Epilepsy is a chronic brain condition in which clusters of nerve cells fire abnormally, causing repeated, unprovoked seizures. More than 50 million people worldwide live with it, making it one of the most common neurological disorders on the planet. A single seizure doesn’t mean you have epilepsy. The diagnosis typically requires at least two unprovoked seizures occurring more than 24 hours apart, or one seizure combined with a high risk of more.
What Happens in the Brain During a Seizure
Your brain cells communicate through a careful balance of excitatory signals (which activate neurons) and inhibitory signals (which quiet them down). In epilepsy, that balance tips toward excitation. Groups of neurons begin firing together in sudden, synchronized bursts that overwhelm the brain’s normal activity.
Several things drive this runaway excitation. One key factor is a buildup of potassium outside the neurons. Normally, the brain clears excess potassium quickly, but during hyperactive firing, the cleanup system can’t keep up. The rising potassium concentration makes neurons even more excitable, creating a feedback loop. At the same time, the brain’s main calming signal, triggered by a chemical called GABA, starts to weaken. As inhibitory cells fire at high frequencies during a seizure, the chemical balance inside cells shifts so that the “off” signal becomes less effective or even reverses direction, further fueling the electrical storm.
Types of Seizures
Seizures fall into three broad categories based on where in the brain they start.
- Focal onset seizures begin in one specific area of the brain. You might remain fully aware during a focal seizure, experiencing unusual sensations, involuntary movements on one side of the body, or a sudden wave of fear or déjà vu. In other cases, awareness is impaired, and you may stare blankly or make repetitive movements like lip-smacking. Focal seizures can also spread to both sides of the brain, producing full-body convulsions.
- Generalized onset seizures involve both sides of the brain from the start. The most recognizable type is the tonic-clonic seizure, where the body stiffens and then jerks rhythmically. Absence seizures are another generalized form, causing brief episodes of staring or subtle blinking that can be mistaken for daydreaming, especially in children.
- Unknown onset seizures are diagnosed when the starting point in the brain can’t be determined, often because no one witnessed the beginning of the event.
Common Causes Across Age Groups
The underlying cause of epilepsy varies significantly depending on when seizures first appear. In children and younger adults under 20, the most common category is idiopathic, meaning no identifiable structural or metabolic cause can be found. Many of these cases have a genetic component, where inherited differences in ion channels or neurotransmitter receptors make the brain more seizure-prone.
In adults, the picture changes. Brain infections account for a significant share of cases, particularly in people under 40. After age 40, stroke becomes the leading cause, responsible for nearly a quarter of adult-onset seizures. Brain tumors, head trauma, and metabolic disturbances like alcohol withdrawal or severe electrolyte imbalances (low sodium, low calcium) round out the list. In elderly patients, stroke and degenerative brain conditions are the most frequent triggers.
How Epilepsy Is Diagnosed
Diagnosis starts with a detailed history of what happened before, during, and after a seizure. Eyewitness accounts are especially valuable since the person experiencing the seizure often can’t remember it clearly.
The most important test is an electroencephalogram (EEG), which records the brain’s electrical activity through sensors placed on the scalp. An EEG can reveal characteristic spike patterns that indicate where seizures originate and what type of epilepsy syndrome is present. One normal EEG doesn’t rule epilepsy out, though. Two or even three recordings may be needed to catch abnormal activity, since the brain doesn’t always produce telltale spikes on demand.
Brain imaging with MRI is used when seizures are focal, when there’s no clear benign syndrome, or when seizures don’t respond to initial treatment. MRI can identify structural problems like scarring, tumors, or areas of abnormal brain development that may be generating seizures. Blood tests help rule out metabolic causes such as low blood sugar, electrolyte problems, or infections.
Living With Epilepsy: Associated Health Challenges
Epilepsy rarely travels alone. CDC data from 2021 to 2022 show that among adults with active epilepsy, 55.8% reported difficulty with memory, 40.2% experienced chronic pain, and 38.6% had obesity. Depression and anxiety are also well-documented companions, though exact rates vary across studies. These conditions aren’t just side effects of medication. The same brain disruptions that cause seizures can independently affect mood, cognition, and pain processing.
Memory difficulty is particularly common and particularly frustrating. Repeated seizures, especially those originating in the temporal lobe (the brain’s memory center), can progressively affect the ability to form and retrieve memories. Some anti-seizure medications contribute to this as well, though newer drugs tend to have fewer cognitive side effects than older ones.
How Seizures Are Treated
Anti-seizure medications are the first line of treatment and control seizures effectively for roughly two-thirds of people with epilepsy. These drugs work through several mechanisms: some stabilize the electrical signals that travel along nerve fibers by acting on sodium or calcium channels, others boost the brain’s natural calming chemical (GABA), and still others reduce the activity of excitatory signals. Most medications work through a combination of these pathways. Finding the right one often takes trial and adjustment, since different seizure types respond to different drugs.
For the roughly one-third of people whose seizures don’t respond adequately to medication, other options exist. Surgery to remove or disconnect the brain area generating seizures is the most established alternative and can be curative when a clear seizure focus is identified. Implanted devices offer another path. Vagus nerve stimulation (VNS) sends regular electrical pulses through a nerve in the neck to reduce brain excitability, achieving at least a 50% reduction in seizure frequency for about half of patients treated. Responsive neurostimulation (RNS) takes a more targeted approach: a device implanted in the skull continuously monitors brain activity and delivers a brief electrical pulse the moment it detects the beginning of abnormal patterns, interrupting a seizure before it fully develops. Deep brain stimulation (DBS), which targets specific structures deep in the brain, is another option for people who aren’t candidates for traditional surgery.
The Ketogenic Diet
A high-fat, very low-carbohydrate diet known as the ketogenic diet has proven effective for drug-resistant epilepsy, particularly in children. In randomized controlled trials, children on the diet were up to three times more likely to become seizure-free and up to six times more likely to cut their seizure frequency by at least half, compared to medication alone. Adults see similar benefits: a meta-analysis found that 53% of adults with drug-resistant epilepsy achieved at least a 50% reduction in seizures on the diet. The diet requires careful medical supervision to maintain nutritional balance and monitor for side effects, but for people who haven’t found relief through medication, it can be a meaningful tool.
Understanding SUDEP
Sudden unexpected death in epilepsy (SUDEP) is rare but worth knowing about. For every 1,000 adults with epilepsy in the United States, roughly one dies from SUDEP per year. In children 17 and younger, the rate is even lower: about one in every 4,500 per year. The exact mechanism isn’t fully understood, but it’s believed to involve seizure-related disruptions to breathing or heart rhythm, typically during or just after a tonic-clonic seizure. The most important thing you can do to reduce this risk is to take seizure medications consistently, since uncontrolled tonic-clonic seizures are the strongest risk factor.
What to Do if Someone Has a Seizure
If you witness someone having a tonic-clonic seizure, staying calm is the most important first step. Ease the person to the ground if they’re falling, and clear away anything nearby that could injure them. Gently roll them onto their side with their mouth pointing toward the ground to keep the airway clear. Place something soft under their head, remove their glasses, and loosen anything around their neck.
Time the seizure. If it lasts longer than five minutes, call 911.
Equally important is knowing what not to do. Never hold the person down or try to restrain their movements. Don’t put anything in their mouth. Don’t attempt mouth-to-mouth breathing during the seizure, and don’t offer food or water until they’re fully alert. Once the seizure ends, stay with them, calmly explain what happened, and help them get to a safe place to rest.