One of my readers emailed me and asked me to talk a little about infantile spasms and hypsarrhythmia as he has a niece who has been diagnosed with this condition. So in this post we shall talk about the same.
First and foremost the term hypsarrhythmia does not refer to a disease, it actually refers to a characteristic EEG pattern seen in some infants who have infantile spasms (their EEG shows some special features and is characteristic for their disorder). So what do we mean by infantile spasms. Infantile spasms as the name suggests are spasms which occur in infants (by infants I mean less than one year of age). These are special kind of seizures in which the infant is noted to have spasm like movements. It is hard to describe what spasms look like clinically but they can be of 2 types: extensor spasms and flexor spasms (the infant is noted to have sudden abduction of the arms and legs, a good example would be to imagine what you would do if some one suddenly frightens you: you shall suddenly jerk and abduct your arms and legs).
In infantile spasms, infants have flexor and extensor spasms. They usually occur in clusters and sometimes an infant may have as many as 15-20 spasms in 5 mins. These spasms represent seizures and when you do an EEG on these infants you do find characteristic EEG findings suggestive of seizures. This now brings us to the term hypsarrhythmia. As I stated earlier this refers to the EEG of a child with infantile spasms (the EEG is disorganized, of very high amplitude and shows multi-focal epileptiform activity. By multi-focal I mean, that there are many spots/ areas in the brain which shows signs of epileptogenicity). Infants who have infantile spasms may also have other types of seizures as they grow up. They may have seizures characterized by sudden jerks (we call these myoclonic jerks) and other more typical seizures where-in they have jerks of the arms and legs.
Etiology/ causes of infantile spasms: an infant may have infantile spasms and no cause may be determined even after a good work up. In that case the condition is referred to as idiopathic infantile spasms (idiopathic meaning for which no cause is determined). Usually though in most infants a cause for infantile spasms can be determined after a thorough work up. Work-up for infantile spasms usually should be carried out in a big center where the doctors have sufficient experience in dealing with these complicated cases. The doctor shall order many tests. Some of them include an EEG (at times the doctor might admit the infant and do a more prolonged EEG test. This is called a video-EEG monitoring test). Other tests which may be carried out include imaging studies of the brain such as an MRI (children and babies usually have to be sedated prior to the MRI test), tests of the blood to rule out any metabolic and storage diseases etc.
Once the diagnosis is secured and the etiology determined, then the question of management arises. Management involves 2 issues, one is the management of the underlying condition which is the cause of the infantile spasms (if the spasms are idiopathic we do not have to deal with this issue), the other is the management of the spasms/ seizures itself.
Infantile spasms usually respond to ACTH (adrenocorticotrophic hormone), a type of steroid preparation. It has been seen that when infants are started on ACTH, their spasms may completely stop and their EEG may also normalize (that is the hypsarrhythmia pattern goes away). There are other drugs which can be used too and your doctor shall help you in deciding the best option. It has been noticed that in some infants as the ACTH is stopped the spasms come back.
It is important that infantile spasms be detected and treated in time because ongoing spasms effect the cognitive development of the child and may lead to developmental arrest.
I hope this shall be helpful to some of you. If you seek more information, please do let me know.
Nitin Sethi, MD