Pathophysiology
Clinical meaning
Seizures result from abnormal, excessive, hypersynchronous neuronal electrical activity in the cerebral cortex. Under normal conditions, excitatory (glutamate) and inhibitory (GABA) neurotransmission are balanced. Seizures occur when this balance shifts toward excitation. Epilepsy is defined as ≥2 unprovoked seizures >24 hours apart, or one unprovoked seizure with high recurrence risk (>60%), or an epilepsy syndrome diagnosis. The 2017 ILAE classification divides seizures into: focal onset (aware or impaired awareness), generalized onset (tonic-clonic, absence, myoclonic, atonic), and unknown onset. Status epilepticus is continuous seizure ≥5 minutes or ≥2 seizures without return to baseline — a medical emergency causing excitotoxic neuronal death. First-line treatment is IV benzodiazepine (lorazepam 0.1 mg/kg or midazolam 10 mg IM), followed by second-line ASM (fosphenytoin, levetiracetam, or valproate) if seizures persist.