The Classification of Epilepsy and Seizures

A discussion on the classification of epilepsy and seizures, and how the process of definition has advanced.

Trevor Resnick, MD: One of the other questions that I think comes up in this scenario is, and this is pertinent to neurologists taking care of patients like this, at the advent of this presentation it’s fair to say we don’t know whether this patient has focal seizures evolving to generalized seizures, or generalized seizures at the outset. I think that if you look at the new classification of epilepsy and the new classification of seizures, and this is a work in progress that’s been going on for the last 30, 40 years. 

But there has been a material change in the terminology in the newer classification. And what’s happened in the new terminology is there’s much less room for ambivalence. The terms that we used previously were not obvious in terms of what they meant. The new classification, it’s a much simpler, more straightforward, less ambivalent classification. The terms such as “partial, partial complex, secondarily generalized seizures” are not used any more, and it’s a simpler way of describing it saying, “This patient has a focal seizure. It’s a focal seizure with intact awareness, or impaired awareness,” and then you describe the actual symptom that the patient has, which may be anxiety, or palpitations, or flushing.

When I’m telling you what kind of seizure this patient had, there’s no second guessing about what I actually mean. I’m actually describing it the way it is. And what the new classification has done, it has allowed for that transparency in terms of its description. In this case you would say, “The seizure is either focal, or it’s generalized,” based upon what I just told you, or it’s unknown. Now that’s a very important part of a classification because it says that we don’t always get all the information we want when we have a patient who presents with epilepsy. Sometimes we just get a clinical story that doesn’t allow us to distinguish between whether this is a seizure that evolved from a focal seizure to a generalized seizure, or whether this was a generalized seizure from the outset. 

Let’s say we would have done the EEG [electroencephalogram] in this patient, and the EEG would have been normal. Under those circumstances we would still have to put this adolescent’s seizures into the unknown bucket. In other words, unknown whether it was generalized, or focal evolving to generalized. 

Then you make decisions based upon that information. I think this happens with all neurologists who treat patients with epilepsy. We have pieces of information, sometimes enough information to diagnose the patient more fully, and sometimes enough information even to diagnose an epilepsy syndrome. So this case is a good case because it shows you how the different pieces add together to provide a fuller picture of what the diagnosis is.

What we discussed earlier is the fact that as we look at this patient’s symptoms, we may or may not get a full picture, and that’s the reason the new classification allows you, when you diagnose or classify the actual seizure itself, to say either it was focal or generalized, or unknown.

In the second layer, which is the classification of epilepsies, it provides for a bit of an expansion because you’re not actually describing just a single seizure, you’re describing that patient and their seizures. It expands it to a certain extent in that now you can say: “This patient has focal seizures, that’s all they have.” Or, “This patient has focal seizures, and they have generalized seizures.” And there are some entities, either genetic or metabolic conditions, or structural conditions of the brain, where the patient, based upon the networks that are involved in the patient’s seizures, they may have both focal seizures and generalized seizures. 

Now the additional points that are made in sense of the epilepsies would be that as opposed to just the description of a specific seizure, we’re now talking about the patient and the patient’s habitual seizures. And we’re saying that this patient’s habitual seizures are just focal; or they are just focal with impaired consciousness; or they are focal and they are generalized; or they are only generalized; or we don’t know.

It gives you again different buckets of the ways to think about patient’s epilepsy. And at every point along the way, you’re thinking about the description of the seizure and where it fits. But you’re also thinking with 2 other hats. And the 2 other hats are, “Well, this patient had a seizure, and whether it’s focal or generalized, why?” And then you have to go through the paradigm of thinking about, well, is there structural pathology in the brain, which would require you to do an MRI?

Is there a genetic mutation that is causing seizures in this patient? Does this patient have some kind of infectious disease or some other form of damage to the brain that has made them susceptible to having seizures? And that’s where the history comes into play where you’re saying, “OK, the patient has a seizure, what do we see in their history, or what questions do I need to ask in terms of evaluating the patient that may have caused these seizures?”

That list of structural versus genetic, versus metabolic, versus infectious disease, or a hypoxic insult to the brain—all those things figure in to an epilepsy syndrome diagnosis at the end of the line. 

The other issue that I think is figured in, very importantly, is what we call comorbidities. If you have an underlying abnormality in the brain, either genetic or structural or whatever the case may be, that underlying abnormality is causing a symptom, and the symptom is a seizure, but it may be causing other symptoms as well. It may be causing the patient to have learning disabilities, cognitive impairments, emotional behavioral abnormalities, etc.

So when again you’re thinking about a patient who presents with a seizure, we have to be thinking about it with a much broader stroke and looking at causation and comorbidities, so that when you plan treatment and counseling, you’re taking all those things into account. 

I think that’s another area where in the newer classification of epilepsy, a lot of the descriptive terms such as catastrophic, or malignant, or benign have been taken out because it doesn’t necessarily apply to every patient. A specific epilepsy syndrome may be relatively benign in one patient and not relatively benign in another patient; therefore, you cannot use it as a descriptive syndrome for all patients. I think a lot of that’s been taken out of the new classification to make sure that it’s much more direct and accurate. 

Additionally, there are patients who may have a specific seizure type. For example, they may have an epileptic spasm, or infantile spasms. And often that ends up being put into specific buckets. But because it is now much more direct in terms of the communication, you can have an epileptic spasm that fits into the focal seizure bucket, or into the generalized seizure bucket. And you’re basing that on what the clinical seizure looks like and what the EEG looks like. So again, the new classification allows for a much more accurate, specific form of classifying patients.