Epilepsy
Seizure Disorder
Side view
Midline view
A neurological condition characterised by a tendency toward recurrent, unprovoked seizures caused by abnormal, excessive electrical activity in the brain.
Common Signs & Symptoms
- Recurrent seizures, which can range from brief lapses of attention to full convulsions
- Temporary confusion or altered awareness
- Uncontrolled jerking movements
- Sensory disturbances (unusual smells, tastes, or visual effects) preceding a seizure
- Loss of consciousness in some seizure types
Why These Symptoms Happen
Each symptom can be traced, at least in part, to the job a particular part of the brain normally does. These links are simplified: real symptoms usually come from several connected regions.
| Symptom | Brain region | Why it happens |
|---|---|---|
| A rising feeling in the stomach, déjà vu, or an odd smell before a seizure | Temporal Lobe | These "auras" are actually the very start of a focal seizure. When it begins in the temporal lobe, which handles memory, emotion, and smell, the person experiences the jobs those areas do - switched on at the wrong moment. |
| Jerking of one arm or one side of the face | Frontal Lobe | If a seizure begins in or spreads to the motor cortex at the back of the frontal lobe, the body part controlled by that patch of cortex moves involuntarily - on the opposite side of the body. |
| Brief blank spells (absence seizures) | Thalamus | In absence seizures, the normal back-and-forth signalling between the thalamus and the cortex falls into an abnormal rhythm across both hemispheres at once, briefly switching off awareness. |
| A seizure that starts on one side and spreads to the whole body | Corpus Callosum | The corpus callosum connects the two hemispheres, and seizure activity can travel across it. This is why cutting it (a callosotomy) can reduce some severe "drop" seizures. |
Overview
Epilepsy is diagnosed when someone has a tendency toward recurring, unprovoked seizures - episodes of abnormal, excessive, or synchronised electrical activity among neurons that temporarily disrupts normal brain function. In practice, doctors usually diagnose it after at least two unprovoked seizures more than 24 hours apart, or after one seizure when tests show a high chance of more. Seizures vary enormously in how they present, from brief staring "absence" episodes to dramatic convulsions, largely depending on where in the brain the abnormal activity starts and how far it spreads.
Affected Brain Regions
The temporal lobe is the most common site of origin for focal seizures in adults, giving rise to temporal lobe epilepsy. Seizures can also originate in the frontal lobe, and the thalamus is thought to play a central role in generalised absence seizures through abnormal thalamocortical rhythms. In severe, treatment-resistant cases, surgically severing the corpus callosum (a callosotomy) has historically been used to prevent seizures from spreading between hemispheres.
How It's Studied
The key test is the electroencephalogram (EEG), which records the brain's electrical activity through sensors on the scalp and can show the sharp "spikes" typical of epilepsy, sometimes even between seizures. MRI scans look for a structural cause, such as scarring of the hippocampus (hippocampal sclerosis), a common finding in temporal lobe epilepsy. When surgery is being considered, patients may spend days on video-EEG monitoring so that doctors can capture seizures and pinpoint where they begin, occasionally using electrodes placed directly on or in the brain. This tradition goes back to neurosurgeon Wilder Penfield, whose stimulation of awake patients' brains during epilepsy surgery produced some of the first detailed maps of the human cortex.
Common Myths
"You should put something in a person's mouth during a seizure."
Never do this. It's impossible to swallow your tongue, and objects in the mouth can break teeth or block breathing. Instead, cushion the head, move hard objects away, time the seizure, and turn the person on their side once the jerking stops. Call emergency services if a seizure lasts more than five minutes, if it's someone's first seizure, or if they're injured.
"All seizures involve falling and shaking."
Many seizures don't. Absence seizures can look like a few seconds of daydreaming, and focal seizures may cause only odd sensations, confusion, or repeated movements such as lip-smacking.
"Flashing lights trigger seizures in everyone with epilepsy."
Only a minority of people with epilepsy are photosensitive. Common triggers are more often missed medication, lack of sleep, stress, or alcohol.
Current Research Directions
Most people with epilepsy achieve good seizure control with anti-seizure medications, and research continues to develop options with fewer side effects. For medication-resistant epilepsy, precise brain mapping now allows surgeons to identify and, where safe, remove or disconnect a specific seizure-origin area. Responsive neurostimulation devices, which detect abnormal activity and deliver a corrective electrical pulse in real time, represent a newer, less invasive direction for treatment-resistant cases.
Key Terms
Related Brain Regions
Explore the regions involved in epilepsy in more depth:
This article is for general education and isn't a substitute for professional medical advice or diagnosis.
Sources & Further Reading
- Epilepsy and Seizures - National Institute of Neurological Disorders and Stroke
- Epilepsy - NHS
- ILAE Official Report: A practical clinical definition of epilepsy - Fisher et al. (2014), Epilepsia
- Epilepsy Foundation - Epilepsy Foundation