Sep 20, 2010
Down Syndrome and Epilepsy
by Len Leshin, MD, FAAP
|Copyright 1997, All rights reserved
|A seizure is a loss of control of the body by the brain. A sudden surge of electrical activity, in a pattern of no particular usefulness, takes over the brain for anywhere from one or two seconds to hours. For children with seizures, most are the type associated with infants and toddlers and fever; these are short and rarely cause health problems or lasting side effects. However, if a child or adult has more than one seizure not associated with fever, then the condition is termed "epilepsy."|
|If you look at the population of all children with mental retardation, there is a very large number (from 20 to 40%) that have epilepsy. The number is quite lower in Down Syndrome, but it's still a larger number than in the general population. Studies in the last two decades have estimated the number of people with DS who have seizures to be from 5 to 10%.|
|There appears to be two "peaks" in ages at which the onset of epilepsy is more common in DS. The first peak occurs in the first two years of life. The type of seizure most often seen in this age range is the "infantile spasm." This type of seizure involves what looks like a spasm of the body, lasting a few seconds, and sometimes not affecting the infant's state of consciousness. It can also look like a quick drop of the head and/or shoulders if the baby is sitting or standing up. Another type of seizure seen is the generalized "tonic-clonic" seizure (also called "grand mal"); this type of seizure involves the whole body, with stiffening of the trunk and jerking of the extremities, followed by a period of sleepiness. Other types of seizures have been described, including atonic (head-drop) seizures and reflex (myoclonic, "startle") seizures.
The second "age peak" at which people with DS tend to develop seizures is in adulthood, usually between 20 and 30 years of age, but it can develop later in life as well. The most common seizure in this age range is the tonic-clonic seizure, but other types are also seen.
Usually the seizures are fairly obvious, but sometimes they're not. Diagnosis of epilepsy is based on the history of the episodes along with an EEG (brain wave study). A normal EEG does not, unfortunately, mean a person does not have epilepsy, so doctors have to rely a lot on the description of the episodes. Sometimes, a doctor may want a video recording of the child while the EEG is being done to help make the diagnosis. When an EEG is abnormal, an MRI scan of the brain is often done to look for structural abnormalities of the brain. When a seizure is accompanied by fever or other signs of infection, a spinal tap (lumbar puncture) may be done to look for infection in the spinal fluid.
Why do some children with DS have seizures? Some seizures are associated with a specific problem, such as cardiovascular diseases. However, a great many seizures have no association with any other clinical condition. The answer lies somewhere in the balance in the brain between the "excitatory" and "inhibitory" pathways. At the risk of oversimplifying things, there are four different ways that this could happen: (1) Decreased inhibition of the electrical pathways; (2) Increased excitation of the brain cells; (3) Structural abnormalities of the brain leading to electrical overstimulation; and (4) changes in the amounts of neurotransmitters (the chemicals made by brain cells to send signals to each other to fire electrical impulses or not fire). However, since not all children with DS have seizures, there must be another factor involved. Unfortunately, we have many clues but no definitive answers.
The treatment of epilepsy involves the use of anticonvulsants, which are designed to increase the effectiveness of the inhibitory part of the brain, so as to decrease the number of seizures. There are many anticonvulsants and the choice of which to use usually falls to the discretion of the neurologist. Most cases of epilepsy are fully controlled by either one anticonvulsant or a combination of more than one. Also, there has been a heightened interest in a dietary treatment called the Ketogenic Diet, which has an anticonvulsant effect on the brain.
Outcomes for children with epilepsy are highly variable, and no less so for children with DS. A few generalizations may be made. Children with seizures due to a specific cause (cardiovascular disease, infection, etc) tend to have epilepsy for longer than do children with no identifiable cause. Persistent seizure activity may cause delay or even regression in development, but almost all children catch back up and continue to make developmental strides forward.
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