Grey's Anatomy, Season 9

Meredith:
[voice over] There is a procedure to treat epilepsy that involves surgically severing the connection between the left and right brain. The goal is to block signals that cause seizures. The problem is this also cuts off the brain's ability to communicate with itself. The left side has no idea what the right side is up to. A patient may experience problems with coordination, memory, speech. It's a drastic solution that's only considered when all other options have failed because once a surgeon makes that cut, there's no going back.