A partial seizure is a seizure that starts in one specific area on one side of the brain, rather than affecting the whole brain at once. The medical term has changed: doctors now call these “focal seizures,” though “partial seizure” is still widely recognized. They are the most common seizure type in adults with epilepsy, and they can look dramatically different from person to person depending on which part of the brain is involved.
Why the Name Changed
The International League Against Epilepsy updated its classification system, replacing “partial seizure” with “focal seizure” to more accurately describe what’s happening: electrical activity that begins at a specific focal point in the brain. The old terms “simple partial” and “complex partial” were also retired. What was once called a simple partial seizure is now a “focal aware seizure,” and a complex partial seizure is now a “focal impaired awareness seizure.” You’ll still see “partial seizure” used in older medical records and everyday conversation, but the meaning is the same.
The Two Main Types
Focal Aware Seizures
During a focal aware seizure, you remain fully conscious. You can often talk through it and remember everything afterward. These seizures may cause a strong sense of déjà vu, a rising feeling in the stomach, unusual sensations like tingling or heat, brief hallucinations, or small repetitive movements in one part of the body. Some people experience a sudden wave of emotion, like fear or joy, that comes out of nowhere. These episodes are sometimes called “auras,” and they can last just a few seconds. Because the person stays alert, bystanders may not even realize a seizure is happening.
Focal Impaired Awareness Seizures
These seizures do cause a loss of awareness. The person appears confused or dazed and typically cannot respond to questions or follow directions for several minutes. Repetitive, automatic behaviors are common: lip smacking, picking at clothing, fumbling with objects, or staring blankly. The person usually has little or no memory of the episode afterward. These seizures can look subtle enough to be mistaken for daydreaming or intoxication, which sometimes delays diagnosis.
How Symptoms Depend on Brain Location
Because focal seizures start in one area, the symptoms you experience map closely to whatever that brain region normally controls. This is one of the most distinctive features of focal seizures compared to generalized seizures, which affect the whole brain and tend to look more uniform.
Temporal lobe seizures are the most common type in adults. They often produce a peculiar smell (like burning rubber), strong emotions such as fear, chest or abdominal discomfort, staring, and automatic movements. Many people describe an intense feeling that they’ve lived through the moment before.
Frontal lobe seizures tend to be very brief, often less than 30 seconds, and frequently happen at night. They can involve sudden, dramatic movements and may spread quickly to other parts of the brain. Parietal lobe seizures cause sensory disturbances: numbness, tingling, heat, dizziness, or a feeling that part of the body is a different size or shape than it actually is. Occipital lobe seizures, originating at the back of the brain, produce visual symptoms like flashing lights or colorful patterns on one side of the visual field.
What Causes Focal Seizures
Focal seizures have a wide range of causes, and in roughly one-third of cases, no clear cause is ever identified, often because current imaging technology simply isn’t sensitive enough to detect subtle abnormalities.
In cases where a cause is found, the most common categories are structural, genetic, and infectious. Structural causes include brain injuries from trauma, stroke, or oxygen deprivation, as well as brain tumors, blood vessel malformations, and abnormalities in how the brain’s outer layer developed before birth. In children, developmental malformations of the brain’s cortex are a particularly common structural cause. In older adults, cerebrovascular disease (damage to blood vessels in the brain, often from stroke) is the leading cause.
Genetic factors play a role in some focal epilepsies. Several inherited syndromes involve focal seizures, including some forms of frontal lobe epilepsy that run in families. These genetic causes often involve disruptions to how brain cells communicate through electrical channels or how they grow and organize. Infections of the central nervous system, including bacterial meningitis, viral encephalitis, and parasitic infections like neurocysticercosis, represent the most common cause of focal epilepsy worldwide. Less frequently, metabolic disorders or autoimmune inflammation of the brain can trigger focal seizures.
How Focal Seizures Are Diagnosed
The primary diagnostic tool is an EEG, which records electrical activity across the brain. In someone with focal epilepsy, the EEG typically shows sharp waves or abnormal slowing confined to one region, both during and between seizures. This localized pattern is what distinguishes focal epilepsy from generalized epilepsy on a brain recording.
Brain imaging, usually an MRI, is used to look for a structural cause. Scans may reveal scarring in the hippocampus (a structure deep in the temporal lobe), cortical malformations, tumors, vascular abnormalities, or evidence of past injury. However, a normal MRI does not rule out focal epilepsy. People with genetic causes or very small structural changes can have completely normal-looking scans.
Treatment Options
Anti-seizure medications are the first-line treatment. For focal seizures in both adults and children, international guidelines recommend starting with either lamotrigine or levetiracetam as a single daily medication. If neither of those is available or effective, carbamazepine is the next option. The approach is to try one medication at a time: if the first doesn’t control seizures adequately, a different first-line option is tried before moving to second-line medications like lacosamide.
About two-thirds of people with focal epilepsy achieve good seizure control with medication. For those who don’t respond to two or more medications (a condition called drug-resistant epilepsy), surgery may be an option, particularly when imaging and EEG data can pinpoint a single seizure focus that can be safely removed. Temporal lobe surgery has the strongest track record, with many patients becoming seizure-free. Other options for drug-resistant cases include nerve stimulation devices and specialized diets.
Focal Seizures That Spread
One important thing to understand is that focal seizures can spread. A seizure that begins in one small area of the brain can recruit surrounding tissue and eventually involve the entire brain, evolving into a full convulsive (tonic-clonic) seizure with loss of consciousness, stiffening, and rhythmic jerking. This is called a “focal to bilateral tonic-clonic seizure.” The initial focal symptoms, if noticed, serve as a warning that a larger seizure is coming. Recognizing that warning can give you or someone nearby a few seconds to get to a safe position.
Most focal seizures last under two minutes. A seizure that continues beyond five minutes, or multiple seizures occurring without recovery in between, is considered a medical emergency called status epilepticus and requires immediate treatment.