Classifying Seizures

A 5-month-old wearing the EEG cap, alongside his mother. Photo courtesy Sid Kouider.

In the comment she left on another post, a reader asked that I describe the various type of seizures. I am not a physician, and I am not an expert on epilepsy or seizures. The information in this post is not for the diagnosis or treatment of seizures. If I miss something in this post, please let me know.

There are two main types of seizures: focal (partial) and generalized. A focal seizure occurs in one part of the brain while a generalized seizure occurs in every lobe of the brain. It is possible for a seizure to begin in one part of the brain and spread to another part or all parts of the brain.

Focal Seizures

Focal seizures are referred to as either simple or complex. During a simple partial seizure, people are usually aware of their surroundings, whereas in a complex partial seizure people are generally not aware of their surroundings.

According to Barrow Neurological Institute, symptoms of people who experience complex partial seizures may include:

  • A glassy stare and lack of response
  • Inappropriate or confused responses to questions
  • Sitting, standing, or walking aimlessly
  • Lip smacking or chewing motions
  • Unusual vocal sounds
  • Fidgeting

Partial seizures with secondary generalization are focal seizures that spread to both sides of the brain causing a grand mal convulsion. Except for beginning locally and spreading, partial seizures look the same as the generalized tonic-clonic seizure, described below. Many families describe a complex partial seizure as the patient’s “small seizure” and the convulsions that result from secondary generalization as “big seizures.”

Generalized Epileptic Seizures

Generalized Epileptic Seizures begin on both sides of the brain simultaneously. Several studies indicate these seizures are genetic or hereditary. Barrow Neurological Institute suggests, “generalized seizures include absence seizures, tonic-clonic seizures, myoclonic seizures, and atonic seizures (also called drop attacks).”

  • Absence seizures — The Mayo Clinic explains, “absence seizures involve brief, sudden lapses of consciousness. They’re more common in children than adults. Someone having an absence seizure may look like he or she is staring into space for a few seconds. This type of seizure usually doesn’t lead to physical injury.
  • Tonic-clonic seizures (formerly known as grand mal seizures) — Johns Hopkins Medicine describes tonic-clonic seizures as a combination of a tonic and colonic seizures. “During a tonic seizure, the person’s muscles initially stiffen and they lose consciousness. The person’s eyes roll back into their head as the muscles contract and the back arches. As the chest muscles tighten, it becomes harder for the person to breathe – the lips and face may take on a bluish hue, and the person may begin to make gargling noises. During a clonic seizure, the individual’s muscles begin to spasm and jerk.  The elbows, legs and head will flex, and then relax rapidly at first, but the frequency of the spasms will gradually subside until they cease altogether. As the jerking stops, it is common for the person to let out a deep sigh, after which normal breathing resumes.”
  • Myoclonic seizures — usually appear as sudden brief jerks or twitches of your arms and legs.
  • Atonic seizures — in an atonic seizure, muscles suddenly lose strength. The eyelids may droop, the head may nod, and the person may drop things and often falls to the ground. These seizures are also called “drop attacks” or “drop seizures.” The person usually remains conscious. These seizures typically last less than 15 seconds. Many people with atonic seizures are injured when they fall, so they may choose to use protection such as a helmet.

Please consult your physician if you have additional questions about the symptoms, diagnosis, or treatment options associated with any seizure activity.

Credits

Thanks to Barrow Neurological Institute; Epilepsy FoundationJohns Hopkins MedicineMayo Clinic; WebMD; Wikipedia; and all the people who, directly or indirectly, made it possible to include the picture and text in this post.

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