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.
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:
At least 2 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 2 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 (SE) 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. It is a feature of grand mal epilepsy (which is often preceded by aura/premonitory symptoms). Most GTCS are self-limited without intervention. 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.
Recurrent generalised seizures are common in childhood and are called epilepsy. Risk factors include genetic predisposition or family history, history of febrile seizures, abnormal perinatal history (e.g., asphyxia), metabolic/neurodegenerative disorders, head trauma, and structural abnormalities of the central nervous system. EEG is the standard diagnostic test, and brain CT/MRI may also be helpful. Main treatment options will depend on the epilepsy syndrome but include anticonvulsants, a ketogenic diet, vagus nerve stimulation, or lifestyle measures.
Seizures in infancy or childhood, usually occurring between 3 months and 5 years of age, associated with high fever but without evidence of intracranial infection or defined cause. Diagnosis is clinical, with lumbar puncture performed to exclude meningitis or encephalitis if clinical suspicion exists. Most febrile seizures are self-limited.
Characterised by abrupt cessation of activity and responsiveness, minimal associated movements, staring episodes, and no aura/postictal state, and lasting 5 to 10 seconds, several times per day. Other features include automatisms (eyelid blinking, upward eye deviation, lip smacking, stereotypical/repetitive hand movements, walking/circling behaviour), childhood onset, and decline in school performance. 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 (JAE), and juvenile myoclonic epilepsy (JME) are treated with anticonvulsants. Atypical absence seizures tend to be medically refractory and associated with mental retardation.
Focal (partial) seizures are the electrical and clinical manifestations of seizures that arise from one portion of the brain. The EEG will indicate a local 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 may be preserved in focal seizures (focal aware seizure) or may include memory loss for the duration of the clinical event or loss of consciousness (focal impaired awareness seizure). 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. EEG demonstrates hypsarrhythmia as a characteristic pattern, although it is not universally present at all times. Treatment options include hormonal therapy (ACTH 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.
BMJ Publishing Group
This overview has been compiled using the information in existing sub-topics.
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