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Seizure Disorders

The definition of a seizure, not the behavioral definition because what we are going to do is go through now a list showing you behaviors that may sometimes resemble a seizure but actually are not seizure disorders, seizures, epilepsy. So from a neurologic point of view a seizure represents excessive and hyper-synchronous neural activity. Epilepsy is the tendency to have recurrent seizures.

That is simply a reactive seizure due to a metabolic derangement. Seizures are relatively common in childhood. If you look at the epidemiology, seizures occur more in childhood and more in old age. Most of the seizures that occur in old age are acquired from tumors, strokes and so on. So true epilepsy and epilepsy-related phenomenon and seizures are significantly noteworthy in childhood; 3-5% of all children may in fact experience a seizure at some time in their childhood. And about 1% of them may in fact have epilepsy. If you look at the overall epidemiology in any society, in fact, the incidence of seizures is always described as approximately 1%.

So we are going to go through a differential of all these behaviors you should know a little bit about, that are in fact not seizures. One of them is benign infantile myoclonus. It looks a lot like infantile spasms, that I’ll describe to you down this lecture, but basically it looks like an exaggerated Moro reflex. The baby may have a little bit of a trunk and head flexion.

There are breath-holding spells, which pediatricians see a lot more. It’s not something that comes to the neurology clinic but there could be seizures associated with it. It begins usually about six months, most common in the second year of life and typically will end by five or six years of age. Sometimes these are cyanotic because of the irritation and the cry that the baby may put up. Other times, if it is vasovagally triggered it may be pallid. You may in fact get a real seizure with this but it’s still not a seizure disorder primarily. Treating this with anticonvulsants is a waste of time.

The next one is syncope, which you all know about. It’s not that common in very young children but by adolescence becomes reasonably prominent. Sometimes you may get a history of impaired vision or sweating and by and large syncope is benign. In rare cases, particularly if it is induced by exercise, then your cardiology specialists will talk about it. Then you will start going into a differential of Wolf-Parkinson-White, all those other things. But those are not vasovagal.

Migraines rarely can be confused with seizures. There may be a case of migraine that we call acute confusional migraine, that I will again describe to you later, and that may resemble a long, complex partial seizure or sometimes it may seem like a non-convulsive status where the patient is kind of disassociated from the environment. If you were to run an EEG you would see continuous spike waves. It may resemble that but it may just be acute confusional migraine.

Then of course you can get seizures from electrolyte abnormalities, hypoglycemia. Many of those we do not call them epilepsy. Those are reactive seizures, and you correct the underlying metabolic abnormality and you don’t have a seizure problem.

Gastroesophageal reflux can occasionally be confused. There is a classic thing called Sandifer’s syndrome where we usually see the infant as advertised as often having these tonic seizures. That is, periodically the baby has just some sort of head-turning, may have some oral automatisms, may even have chewing, and it gets very tense and looks uncomfortable. Looks like a seizure.

Cataplexy is a neurologic syndrome. This often accompanies folks with narcolepsy. Narcolepsy is not common in the first decade of life, but may occur in the second decade and it’s one of the sleep disorders. I think you are all familiar with tic disorders. By and large I don’t think we would confuse them with epilepsy, but every once in a while people wonder if a tic is a myoclonic attack.

Then there are these movement disorders. What distinguishes a movement disorder from a seizure, from a neurophysiologic point of view, and neuroanatomic point of view, is epilepsy/seizures always come from the cerebral cortex. Movement disorders come from subcortical structures, typically basal ganglia. So we call it a movement disorder when we describe a tic or a chorea, but we can also have chorea athetosis that is familial, and there are two forms. One of them is the kinesigenic one.

Another very common pediatric occurrence is night terrors. This is again in the spectrum of parasomnias or sleep disorders. Again, we do not treat. We merely reassure parents. But if you hear the example of the behavior of night terrors in your Board exam, you should be able to recognize that. There are also some psychiatric conditions, such as Munchausen’s syndrome. We don’t see Munchausen’s syndrome, which I’m sure you’ve heard of in medical school, as commonly but Munchausen’s by proxy is seen.

The term simple versus complex refers to, simple meaning there is no alteration in consciousness. As the simple seizure spreads, eventually it becomes complex because then there is loss of consciousness and it can generalize to involve both hemispheres. The other interesting term, we hear the term aura all the time. The term aura does not mean premonition. The term aura actually describes the beginning of the simple partial seizure. The patient describes this and is kind of comes across as a so-called aura in lay language because that’s the part they can remember. So once it spreads to the bilateral regions they are no longer able to recall events, and it is no longer called an aura. But if you monitor during the aura, there are what we call ictal-electrographic discharges.

Then we will go, in the next slide, to generalized onset seizures. Here we have many many subtypes. We’ll talk a little bit more down the road about them. A common generalized seizure in childhood is the absence seizures, which in the old days was called petit mal. Myoclonic seizures can be generalized. Tonic seizures can be, where the whole body stiffens; maybe posturing. Then clonic, which just means shaking, clonic seizures. Rhythmic shaking is clonic. Shaking of extremities without a rhythmic feature is myoclonic, as you know. Then there are grand mal, or tonic-clonic seizures. There may be atonic seizures in some syndromes, where there is a drop attack. These are the kids you see running around with helmets.

So what I am going to do is, because pediatrics being what it is, the seizure behavior is very very classic for a certain age types so we are going to talk in terms of seizure syndromes. When we talk about a seizure syndrome it’s a little different than a seizure type. What a seizure syndrome implies, is that there is a characteristic age of onset, there is a characteristic prognosis, possibly remission. It also tells us whether there is going to be mental retardation or not, whether it will be readily responsive to medication or not, and so on. So it’s a constellation of things that go together. So there are neonatal seizures, febrile convulsions.

Hypoxic ischemic encephalopathy; (that is what the HIE stands for) that is like perinatal asphyxia, related seizures may of course eventually prognosticate developmental delay, cerebral palsy and so on. As I told you, the outcome can be benign. There is an interesting variant that you should know about. That’s called benign neonatal convulsions. In the English literature, often referred to as fifth-day fits. And I bet you have all encountered one or two of them in your training.

Febrile convulsions; another entity that you see more often than I do. They are most common in childhood. Probably peaks around a year-and-a-half. It can occur up to the age of six years, although it’s fairly uncommon. Can be familial. There are many many linkage analyses now to multiple sites. The simple ones here last less than 15 minutes and are generalized. The complex ones are longer, they may have focal features, or they may involve multiple seizures during a single febrile illness.

Early infantile epileptic encephalopathy; we don’t need to say much. There are many causes, but they are all kind of rare things. The child looks terrible right in the nursery, the prognosis is bad. I don’t think you need to know too much about it other than the fact that it exists.

Infantile spasms, on the other hand, you should know a little bit about. It’s also called West’s syndrome and the important thing about infantile spasms is it’s very age-specific. It does not have a single cause. The etiology can in fact be widely varied. It occurs usually between 4-6 months, although it can occur later but it will be uncommon after 14 months or so.

The classic treatments are; you should rule out pyridoxine deficiency and ACTH is the accepted treatment in this country. Most of the world has moved on to a drug called vigabatrin that is not approved here, so we will not talk about it. This is just to give you a little graphic thing. We will talk a little bit more about tuberous sclerosis in my third lecture, but you have to examine these kids carefully. So here you are looking at a ash-leaf spot.