Types of Seizures

ILAE 2017 Classification at a Glance

1. Focal Onset Seizures (formerly "Partial")

a) Focal Aware Seizure (formerly Simple Partial)

• Consciousness is fully preserved
• Symptoms reflect the focal cortical region: localized jerking (motor cortex), sensory disturbance, autonomic changes, or psychic phenomena
• An aura is itself a focal aware seizure and represents the initial phase of a larger seizure
• Example: rhythmic jerking of one hand progressing to the entire arm (Jacksonian march), lasting 60-90 seconds

b) Focal Impaired Awareness Seizure (formerly Complex Partial)

• Consciousness or awareness is impaired
• Often begins with a motionless stare, followed by automatisms (lip smacking, chewing, picking movements, fumbling)
• Most commonly arise from the temporal lobe
• Followed by a postictal period of confusion

c) Focal-to-Bilateral Tonic-Clonic (formerly Secondarily Generalized)

• Begins focally, then spreads to involve both hemispheres
• Implies an underlying focal brain lesion
• The initial focal phase may be brief and unwitnessed

Key point: Focal seizures can be convulsive or nonconvulsive, and can secondarily generalize into any generalized type. - Adams and Victor's Principles of Neurology, 12th Ed.

2. Generalized Onset Seizures

a) Generalized Tonic-Clonic (GTC) - formerly Grand Mal

• Tonic phase (10-20 s): Sudden loss of consciousness + fall, body rigidity, jaw clamping (tongue bite risk), apnea, cyanosis, dilated unreactive pupils, bladder emptying possible
• Clonic phase (1-2 min): Rhythmic jerking of limbs at ~4-8/second, prominent autonomic signs (tachycardia, hypertension, hypersalivation)
• Postictal phase: Deep coma transitioning to confusion, lethargy, headache; lasts minutes to hours
• EEG: fast activity during tonic phase; spike-slow wave complexes during clonic jerks

b) Absence Seizure - formerly Petit Mal

• Momentary (5-20 s) lapse of consciousness with sudden onset and offset
• Patient freezes mid-activity; eyelid flickering may occur; no falling
• No aura, no postictal period - distinguishes it from focal impaired awareness seizures
• EEG hallmark: 3 Hz spike-and-wave complexes (generated by T-type Ca²+ channels in thalamic neurons)
• Predominantly in children; multiple episodes per day possible

Absence seizure EEG: 3/s spike-and-wave pattern - Ganong's Review of Medical Physiology, 26th Ed.

c) Myoclonic Seizures

• Sudden, brief, bilateral muscle jerks without loss of consciousness (or very brief impairment)
• Typically occur on awakening; can be triggered by sleep deprivation or photic stimulation
• Seen in juvenile myoclonic epilepsy (JME) and Dravet syndrome
• EEG: polyspike-and-wave discharges

d) Atonic Seizures (Drop Attacks)

• Sudden loss of postural muscle tone causing the patient to fall
• Very brief (1-2 s); risk of injury from falls
• Also called drop seizures or akinetic seizures
• Associated with Lennox-Gastaut syndrome
• EEG: slow spike-wave or flattening

e) Tonic Seizures

• Sudden sustained muscle stiffening/rigidity without a clonic phase
• Often nocturnal; common in Lennox-Gastaut syndrome
• Brief (seconds); postictal confusion is minimal

f) Clonic Seizures

• Rhythmic jerking movements without a preceding tonic phase
• Rarer than tonic-clonic; more common in neonates and young children

g) Epileptic Spasms (Infantile Spasms)

• Brief flexion/extension of trunk and limbs in clusters, typically on waking
• Onset in infancy (3-12 months); signature of West syndrome
• EEG: hypsarrhythmia (chaotic, high-voltage, disorganized pattern)

3. Unknown Onset

Age Distribution of Seizure Types

Distribution of seizure types by age. Absence and myoclonic seizures predominate in childhood; complex partial (focal impaired awareness) seizures are most common in adults over 35. - Adams and Victor's Principles of Neurology, 12th Ed.

Quick Comparison: Key Differentiators

Terminology Update (Old vs. New)

Sources: Adams and Victor's Principles of Neurology (12th Ed.), Katzung's Basic and Clinical Pharmacology (16th Ed.), Ganong's Review of Medical Physiology (26th Ed.), Bradley and Daroff's Neurology in Clinical Practice