A six-year-old boy who fell from the 10th floor of the Tate Modern fractured his spine, a court has heard.
The French national, who was visiting London with his family, was found on a fifth-floor roof after he fell from the gallery's viewing platform on Sunday.
Prosecutors told Bromley Youth Court he also suffered a "deep" bleed to the brain and leg and arm fractures.
A 17-year-old boy charged with attempted murder was remanded in custody.
The youth, who cannot be named because of his age, is due to appear at the Old Bailey on Thursday.
Prosecutor Sian Morgan said the boy had suffered the "deep" brain bleed as she gave details of his injuries during the short hearing.
The Met Police have said he is in a critical but stable condition.
There is no link between the suspect and the victim who was visiting London with his family, the force have said.
Emergency services were called to the gallery, in Bankside near London Bridge Station, at 14:40 BST on Sunday.
The Tate Modern opened in the disused power station on the River Thames in 2000, while the extension with the viewing platform was opened in 2016.
It was the UK's most popular tourist attraction in 2018 with 5.9 million visitors, according to the Association of Leading Visitor Attractions.