Tonic seizures cause a stiffening of muscles while clonic seizures are characterized by jerking or twitching

Demographics

• Incidence increases with advanced age

• People older than 75 years are twice as likely to develop new-onset epilepsy than all adult age groups younger than 65 years

• Nearly 80% of people with epilepsy live in low- and middle-income countries

• Triggers

Pathophysiology

• A seizure can be conceptualized as occurring when there is distortion of the normal balance between excitation (E) and inhibition (I) in the brain
• The factors that alter E/I balance can be genetic or acquired
• Genetic pathologies leading to epilepsy can occur anywhere from the circuit level (e.g., abnormal synaptic connectivity in cortical dysplasia) to the receptor level (e.g., abnormal γ-aminobutyric acid [GABA] receptor subunits in Angelman syndrome) to abnormal ionic channel function (e.g., potassium channel mutations in benign familial neonatal epilepsy [BFNE])
• Acquired cerebral insults can alter circuit function (e.g., structural alteration of hippocampal circuitry following prolonged febrile seizures or head trauma)

Risk factors

• First-degree relatives of patients with idiopathic epilepsy
• Head trauma
• Stroke
• Degenerative changes in the brain (eg, Alzheimer disease)
• Central nervous system infection (eg, neurocysticercosis; responsible for 10% of epilepsy in endemic areas)
• History of neurologic deficit from birth (eg, cerebral palsy)