Seizures and epilepsy: What you need to know
March 3, 2026
Foaming at the mouth during a seizure commonly occurs in tonic-clonic seizures, caused by involuntary muscle contractions forcing saliva through clenched teeth, with convulsions, breathing changes, and loss of consciousness.
Epilepsy is the third most common neurologic disorder worldwide. The incidence of first seizures ranges from 20 to 70 per 100,000 population. The incidence of epilepsy is approximately 30 to 50 per 100,000 population. The cumulative lifetime risk ranges from 1.3% to 3.3%. Prevalence is generally higher in developing countries.
What is a seizure? “The definition of seizure itself is to take hold. Generally, it refers to a sudden and severe event. It can be an epileptic seizure or a non-epileptic seizure. An epileptic seizure is a transient occurrence of signs or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Seizures can be divided into generalized or focal,” explains Dr Raymond Tan Yen Leong, Consultant Neurologist at Sunway Medical Center, Sunway City, during the International Epilepsy Day – Enhancing Epilepsy Awareness and Improving Care in Malaysia symposium. Generalized epileptic seizure Many people assume that a generalized seizure begins with electrical activity occurring simultaneously throughout the entire brain. However, it may actually originate from a single focal point and spread so rapidly that the clinical manifestations appear bilateral. Although it starts at one location, the symptoms involve both sides of the body, and therefore it is classified as a generalized seizure. Focal epileptic seizure A focal epileptic seizure begins in a specific area of the brain. The abnormal electrical activity initially remains confined to a particular lobe, producing symptoms on one side of the body. However, it may spread and become bilateral. Approximately two-thirds of seizures are focal, while one-third are generalized. ILAE classification of seizures The original classification introduced approximately 45 years ago by the International League Against Epilepsy (ILAE) categorized seizures as either partial or generalized. The updated classification in 2025 divides seizures into four categories:
In many cases, the initial phase of a seizure is not witnessed. When it is unclear whether the seizure began as focal or generalized, it is categorized as unknown onset. Unclassified seizures refer to cases in which insufficient information is available to determine seizure type, such as when a patient is found unconscious and no one witnessed the event. Focal and unknown-onset seizures can further be classified based on level of awareness:
Generalized tonic-clonic seizure The generalized tonic-clonic seizure is the archetypal seizure most commonly recognized. There is loss of consciousness from onset through the recovery phase. This is followed by tonic stiffening and then clonic convulsive movements. Autonomic disturbances may also occur. Patients may experience prodromal symptoms, including headache, behavioral changes, anxiety, and poor concentration. Some patients experience myoclonic jerks or absence seizures before a generalized tonic-clonic seizure. In focal seizures that evolve bilaterally, the episode may begin with focal symptoms such as a blank spell or focal motor activity before spreading into a bilateral tonic-clonic seizure. The bilateral tonic contractions last approximately 10 to 20 seconds. This is followed by clonic movements of the arms and legs, often accompanied by autonomic phenomena. Some patients exhibit a clonic–tonic–clonic sequence, beginning with jerking movements, followed by stiffening, and then recurrent jerking. The patient loses consciousness, develops postural stiffening, progresses into clonic movements, then loses muscle tone and enters the postictal phase. The average duration of a seizure is 60 to 120 seconds. During the recovery phase, patients are usually unresponsive, hypotonic, and pale, with gradual return of breathing. Urinary incontinence may occur. Autonomic abnormalities such as tachycardia, dilated pupils, and exaggerated deep tendon reflexes may be present. Recovery typically occurs within 5 to 10 minutes. Absence seizure Absence seizures are brief, with sudden onset and termination. There is loss of awareness and generalized spike-and-wave discharges on electroencephalography (EEG). They may be associated with other seizure types. Automatisms such as blinking may occur. In genetic forms such as childhood absence epilepsy or juvenile absence epilepsy, seizures are often precipitated by hyperventilation. Myoclonic seizures Myoclonic seizures consist of a single jerk or a series of jerks, typically lasting milliseconds.
