Difference Between Absence Seizure and Focal Seizure

Both absence seizure and focal seizure involve abnormal electric activity in the brain. They occur when the firing pattern of neurons’ electric signals suddenly change. Regarding their differences, absence seizure is classified under generalized seizures and is typically exhibited as a few seconds of staring or rapid blinking. On the other hand, focal seizures are caused by a disruption of electrical impulses in one part of the brain. They last longer than absence seizures; they may last as long as a few minutes. The following discussions further delve into their distinctions. 

What is Absence Seizure? 

Absence seizure, also known as petit mal seizures, can be exhibited as a few seconds of staring or rapid blinking (Center for Disease Control and Prevention, 2020). It is classified under generalized seizures (grand mal seizures) that occurs when the abnormal electric activity begins in both the left and right brain hemispheres at the same time. The staring spells start suddenly, the individual going through an absence seizure may stop moving and just stare in one direction; this may be perceived as simply daydreaming. The episode resolves on its own after around 15 seconds or less (other sources say 30 seconds or less) and the normal state of alertness immediately returns. The person typically does not remember what transpired during the seizure and may just continue with what he was saying or doing like nothing happened (Johns Hopkins Medicine, 2021). 

The symptoms of absence seizure includes the following (Harvard Health Publishing, 2018): 

• Staring for a few brief seconds 
• Does not respond to people speaking 
• Blinking rapidly
• Twitching or jerking of an arm or a leg 
• Having no memory of the episode 
• Usually no confusion during the recovery period 

What is Focal Seizure? 

Focal seizure, also known as focal onset seizure or partial seizure, is caused by a disruption of electrical impulses in one part of the brain. It lasts longer than an absence seizure; it may last as long as a few minutes. There are times when a focal seizure changes to become a generalized seizure (i.e., secondary generalized seizures). The following are the types of focal seizures (Centers for Disease Control and Prevention, 2020): 

Simple Focal Seizures

These seizures only affect a small part of the brain; they can cause twitching, and/or having a strange taste, smell, or other odd sensations. The symptoms include abrupt change of emotions without reason, jerking of a body part (usually leg or arm), difficulty in speaking, a feeling of déjà vu, goosebumps, seeing flashing lights, and changes in how something might smell, taste, look, sound, or feel (Wells, 2017)

Complex Focal Seizures (complex partial seizures) 

An individual who has these seizures may feel dazed and confused; he will typically be unable to answer questions or follow directions for a few minutes. The symptoms include staring blankly, saying words repetitively, perform actions like riding a bike, hallucination, trying to hurt themselves, repetitively moving the mouth or smacking lips, and confusion after seizure (Wells, 2017). 

Secondary Generalized Seizures (Secondarily generalized seizures or focal to bilateral tonic-clonic seizures) 

A person who has this type will first experience a focal seizure, followed by a generalized seizure. Although it begins in one part of the brain, it eventually spreads to both sides of the brain. Regarding its symptoms, the seizures may begin with a change in sensation or movement; during this phase, the person is still aware of what is happening. In certain situations, it may begin with complex focal seizures that renders the person confused or unaware. Afterwards, the tonic phase often begins with stiffening of the muscles, since air is being forced past the vocal cords, the person emits a groan or a cry (probably does not reflect pain since the person is unaware at this phase). At this point, the person loses consciousness, breathing may be temporarily impaired, and jerking movements happen and there may be a loss of control of the bladder or bowel. The seizure’s active part usually lasts for 1 to 3 minutes (if it lasts longer than 5 minutes, it is already a medical emergency); consciousness returns slowly and the person may feel drowsy, confused, agitated, or depressed for hours or even for days (Kiriakopoulos, 2017).  

Difference between Absence Seizure and Focal Seizure

Definition 

Absence seizure can be exhibited as a few seconds of staring or rapid blinking (Center for Disease Control and Prevention, 2020). It is classified under generalized seizures (grand mal seizures) that occurs when the abnormal electric activity begins in both the left and right brain hemispheres at the same time. The staring spells start suddenly, the individual going through an absence seizure may stop moving and just stare in one direction; this may be perceived as simply daydreaming. On the other hand, focal seizure, also known as focal onset seizure or partial seizures, is caused by a disruption of electrical impulses in one part of the brain. It has three types: simple focal seizure, complex focal seizure (complex partial seizures), and secondary generalized seizures (Centers for Disease Control and Prevention, 2020). 

Other names/terms  

Absence seizure is also known as petit mal seizures while focal seizure is also known as focal onset seizure or partial seizure. 

Duration 

Regarding absence seizure, the episode resolves on its own after around 15 seconds or less (other sources say 30 seconds or less) and the normal state of alertness immediately returns. In comparison, a focal seizure lasts longer than an absence seizure; it may be as long as a few minutes. 

Symptoms

The symptoms of absence seizure includes the following (Harvard Health Publishing, 2018): staring for a few brief seconds, does not respond to people speaking, blinking rapidly, twitching or jerking of an arm or a leg, having no memory of the episode, and usually having no confusion during the recovery period. 

As for focal seizure, the symptoms may depend on the type. For simple focal seizure, the symptoms include abrupt change of emotions without reason, jerking of a body part (usually leg or arm), difficulty in speaking, a feeling of déjà vu, goosebumps, seeing flashing lights, and changes in how something might smell, taste, look, sound, or feel. For complex focal seizures, the symptoms include staring blankly, saying words repetitively, perform actions like riding a bike, hallucination, trying to hurt themselves, repetitively moving the mouth or smacking lips, and confusion after seizure (Wells, 2017). Moreover, for secondary generalized seizures, the tonic phase often begins with stiffening of the muscles, since air is being forced past the vocal cords; the person emits a groan or a cry. At this point, the person loses consciousness, breathing may be temporarily impaired, and jerking movements happen and there may be a loss of control of the bladder or bowel (Kiriakopoulos, 2017).

Absence Seizure vs Focal Seizure

Summary 

• Absence seizure, also known as petit mal seizures, can be exhibited as a few seconds of staring or rapid blinking. 
• Absence seizure is classified under generalized seizures (grand mal seizures) that occurs when the abnormal electric activity begins in both the left and right brain hemispheres at the same time.
• Focal seizure, also known as focal onset seizure or partial seizures, is caused by a disruption of electrical impulses in one part of the brain.

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