Focal onset seizures are seizures that start in one specific area of the brain, on one side, rather than involving the whole brain at once. They are the most common seizure type, accounting for roughly 55% of all epilepsy cases. What a focal seizure looks and feels like depends entirely on where in the brain it begins, and whether or not awareness is affected during the episode.
How Focal Seizures Are Classified
The current classification system splits focal onset seizures into two main groups based on awareness. A “focal aware” seizure means you remain conscious and aware of what’s happening throughout the episode, even if you can’t control your movements or sensations. A “focal impaired awareness” seizure means that at some point during the event, your awareness is disrupted. You may appear confused, seem “out of it,” or have no memory of the seizure afterward.
Beyond awareness, focal seizures are further described by what happens during them. Motor onset seizures involve some kind of physical movement: jerking, stiffening, repeated automatic behaviors like lip-smacking or hand-picking, or sudden loss of muscle tone. Nonmotor onset seizures produce changes you might not see from the outside: unusual sensory experiences, sudden emotions, altered thinking, or changes in heart rate and other automatic body functions.
A seizure is classified by its first sign, not its most dramatic feature. So if a seizure begins with a strange taste in your mouth and then progresses to arm jerking, it’s still categorized based on that initial sensory symptom.
What Focal Aware Seizures Feel Like
Because you stay fully conscious during a focal aware seizure, the experience can be strange and disorienting even though you know exactly what’s happening. Common sensations include a sudden wave of déjà vu, an odd feeling rising in your stomach, a metallic taste, or a flash of unexplained fear or joy. Some people see flashing lights, smell something that isn’t there, or feel tingling in one part of the body.
These episodes are often brief, lasting seconds to under two minutes. They were previously called “simple partial seizures” or, more informally, “auras.” That last term is still used by many people with epilepsy to describe the warning signal they feel before a larger seizure, because a focal aware seizure can sometimes be the opening phase of a bigger event.
What Focal Impaired Awareness Seizures Look Like
These seizures are often more noticeable to the people around you than to you yourself. During an episode, you may stare blankly, appear confused or dazed, and perform repetitive automatic movements called automatisms. Lip-smacking, chewing motions, picking at clothing, fumbling with objects, or aimless walking are all typical. You generally can’t respond to questions or follow directions during the seizure, and you likely won’t remember it afterward.
These episodes usually last one to three minutes. The period immediately after, called the postictal phase, can involve additional minutes of confusion, fatigue, or difficulty speaking before you return to normal. Previously, these were known as “complex partial seizures.”
When a Focal Seizure Spreads
A focal seizure can sometimes escalate. The abnormal electrical activity that started on one side of the brain crosses to the other hemisphere and triggers a full-body convulsive seizure with stiffening and rhythmic jerking. The modern term for this is a “focal to bilateral tonic-clonic seizure.” It used to be called a secondarily generalized seizure.
This progression is one reason focal seizures are taken seriously even when they seem mild. A brief aura or a few seconds of confusion may, on another occasion, evolve into a convulsion. Preventing that spread is a key goal of treatment.
How Symptoms Vary by Brain Location
The specific symptoms of a focal seizure are a direct reflection of what that part of the brain normally does. Seizures originating in areas that process vision may produce flashing lights or visual distortions. Those starting in regions that control movement may cause jerking or stiffening on the opposite side of the body. Seizures in areas involved in memory and emotion, particularly the temporal lobe, often produce déjà vu, a rising stomach sensation, sudden fear, or automatisms like lip-smacking.
The temporal lobe is the single most common origin point for focal seizures in adults. Frontal lobe seizures tend to be shorter, may occur in clusters, and can produce unusual thrashing or cycling movements, especially during sleep. Seizures from the parietal lobe often cause tingling or numbness, while occipital lobe seizures typically involve visual symptoms.
How Focal Seizures Are Diagnosed
An EEG (electroencephalogram) is the primary tool for confirming focal seizures. Between seizures, the EEG may pick up localized spike or sharp-wave discharges in one area of the brain, pinpointing the irritable zone where seizures originate. The most common pattern seen in adults with focal epilepsy is a spike discharge in the front part of the temporal lobe.
Sometimes the EEG between seizures looks normal, and a recording during an actual seizure is needed to confirm the diagnosis. Brain imaging, typically an MRI, is also used to look for structural causes like scar tissue, tumors, blood vessel abnormalities, or areas of abnormal brain development that could be triggering the seizures. A detailed description of what happens during the seizure, ideally captured on video, is often just as valuable as any test.
Treatment for Focal Seizures
Anti-seizure medications are the first step. The World Health Organization recommends lamotrigine or levetiracetam as first-line options for focal onset seizures in both children and adults, with strong evidence supporting their use. If neither is available or effective, carbamazepine is the next choice. Lacosamide is recommended as a second-line option when first-line medications don’t work well enough.
Many people achieve good seizure control with a single medication. Finding the right one, and the right dose, can take time because side effects like drowsiness, dizziness, or mood changes vary from person to person. If two or more medications fail to control seizures, the epilepsy is considered drug-resistant, which affects roughly a third of people with focal epilepsy.
For drug-resistant cases, epilepsy surgery can be highly effective when a clear seizure focus is identified. The surgeon removes or disconnects the small area of brain tissue where seizures start. Vagus nerve stimulation (VNS) is another option: a small device implanted under the skin sends regular electrical pulses to the brain through a nerve in the neck. In studies of adults with focal epilepsy, about 37% had their seizure frequency cut in half after one year, improving to around 43% by the second year. The benefits tend to grow gradually over time, with effectiveness continuing to increase for up to five years.
What to Do if Someone Has a Focal Seizure
If someone near you is having a focal impaired awareness seizure, the most important thing is to stay calm and stay with them. Gently guide them away from anything that could cause injury, like traffic, stairs, or sharp objects. Don’t restrain them or put anything in their mouth. If they’re lying down, turn them gently on their side with the mouth pointing toward the ground to keep the airway clear.
Time the seizure. If it lasts longer than five minutes, call 911. You should also call for help if a second seizure follows closely after the first, if the person has trouble breathing or waking afterward, if they’re injured, or if it’s their first seizure. Once the episode ends, help them sit somewhere safe. They may be disoriented and need several minutes to fully recover. Calmly explain what happened and offer to help them get home.