epilepsy

Epilepsy is a long-term brain condition in which a person has seizures again and again. A seizure is a sudden burst of disorderly electrical activity in the brain — picture a stadium crowd that normally cheers in scattered, independent voices, but for a few seconds everyone shouts the exact same word at the exact same instant. That runaway synchrony is what a seizure looks like inside the brain: large groups of neurons firing together, too strongly and too much in step. Having a single seizure does not mean someone has epilepsy; the diagnosis is about the brain's lasting tendency to produce them repeatedly.

Normally the brain keeps a careful balance between signals that excite neurons (telling them to fire) and signals that calm them down (telling them to stay quiet). In epilepsy that balance tips toward over-excitement in some region, so a small flicker of activity can snowball and recruit its neighbors instead of fizzling out. What a seizure feels like depends on which part of the brain is swept up: it might be a brief blank stare, a strange smell or rising feeling, jerking of one limb, or the whole body stiffening and shaking with loss of consciousness. The causes are varied — genetics, a past head injury, a stroke, a brain infection, or an unknown reason — and many people gain good control with medicines that dampen the brain's excitability, while others are helped by special diets, devices, or surgery.