Seizure Types - International Classification of Seizure Types (1981)

International Classification of Seizure Types (1981)

This classification is based on observation (clinical and EEG) rather than the underlying pathophysiology or anatomy.

I Partial seizures (Older term: focal seizures)

A Simple partial seizures - consciousness is not impaired

1 With motor signs

2 With sensory symptoms

3 With autonomic symptoms or signs

4 With psychic symptoms

B Complex partial seizures - consciousness is impaired (Older terms: temporal lobe or psychomotor seizures)

1 Simple partial onset, followed by impairment of consciousness

2 With impairment of consciousness at onset

C Partial seizures evolving to secondarily generalized seizures

1 Simple partial seizures evolving to generalized seizures

2 Complex partial seizures evolving to generalized seizures

3 Simple partial seizures evolving to complex partial seizures evolving to generalized seizures

II Generalized seizures

A Absence seizures (Older term: petit mal)

1 Typical absence seizures

2 Atypical absence seizures

B Myoclonic seizures

C Clonic seizures

D Tonic seizures

E Tonic–clonic seizures (Older term: grand mal)

F Atonic seizures

III Unclassified epileptic seizures

In terms of their origin within the brain, seizures may be described as either partial (focal) or generalized. Partial seizures only involve a localized part of the brain, whereas generalized seizures involve the whole of both hemispheres. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalized.

Whilst most seizures can be neatly split into partial and generalized, there exists some that don't fit. For example: the seizure may be generalized only within one hemisphere. Alternatively there may be many focal points (multifocal seizures) that are distributed in a symmetrical or asymmetrical pattern.