Why Classify Epilepsy?
The classification of the epilepsies is essential for enabling understanding and communication. It gives a vocabulary, a defined set of words that make possible the communication between scientists and physicians. Seizures are organized into groups based upon similarities in behavior or experience displayed during a seizure. These similarities relate to where in the brain the seizure activity is occurring. There are two main groups of seizures: focal (previously called partial seizures) and generalized. Focal seizures are those that involve part of the brain and are limited to one hemisphere or half of the brain. Generalized seizures involve both hemispheres/halves of the brain.
Why change the names given to different types of seizures?
One reason to change the names used to describe seizures is to simplify the terms currently in use. An example is the change from idiopathic and cryptogenic to genetic and unknown, respectively, to describe the cause of the epilepsy. Another change in the classification system is the change from partial to focal and the change from complex partial seizure to focal dyscognitive seizure. Although these changes do not necessarily simplify the terms in use, they are more descriptive of what changes occur in the brain during a seizure. The goal of this report is to clarify the recent changes in the classification of focal seizures (previously referred to as partial seizures).
What is meant by focal seizures?
Focal seizures are divided into two categories: focal seizures without loss of consciousness (previously referred to as simple partial seizures) and focal dyscognitive seizures (previously referred to as complex partial seizures) which involve a loss or change in consciousness or awareness. Focal seizures are categorized by the location/lobe in the brain in which the ictal activity occurs. Focal seizures without loss of consciousness may alter emotions or change the way things look, smell, feel, taste, or sound. Sometimes they also involve arm or leg jerking and other sensory symptoms such as tingling, dizziness, and flashing lights. These symptoms may be confused with other neurological disorders such as migraine, narcolepsy, or mental illness. A thorough examination and testing are needed to distinguish epilepsy from other disorders.
Dyscognition, also known as “fibro fog,” is a medical term in recent use to describe symptoms related to difficulty concentrating, disorganized thinking, memory problems, and the inability to stay focused or alert. Focal dyscognitive seizures produce impairment(s) in perception, attention, emotion, memory, or executive function and may present as staring into space without responding to surroundings normally or performing repetitive movements, such as hand rubbing, chewing, swallowing, or walking in circles. They usually last around 2 minutes and the most important factor in the classification of the focal epilepsies is the history provided by the patient and, when available, a seizure witness.
Another terminological change is a focal seizure evolving into a bilateral or convulsive seizure (previously referred to as a secondary generalization). Again, the goal of this name change is to provide a more accurate description of the changes that occur in the brain during this type of seizure. The seizure starts as a focal episode, limited to one hemisphere, and as both hemispheres become involved it changes into a convulsive seizure.
“If I wished to show a student the difficulties of getting at truth from medical experience, I would give him the history of epilepsy to read.” Oliver Wendell Holmes, Sr. He was a physician during the early 1900s and the father of Oliver Wendell Holmes, a justice of the Supreme Court. This quote gets at the heart of the problem with the classification of the epilepsies throughout time, throughout stigma, throughout scientific technological advancements, and throughout all the experts along the way; the classification of the epilepsies is mired with controversy and change to this day.
*Focal without loss of consciousness and focal dyscognitive seizures are then further classified by the location in the brain where the seizure activity takes place as seen on EEG or based on patient history.