Exploring hemispherectomy and its impact on memory

Many parents are cautious about allowing their child to have hemispheric surgery because of the potential outcomes such as losing some ability to move, or more importantly, losing memory. 

In 2019, the Pediatric Epilepsy Surgery Alliance (then known as The Brain Recovery Project) held an important meeting where scientists identified gaps in research after big surgeries like hemispherectomy. One scientist, Dr. Mary Lou Smith, identified many gaps in research around memory. After the meeting, Dr. Smith was inspired to look at her own data to understand memory after hemispherectomy. In 2020, she and her colleagues published the research paper Memory Outcomes Following Hemispherectomy In Children.

Investigating Memory Function In Children After Hemispherectomy Surgery

Dr. Smith and her team wanted to find out more about how memory works in children who have had hemispherectomy surgery. The goal was to look at how the children’s memory changed before and after the surgery.

Profile of Hemispherectomy Patients: Age, Conditions, and Surgery Outcomes

The study included 22 children who had hemispherectomy surgery at the Hospital for Sick Children in Toronto between 1999 and 2016. All the children had seizures that did not stop with medication. Some of the children were as young as 3 1/2 years old when they had surgery, and the average age at the time of surgery was a little over ten years old.

Before the surgery, the children were having seizures from a young age. After the surgery, some children still had seizures, but the researchers were more interested in how their memory was affected.

Assessing Memory After Hemispherectomy: Tools and Techniques

To check memory, the children were given different tests before and after surgery that were appropriate for their age. They had to remember stories, words, faces, and locations. Lower scores on these tests meant their memory wasn’t good.

The tests included:

• Stories and Word Pairs subtests (Children’s Memory Scale or Denman Neuropsychological Memory Scale)
• Digit span (Wechsler Intelligence Scale for Children IV)
• Word list (California Verbal Learning Test-II or CHildren’s Auditory Verbal Learning Test).
• Visual memory (Faces and Dot Location subtests Children’s Memory Scale or Denman Neuropsychological Memory Scale)

The children did not perform all the tests before and after surgery. For example, only four children were able to complete the digit span test.

Memory After Hemispherectomy: Results of the Memory Tests

The researchers found that, as a group, the kids had a hard time with memory tasks both before and after the surgery. On average, they did well on only 23% of memory tasks before surgery. A year after surgery, they showed stable performance in about 65% of the memory tests. This means that, for many kids, their memory stayed the same after the surgery.

In this small group studied, younger patients showed more improvement in memory tasks compared to older patients who generally didn’t show any improvement.

However, to be sure about these results, we need to study more children over a longer time. Future studies should try to find clues that can help predict which kids might see their memory get better or stay the same, and which might not, after having a hemispherectomy.

A Guide for Parents

Parents should know that memory issues are common in kids who need hemispherectomy surgery. The study shows that, for most kids, their memory stays the same after the surgery. Some may see improvements, but it’s also possible for memory to get a little worse. It’s important for parents to work closely with neuropsychologists to understand their child’s memory changes and provide the right support.

Supporting Students with Memory Challenges After Hemispherectomy

Schools can use this information to understand that kids who had hemispherectomy surgery might have memory challenges. Teachers and school staff can work with parents to support these kids in their learning. It’s crucial to be patient and help them succeed in school despite their memory difficulties.

Beyond the Current Understanding: The Future of Memory Studies in Hemispherectomy Patients

More research is needed to understand how memory changes in the long term after hemispherectomy surgery. Scientists want to find ways to predict which kids will see improvements, which will stay the same, and which might face challenges in their memory abilities. For example, scientists may look for a marker or similarity in the brain between kids who have memory impairments. This will help parents, doctors, and schools provide the best possible support for these kids.

Tavares TP, Kerr EN, Smith ML. Memory outcomes following hemispherectomy in children. Epilepsy Behav. 2020 Nov;112:107360. doi: 10.1016/j.yebeh.2020.107360. Epub 2020 Aug 31. PMID: 32882625.

Dr. Mary Lou Smith gave a great presentation about memory after large epilepsy surgeries at our 2019 research meeting. You can watch it here: