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Canadian League Against Epilepsy

Seizure Classification

CLASSIFICATION

There are many different types of seizures and epilepsies, all with different disease trajectories and outcomes. The goal of classification is to identify the type of seizure and epilepsy a person has, to help provide further information regarding treatment choices and seizure outcomes.

There are 2 main types of seizures/epilepsies: focal and generalized. Focal seizures arise from one hemisphere of the brain whereas generalized seizures originate from both sides of the brain.  In some cases, the seizure cannot be immediately classified, and is referred to an unclassified seizure or seizure of unknown onset.

TYPES OF SEIZURES

Focal aware seizures
Formerly simple partial seizures or focal seizures

During these seizures, the person will experience symptoms, but remain aware and able to interact with their environment.  Different types of these seizures include:
    • Motor
      • Automatisms: automatic, semi-purposeful movements of the face, hands, legs
      • Clonic: rhythmic jerking movements of a body part(s)
      • Tonic: stiffening of a body part(s)
      • Myoclonic: very quick, lightning-like movements of a body part(s). These movements are quicker than clonic movements, and usually less rhythmic.
      • Atonic: loss of motor tone, often leading to collapse. Most common form of atonic seizures is a head drop.
      • Hyperkinetic: agitated thrashing or leg pedaling movements.
      • Epileptic spasms: characterized by a sudden flexion or extension movement of the trunk followed by a delayed relaxation phase.  These seizures typically last seconds.
    • Non-motor
      • Emotional: strong emotional effect of the seizure, such as joy, fear, laughter, panic
      • Cognitive: refers to any sort of cognitive impairment occurring in a seizure, such as aphasia (language difficulties), déjà vu, jamais vu, auditory hallucinations or visual hallucinations
      • Sensory: sensory phenomena, such as pins and needles, pain, goosebumps
      • Autonomic: sweating, redness/flushing of skin, increases in heart rate and/or breathing
      • Behavioural arrest: cessation of activity, and may appear “frozen”.

Focal seizures can evolve into bilateral tonic-clonic seizures. 
Previously referred to as secondarily generalized seizures.

Focal seizures with impaired awareness
Formerly complex partial seizures, focal dyscognitive seizures, psychic seizures

These seizures can have any of the onset symptoms as described for focal seizures without loss of awareness.  However, during these seizures, the individual loses contact with the environment and may stop responding to it, or have no idea that they had a seizure.

Generalized seizures

    • Motor
      • Tonic-clonic (formerly Grand Mal): typically start with stiffening of the whole body, followed by rhythmic clonic movements of the whole body.
      • Clonic
      • Tonic
      • Atonic
      • Myoclonic
      • Myoclonic-tonic-clonic
      • Myoclonic-atonic
      • Epileptic spasms
    • Non-Motor (also known as absence, formerly Petit Mal)
      • Typical
      • Atypical
      • Myoclonic
      • Eyelid myoclonia

Seizures of unknown onset

Seizures with unknown onset are seizures where the onset of the seizure was not observed or noticed, and only later symptoms are noted.  In this situation, clinicians are unable to accurately determine localization of the seizure (focal vs. generalized) based on the information available. These seizures can be sub-categorized into:

    • Motor
      • Tonic-clonic
      • Epileptic spasms
    • Non-Motor
      • Behavioral arrest

Unclassified seizures

Only to be used if the clinician is certain the event is a seizure, but cannot classify it further because of incomplete information, or the unusual nature of the seizure.

Both modern MRI techniques and advances in genetics have increased our understanding of the causes of epilepsy. We now recognize a number of causes for epilepsy:

    • Structural, such as a brain tumor
    • Metabolic, such as inborn errors of metabolism or mitochondrial disorders such as MELAS
    • Genetic, often due to multiple genetic factors, such as childhood absence epilepsy.
    • Infectious, such as herpes simplex encephalitis
    • Immune-related, such as anti-NMDA receptor encephalitis
    • Unknown


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