Brain surgeons occasionally cut the brain in half by a CORPUS CALLOSOTOMY operation. It can better control intractable seizures. This procedure cuts the corpus callosum (cc), the major broad structure containing nerve fiber tracts that connects the right and left halves of the brain from front to back of the brain.
|Green is the Corpus Callosum|
The procedure disconnects spread of epileptic brain activity. It has been performed for over 75 years. It seems to benefit atonic (Atonic seizures, or drop attacks, cause a loss of muscle tone resulting in the person dropping to the ground with loss of awareness. This is the Lennox-Gestaut Syndrome. The fall can result in serious injury. It is recommended that affected children wear helmets to minimize fall-injury) and tonic seizures (Tonic seizures are a tightening of muscles, especially of the trunk and face, without jerking or falling but with loss of awareness). These two epilepsy forms primarily affect children and are resistant to anticonvulsant medications. Occasionally, CORPUS CALLOSOTOMY is performed to improve grand mal epilepsy, too.
Paglioli’s research team 1 found CORPUS CALLOSOTOMY to be safe and effective. Their study revealed that median monthly frequency of drop attacks decreased from 150 per month to, on average, less than one per month.
Cut the brain in two? How can a person function like that? CORPUS CALLOSOTOMY usually leaves the patient with undetectable changes except for improved seizure control.
What does the corpus callosum structure do? Other than allow the right and the left cerebral hemispheres sharing information across it, neuroscientists can’t give complete explanations. Once the cc is cut, sophisticated neuropsychological testing may be required to detect abnormalities that are undetectable to the casual observer.
Rarely, people are born without a corpus callosum. The absence of the structure is found on routine brain scans done for other reasons, e.g. trauma, headaches and paralysis, etc. Yet, they appear entirely normal on routine interactions and physical examinations.
One side-effect caused by CORPUS CALLOSOTOMY is described: most people are right-handed and have their language center in the frontal lobe of the left cerebral hemisphere. If a coin is placed in the left hand after CORPUS CALLOSOTOMY, the patient feels the coin in his right brain because the normal human brain senses the opposite body via crossing nerves low in the spinal cord. He’ll detect something is in his hand but he cannot name the object. This is because the information about the perceived object will reach the right hemisphere but the information must then pass over the corpus callosum to get to the language center in the left hemisphere. The information from the right hemisphere can’t get to the naming part of the language center in the left hemisphere because the CORPUS CALLOSOTOMY cut the “bridge.” However, if the same test is done with the object placed in the person’s right hand, the information of what is felt in the hand passes directly to the language center in the left hemisphere after it crossed to the opposite side low in the spinal cord. The person can immediately name what is felt in the opposite right hand since the information does not need to cross the cut corpus callosum, the cut “bridge.”
1) Paglioli E., Martins AA, Azambuja N, et.al. Selective posterior callosotomy for drop attacks. Neurology 2016; 87: 1968-74.
Lance Fogan, M.D. is Clinical Professor of Neurology at the David Geffen School of Medicine at UCLA. “DINGS” is his first novel. It is a mother’s dramatic story that teaches epilepsy, now available in eBook, audiobook and soft cover editions.