Revised operational classification of seizure types and epilepsies by the International League Against Epilepsy (ILAE)
The classification has been revised. Seizures are divided into those of focal, generalised, unknown onset, with sub-categories of motor, non-motor, with retained or impaired awareness for focal seizures.
Levels of classification to aid the diagnosis include seizure type, epilepsy type (focal, generalised, combined generalized and focal, unknown) and epilepsy syndrome.
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A seizure is defined as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain". Epilepsy is considered to be a disease of the brain defined by any of the following conditions: ILAE: EpilepsyDiagnosis.org external link opens in a new window
At least two unprovoked (or reflex) seizures occurring more than 24 hours apart
One unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years
Diagnosis of an epilepsy syndrome.
A life-threatening neurological condition defined as 5 or more minutes of either continuous seizure activity or repetitive seizures without regaining consciousness. Generalised convulsive status epilepticus in both its subtle and overt subtypes constitutes the most frequent variant. Recognition is crucial because rapid termination helps prevent serious brain injury, especially in patients with impaired consciousness. Treatment involves a stepwise medication approach aimed at aborting the clinical and electrographic seizures.
Generalised seizures (generalised tonic-clonic seizures [GTCS]) classically involve loss of consciousness and a phasic tonic stiffening of the limbs, followed by repetitive clonic jerking. Most GTCS are self-limiting without intervention. The electroencephalogram (EEG) shows bisynchronous epileptiform activity in both cerebral hemispheres. GTCS occur in many different types of epilepsy. Anti-epileptic agents are the primary treatment for all types. GTCS may also be provoked by an insult in an individual who does not have epilepsy.
Seizures may occur as a stand-alone event or may be recurrent. Risk factors include a past medical history of perinatal insult (e.g., asphyxia) or febrile seizures; a genetic predisposition or family history; neurodegenerative disorders; infection; metabolic or immune disorders; head trauma; and structural abnormalities of the central nervous system. EEG is the standard diagnostic test, and brain CT or MRI may also be helpful. The main treatment options will depend on the epilepsy syndrome but include anticonvulsants, a ketogenic diet, vagus nerve stimulation, or lifestyle measures.
Seizures occurring in a febrile child, between the ages of 6 and 60 months, without evidence of intracranial infection, metabolic disturbance, or history of afebrile seizures. The diagnosis is made by clinical assessment, with lumbar puncture performed to exclude meningitis or encephalitis if suspicion exists. Most febrile seizures resolve spontaneously and do not require acute or long-term anticonvulsant treatment.
Typically characterised by abrupt cessation of activity and responsiveness, lasting between 5 to 10 seconds, with minimal associated movements, staring episodes, and no aura/postictal state. Typical absence seizures may be precipitated by hyperventilation and photic stimulation. EEG is the definitive test. Most typical absence seizures are medically responsive, and childhood absence epilepsy (CAE) tends to remit by adulthood. Typical absence seizures in CAE, juvenile absence epilepsy, and juvenile myoclonic epilepsy are treated with anticonvulsants. Atypical absence seizures have a less distinct beginning and end, and are not usually precipitated by hyperventilation. Atypical absence seizures tend to be medically refractory and associated with cognitive impairment.
Focal (partial) seizures are the electrical and clinical manifestations of seizures that arise from one portion of the brain. They may occur in the context of an underlying structural brain abnormality, or may be idiopathic. The EEG typically indicates a localised discharge over the area of onset. The temporal lobe is the most common area of onset for focal seizures, but they may arise from any lobe. Consciousness is preserved in focal aware seizures, whereas focal impaired awareness seizures feature memory loss for the duration of the clinical event or impaired responsiveness at the time of the event. Focal seizures may lead to secondary generalised seizures. Monotherapy with antiepileptic medication is the preferred initial treatment.
An epilepsy syndrome typically presenting in infancy, with a varying aetiology. Spasms may be flexor, extensor, mixed flexor-extensor, symmetrical or asymmetrical, and typically occur in clusters. A hypsarrhythmic pattern on EEG is characteristic, but not universally present at all times. Infantile spasms are often associated with an underlying disorder. Where no underlying cause is detected (10% to 40% of patients) and there is normal development prior to onset, the prognosis tends to be better. Treatment options include hormonal therapy (adrenocorticotrophic hormone or corticosteroids) or vigabatrin.
Differentiating between syncope and epileptic seizures can sometimes be challenging. Twitching and jerking are often seen with vasovagal or cardiac syncope, which can be differentiated from rhythmic jerking of all the limbs in tonic-clonic seizures. Loss of bowel and bladder control, commonly seen with seizures, is rare during syncope. Postictal confusion is one of the key differentiating factors for seizures. The presence of an aura and unconsciousness for >5 minutes is more typical of a seizure.
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This overview has been compiled using the information in existing sub-topics.
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