A seizure is an abnormal electrical discharge in the brain — not always convulsions. Dr. Anand Karnam explains the full spectrum of seizure types, their causes, and the difference between a seizure and epilepsy.
Key Points
- The ILAE 2017 classification divides seizures into focal (starting in one part of the brain), generalised, and unknown onset.
- Generalised tonic-clonic seizures (GTC) are the most recognised — involving stiffening followed by rhythmic jerking.
- Absence seizures: brief (5–10 second) blank stares with eye flutter — often missed or labelled as 'daydreaming'.
- Focal aware seizures (simple partial): the patient is conscious and may experience déjà vu, smells, or jerking of one limb.
- The seizure type determines which anti-epileptic medication is chosen — getting this right matters significantly.
50M
people worldwide live with epilepsy
Source: WHO
25%
of childhood epilepsy cases are absence epilepsy — commonly misdiagnosed as inattention
Source: NCBI
2017
year of the latest ILAE seizure classification — now standard in practice
Source: ILAE
"Seizures are not all convulsions. A child who stares blankly for 5 seconds and resumes mid-sentence — that is likely an absence seizure. A person who smells something burning just before a convulsion — that is a focal aware seizure. The type of seizure is the most important piece of information I need."
A seizure is a transient abnormal electrical event in the brain — a sudden, uncontrolled surge of electrical activity that temporarily disrupts normal brain function. Seizures are not a disease — they are a symptom, like fever or pain. A single seizure has many possible causes; epilepsy is the condition of recurrent unprovoked seizures. Understanding the different seizure types is crucial because they have different causes, different treatments, and different meanings for the patient.
Focal Seizures (starting in one part of the brain)
Focal aware seizure (previously called simple partial): The person is fully conscious throughout. Symptoms depend entirely on which part of the brain is discharging — motor cortex produces jerking of one limb; temporal lobe produces a déjà vu sensation, rising epigastric feeling, or smell/taste hallucination; occipital lobe produces visual phenomena. The person can describe what happened afterward.
Focal unaware seizure (previously complex partial): Consciousness is impaired. The person is unresponsive, may stare blankly, and often performs automatic movements — lip smacking, hand fumbling, walking in circles. They have no memory of the episode. Most common cause: temporal lobe epilepsy (often due to hippocampal sclerosis — scarring of the hippocampus from a childhood febrile seizure).
Focal to bilateral tonic-clonic: A focal seizure that secondarily spreads to both hemispheres, causing a generalised convulsion.
Generalised Seizures (involving both hemispheres from onset)
Tonic-clonic (the classical "grand mal fit"): Loss of consciousness → tonic phase (rigid extension) → clonic phase (rhythmic jerking) → postictal phase (confusion, deep sleep for minutes to hours). Usually lasts 1–3 minutes. Absence: Brief (5–15 seconds) blank staring with abrupt onset and offset — common in children; mistaken for daydreaming. Myoclonic: Sudden brief muscle jerks — typically on waking. Atonic: Sudden loss of muscle tone — the person drops to the ground ("drop attacks").
Provoked vs Unprovoked Seizures
A provoked seizure has an identifiable immediate cause: fever (febrile seizure), low blood glucose (hypoglycaemia), very low sodium, alcohol withdrawal, drug toxicity, or acute brain injury. A provoked seizure is not epilepsy — treat the underlying cause. For EEG and seizure evaluation: Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.
Dr. Anand Karnam
DrNB Neurology · Sri Anand CNC, Chanda Nagar Hyderabad · Sri Anand Child and Neuro Center
DrNB-qualified Neurologist, Fellow of the World Headache Society (FWHS), and Headache Specialist with 12+ years of experience treating epilepsy, stroke, migraine, and movement disorders. Practices at Sri Anand Child and Neuro Center, Chanda Nagar, Hyderabad.
References & Sources
- 1.Epilepsy — WHO Fact Sheet — World Health Organization
- 2.ILAE Seizure Classification — International League Against Epilepsy
- 3.Seizures — NIH MedlinePlus — NIH MedlinePlus
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