DANIEL KANTER: Based upon our analysis of those images, the brain injury likely occurred in the preceding weeks.
Warmbier's scan, though, is consistent with what's usually seen after cardio-pulmonary arrest, where the blood supply to the brain is inadequate for a period of time.
American college student Otto Warmbier only meant to spend five days sightseeing in North Korea in 2016.
Warmbier's father, Fred Warmbier, also talked about his son's medical condition after his release Tuesday from the totalitarian nation.
North Korean authorities said the coma was a result of botulism and Warmbier taking a sleeping pill after the trial.
Information on prisons is scarce in North Korea. "We went for 15 months without a word from or about Otto". Two American university professors in Pyongyang were arrested this year for allegedly plotting anti-state acts.
Warmbier also expressed disbelief at North Korea's explanation for his son's condition. She says there are plenty of restrictions on what Americans can do in countries that face US sanctions - like North Korea or Iran.
Doctors declined to speculate on what may have caused Warmbier's condition and said they would not discuss his prospects or treatment out of respect for his family.
Otto Frederick Warmbier, a University of Virginia student who has been detained in North Korea since early January, attends a news conference in Pyongyang, North Korea, in this photo released by Kyodo on February 29, 2016.
"It appears to be exotic to go to the country, but it's all staged", he says.
To honour his son, Fred Warmbier wore the same jacket Otto wore when North Korea presented him before the media in 2015 at an event where he tearfully confessed that he tried to steal a propaganda banner while visiting the country.
That was used as evidence in his hourlong trial.
North Korea officials have stated that Warmbier fell into a coma shortly after his incarceration in March, 2016.
Though Warmbier supposedly had been in a coma for more than a year, the US didn't learn the full extent of his condition until Yun and the doctors saw him in a Pyongyang hospital.
WARMBIER: I would say, I'm so proud of Otto, my son, who has been in a pariah regime for the last 18 months, brutalized and terrorized. "North Korea has proven they are not nature's noble men".
The next time the world saw Warmbier he was distraught, breaking down in front of Korean journalists in a video released by North Korea in February of 2016.
Otto Warmbier, 22, returned home to OH on Tuesday after being jailed in the communist state for more than 17 months following months of covert diplomacy led by Joseph Yun, a special representative for North Korea policy at the US State Department.
Fred and Cindy Warmbier have said their son was "terrorised and brutalised" by Kim Jong-Un's regime.
Fred Warmbier praised the Trump administration's efforts: "They have our thanks for bringing Otto home".
"The question is, do I think the past administration could have done more", Fred Warmbier said. The news conference will be aired live on this website.