Department of Neurology

The "split-brain" procedure

Q: My sister underwent surgery in 1988 to sever the hemispheres of the brain. This was supposed to correct her epilepsy. At the time of the surgery, she was 23 years old, and it seems to have failed. Could it be due to her age at the time of the surgery? Your comments would be appreciated. She began having seizure activity at the age of two, but was controlled until she reached puberty. At that point, her seizure activity became uncontrollable with medications. She continues to have bouts of seizure activity every 10 to 14 days, during which time she is like a zombie. Then, she gradually recovers and becomes very talkative and active. Just as she peaks, the seizure activity begins again.

A: By "severing the hemispheres," I presume you mean corpus callosotomy. This has also been called the "split brain" procedure. The corpus callosum is a thick bundle of nerves that connect both sides of the brain. Their function is to relay data from each side of the brain so that they can function in a coordinated way. The corpus callosum may provide a pathway for seizures to spread in the brain. Thus, cutting this structure ("callosotomy") may help to limit the spread, and hence, severity of seizures. It is generally performed in two steps, to reduce the impact of surgery on function.

Corpus callosotomy is usually reserved for persons with seizures that cause severe injury, that is, drop-attack seizures and tonic-clonic seizures. For these type of seizures, callosotomy can be very effective. However, this type of surgery does not eliminate whatever is causing the seizures, and thus often has no effect on less severe seizures. Some patients have even reported increases in small seizures after the surgery. We now understand that in general, this type of surgery does not cure, but rather may make the severe types less injurious.

Although the surgery did not seem to help your sister, she may benefit from one of the many new seizure medications that have been released since her operation.

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