and Vascular Dementia

• Cumulative risk of post-stroke epilepsy: 7.4–8.7% within 2–5 years after ischemic stroke; 11.8–15.4% after intracerebral hemorrhage

• Stroke elevates epilepsy risk by 11.5 times within the initial 5 years post-event

• Post-stroke seizures significantly increase the risk of subsequent Vascular Dementia

• Subclinical vascular and degenerative lesions lower seizure thresholds; pre-existing white matter changes and microbleeds predispose to both seizures and new-onset dementia (Sung et al., 2024)

Temporal Lobe Epilepsy and Hippocampal Sclerosis

Temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) is the most common drug-resistant focal epilepsy, with hallmark pathology including: ^{5PMC5042290Open reference}

• Neuronal cell loss (especially in hippocampal CA1), reactive astrogliosis, mossy fiber sprouting, and granule cell dispersion

• 94% of TLE patients undergoing temporal lobectomy showed hyperphosphorylated tau] in the form of neuropil threads and neurofibrillary tangles (Tai et al., 2016)

• Strong correlation between tau] pathology burden and postoperative cognitive decline

• Abnormal neurogenesis: increased dentate gyrus neurogenesis in early phases but substantial decline in the chronic phase

Autoimmune Epilepsy

Autoimmune encephalitis-related epilepsies involve autoantibodies against surface neuronal proteins: ^{6CitationPMID 40197800Open reference}

| Antibody Target | Mechanism | Clinical Features | ^{7Epilepsia - Epilepsy Treatment (2024)2024Open reference} |---|---|---| ^{8PMC10771847Open reference} | Anti-NMDAR | IgG binds NR1 subunit → receptor internalization, reduced Ca²⁺ influx | Most common autoimmune encephalitis; psychiatric symptoms, seizures | ^{9PMC10275542Open reference} | Anti-LGI1 | Disrupts trans-synaptic complex regulating transmission | Faciobrachial dystonic seizures, limbic encephalitis | ^{10ScienceDirect - Epilepsy Treatment (2024)2024Open reference} | Anti-CASPR2 | Blocks contactin-2 interaction → hyperexcitability | Neuromyotonia, Morvan syndrome | ^{2Epilepsia - Seizure Classification (2024)2024Open reference}0 | Anti-GABAₐR | Impairs GABAergic inhibition | Seizures, status epilepticus, limbic encephalitis |

Seizure freedom is achieved faster and more frequently with immunotherapy than antiseizure medications alone in autoimmune epilepsies (Irani et al., 2016).

Molecular Mechanisms

Excitotoxicity and Glutamate Dysfunction

Seizures induce elevations in extracellular glutamate, contributing to excitotoxic neuronal damage through excessive Ca²⁺ influx via extrasynaptic GluN2B-containing NMDA receptor receptors]. During status epilepticus, GABA receptors are internalized while NMDA receptor receptors migrate to synapses, reducing inhibition and enhancing excitability. Downregulation of glutamate transporter EAAT2 (GLT-1) reduces glutamate clearance, sustaining excitotoxic damage (PMC, 2023).

GABAergic Interneuron Loss

Loss of GABAergic interneurons — particularly parvalbumin-positive (PV+ and somatostatin-positive subtypes — is a hallmark of epileptic foci. In hippocampal sclerosis, selective loss of inhibitory interneurons disinhibits pyramidal neurons, creating hyperexcitable circuits. Pro-inflammatory cytokines from activated [microglia.

neuroinflammation

Activated [microglia.

mTOR Pathway Dysregulation

Tuberous Sclerosis Complex (TSC), caused by mutations in TSC1 (hamartin) or TSC2 (tuberin), is the prototypic monogenic mTOR pathway disorder. mTOR hyperactivation affects protein synthesis, cell growth, synaptic plasticity, and neuronal excitability. DEPDC5 mutations (also in the mTOR pathway) are now recognized as a major cause of focal cortical dysplasia type II and familial focal epilepsy. Everolimus (an mTOR inhibitor) is approved for TSC-associated subependymal giant cell astrocytomas and effectively reduces seizures (PMC, 2023).

Tau Hyperphosphorylation

Network hyperexcitability in epilepsy activates tau] kinases (especially GSK-3β and the mTOR pathway, leading to abnormal tau] phosphorylation. Hyperphosphorylated tau loses its microtubule-stabilizing function, leading to axonal transport collapse, synaptic dysfunction, and neuronal death — mirroring Alzheimer’s disease pathology. Reducing tauopathy alleviates both epileptic seizures and spatial memory impairment in animal models (Frontiers in Aging Neuroscience, 2022).

Genetics

Over 1,800 mutations in SCN1A alone have been identified, with ~90% arising de novo (GeneReviews; IJMS, 2023).

Biomarkers

Fluid Biomarkers:

• Neurofilament light chain (NfL)): Elevated in plasma/CSF of epilepsy patients vs. non-epileptic disorders

• GFAP: Elevated plasma levels indicate astrocytic injury/reactivity

• Phosphorylated tau] (p-tau: Diagnostic potential for TLE; correlates with hippocampal sclerosis severity

• amyloid-beta: Mid-life Aβ levels emerge as risk factor for late-onset epilepsy

(Farhan et al., 2025; Epilepsy & Behavior, 2025)

Neuroimaging:

• MRI: Standard for detecting hippocampal sclerosis, focal cortical dysplasia, and tumors

• FDG-PET: Interictal hypometabolism localizes epileptic foci

• Advanced MRI: Diffusion tensor imaging for white matter integrity; MR spectroscopy for metabolite abnormalities

BCI Technologies

• Epilepsy BCI — Seizure prediction and responsive neurostimulation

Treatment

Antiseizure Medications (ASMs)

First-generation: Phenytoin, carbamazepine, valproate, phenobarbital, ethosuximide.

