Focal seizures are seizures that start in one specific area of the brain, rather than across both sides at once. They are the most common seizure type, affecting up to 61% of people with epilepsy. You may also hear them called “partial seizures,” which is an older term for the same thing. What makes focal seizures distinctive is how varied they can look: some cause visible shaking in one hand, while others produce strange sensations or emotions that only the person experiencing them can feel.
Focal Aware vs. Focal Impaired Awareness
Focal seizures fall into two main categories based on whether you remain conscious during the event. In a focal aware seizure, you stay fully alert the entire time. You know what’s happening, you can recall it afterward, and you respond normally if someone speaks to you. These were previously called “simple partial seizures.”
In a focal impaired awareness seizure (formerly “complex partial seizure”), consciousness is disrupted at some point. You might stare blankly, respond slowly or inappropriately, or have no memory of the episode afterward. The key rule in classification: if consciousness is impaired at any point during the seizure, even briefly, it’s categorized as impaired awareness. This distinction matters practically because it affects things like whether you can safely drive.
Consciousness here has two components: awareness (whether you remember the event) and responsiveness (whether you react appropriately during it). If either one is impaired, the seizure is classified as having impaired consciousness.
What Focal Seizures Feel Like
Because focal seizures originate in one part of the brain, their symptoms depend on what that part of the brain normally does. This is why focal seizures can look so different from person to person.
Many focal seizures begin with an “aura,” a brief warning period that is actually a seizure itself, just a very mild one. Auras can include vision changes, a rising sensation in the stomach, déjà vu, tingling or numbness, hearing disturbances, or unusual tastes or smells. Some people experience the same aura before every seizure, which can serve as a useful signal that a larger event may follow.
Beyond auras, focal seizures produce several categories of symptoms:
- Motor symptoms: Jerking or twitching in one hand, arm, or side of the face. Some people make repetitive movements like lip-smacking, fumbling with clothing, or picking at things.
- Sensory symptoms: Abnormal sensations of vision, tingling, pain, unusual smells, or sounds that aren’t there.
- Autonomic symptoms: Changes in heart rate, blood pressure, sweating, skin color, or sudden stomach upset. These can be mistaken for panic attacks or heart problems.
- Cognitive symptoms: Disrupted language or thinking, déjà vu (feeling something has happened before), or jamais vu (feeling something familiar is suddenly strange). Some people experience hallucinations or distorted perceptions.
- Emotional symptoms: Sudden waves of fear, dread, anxiety, or sometimes pleasure that come on without any obvious trigger. In rare cases, focal seizures cause involuntary laughing or crying.
Most focal seizures last from a few seconds to a couple of minutes. They often end on their own, though the person may feel confused, tired, or “off” for a period afterward.
What Causes Focal Seizures
In more than half of people with epilepsy, no specific cause is ever identified. When a cause is found, it varies significantly by age. In children, congenital brain abnormalities are the most common. In young adults, head injuries take the lead. For people between 35 and 64, the main causes are head trauma, brain tumors, and vascular problems. In those over 65, stroke and degenerative brain diseases are the most frequent culprits.
The full range of known causes includes:
- Structural brain changes: Stroke, traumatic brain injury, tumors, scarring in the hippocampus (a memory-related structure in the temporal lobe), blood vessel malformations, or changes from prior brain surgery.
- Infections: Brain infections are the most common cause of epilepsy worldwide. Tuberculosis, parasitic infections, HIV, malaria, and bacterial or viral infections of the brain and its surrounding membranes can all trigger seizures.
- Metabolic problems: Low sodium, low calcium, or low blood sugar can provoke seizures. Some inherited enzyme disorders also cause them.
- Genetic factors: Several chromosomal conditions and gene variants are associated with epilepsy, including Down syndrome, Fragile X syndrome, and Angelman syndrome.
- Oxygen deprivation: Reduced oxygen to the brain, whether during birth or later in life, can create areas of damage that become seizure-prone.
When Focal Seizures Spread
A focal seizure can sometimes spread from one hemisphere of the brain to both sides, becoming what’s called a focal to bilateral tonic-clonic seizure. When this happens, the person loses consciousness and experiences the stiffening and rhythmic jerking that most people associate with seizures. In one study of patients with a specific type of structural brain abnormality, about 17% experienced this kind of spread. The presence of these spreading seizures is also linked to a higher chance that medication alone won’t fully control the epilepsy.
Not all focal seizures carry the same risk of spreading. The brain region involved and how connected it is to other networks both play a role. If your focal seizures consistently include an aura before progressing, that warning period can be valuable because it gives you time to get to a safe position.
How Focal Seizures Are Diagnosed
Diagnosis typically involves a detailed description of what happens during your episodes, ideally from both you and someone who has witnessed them. An EEG (a test that records electrical activity in the brain) can detect abnormal patterns localized to one area, which supports a focal seizure diagnosis. Brain imaging with MRI looks for structural problems like tumors, scarring, or blood vessel abnormalities that could be triggering the seizures.
Because many focal seizures, particularly the aware type, don’t involve dramatic visible symptoms, they’re frequently misdiagnosed or dismissed. Autonomic symptoms get mistaken for anxiety disorders. Emotional symptoms get attributed to psychiatric conditions. Cognitive symptoms like déjà vu seem too ordinary to report. If you’re experiencing brief, repetitive episodes of any of these symptoms that feel involuntary and follow a consistent pattern, that history is worth bringing up to a neurologist.
Treatment Options
Anti-seizure medications are the first line of treatment. The most commonly used options for focal epilepsy include lamotrigine, levetiracetam, and carbamazepine. Treatment typically starts at a low dose and increases gradually to minimize side effects. If the first medication doesn’t work well enough or causes problems, switching to a different single medication is preferred over adding a second one right away.
For people whose seizures don’t respond to medications (roughly one-third of focal epilepsy patients), other options exist. If imaging identifies a clear structural source for the seizures, surgery to remove that area can sometimes eliminate them entirely. Nerve stimulation devices and dietary therapies are additional options for drug-resistant cases.
What to Do During a Focal Seizure
If you’re with someone having a focal seizure, the CDC recommends staying calm and staying with them. Move anything nearby that could cause injury. If the person is lying down, gently turn them on their side with their mouth pointing toward the ground to keep their airway clear. Time the seizure. Once it ends, help them sit somewhere safe, tell them what happened, and offer to help them get home.
Call 911 if the seizure lasts longer than five minutes, if a second seizure follows closely after the first, if the person has trouble breathing or waking up afterward, if they’re injured, or if it happens in water. You should also call for help if the person has never had a seizure before, has diabetes and loses consciousness, or is pregnant.