Can we live normally with only half a brain?

Maya Patel (WHS)

Following on from a lecture from Dr Guy Sutton on the brain, I researched further and found out about hemispherectomies, which is the procedure where half your brain (either the right side or the left) is removed from your body. The procedure, hemispherectomy is done usually in children from birth to 10 years old. This is because these children usually have severe epilepsy or brain seizures that cannot be controlled by medication and are caused by one side of the brain that has been working very poorly. After the procedure has taken place, the risk of seizures decreases to very few or none at all. 86% of the 111 children that underwent the procedure from 1975 to 2001 either experience nondisabling seizures that no longer require medication or no seizures at all [1]. Two main syndromes are the cause for having the procedure done; which are Rasmussen’s Encephalitis and Aicardi’s syndrome. Khloe Guy, three years old, had a hemispherectomy when she was two years old in April 2018, to stop her from seizing. Khloe was diagnosed with Aicardi syndrome at three months old, which means that the tissue that connects both halves of her brain wasn’t there, causing her to have seizures. For two years, Khloe lived with having up to 100 seizures every hour and using eight different anticonvulsant medication that had little impact. A solution to the uncontrollable seizures was hemispherectomy, which when Khloe had completed, meant that she no longer had any seizures. [6] Hemispherectomy is a dangerous procedure but it means that children with syndromes like Aicardi or Rasmussen’s Encephalitis, can lead normal lives after the procedure. Rasmussen’s encephalitis is an autoimmune process that causes one half of the brain to become inflamed and deteriorate. A symptom of the syndrome is epilepsy and so in extreme cases, hemispherectomy is used to treat the seizures. Anatomical Hemispherectomy is a procedure that takes out half of the brain that has not been well developed and is the reason seizures to occur. The brain is divided into two hemispheres by a deep groove separating the left and the right side of the brain. The corpus callosum is a thick block of nerves that allows each side to communicate with the other. During the procedure, a doctor will make an incision in your scalp and take out a piece of bone from the skull, which is later replaced. The doctor will then move aside the tough membrane that covers the brain called the dura and take out the half of the hemisphere from where your seizures occur from. The final part of the procedure will be the doctor removing the corpus callosum so that no signals can be sent across for a seizure to start [2]. In functional hemispherectomy, the doctor will only remove the parts

of the brain that is afflicted, however neurologist John Freeman from John Hopkins Hospital stated ‘leaving even a little bit of the brain behind can lead seizures to return’ [1] . This type of procedure can lead to side effects such as scalp numbness, nausea, depression, fatigue, headaches and depending on which hemisphere of the brain that is removed, there can be trouble with speech and memory. More serious side effects can occur during the procedure itself where the brain is exposed, and infection can occur along with bleeding [3]. However, while these are immediate side effects, the other hemisphere of the brain will take over many of the functions that the other hemisphere used to do, and so problems such as speech difficulty will return after some time. After the procedure, you can return to your normal life after 6-8 weeks, after controlled tests to make sure that the patient is okay [2]. Arron Purnell, at 17 years old, underwent functional hemispherectomy to help stop life-threatening seizures that had placed him in two medically induced comas. He was diagnosed with Rasmussen’s Encephalitis that left him with up to 200 devastating seizures every day. The procedure led for Purnell to a reduced vision, partial intellectual disability and an infection in his brain forcing him to remain in hospital for 12 months after his operation. The hemisphere of the brain that was left behind, naturally rewired so that Purnell could relearn to walk and regain use of his arm, both of which would have been coordinated by the left hemisphere of the brain that was taken out [4]. A research case took place at Great Ormond Street Hospital where 33 children from 3 months to 17 years underwent either functional or anatomical hemispherectomy. After the procedure, 52% of the children became seizure free, 9% of the children were only affected by rare seizures, 30% experienced a reduction in the number of seizures and 9% experienced relatively little change. From this procedure, 16 children no longer had to take anti-convulsant medication and the remaining children were taking a median of one medication, an inordinate difference to the amount of medication that they were taking previously. Another improvement for the patients that came from surgery was that 11 out of 12 children that had previously been reported as having behavioural issues, had improved drastically [5]. The brain is the most complex organ in our body that even the slightest injury can affect how it operates and the signals that it sends. Although it sounds inconceivable, a person can function normally with only half their brain because both hemispheres of the brain have the capability to control most of the body through the formation of new neural pathways. This however can only work if you have the complete function of one of the hemispheres, this meaning that it is not damaged, because as stated by John Freeman ‘You can’t take more than half ’ referring to the brain as it will lead to severe complications[1]. Therefore, living with half a brain is plausible, but if possible, should be avoidable.

[1]https://www.scientificamerican.com/article/ strange-but-true-when-half-brain-better-than-whole/

Choi, Charles (24/05/2007) Strange but true: When half a brain is better than a whole, Scientific American

[2]https://www.webmd.com/epilepsy/guide/ functional-hemispherectomy#1 Lava, Neil (19/07/17) What is functional Hemispherectomy? Web MD medical reference

[3]http://www.chp.edu/our-services/brain/ neurosurgery/epilepsy-surgery/services/ hemispherectomy

(2019) Functional Hemispherectomy in children, UPMC [4] http://hemifoundation.homestead.com/ aaronsstory.html

Purnell, Aaron (2008) Aaron’s story, The hemispherectomy foundation

[5] https://academic.oup.com/brain/ article/126/3/556/321214 A. M. Devlin J. H. Cross W. Harkness W. K. Chong B. Harding F. Vargha‐Khadem B. G. R. Neville (01/04/03) Clinical outcomes of hemispherectomy for epilepsy in childhood and adolescence, Oxford Academic

[6]https://www.dailymail.co.uk/health/ article-6856589/Girl-2-100-seizures-HOUR-halfbrain-removed.html

Kekatos, Mary (27/03/2019) Girl, 2, who has 100 seizures an hour, has half of her brain removed to treat rare disorder that doctor’s feared would leave her paralysed Daily Mail [7]https://www.hopkinsmedicine.org/health/ conditions-and-diseases/epilepsy/epilepsy-syndromesin-children

(2019) Epilepsy syndromes in children John Hopkins Medicine