Epilepsy is a prevalent neurological disorder characterized by recurrent unprovoked seizures. It affects about one in ten people at some point in their lives, and a third of these individuals may go on to develop epilepsy. Rather than being a single disease or syndrome, epilepsy represents a diverse range of conditions resulting from various disruptions in brain function due to different underlying pathological processes.
Not everyone who experiences a seizure has epilepsy, but all individuals with epilepsy experience seizures. The term “epilepsy” encompasses a broad array of neurologic disorders marked by recurring unprovoked seizures. Seizures are manifestations of abnormal electrical activity in the brain, where epileptic seizures specifically involve the hypersynchronous discharge of cortical neurons. This abnormal activity may produce subjective experiences or observable signs (clinical seizures) or may be detected only through an electroencephalogram (EEG) as subclinical or electrographic seizures.
The International Classification of Epileptic Seizures categorizes seizures based on their onset and characteristics:
– **Focal onset seizures** can be further classified into those with preserved awareness, which may involve motor signs, sensory symptoms, autonomic symptoms, or cognitive symptoms, and those with impaired awareness, which include automatisms and may evolve into bilateral tonic-clonic seizures.
– **Generalized seizures** include a variety of types such as absence seizures, myoclonic seizures, clonic seizures, tonic seizures, tonic-clonic seizures, and atonic seizures.
– **Unknown onset seizures** are categorized as motor or non-motor and may not fit neatly into the other classifications.
Epilepsy syndromes are classified based on their onset and associated features:
– **Focal epilepsies** include idiopathic types with age-related onset (e.g., benign childhood epilepsy with centrotemporal spikes), symptomatic types (e.g., temporal lobe epilepsy), and cryptogenic types.
– **Generalized epilepsies** may be idiopathic (e.g., benign neonatal convulsions, juvenile myoclonic epilepsy) or symptomatic with specific etiology (e.g., West syndrome, Lennox-Gastaut syndrome).
– **Epilepsies of unknown origin** include conditions where the precise origin of seizures is uncertain or involves both focal and generalized features.
Common seizure types include:
– **Focal seizures with preserved awareness** (previously termed simple partial seizures) involve localized brain activity without loss of consciousness. These may include motor manifestations, sensory experiences, or other localized symptoms.
– **Focal seizures with impaired awareness** (previously complex partial seizures) involve a loss of consciousness, with a typical sequence of an aura, impaired awareness, and automatisms. Automatisms may include involuntary movements such as chewing or tapping.
– **Generalized seizures** involve impaired consciousness from the start, with bilateral motor changes and symmetric EEG patterns. Examples include typical absence seizures, generalized tonic-clonic seizures, and myoclonic seizures.
In summary, epilepsy is a complex condition with a wide range of symptoms and underlying causes. Effective diagnosis and treatment require a nuanced understanding of the different types and syndromes associated with epilepsy.