By Joost Kools
During my internships, a colleague held a presentation about epilepsy and claimed that a hemispherectomy, a type of surgery where half of the brain is removed, can be a possible treatment for children with severe epilepsy. I was completely baffled when I heard this. How can we possibly remove one half of the brain and still retain a decent quality of life? After all, our brain is one of the most important and complex parts of our bodies, but also very fragile, where damage to relatively small areas can lead to high morbidity, like hemiparesis. Since I had a hard time believing that a hemispherectomy could be a successful treatment, I went and did my own literature search.
First of all, it is important to note that children with severe epilepsy suffer from chronic recurrent seizures which cannot be controlled pharmacologically or nutritionally. These seizures damage the brain by changing the metabolic rate of glucose and oxygen consumption, eventually leading to the loss of neuronal cells. One way to abolish the seizures is to remove the area in the brain which causes the seizures. In some cases, this means a total hemispherectomy.
Samargia et al. performed a review regarding the cognitive and motor outcomes in children with epilepsy undergoing a hemispherectomy. Regarding the cognitive functions, roughly 25% declined, 50% stayed unchanged and 25% improved after undergoing a hemispherectomy. The studies that reported motor outcomes all reported an impairment before the start of the surgery, typically characterized as decreased strength, increased muscle tone and decreased the active range of motion. After surgery, approximately 50% of the children remained unchanged regarding paresis. Worsening of the paresis was mostly found in the distal parts of the arms. The children who could walk before surgery, still could afterwards. One study even reported four children who were able to walk after the surgery, while they could not before. Three studies found an increase in muscle tone in the arms, however, they also reported an increase in functional skills of the arms.
So interestingly enough, children with severe types of epilepsy on average remain unchanged (with even a possible improvement) regarding motor and cognitive outcomes but are relieved of most or all of their seizures.
These relatively positive outcomes are mostly seen in children and not in adults undergoing hemispherectomy. Benecke et al. performed a study using fMRI, researching the ipsilateral pathways in patients with early and late acquired brain damage. Patients with early acquired brain damage showed larger amplitudes and shorter latencies than patients with later acquired brain damage. Therefore, they suggest that in our younger years, our brains can reorganize the descending motor pathways and strengthen the ipsilateral pathways which make it possible to regain some motor functions after suffering from hemiparesis.
I had a hard time believing my colleague when she told me about the hemispherectomy, but every article I found reported positive outcomes. I guess you could say I underestimated the power of our brain. Even if it is such a fragile organ, I now know the brain is also flexible enough that it can compensate for lost functions, especially when it is still developing.
 Griessenauer, C.J., et al. Hemispherectomy for treatment of refractory epilepsy in the pediatric age group: a systematic review. Journal of neurosurgery. Pediatrics 15, 34-44 (2015).
 Samargia, S.A. & Kimberley, T.J. Motor and cognitive outcomes in children after functional hemispherectomy. Pediatric physical therapy : the official publication of the Section on Pediatrics of the American Physical Therapy Association 21, 356-361 (2009).
 Benecke, R., Meyer, B.U. & Freund, H.J. Reorganisation of descending motor pathways in patients after hemispherectomy and severe hemispheric lesions demonstrated by magnetic brain stimulation. Experimental brain research 83, 419-426 (1991).