Partial seizures are seizures that start in one specific area of the brain rather than across the entire brain at once. They’re now officially called focal seizures, though the older term “partial” is still widely used by patients and doctors alike. About 60% of all people with epilepsy have this type, making it the most common form. Focal seizures vary enormously in how they look and feel, depending on which part of the brain is involved.
Why the Name Changed
In 2017, the International League Against Epilepsy updated its classification system and replaced “partial seizure” with “focal seizure.” The word “focal” more accurately describes what’s happening: abnormal electrical activity firing from a specific focus point in the brain. Under the old system, partial seizures were split into “simple partial” (you stay aware) and “complex partial” (awareness is affected). The new system uses clearer labels: focal aware seizures and focal impaired awareness seizures. If you see either set of terms in medical records or online, they refer to the same thing.
Focal Aware Seizures
During a focal aware seizure, you remain fully conscious, alert, and able to remember everything that happens. These seizures are typically brief, lasting less than two minutes. What you experience depends entirely on where in the brain the electrical surge occurs. If it hits a motor area, one arm or one side of your face might twitch or shake involuntarily. If it hits a sensory area, you might feel tingling, see flashing lights, or notice a strange smell or taste that isn’t there.
Some people experience a sudden wave of nausea, a rush of fear or déjà vu, or a rising sensation in the stomach. These episodes can be subtle enough that others around you won’t notice anything unusual. Many people initially mistake them for anxiety attacks, migraines, or just “weird moments” before getting a diagnosis. Because you stay aware throughout, you can describe the experience in detail afterward, which is actually very useful for pinpointing where in the brain the seizure originates.
Focal Impaired Awareness Seizures
These seizures alter or reduce your consciousness. You may appear awake but seem confused, disconnected, or “zoned out.” Most last between 30 seconds and two minutes, though some can stretch to 10 minutes. The hallmark of these seizures is automatisms: repetitive, purposeless movements your body performs without your conscious direction. Between 40% and 80% of people with temporal lobe epilepsy experience them.
The most common automatisms are lip-smacking, chewing, swallowing, or fumbling with clothing or nearby objects. Some people wander aimlessly, make vocal sounds, or display emotional expressions like crying. Less commonly, seizures originating in the frontal lobe can produce more dramatic movements like pedaling motions of the legs or complex body movements that can look bizarre to bystanders. After the seizure ends, most people feel confused or disoriented for several minutes and have little or no memory of what happened.
An aura, which is itself a brief focal aware seizure, often precedes the loss of awareness by a few seconds to one or two minutes. Recognizing your aura pattern can serve as a warning signal to get to a safe place before awareness fades.
How Symptoms Vary by Brain Region
The brain is organized by function, so the location of abnormal electrical activity determines what a person feels or does during a seizure. Temporal lobe seizures, the most common type, tend to produce emotional symptoms (sudden fear, a sense of familiarity), stomach sensations, and oral automatisms like lip-smacking. Frontal lobe seizures often involve more vigorous body movements, vocalizations, and unusual behaviors, and they tend to be shorter and happen more often at night.
Seizures starting in the occipital lobe (the visual processing area at the back of the head) commonly cause flashing lights, colors, or visual distortions. Those originating in the parietal lobe may produce tingling, numbness, or a distorted sense of body position. Because the symptoms map so closely to brain anatomy, the specific pattern of what someone experiences during a seizure helps doctors locate the source.
When a Focal Seizure Spreads
Sometimes a focal seizure doesn’t stay contained. The abnormal electrical activity can spread from its starting point across both sides of the brain, triggering a full convulsive episode with body stiffening and rhythmic jerking. This is called a focal to bilateral tonic-clonic seizure (previously known as a secondarily generalized seizure).
The spread happens through a relay system. The electrical discharge crosses the corpus callosum, the bridge connecting the brain’s two hemispheres, and reaches motor areas on both sides. From there, the activity loops through the thalamus and other deep brain structures, overwhelming the brain’s normal ability to contain it. The tonic-clonic phase that follows looks identical to a generalized seizure, which is why it can be misdiagnosed as one if nobody witnesses the focal onset that preceded it. Identifying that a convulsive seizure actually started focally matters because it points to a specific treatable source in the brain.
Causes and Risk Factors
Focal epilepsy has traditionally been viewed as something caused by a specific brain injury: a stroke, head trauma, brain tumor, or infection that damages tissue in one area. Scar tissue, abnormal blood vessel formations, and structural brain abnormalities present from birth (like focal cortical dysplasia, where a patch of brain tissue didn’t develop normally) are all well-established causes.
Genetics play a larger role than previously appreciated. Research has identified families where temporal lobe epilepsy runs across generations, sometimes linked to a history of childhood febrile seizures and changes in the hippocampus. Somatic mutations, genetic changes that occur during brain development rather than being inherited, can cause structural abnormalities that become seizure sources. In many cases, though, no single cause is identified, and the epilepsy likely results from a combination of genetic susceptibility and environmental factors.
How Focal Seizures Are Diagnosed
Diagnosis relies on two main tools: an EEG (electroencephalogram), which records the brain’s electrical activity, and an MRI of the brain. On an EEG, focal seizures show up as spike or sharp-wave discharges concentrated in one region, such as the left temporal area. A routine EEG may catch these abnormal patterns even between seizures, though sometimes longer monitoring over days is needed.
MRI looks for structural problems that could be generating the seizures. The scan might reveal hippocampal sclerosis (shrinkage and scarring of the hippocampus, a key memory structure), areas of abnormal brain development, evidence of old head injuries, low-grade tumors, or blood vessel malformations. Each of these has a distinct appearance on imaging. In some people, the MRI looks completely normal, which doesn’t rule out focal epilepsy but does make locating the source more challenging.
Treatment Options
Anti-seizure medications are the first line of treatment. Several drugs have proven effective for focal epilepsy with similar seizure control rates but varying side effect profiles. Your doctor will typically choose based on your age, other medications, and how well you tolerate specific side effects like drowsiness, mood changes, or weight fluctuation. Most people start on a single medication, and about half achieve good seizure control that way.
For the substantial number of people whose seizures aren’t fully controlled by medication, surgery can be highly effective if imaging and monitoring pinpoint a clear seizure focus. The goal is to remove or disconnect the small area of brain tissue generating the seizures. Other options include nerve stimulation devices and specialized diets, particularly for people who aren’t surgical candidates. Focal epilepsy that stems from a visible structural abnormality on MRI tends to respond better to surgery than cases where no lesion is found.
What to Do if You Witness One
Focal aware seizures rarely require intervention from bystanders since the person remains conscious, though checking in with them afterward is helpful. Focal impaired awareness seizures need a different approach because the person may wander, fumble with objects, or be unable to respond to you.
- Stay calm and stay with the person until the seizure passes and they’re fully alert again.
- Move hazards away rather than trying to restrain the person or force them to sit down.
- Guide them gently away from danger like traffic or stairs if they’re walking during the seizure.
- Time the seizure. If it lasts more than five minutes, call emergency services.
- If the person falls or has convulsions, turn them gently on their side with their mouth pointing toward the ground to keep the airway clear.
- After the seizure, help them sit somewhere safe, explain calmly what happened, and offer to help them get home.
Never put anything in someone’s mouth during a seizure. Check for a medical alert bracelet, which may list their condition, medications, and emergency contacts.