Fits (Seizures) - What They Are and How They Occur

Definition

A fit, medically called a seizure, is a sudden, transient episode caused by abnormal, excessive, and synchronous electrical discharge of neurons in the brain. This disrupts normal brain function and can cause changes in consciousness, behavior, movement, sensation, or feelings.

The term "convulsion" refers specifically to involuntary, repetitive muscle contractions - but not all seizures cause convulsions. A seizure is the broader, preferred term.

Adams and Victor's Principles of Neurology, 12th Edition: "A seizure represents the uncontrolled, abnormal electrical activity of the brain that may cause changes in the level of consciousness, behavior, memory, or feelings."

How a Fit/Seizure Occurs (Mechanism)

The brain normally has a delicate balance between excitation (firing of neurons) and inhibition (suppression of firing). A seizure occurs when this balance is disrupted:

Excessive neuronal excitation - too many neurons fire at once
Reduced inhibition - the brain's natural "brakes" (mainly the neurotransmitter GABA) fail
Synchronous spread - the abnormal electrical discharge spreads to nearby or distant brain areas

The result is a sudden "electrical storm" in the brain. Depending on where it starts and how far it spreads, different symptoms appear.

Phases of a Seizure

Phase	What Happens
Prodrome	Hours to days before: mood changes, irritability, depression, headache, disturbed sleep
Aura	Seconds before: unusual smell, taste, fear, visual changes, a rising feeling in the stomach - this is actually the very beginning of the seizure (a focal onset)
Ictal phase	The seizure itself: convulsions, loss of consciousness, staring, muscle jerking
Postictal phase	After: confusion, drowsiness, headache, muscle soreness, weakness (may last minutes to hours)

Types of Seizures (ILAE Classification)

Seizures are classified based on where in the brain they start:

1. Focal (Partial) Seizures

Start in one specific area of the brain.

Focal Aware (Simple Partial) - person remains conscious; may have jerking of one limb, abnormal sensations, déjà vu, or a rising feeling in the stomach
Focal Impaired Awareness (Complex Partial) - consciousness is impaired; person may stare blankly, make repetitive movements (lip smacking, picking at clothes), and not remember the episode
Focal to Bilateral Tonic-Clonic - starts focal, then spreads to involve both sides of the brain

2. Generalized Seizures

Involve both halves of the brain from the start.

Type	Description
Tonic-Clonic (Grand Mal)	Sudden stiffening (tonic) followed by rhythmic jerking (clonic); loss of consciousness; may bite tongue, be incontinent
Absence (Petit Mal)	Brief staring spell, 5-30 seconds; person appears to "check out"; common in children
Myoclonic	Sudden, brief muscle jerks, often on waking
Tonic	Sudden muscle stiffening without jerking
Clonic	Rhythmic jerking movements only
Atonic (Drop attack)	Sudden loss of muscle tone; person drops to ground

Age Distribution of Seizure Types

The chart below (from Adams and Victor's Neurology) shows how seizure types vary with age - absence and myoclonic seizures are more common in children, while complex partial (focal impaired awareness) seizures dominate in adults and the elderly:

Causes of Seizures

Seizures are divided into provoked (triggered by a temporary cause) and unprovoked (epilepsy).

Provoked (Non-Epileptic) Causes

High fever - febrile seizures (very common in young children ages 6 months to 5 years)
Low blood sugar (hypoglycemia)
Low sodium, calcium, or magnesium
Alcohol withdrawal or drug overdose
Head injury or brain trauma
Meningitis or encephalitis (brain infections)
Stroke or lack of oxygen to the brain
Eclampsia (in pregnancy)
High blood pressure crisis

Unprovoked (Epilepsy) Causes

Genetic/idiopathic - inherited tendency, no structural cause
Structural - brain scar from old injury, stroke, tumor, cortical dysplasia, hippocampal sclerosis
Metabolic - enzyme defects, mitochondrial disease
Immune - autoimmune encephalitis (antibodies attacking the brain)

Epidemiology

About 10% of people will have at least one seizure in their lifetime
True epilepsy (recurrent, unprovoked seizures) affects roughly 1% of the population
Approximately 2 million people in the US have epilepsy
Incidence peaks in early childhood (especially the first year of life) and again after age 60
Over two-thirds of all epileptic seizures begin in childhood

Status Epilepticus

A seizure lasting more than 5 minutes, or two or more seizures without full recovery between them, is called status epilepticus - a medical emergency requiring immediate treatment.

Key Points Summary

Feature	Detail
Core mechanism	Abnormal synchronous electrical discharge in the brain
Main classification	Focal (one brain area) vs. Generalized (both hemispheres)
Most common adult type	Complex partial (focal impaired awareness)
Most common childhood type	Febrile seizures, absence seizures
Emergency form	Status epilepticus (seizure >5 min)

If you or someone you know experiences a seizure, seek medical evaluation - especially after a first-ever seizure, to identify the cause and determine if treatment is needed.

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