Alex Zanardi will be kept in an induced coma until at least next week after he suffered injuries in a handbike crash.
The ex-Formula One driver was airlifted to the Santa Maria alle Scotte hospital in Siena after a collision with a large vehicle on Friday.
An update on the Italian's condition was provided by the hospital on Tuesday amid grave concerns for the 2012 and 2016 Paralympic gold medallist, who had both of his legs amputated above the knee following a motorsport accident in 2001.
"The patient spent the fourth night of hospitalisation in the intensive care unit of the Santa Maria alle Scotte polyclinic in Siena in conditions of stability in cardio-respiratory and metabolic parameters," a hospital statement read.
"The neurological picture remains unchanged in its severity. The patient remains sedated, intubated and mechanically ventilated.
"Any reductions in sedo-analgesia, for the assessment of neurological status, will be considered starting next week. The prognosis remains confidential."