Down syndrome and seizures

Seizures either occur alone or affect people who are already suffering from certain medical conditions. They are defined as a sudden burst of electrical activity in the brain which leads to muscle twitching of certain parts of the body or the entire body. One of many conditions which may be accompanied by seizures is Down syndrome.

This is a genetic disorder that develops due to the presence of an extra chromosome 21. People suffering from Down syndrome are prone to many health problems and epilepsy is only one of them. However, if a person suffers from Down syndrome, it does not necessarily mean he/she will develop seizures. The presence of the syndrome only increases the chances of developing seizures.

Individuals with Down syndrome (DS) have an increased risk for epilepsy during the whole lifespan, but especially after age 40 years. The increase in the number of individuals with DS living into late middle age due to improved health care is resulting in an increase in epilepsy prevalence in this population. However, these epileptic seizures are probably underdiagnosed and inadequately treated. This late onset epilepsy is linked to the development of symptomatic Alzheimer’s disease (AD), which is the main comorbidity in adults with DS with a cumulative incidence of more than 90% of adults by the seventh decade.

More than 50% of patients with DS and AD dementia will most likely develop epilepsy, which in this context has a specific clinical presentation in the form of generalized myoclonic epilepsy.
Down syndrome, caused by an extra chromosome 21, is the most frequent cause of intellectual disability of genetic origin. Its prevalence ranges from 1/650 to 1/1000 births. During the last decades the life expectancy of people of DS has significantly increased, and it is estimated that children with DS born in 2010 will now live up to 60–65 years.
The prevalence of seizures at any age in DS is estimated to be between 8.1–26% (versus 1.5–5% in the general population) and has a clear bimodal distribution. The first peak/mode of incidence occurs in the early childhood (0–2 years) of life and the second in the 6th decade.
The prevalence of untriggered seizures in DS increases dramatically with age after age 45, in parallel with the emergence of symptomatic AD. The prevalence of epilepsy can be as high as 46% in those over 50 years of age, driven by the patients with symptomatic AD. This association is so close that the occurrence of a first episode of an untriggered seizure after the age 40–45 years is highly suggestive of symptomatic AD.
The development of epileptic seizures in DSAD has been associated with a more rapid cognitive and functional decline. Epilepsy is also considered as a risk factor for more frequent hospital admissions. Finally, epilepsy is also an independent risk factor for mortality in adults with DS.

✓ Fact confirmed: Epilepsy in Down Syndrome: A Highly Prevalent Comorbidity Miren Altuna, Sandra Giménez, and Juan Fortea1; 2021 Jun 24.

It is estimated that around 5-10% of people with Down syndrome will eventually develop seizures. The risk is higher in individuals who have physiological and structural abnormalities of the brain (brain dysgenesis). Furthermore, there is some connection between the onset of seizures in these people and their age. Namely, they are most likely to develop seizures in their first year of life and the risk again becomes high when they reach the fourth or fifth decade of their lives.

Types of Seizures Associated with Down Syndrome

These people are affected by all types of seizures. Still, the most commonly reported ones are tonic-clonic seizures. Reflex seizures are frequently reported as well. On the other hand, febrile seizures usually do not affect people with this genetic disorder.

The Connection between Seizures and Down Syndrome

There are many explanations for why seizures affect people with Down syndrome. For instance, some seizures develop due to cardiovascular disease. However, most seizures are actually not connected with any other condition the person is suffering from.

The abnormal electrical activity of the brain in such patients develops as a consequence of decreased inhibition of the electrical pathways, increased excitation of brain cells, structural abnormalities of the brain and changes in the number of certain neurotransmitters. There are certainly several more explanations for why seizures in these patients occur. They are yet to be explained.

Seizures in Down Syndrome Clinical Characteristics

Seizures affecting these people are actually not different from seizures in other people. Depending on the type, some affect only one part of the body while generalized seizures lead to jerky movements of the entire body. Loss of consciousness, incontinence and fatigue may be several more characteristics of seizures in people suffering from Down syndrome. Fortunately, with appropriate therapy, they are successfully brought under control.