Jerusalem ? Prime Minister Ariel Sharon’s chances of surviving his severe stroke are very high, but his ability to think and reason have been damaged, one of his surgeons said Saturday.

The 77-year-old Israeli leader remained in critical condition today, according to a statement from Jerusalem’s Hadassah hospital.

“There was no change in the prime minister’s condition overnight,” the statement said. “His condition is stable but continues to be critical.”

Doctors were to decide today when to begin lifting Sharon’s medically induced coma to examine the severity of the brain damage. His vital signs were stable and a brain scan Saturday showed a slight reduction in swelling.

“Tomorrow is the day of truth,” Dr. Jose Cohen, one of Sharon’s surgeons, told Channel 2 TV on Saturday. “Tomorrow we will all know if what we did for him helped him or not.”

Cohen said he was “quite optimistic” about Sharon’s prospects for survival, which he said were “very high now.”

But when asked about possible cognitive impairment, Cohen replied, “To say after such a severe trauma as this that there will be no cognitive problems is simply not to recognize the reality.”

Cohen’s comments appeared on Channel 2 as a transcript broadcast on the screen. He did not appear himself. It was not immediately possible to contact Cohen by phone, and Sharon’s other surgeon, Dr. Felix Umansky, declined to speak with The Associated Press.

However, Umansky talked to an Argentine radio station, and Israel Radio reported that he said he would be pleased if Sharon can recover enough to be with his family, despite inevitable brain damage from the stroke.

The comments reinforced a widespread assumption that Sharon will never return to power. Israelis from all walks of life have lamented Sharon’s likely departure from the political scene.