Seizures: Types, Diagnosis and Treatment

How seizures happen

Brain cells communicate through tightly regulated electrical signals, balanced between excitation and inhibition. A seizure happens when that balance tips and a large group of neurons fires together abnormally. The symptoms depend on which part of the brain is involved:

• the motor cortex: jerking or stiffening
• the temporal lobe: déjà vu, fear, smells, a rising stomach feeling, automatic movements
• the occipital lobe: flashing lights or visual distortions
• both hemispheres: loss of consciousness

After a seizure, the brain needs time to recover. This postictal phase can bring confusion, sleepiness, headache, aching muscles and sometimes temporary weakness (Todd's paralysis).

Types of seizures

The 2017 ILAE classification groups seizures by where they start, the person's awareness, and the main features.

Focal onset seizures

Focal seizures start in one area on one side of the brain.

• Focal aware seizures (formerly simple partial): the person is fully aware. Symptoms can be motor (jerking of a hand or face) or non-motor (tingling, visual changes, déjà vu, fear, nausea). People sometimes call these "auras".
• Focal impaired awareness seizures (formerly complex partial): awareness is impaired. The person stares, does not respond normally and may make automatic movements (automatisms) such as chewing, lip smacking or picking at clothes. They usually have no memory of it.
• Focal to bilateral tonic-clonic seizures (formerly secondary generalized): a focal seizure that spreads to both sides and becomes a convulsion.

Generalized onset seizures

These involve networks on both sides of the brain from the start.

Unknown onset

When nobody saw how a seizure began, or tests cannot tell, it is classified as unknown onset until more information is available.

Special situations

• Status epilepticus: a seizure lasting 5 minutes or longer, or repeated seizures without recovery. It is a medical emergency.
• Febrile seizures: seizures with fever in children aged 6 months to 5 years. Most are simple, brief and harmless.
• Provoked (acute symptomatic) seizures: caused by a temporary problem such as low blood sugar, alcohol withdrawal, low sodium, head injury or stroke in its first week.
• Psychogenic non-epileptic seizures (PNES): episodes that resemble seizures but are not caused by abnormal electrical activity. They are a real condition treated with psychological therapy, not anti-seizure medicine.

For first aid and the immediate causes of a seizure, see seizure symptoms and first aid.

Seizures vs epilepsy

A seizure is a single event. Epilepsy is diagnosed when someone has:

• two or more unprovoked seizures more than 24 hours apart, or
• one unprovoked seizure plus a high risk (around 60% or more) of another, for example because of an abnormal EEG or a brain lesion, or
• an epilepsy syndrome.

Many people have one seizure in their life and never have another. Provoked seizures, such as those from alcohol withdrawal or hypoglycemia, are not epilepsy.

Causes and risk factors

• Genetic: many generalized epilepsies, such as childhood absence epilepsy and juvenile myoclonic epilepsy, have a genetic basis.
• Structural: stroke, traumatic brain injury, brain tumors, malformations of brain development, scarring of the hippocampus (hippocampal sclerosis).
• Infectious: meningitis, encephalitis, brain abscess, neurocysticercosis (a common cause worldwide).
• Metabolic: low sodium, calcium, magnesium or glucose, and kidney or liver failure.
• Immune: autoimmune encephalitis.
• Neurodegenerative: Alzheimer's disease and other dementias.
• Unknown: in a large share of people, no cause is found.

Diagnosis

1. Detailed history: from the person and an eyewitness. A smartphone video of an episode is extremely valuable.
2. Examination of the nervous system and heart.
3. Blood tests: glucose, electrolytes, kidney and liver function, and toxicology.
4. ECG: to rule out heart rhythm problems that cause collapse.
5. EEG: records brain waves. It can show epileptic discharges and help identify the seizure type and syndrome. A normal EEG between seizures does not rule out epilepsy. Sleep-deprived, ambulatory or video EEG increases the yield.
6. MRI of the brain: the preferred scan to find structural causes. CT is used in emergencies.
7. Lumbar puncture if infection or autoimmune encephalitis is suspected.

Doctors must also exclude conditions that mimic seizures: syncope, TIA, migraine, panic attacks, sleep disorders and PNES.

Treatment

Emergency treatment

Seizures lasting more than 5 minutes are treated with benzodiazepines (given as nasal spray, buccal liquid, rectal gel or injection), followed by intravenous anti-seizure medicines in hospital if needed.

Treating provoked seizures

Correcting the cause, such as giving glucose, managing alcohol withdrawal, or correcting sodium, usually prevents further seizures without long-term medicine.

Anti-seizure medicines

Commonly used medicines include levetiracetam, lamotrigine, carbamazepine, oxcarbazepine, lacosamide, valproate, topiramate and ethosuximide (for absence seizures). Choice depends on seizure type, age, sex, pregnancy plans, other conditions and side effects. Valproate carries a high risk of birth defects and is avoided in women who could become pregnant unless no alternative works.

About two-thirds of people become seizure-free with the first or second medicine tried. Seizures that continue after two appropriate medicines are called drug-resistant, and referral to a comprehensive epilepsy center is recommended.

Options for drug-resistant epilepsy

• Epilepsy surgery: removing the seizure focus, for example in temporal lobe epilepsy, can make many people seizure-free.
• Laser ablation guided by MRI.
• Neurostimulation: vagus nerve stimulation, responsive neurostimulation and deep brain stimulation.
• Dietary therapy: the ketogenic or modified Atkins diet, particularly in children.

Living with seizures

• Take medicines regularly. Missed doses are the most common trigger of breakthrough seizures.
• Keep a seizure diary.
• Sleep regularly and limit alcohol.
• Follow local driving laws.
• Plan pregnancy with your neurologist, and take folic acid.
• Teach family and coworkers seizure first aid.
• SUDEP (sudden unexpected death in epilepsy) is rare but more likely with frequent uncontrolled tonic-clonic seizures, especially at night. Good seizure control is the best protection.

Frequently asked questions

What are the main types of seizures?

Seizures are classified as focal onset (starting in one area, with or without impaired awareness), generalized onset (involving both sides from the start, such as tonic-clonic, absence, myoclonic and atonic seizures), and unknown onset. Focal seizures can spread to become bilateral tonic-clonic seizures.

What is the difference between a seizure and epilepsy?

A seizure is a single episode of abnormal brain electrical activity. Epilepsy is a condition with a lasting tendency to have unprovoked seizures, usually diagnosed after two unprovoked seizures or one with a high risk of recurrence. Many people have a single seizure and never develop epilepsy.

How are seizures diagnosed?

Diagnosis relies mainly on a detailed description from the person and witnesses, ideally with video. Tests include blood tests, an ECG, an EEG to record brain waves, and an MRI of the brain. These identify the seizure type, possible causes and the risk of further seizures.

Can seizures be cured?

Many can be controlled completely. About 70% of people with epilepsy become seizure-free with medicine, and some children outgrow their epilepsy. Surgery can cure certain focal epilepsies. Provoked seizures usually stop once the underlying cause is treated.

Do all seizures cause convulsions?

No. Many seizures involve no jerking at all. Absence seizures cause brief staring, focal seizures can cause odd sensations, déjà vu or automatic movements, and atonic seizures cause sudden falls. Non-convulsive seizures are easily missed, so describe any unusual episodes to a doctor.