Second-generation: Lamotrigine, levetiracetam, topiramate, oxcarbazepine, gabapentin, pregabalin, zonisamide, lacosamide.

Recently approved ASMs:

• Cenobamate (FDA 2019): For focal seizures; dual mechanism (persistent sodium current inhibition + GABA enhancement); achieved 21% seizure freedom in RCTs

• Fenfluramine (FDA 2020): For Dravet syndrome; serotonin release and 5-HT receptor agonism

• Ganaxolone (FDA 2022): For CDKL5 deficiency disorder; neuroactive steroid GABA_A modulator

(Epilepsia Drug Pipeline, 2024)

Surgical Approaches

• Resective surgery: Anterior temporal lobectomy (gold standard for drug-resistant TLE-HS)

• Laser interstitial thermal therapy (LITT): Minimally invasive stereotactic ablation

• Corpus callosotomy: For drop attacks in generalized epilepsy

• Hemispherectomy: For catastrophic hemisphere-limited epilepsy in children

Neurostimulation

• Vagus Nerve Stimulation (VNS): Modulates thalamocortical circuits; ~50% seizure reduction

• Responsive Neurostimulation (RNS): Real-time seizure detection and targeted stimulation; 77% of patients had seizures cut in half by year 2

• Deep Brain Stimulation (DBS): Anterior thalamic nucleus for focal epilepsy; centromedian nucleus for generalized epilepsy

Emerging Therapies

• Gene therapy: Gene replacement/modulation for monogenic epilepsies (SCN1A, CDKL5, STXBP1); antisense oligonucleotides in development

• mTOR inhibitors: Everolimus for TSC-related epilepsy

• Immunotherapy: For autoimmune-related epilepsies (rituximab, IVIG, plasma exchange)

• Levetiracetam for AD-related epilepsy: May slow cognitive decline in AD patients with subclinical epileptiform activity

Pathway & Interaction Diagram

Interactive diagram showing EPILEPSY key relationships in the SciDEX knowledge graph (15 connections shown).

flowchart TD
    EPILEPSY(["EPILEPSY"])
    Epilepsy["Epilepsy"]
    Als["Als"]
    Inflammation["Inflammation"]
    Neurodegeneration["Neurodegeneration"]
    ALZHEIMER_S_DISEASE(["ALZHEIMER'S DISEASE"])
    ALZHEIMER(["ALZHEIMER"])
    Mtor["Mtor"]
    MTOR(["MTOR"])
    Alzheimer["Alzheimer"]
    Parkinson["Parkinson"]
    Neuroinflammation["Neuroinflammation"]

    EPILEPSY -->|"associated with"| Epilepsy
    EPILEPSY -->|"therapeutic target"| Als
    EPILEPSY -->|"therapeutic target"| Epilepsy
    EPILEPSY -->|"activates"| Inflammation
    EPILEPSY -->|"activates"| Als
    EPILEPSY -->|"activates"| Neurodegeneration
    EPILEPSY -->|"associated with"| ALZHEIMER_S_DISEASE
    EPILEPSY -->|"associated with"| ALZHEIMER
    EPILEPSY -->|"therapeutic target"| Mtor
    EPILEPSY -->|"therapeutic target"| MTOR
    ALZHEIMER_S_DISEASE -->|"associated with"| EPILEPSY
    EPILEPSY -->|"associated with"| Alzheimer
    EPILEPSY -->|"causes"| Epilepsy
    EPILEPSY -->|"associated with"| Parkinson
    EPILEPSY -->|"activates"| Neuroinflammation

    style EPILEPSY fill:#006494,stroke:#4fc3f7,stroke-width:3px,color:#e0e0e0

See Also

• Alzheimer’s disease — Bidirectional relationship with epileptiform activity

• excitotoxicity — Core mechanism of seizure-induced neuronal damage

• Autoimmune Encephalitis — Autoimmune epilepsy subtypes

• hippocampus — Primary region affected in temporal lobe epilepsy

• neuroinflammation — Shared inflammatory cascade in epilepsy and neurodegeneration

• tau protein] — Hyperphosphorylated tau pathology in chronic epilepsy

• blood-brain barrier — BBB disruption as driver of epileptogenesis

• Cell Types/GABRA2 Neurons

Background

The study of Epilepsy has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

Recent Research (2024-2026)

Recent advances in Epilepsy have focused on understanding disease mechanisms, identifying biomarkers, and developing novel therapeutic approaches. Key developments include:

• Genetic studies: Identification of new genetic risk factors and mechanistic insights

• Biomarker research: Development of diagnostic and prognostic biomarkers

• Therapeutic approaches: Investigation of novel treatment strategies

• Clinical trials: Ongoing Phase I-III trials for new therapies

Allen Brain Atlas Resources

• Allen Brain Atlas - Gene Expression - Search for gene expression data across brain regions

• Allen Brain Atlas - Cell Types - Explore neuronal cell type taxonomy

• Allen Brain Atlas - Aging, Dementia & TBI - Data on aging and traumatic brain injury

• BrainSpan Atlas of the Developing Human Brain - Developmental gene expression data

External Links

• OMIM

• GeneReviews

• PubMed

• Epilepsy Foundation

• ILAE - International League Against Epilepsy

• NINDS Epilepsy Information