When she began to become incoherent...

"We went through the top of the head, I think she was awake. She had a mild tranquilizer. I made a surgical incision in the brain through the skull. It was near the front. It was on both sides. We just made a small incision, no more than an inch." The instrument Dr. Watts used looked like a butter knife. He swung it up and down to cut brain tissue. "We put an instrument inside," he said. As Dr. Watts cut, Dr. Freeman put questions to Rosemary. For example, he asked her to recite the Lord's Prayer or sing "God Bless America" or count backwards. ... "We made an estimate on how far to cut based on how she responded." ... When she began to become incoherent, they stopped."

Från Wikipedias artikel om Rosemary Kennedy.


PS.
Från Wikipedias artikel om lobotomi
"Sweden lobotomized at least 4,500 people between 1944 and 1966, mainly women. This figure includes young children."