Surgery and Memory
As a writer for this website, I was asked to interview Dr. Daniel Drane, a neuropsychologist who deals with memory issues in epilepsy patients. Dr. Drane received a Ph.D. from the Fuller Graduate School of Psychology. He is currently practicing at the University of Washington's Epilepsy Program.
Dr. Drane talked about the relationship between memory and epilepsy surgery.
If you are looking at surgery, what might you want to be concerned about?
In deciding whether to have this procedure done, you have to weigh the benefits of potentially eliminating or greatly reducing seizures against any negative impact it might have. There are factors that give a greater risk for memory loss following surgery. Among those are age at time of surgery. Research suggests that older patients (beyond age 40 or so) are more likely to have memory loss. If you are already a little older, have lost some cells due to aging, and surgery takes out more tissue, particularly in the temporal lobe, that can lead to a greater loss.
Another factor is age at the onset of your neurological condition. With children who had early seizures or maybe some sort of brain injury at birth, their brain may have developed a little differently. Memory may be somewhere else, so to speak, because their brain has adapted to the injury that was there from the start. After age 10, your brain is pretty much in place. It’s not as capable of change as it was. If you have a head injury after age 10, your brain is already set up. If the injury happens to be around the region where memory is located, your brain is not going to reorganize around the injury. You may lose some functioning or have a greater risk of losing some functioning when that part of the brain is removed.
A third factor is preoperative memory level. The better memory you have, the more you have to lose. The more likely you are to experience some objective loss. On the surface it seems pretty obvious. If you have a poor memory before you have surgery, you're probably not going to be any worse. That is, we're not going to be able to detect a whole lot of difference later.
Another factor is the amount of mesial temporal sclerosis (hardening of brain tissue and loss of neurons in parts of the temporal lobe, especially the hippocampus). If MRI or other neuroimaging has found this on the side of surgery, there is usually less of an impact from surgery. That hippocampus is already damaged; it already has sclerosis. So we’re taking out bad brain, and it’s not going to produce a loss. If you don’t have mesial temporal sclerosis, you’re at a little more risk because we are now taking out good brain, brain that was doing something.
A fifth factor is side of surgery versus side of speech. When they are the same, memory loss is more likely. If your verbal memory and speech are in the dominant (left) hemisphere and that's the side of surgery, there's a greater risk than if we wanted to do surgery on the right side of your brain.
What might someone expect right after temporal lobe surgery?
Once the decision is made to have surgery, results really depend on the side of the surgery and all these factors. But, typically, if we are taking out a healthy temporal lobe there may be some memory loss. Immediately after surgery, you're going to have a period of recovery where you're going to function less well while your brain is healing. Certainly after a few months or after a year, your recovery is going to be pretty complete. After that, you're probably not going to see much changeyour memory is not going to keep improving beyond a year or so. At that point, if you're still experiencing an appreciable memory loss, your only option will be compensatory memory strategies. Hopefully we would have implemented those earlier on through rehab.
Again, many people have really good outcomes. Some people don't have great memories to start with, most likely because that temporal lobe wasn't working all that well to begin with; its removal didn't cause them to function any worse. Some people actually do better. The seizures themselves were so out of control or were having such an impact on their brain that even though we've removed tissue, the tissue that's left can function better. Some individuals have generalized seizures that start in the temporal lobe and spread to the rest of the brain. After surgery, they're not having those any more because we've removed the part of the brain where they started.