Once the physician decides the patient has epilepsy, it is important for the physician to properly classify the seizure disorder. Many of the antiepileptic drugs (AEDs) only work for one or some classes of seizures and not others. Classification of seizures has changed throughout the years. For an adult neurologist like myself, it is easiest to think of epilepsy as divided into two major types.

The first type of seizure is one that begins in a focal part (i.e. in one area) of the brain. This type of seizure is known as partial-onset seizure. A seizure which begins in a focal part of the brain and does not cause loss of consciousness is known as a simple partial seizure. An example of a simple partial seizure is a shaking limb that cannot be controlled. (Shaking limbs can be from things other than seizures as well.) Next, there is a type of partial seizure that does cause a loss of consciousness. This type of seizure is known as complex partial seizure. This is the most common type of seizure that begins during the adult years. A third type of partial seizure is one that begins in part of the brain and then spreads to both sides of the brain. This is known as a partial complex seizure with secondary generalization.

The second type of seizures is one that begins over the entire brain at once. An example of this type of seizure is the classic absence seizures of childhood, formerly called petit mal seizures. The typical event consists of staring spells that coincide with a characteristic three cycle per second spike and wave pattern on EEG. Another generalized seizure type is one that begins with violent shaking all over the body, also called generalized tonic-clonic seizures. Still another generalized seizure type is the atonic seizure, drop-attack, which is manifested by a sudden loss of consciousness with a fall to the floor.

After evaluating and treating hundreds of patients with epilepsy in over 14 years of training and practice, I have personally witnessed only about a dozen live seizures. Therefore, one of the major problems with epilepsy is classification when not even the patient is able to give a detailed history. For example, a patient may have a partial onset seizure that generalizes and causes tonic-clonic movements all over the body. The patient may have had this in public and the only history he will know is that the paramedics told him when he was on the way to the hospital that they were told by people on the scene that he had a grand mal seizure. The patient himself may remember nothing except being in a store one minute and waking up confused, tired, and aching in an ambulance or emergency room. At the other extreme, a generalized absence seizure and a partial complex seizure may both present as staring spells that the epileptologist (an epilepsy expert) can only tell apart from the EEG.