Beltrametti was conscious throughout the ordeal
"Unfortunately we can confirm the diagnosis of yesterday that Silvano is a paraplegic," said Thierry Maitre on Sunday.
"He is in a stable but fragile condition. He is still in intensive care. We cannot plan to move him back to Switzerland just yet," he added.
Beltrametti lost control on the top part of the course in Val d'Isere, France, and smashed straight through the safety netting.
The 22-year-old was travelling at more than 80mph when he crashed.
He suffered a displaced fracture of the spine between vertebraes six and seven, high in the back, and can no longer feel anything in his legs or pelvis.
He also suffered haemorrhaging behind his lungs.
Maitre said the likely cause of a number of his injuries was the impact against the rock he was found lying on after the accident.
"His spine was moulded to that rock. I think this is what fractured his spine," said Maitre.
Beltrametti was wearing a back brace and could have been killed otherwise.
The team doctor also revealed that Beltrametti had been conscious throughout the entire event.
"He was conscious but wanted to sleep. He was very fragile and the conditions for stabilising him were bad," Maitre said.
"The desire to constantly look up and see the helicopter coming was very great.
"But he was remarkably calm. He surprised us with his maturity and stoic character. The only thing he said every once in a while is 'I have pain'."
The race, the first men's downhill of the season, was immediately stopped while paramedics tended to the injured skier.
It resumed more than an hour later, with Austria's Stephan Eberharter winning.
Course officials had to repair the safety netting before the race could continue.
French police have launched an investigation, standard procedure in such an accident.
Race officials said they had taken all the necessary precautions and had followed FIS regulations.
Beltrametti was Switzerland's young bright hope and had finished third in Friday's super-G.
His highest ever World Cup finish was second in the downhill at Lake Louise, Canada, last season.
In October, France's world super-G champion Regine Cavagnoud was killed when she collided with a German trainer during a training run in Austria.