Introduction 

Seizures are neurological events caused by uncontrollable electrical signaling among malfunctioning neurons.¹ While each type has distinct symptoms and characteristics, understanding its subtypes are essential for medical professionals, individuals with epilepsy, and their caregivers. This concise introduction will provide a seizure subtypes overview, including focal seizures, originated in a specific brain region, and generalized seizures, involving the entire brain. Further subtypes namely absence, myoclonic, tonic-clonic, atonic,  febrile, reflex, non-epileptic seizures, and infantile spasms will also be covered. By familiarizing ourselves with these subtypes, the accurate diagnosis, management and support among seizure populations can be improved. 

Overview

Basic mechanisms and causes

Seizure occurs when the brain is having a temporary unstoppable electrical activity surge, involving a sudden and excessive discharge of neurons, overloading normal brain functioning, causing a wide range of symptoms such as abnormal sensations, passing out and uncontrollable muscle movements. While the exact cause of seizure is still unclear, it is generally caused by strokes, brain tumors, injuries, structural brain abnormalities, electrolyte imbalances, infections, mental illnesses, drug or alcohol withdrawals, and certain medications.¹    

General classifications

• Provoked: Caused by other medical conditions 
• Unprovoked: Spontaneous, not a symptom of medical condition 
• Focal (partial) seizures: Originates from a specific brain area
  • Simple focal 
  • Complex focal
• Generalized seizures: Involves entire brain/ both hemispheres
  • Absence 
  • Tonic-clonic 
  • Myoclonic 
  • Atonic
  • Febrile 
  • Reflex 
  • Infantile spasms
  • Non-epileptic 

Focal seizures 

Focal (partial) seizures begin in a specific brain region, causing a range of symptoms corresponding to the affected regional functionality, such as sensory changes, motor movements changes, altered emotions, or cognitive disturbances.² 

Focal aware seizures

Among focal aware (simple focal/partial)seizures, consciousness are preserved, with varying auras (odd experiences) depending on the affected brain regions, as follows:

Symptoms 

• Sensory changes (eg., flashing lights, strange odors, dizziness, and tingling sensations ) 
• Emotional changes (e.g., joy, excitement, fear, anxiety, déjá vu, jamais vu) 
• Involuntary muscle jerking (in limbs) 
• Cognitive changes (e.g., memory and language problems)²

Possible causes and triggers

• Structural brain abnormalities (e.g., Tumors, developmental malformations, stroke) 
• Previous head injuries (e.g., TBI)
• Genetic disorders  
• Emotional stress 
• Sleep deprivation² 

Focal impaired awareness (complex partial) seizures 

Focal impaired awareness (complex partial) seizure is the most common subtype with consciousness disruptions, usually confusion, repetitive movements, automatisms, and amnesia less than three minutes after an aura.^1,2

Potential underlying conditions 

• Structural brain abnormalities (e.g., Tumors, cortical dysplasia)
• Previous head injuries (e.g., TBI)
• Temporal lobe epilepsy 
• Emotional stress 
• Sleep deprivation²  

Partial with secondary generalization 

Also known as evolving partial seizures, it begins as focal seizures but then as electrical activity surge intensifies and progresses to both cerebral hemispheres, resulting in generalized “focal to bilateral tonic-clonic seizures”, affecting full body muscle movements with convulsions.³

Generalized Seizures

Generalized seizures are epileptic subtypes involving widespread electrical disturbances among both cerebral hemispheres. They are typically more severe, resulting in a loss of consciousness, manifesting as tonic-clonic movements, myoclonic jerks, absence and atonic (drop) seizures, affecting the entire body simultaneously.¹ 

Absence seizures 

Absence (petit mal) seizures are brief, sudden lapses of awareness, typically lasting 5-20 seconds, less commonly a few minutes among children. Although brief, it can be frequent from 10-30 times, even hundreds daily in some cases. Yet, they are mostly outgrown during teenages.⁴ 

Signs and symptoms

• Brief, sudden loss of awareness and responsiveness 
• Absence or vacant stare 
• Interrupted activities during episodes 
• Occasional eyelid myoclonia, head nodding, or other “automatic” hand or mouth movements⁴

While the exact cause is still unclear. It can coexist with other seizure types and is potentially associated with genetic epilepsy syndromes, developmental disorders, or brain abnormalities. 

