Alex Zanardi, who remains stable but serious, is to be kept in an induced coma for the next week.

"The patient spent the fourth night in the intensive care unit of the Santa Maria alle Scotte polyclinic in conditions of stability in the parameters cardio-respiratory and metabolic," reads today's official statement from the hospital.

"The neurological picture remains unchanged in its severity," it continued. "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."

"Zanardi is in stable condition and the parameters are stable too," professor Giuseppe Oliveri, the neurosurgeon who operated on the two-time IndyCar champion, told Sky Italia. "This is what we can expect at best at the moment.

"It will take a long time," he admitted. "He will remain sedated for another 10-15 days.

"At present, his response is good," he added. "We do not know to which extent his coma is due to medications and to his medical conditions."

In an interview with Gazzetta dello Sport, Oliveri dismissed claims that Zanardi's injuries to his forehead, face and eyes are at the same level as Michael Schumacher.

"(They) are less than those of Michael Schumacher," he said. "Diffuse axonal damage is a very extensive injury throughout the cerebral cortex, from which there is little chance of returning to normal cognitive and motor functions," he continued, referring to the seven-time world champion's injuries. "At least from what we as doctors can understand for now, Zanardi does not suffer from this injury.

"The point of impact is not what counts," he added. "What matters is the internal injuries and how much damage has spread within the skull.

"In injuries of this type, it takes a few days to start waking up the patient and assessing the damage. A week or maybe two.

"We are talking about a fragile patient who has suffered a major head injury, so you have to be very careful. The fact that he is an athlete and in such good physical condition is a cause for optimism."