Myoclonic-atonic seizures consist of a myoclonic seizure followed by an atonic seizure, often resulting in a rapid fall. Focal seizures Temporal lobe seizures are the most common form of focal epilepsy. They arise from abnormal electrical activity in the temporal lobes, which are responsible for memory, emotion, and language. These seizures typically last 1 to 2 minutes and often cause impaired awareness, blank staring, and automatisms such as lip-smacking or repetitive hand movements. Key symptoms include:
Updated seizure classification 2025: Practical descriptors For focal seizures or seizures of unknown onset, descriptors are used to enhance classification:
Seizures are categorized as focal, generalized, or unknown onset, and further classified by awareness level or bilateral tonic-clonic evolution, with additional descriptors as needed. What Is epilepsy? Seizures are a symptom; epilepsy is a condition. Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures and by the neurobiological, cognitive, psychological, and social consequences of this condition. It requires the occurrence of at least one epileptic seizure. A practical clinical definition of epilepsy includes:
If multiple seizures occur on the same day, they are considered a single unprovoked seizure. To meet the diagnostic criteria, seizures must occur on separate days. If a patient has one unprovoked seizure and investigations such as EEG or brain imaging demonstrate findings associated with a recurrence risk of at least 60% over the next 10 years, epilepsy may be diagnosed. For example, if imaging reveals a brain tumor and EEG shows epileptiform discharges at the same site, the diagnosis of epilepsy can be established. Epilepsy syndromes are well-recognized electroclinical conditions defined by specific EEG patterns, clinical features, and seizure types. Risk of recurrence after unprovoked seizures If a patient experiences a single unprovoked seizure, the risk of a second unprovoked seizure is approximately 33% over the next five years. After two unprovoked seizures, the recurrence risk increases to approximately 73%. With subsequent seizures, the recurrence risk remains above 70%. Diagnosis involves determining seizure type—focal, generalized, or unknown onset. If two or more unprovoked seizures occur, or if sufficient clinical or investigative evidence exists, the condition may be classified as focal epilepsy or generalized epilepsy. Etiology is critical in guiding treatment decisions and identifying comorbidities. Most recognized epilepsy syndromes fall under electroclinical syndromes. 
Evaluation of a first seizure
The goals of immediate evaluation are:
Seizures are categorized as provoked or unprovoked. Provoked seizures Provoked seizures occur in the setting of transient factors that lower the seizure threshold, such as infection, drug exposure, injury, or metabolic disturbance. In patients with known epilepsy, delayed or missed medications are a common cause of provoked seizures. Sleep deprivation, stress, and intercurrent illness may also reduce seizure threshold. Once the underlying trigger, such as infection, is resolved and regular medication is continued, seizure control often improves. Unprovoked seizures If a seizure is unprovoked, further evaluation is required to determine seizure type and pattern through additional testing. Seizure incidence shows a bimodal distribution, occurring more frequently in pediatric populations and in older adults. Clinical history should include:
Differential diagnosis: Fits, faints, and paroxysmal events If the event is not a seizure, differential diagnoses must be considered. Causes may be divided into traumatic and non-traumatic categories. Traumatic Brain concussion or structural brain injury may result in events that mimic seizures. Non-traumatic Non-traumatic causes include epileptic seizures and non-epileptic paroxysmal events (NEPEs). NEPEs are sudden, time-limited episodes that resemble epileptic seizures but do not result from abnormal excessive electrical discharge in the brain. Non-epileptic paroxysmal events (NEPEs) NEPEs are classified into physiological (organic) and psychogenic (functional) causes. Physiological (organic) Reflex syncope is a common NEPE caused by temporary global cerebral hypoperfusion, often triggered by stress, pain, or prolonged standing. It presents as transient loss of consciousness, usually lasting less than 1 to 2 minutes, with rapid recovery. It is frequently preceded by lightheadedness, nausea, or sweating. Unlike epilepsy, it lacks ictal EEG discharges. Other neurological or metabolic conditions that may cause transient loss of consciousness or abnormal movements include:
Psychogenic Psychogenic non-epileptic seizures (PNES), also referred to as non-epileptic attack disorders (NEAD), are associated with conversion disorder, malingering, depression, personality disorders, panic attacks, phobias, and anxiety disorders. Investigations Electroencephalography (EEG) EEG is performed after careful clinical evaluation to confirm suspicion of epilepsy. It assists in predicting seizure recurrence risk after a first unprovoked seizure and helps determine seizure type (focal or generalized). EEG findings may support the diagnosis of an epilepsy syndrome and guide selection of anti-seizure medication. Routine EEG is not indicated:
Neuroimaging Two primary imaging modalities are available: computed tomography (CT) and magnetic resonance imaging (MRI). In the acute setting, CT is faster, more accessible, and often preferred. MRI provides superior detail and is indicated in patients with suspected focal onset epilepsy based on history, examination, or EEG findings; poor seizure control; children under two years of age; or individuals experiencing a first seizure after age 20. Patients between ages 2 and 20 more commonly have genetic epilepsy. Additional investigations include blood tests to evaluate electrolytes, glucose, renal and liver function, and drug toxicology. Cardiac evaluation may be necessary to assess for arrhythmias that could mimic seizures. Management Prophylactic treatment Prophylactic treatment refers to the use of anti-seizure medications to prevent seizures in high-risk patients, such as those with brain trauma, neurosurgery, or severe brain infection. Anti-seizure medications reduce the short-term risk of seizure recurrence but do not alter the long-term prognosis. If a patient is predisposed to recurrent seizures, treatment reduces early recurrence risk but does not change ultimate remission rates. Single Seizure After a first unprovoked seizure, the risk of recurrence is approximately 30% to 40%. Initiating medication may reduce recurrence risk from approximately 40% to 20% within the first two years. However, long-term remission rates remain unchanged. Treatment primarily reduces short-term recurrence risk rather than long-term outcome. Non-drug treatment and lifestyle modifications Lifestyle measures apply to all individuals with seizures or epilepsy:
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