Cutting the Brain in Half — The Corpus Callosotomy

Adam Gulamhusein
5 min readJul 6, 2020
Diagram from Google Images shows different parts of the forebrain and hindbrain.

Our brain is phenomenal. Its ability is endless, and the potential is limitless. Development starts in utero and changes still occur until the day we die. Our brain defines our individuality — our choices, emotions, personality. The piece of us that “holds” our consciousness, executes our decisions, and understands the world around us. Given the role our brain holds, it’s no wonder it is so complex. A part of this complexity is the variety of neurological disorders that millions of individuals across the world deal with on a daily basis. There is one particular disorder that affects more than 3 million Americans and 65 million people worldwideepilepsy.

Image from John Hopkins Medicine of brain model on top of printed EEG data.

What is Epilepsy?

If someone has two or more seizures that cannot be explained by a temporary underlying condition (i.e. Hypoglycemia) their medical diagnosis will be “epilepsy”. Seizures result from irregular activities in neurons which can last multiple minutes. These irregular activities can have a number of causes — therefore, epilepsy is considered a spectrum instead of a disorder. Contrary to popular belief, seizures aren’t all uncontrollable shaking. While this can occur, seizures can also look like staring spells, rapid blinking, or crying out. The pattern of symptoms and after-seizure electroencephalogram (“EEGs”) are used to determine between different types of epilepsy and confirm the diagnosis.

What are the different types of Epilepsy?

There are three types of epilepsy: Generalized, Focal, and Unknown onset.

Image from Healthline.

Generalized seizures affect both sides of the cerebral hemisphere. Secondary-generalized seizures can begin on one side and spread to affect both sides of the cerebrum. There are different types of generalized seizures which include absence and tonic-clonic seizures. Absence seizures are a type of generalized seizure that includes rapid blinking or a few seconds staring into space and tonic-clonic seizures which can cause the patient to fall, cry out, have muscle spasms, and/or lose consciousness. Many people are familiar with photosensitive epilepsy (even though a much smaller portion of patients with epilepsy have this type) which refers to seizures caused by a change in visual stimulation, typically flashing lights.

Focal seizures are localized to one area of the brain. A simple focal seizure is characterized by a change in sensation or twitching. However, complex focal seizures can cause confusion leaving the individual unable to answer questions or follow directions. “Unkown” seizures have an unknown origin. They result in the extension or flexion of different limbs.

Seizures often lead to intellectual or psychiatric conditions and can lead to the suppression of dendrites (receiving end of neurons). In children, 20% have an intellectual disability, and 20–50% have a specific learning disability.

The treatment for epilepsy can vary from patient to patient. Many patients choose to combine medication(s) with a ketogenic diet. Up to 70% of patients with epilepsy are able to manage seizures with anti-epileptic drugs (AEDs). However, a ketogenic diet which focuses on high fat, low carb foods, has been found to help.

For patients that do not respond to AEDS, a corpus callosotomy also called “split-brain surgery” may be performed.

What is the Corpus Callosotomy?

Image from Neuroscientifically Challenged shows the corpus callosum highlighted in green.

The corpus callosotomy is a 4-hour operation where the corpus callosum is severed. The corpus callosum is a band of nerve fibers that connects the two cerebral hemispheres in the brain and sends electrical impulses from one side to another. It is also the largest collection of white nerve fibers within the brain (which means it has high myelin content).

This structure helps the hemispheres share information, but it also contributes to the spread of seizure impulses from one side of the brain to the other. This surgery interrupts the spread of seizures from hemisphere to hemisphere. Seizures generally do not completely stop after this procedure (they continue on the side of the brain in which they originate). However, the seizures usually become less severe, as they cannot spread to the opposite side of the brain.

“A corpus callosotomy, sometimes called split-brain surgery, may be performed in people with the most extreme and uncontrollable forms of epilepsy, when frequent seizures affect both sides of the brain. People considered for corpus callosotomy are typically those who do not respond to treatment with antiseizure medications.” - WebMD

Side effects of this operation include scalp numbness, nausea, feeling depressed, headaches, difficulty with cognitive processing, paralysis or less os sensation, and a change in personality. These symptoms will generally pass with time, but there are other risks including stroke, lack of coordination, and/or problems with speech which may be longer-lasting.

Neuropace and BCIs to Improve Treatment

Image shows Neuropace device designed to treat seizures.

Neuropace is a relatively unknown company based in California and founded in 1997. The company has a collection of surgeons and doctors which it has worked with to develop its piece of remarkable technology. Neuropace currently focuses on patients with Epilepsy and uses its developed technology — called the RNS System, to stop seizures from occurring.

The RNS System is a type of Brain-Controlled Interface (BCI) that is implanted past the skull with a surgical procedure. It is able to detect brain waves (similar to an EEG), interpret the data, and use electrical stimulation to stop the seizure from occurring — with no input from the patient. This is far better than the current treatment available, and could ultimately be applied to a variety of neurological disorders to treat symptoms or illnesses.



Adam Gulamhusein

TEDx Speaker | HYRS Alum (Neurosurgical RA) | TKS Student | SHAD Alum | 2021 Calgary Brain Bee Winner