Living With Half a Brain (Spotlight Series #1)

By Julia Zeng (Editor)

For four years, 13-year-old Kaci Caves suffered from a very rare form of epilepsy, Rasmussen’s encephalitis, which caused up to a hundred seizures a day. The seizures, which progressively destroyed her brain’s left hemisphere, would not respond to diets, strong medications, or minor surgeries. She could hardly walk and found talking and thinking difficult. In 1996, she traveled to Johns Hopkins Hospital in Baltimore for a procedure that would remove the left half of her brain.

Hemispherectomy, the surgery that involves removing or disconnecting one half of the brain, has been performed since 1928 on patients with severe neurological diseases in one hemisphere. In the first few decades, many patients died from complications such as internal bleeding. Since then, techniques and outcomes have improved drastically. Despite this, hemispherectomy remains a risky and rare surgery that is performed only dozens of times in the United States each year.

The two main types of hemispherectomies are anatomical and functional. Anatomical hemispherectomies, like the one Kaci had, remove the cerebral cortex (the pale pink region labeled on the left picture below) in the diseased hemisphere and fill the empty space with spinal fluid. Functional hemispherectomies remove parts of the cerebral cortex and sever connections between the two hemispheres, preventing seizures that used to affect the disconnected hemisphere from spreading to the other half of the brain. Although functional hemispherectomies are not effective for all patients, they pose a somewhat smaller risk of blood loss and other complications.

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Since the left hemisphere controls speech and movement in the right side of the body, Kaci risked paralyzing her right side, along with losing her cognition and ability to speak. However, she also had hope of finally stopping the brain damage and seizures, which is indeed what happened. Since most hemispherectomy patients are small children, and Kaci was a teenager, Kaci’s doctor and parents were concerned if she could recover successfully. But after 5 months of physical, speech, and occupational therapy, she was speaking again and could walk better than she did before the surgery. Although her right arm stays paralyzed and her reading skills are impaired, she returned to school and became a high school freshman, took up swimming, learned to drive, and grew to lead a relatively normal, seizure-free life.

How was Kaci’s brain able to regain speech and movement on her right side, even though the parts that controlled these functions were gone? The success that many hemispherectomy patients have had comes from plasticity-- the human brain’s ability to reshape itself and through learning, create new connections between neurons to replace damaged or lost regions. This is why hemispherectomies are typically performed on children, whose brains are still flexible enough for one hemisphere to take on important functions in the other half. While hemispherectomy is an extreme example of plasticity, it demonstrates the remarkable resilience of our brains as we learn and grow.

Feel free to check out this video about Jodie, another young woman who has had a hemispherectomy: https://youtu.be/f2fCY_M7Vms. Thank you for reading. See you in our next article!

Vivian Lu