Tonic-clonic seizures 

Tonic-clonic (convulsive/grand mal) seizures are the most visible and recognized subtype causing uncontrollable convulsions and strong muscle movements on the entire body not more than a few minutes. It typically consist of 3 phrases:  

• Tonic (10-30 seconds): Muscle stiffness, loss of consciousness, rigid body posture 
• Clonic (30-60 seconds, or longer): Rhythmic jerking movements (oftenly affect the limbs), altered breathing, loss of bladder and bowel control 
• Postictal (~30 minutes): Post seizure recovery returning, may feel confused, headache or muscle aches⁵

Potential triggers and complications of tonic-clonic seizures

While tonic clonic seizures are most commonly triggered by epilepsy, medical non-compliance, sleep deprivation, alcohol or drug use, and flickering visual stimuli. Severe complications such as injuries from falling, tongue biting, breathing difficulties, post-seizure confusion, and potential risks associated with seizure duration and frequency.⁵ 

Despite tonic-clonic seizures, there are also specific separated tonic and clonic seizures subtypes with specific tonic or clonic manifestations.⁶  

Myoclonic seizures

Myotonic seizures are the most common childhood seizure, characterized by sudden, brief, shock-like involuntary muscle jerks or twitches, affecting specific muscles or the entire body for a couple of seconds, without or minimal awareness changes.⁷  

Possible causes and associated conditions

While myoclonic seizure are usually no disabling and happen alone, it is also typically associated with conditions such as:

• Juvenile Myoclonic Epilepsy (JME)
• Progressive Myoclonic Epilepsy (PME)
• Metabolic disorders 
• Neurodegenerative diseases (e.g., Alzheimer’s disease or frontotemporal dementia)⁷ 

Atonic seizures 

Atonic (drop) seizures (drop attack) are a brief and sudden weakness and loss of muscle tone, leading to drop or collapse in one or various body parts, even sudden falling to the ground, with a brief unconscious period. Although they are usually brief, varying from less than 15 seconds to a few minutes, the individual might be able to get back up when seizure passes. The unpredictable, generalized loss of postural control, fall or collapse, can still leave the individuals vulnerable to potential injuries, like head trauma, fractures, or bruises.^1,6 

Specific features

• Sudden limp of part or entire body, causing droopy eyelids, head nod/drop, dropping things
• Falling to the ground like a rag doll when muscles are limp while standing
• Falling like tree trunk (as tonic seizures), when muscles are stiff or rigid  
• Head or upper body slumping when sitting⁸   

While atonic seizure is commonly seen among Lennox-Gastaut or Dravet syndrome, it can also happen in combination with other seizure subtypes.⁸  

Other types of seizures

Febrile seizures

Febrile seizures are brief convulsions among young children between ages of 6 months to 5 years, in response to high fever caused by viral infection. Ranging from shaky movements, loss of consciousness and control, they are generally less than 5 minutes and harmless, without lasting effects.⁹  

Reflex seizures

Reflex seizures are the subtype triggered by specific stimuli or activities, which generally varies among individuals, including touch, flashlights, specific visual patterns, certain sounds, even specific movements. The specific characteristics are also diverse among types and underlying conditions.¹⁰ 

Infantile spasms

Infantile spasms are a form of epilepsy among babies under 12 months old. Characterized by brief abdomen, head, neck, and limbs tensing or jerking, lasting for 1-2 seconds, with one after another every 5-10 seconds, they are most common after infants awake from sleep. While this is usually a sign of developmental delays or regression associated with gene mutations, brain infections, injuries, and metabolic conditions, proper medical evaluation is crucial.¹¹ 

Non-epileptic seizures 

Non-epileptic (functional) seizures (NES) are similar to epileptic seizures but not caused by abnormal neurological electrical signals. They are often resulted from traumatic events or underlying mental health issues, such as major accidents, severe emotional upsets, physical or sexual abuses, being bullied, conversion disorder, or post-traumatic stress disorder (PTSD).^12,13  

Diagnosis and treatment 

Medical evaluation and diagnosis

Diagnosing seizures is usually a comprehensive evaluation by neurologists involving a detailed medical history, symptoms, and various diagnostic tests. These may include blood tests, electroencephalogram (EEG) which records brain activity, spinal tap for infections check, and imaging studies like CT or MRI scans to identify structural abnormalities and potential underlying causes.^1,14 

Antiepileptic medications 

Once seizure disorder is diagnosed, despite provoked seizure in treating its underlying causes, antiepileptic medications (AEDs) are usually the primary treatment for first-time unprovoked seizures. Prescribed based on specific seizure type, underlying causes, and individual factors, AEDs can help reduce the hyperactivated neuroelectrical activities, thus prevent or reduce seizure severity and frequency.^1,14 

Treatment options for refractory seizures

For those with refractory seizures, which seizures persist despite adequate trials of AEDs, several treatment options are still available, including:

Ketogenic diet

Ketogenic diets with low or no carbohydrates consumption can be effective for certain types of seizures, in reducing their frequency or stopping seizures entirely, especially among children. This is a particular worth trying alternative for those when AEDs can’t help and surgery is inappropriate.^1,15,16  

Vagal nerve stimulation (VNS)

Vagal nerve stimulation (VNS) is an often adjunctive treatment for refractory seizure.It involves stimulating device implantation to the left side of the vagus nerve (10th cranial nerve) that connects to the brain directly, in reducing seizures frequency and severity.¹

Brain stimulation 

Brain stimulation uses an implanted device to detect abnormal electrical activity in the brain and deliver mild electrical currents to the specific area in interfering or stopping the electrical activity of a seizure. The two forms of brain stimulation, deep brain stimulation and responsive neurostimulation (RNS) are currently available.¹ 

Epilepsy surgery

When AEDs and alternatives are ineffective, surgical interventions are considered in some cases to stop seizures by removing or disconnecting the affected brain area(s) from the rest. This is usually explored when seizure continues despite two ineffective AED trials at recommended doses, as well as seizures originating from a well-defined, surgically accessible region.¹

Living with seizures 

Seizure or epilepsy safety precautions and first aid

Dos 

• Make sure the person can breathe
• Removing them from sharp and dangerous objects and places (water or heights) 
• Pad the area if possible 
• Put them in rescue position 
• Time the seizure the best you can 
• Stay with the person, reassure and comfort them as they come out of seizure and recover
• Call for help if the person is having status epilepticus  

Don’t 

• Don’t restrain them 
• Don’t put anything in their mouth
• Don’t panic¹ 

Preventions  

Even though everyone is at risk of unpredictable seizures, there are still some lifestyle modifications and management tips to avoid the possible causes and reduce the risk.¹

• Having a balanced diet with healthy weight maintenance
• Manage infections carefully 
• Wear safety equipment 
• Don’t misuse alcohol, prescribed, or recreational drugs 
• Manage your overall health condition (especially blood sugar)
• Avoid possible seizure triggers (flashlights, loud sound)   

Summary 

Seizures characterized by abnormal electrical brain activity. While initially classified as unprovoked and provoked seizures, they can broadly be classified into focal seizures (originating from specific brain regions) and generalized (involves entire brain). Focal seizures can be further divided into simple forms (without loss of consciousness) and complex forms (altered consciousness). Generalized seizures include absence, tonic-clonic, myoclonic, and atonic seizures, and others like febrile, reflex seizures, and infantile spasms. While each seizure subtypes has its distinct features associated with different causes, accurate diagnosis, plus and appropriate treatment are crucial for effective management, to maximize the overall well-being and quality of life among the affected population. 

FAQs 

What is the difference between seizure and epilepsy? 

A seizure is a single event of abnormal electrical activity in the brain, while epilepsy is a chronic neurological condition involving recurrent seizures, whereas epilepsy is usually diagnosed when someone experiences two or more unprovoked seizures, indicating a tendency of recurrent seizure activities. 

What is status epilepticus? 

Status epilepticus is a medical emergency characterized by continuous or recurrent seizures without full recovery in between.