Hypoxia and memory impairment in children

The brain uses a tremendous amount of oxygen in order to function. When the amount of oxygen that is available to the brain is temporarily reduced, we know that vulnerable brain structures can become damaged. MRI (magnetic resonance imagining) scans tell us that hypoxia can target a part of the brain called the hippocampus and cause damage. This area of the brain allows us to lay-down or save memories. When the hippocampus is damaged, it can impact on a child’s ability to remember past events and learn new information. Sometimes the child’s understanding might remain the same, but they simply cannot remember the information later on.

We call this type of memory disorder developmental amnesia. Not only can it interfere profoundly with a child’s life, especially in relation to their schooling, daily routines and their self-esteem, it can be very difficult for their parents too.

How is developmental amnesia diagnosed?

Developmental amnesia can occur without any other signs of brain damage, which can make this problem difficult to diagnose. But our ability to recognise and diagnose this condition is improving all the time. Once identified we can draw up a plan of management and support for the child at home and at school, and make recommendations for interventions. In order to diagnose the condition we use a series of neuropsychological tests and a brain scan (MRI) to take detailed pictures of the brain.

As our understanding of memory and the brain improves, we have learnt that some children are more at risk of developing developmental amnesia than others. These include children who have been born prematurely, those born with complex heart problems requiring surgery, or those who have been so sick in intensive care that they have needed to go on a heart-lung bypass machine to enable medical treatment.

How are we trying to help children with developmental amnesia?

In order to understand how we can help those children who are diagnosed with developmental amnesia, we first need to understand more about how reduced oxygen supply (ie hypoxia) can affect the brain.

In our study, we use MRI scans to take images of the brain. This allows us to compare how a brain that has been exposed to reduced oxygen might look compared to a brain that has always had a normal supply. By using MRI scans alongside our neuropsychological tests of memory and other functions, we are able to look for and diagnose different patterns of memory problems, ranging from mild to severe difficulties (ie developmental amnesia) earlier on in life, so that we can organise the support that the child might need.

Identifying the child’s continuing needs is also forming the basis of our second study on hypoxia in infancy through to adolescence.

With funding from the Medical Research Council, our study has been running for five years and has interested many parents and children who are keen to help us make a breakthrough in how we support and remediate memory problems. Our preliminary findings have been very informative and they have already helped us to think about ways we can better care for patients. But there is still work to do.

So far we have focused on children with pronounced memory problems associated with prematurity, open-heart surgery, or intensive care treatment for acute cardiorespiratory problems. We are now looking at children who have other cardiorespiratory problems and complications and comparing them to healthy children in our study.