Brain function and brain surgery in children with epilepsy

Our actions, thoughts, perceptions, feelings, and memories are underpinned by electrical activity, which passes through networks of neurons in the brain. As a child grows and gains new skills their brain changes rapidly and brain networks are formed and strengthened with learning and experience. Neurons within brain networks form a unique representation of a person’s external and internal world, storing information from the past and capturing new experiences and knowledge. A person’s brain will continue to develop throughout their life, but the greatest changes take place early.

Epilepsy affects around one in every 100 people, most of whom experience their first epileptic seizure during childhood or old age. Seizures are the result of abnormal electrical activity in neurons, which disrupts normal brain function and behaviour: people may abruptly change what they are doing, lose consciousness, or suddenly fall down to the ground and shake. Frequent seizures can have a profound effect on a child’s cognitive abilities, such as their attention, reasoning skills, language, and memory. The recurrent abnormal electrical activity disrupts the function and development of the healthy brain networks. Children with severe epilepsy often don’t learn as quickly as their peers, and as a result often fall behind in school.

Medications usually control epilepsy well, but in 30% of people, the drugs just don’t work. Where the source of abnormal electrical activity can be pinpointed in the brain, surgery can be option for treatment. However, surgery for epilepsy is not straightforward: whilst taking out the brain tissue responsible for causing seizures, the surgeon might also remove tissue that supports important cognitive abilities. This happened in 1953 to a young man called Henry Molaison. To treat his highly disabling epilepsy, surgeons removed tissue in both of the temporal lobes of his brain. The procedure was successful in treating his epilepsy, and in many ways he was unchanged — he retained his sense of humour, language skills, intellect, interests, and values. But Henry couldn’t keep hold of any new personal memories. At age 82 he died with the memories of a 27-year-old man.

Although we now know that the temporal lobes are vital for creating and storing new memories, they continue to be vulnerable to frequent, devastating and drug resistant seizures. As a result, temporal lobe surgery has endured as a treatment for epilepsy to this day. Surgical methods have changed notably. For example, brain tissue is now only ever removed from one temporal lobe, which limits risks of amnesia like Henry’s. Surgeons can also more carefully target brain tissue involved in generating seizures through modern brain imaging and new surgical techniques. Even so, adults with temporal lobe surgery often have memory problems. Most often, problems with remembering lists of words and stories are reported after surgery to the left temporal lobe.

Almost two thirds of children and adults are cured of their seizures after temporal lobe surgery. When faced with a choice between living with frequent and impairing seizures for the indefinite future, and brain surgery with risks to their cognitive abilities, many patients and their families choose surgery. Doctors will advise earlier surgery if a child rapidly starts to fall behind their peers and lose skills. The hope is that stopping the seizures will also stop the child from losing skills, and that the adaptability of the young brain will help them to recover after brain tissue has been removed.

Until recently, the long-term impacts of epilepsy surgery in childhood were unclear. New research published in the journal Brain finds that surgery for drug resistant epilepsy not only reduces seizures, but also has a protective effect on the memory of children. A group of 53 children with drug-resistant epilepsy, 42 of whom had temporal lobe surgery, were re-evaluated on average nine years after surgery. Seizures had stopped after surgery in 36 children (86%), and overall their memory had improved. Those with right temporal lobe surgery had improved memory for stories, whilst those with left temporal lobe surgery had improved memory for simple drawings. Better memory was seen after smaller surgical interventions, with less brain tissue removed. An earlier research report published in 2011 in the journal Neurology, showed that these same children also improved in a measure of intelligence (IQ) after surgery, which was linked to greater growth of grey matter in the brain after surgery.

This new research suggests that uncontrolled seizures may obstruct cognitive development in children. After temporal lobe surgery, brain function in healthy and intact brain tissue can be restored or even improved. However, while surgery benefited most children in this study, responses to surgery varied greatly from child to child. Some improved straight away, others lost skills and then improved, some showed no change, and others declined. The finding that less extensive surgery can help to improve memory may be an important first step in bettering outcomes after epilepsy surgery in children. Ever evolving and improving brain imaging techniques can help us to better target brain tissue causing seizures, and tailor surgery to help improve memory outcome. Beyond this, what makes different children respond so differently to severe epilepsy, and to epilepsy surgery remains a puzzle to be solved.

Featured image: Computed tomography of human brain. Department of Radiology, Uppsala University Hospital. Uploaded by Mikael Häggström. CC0 via Wikimedia Commons.