Alex Zanardi underwent a second neurological intervention deemed "necessary" by his Siena University Hospital doctors.
The surgery was conducted 10 days after Zanardi suffered a head-on crash with a truck on an open-road during a hand bike event in Italy.
The Italian racer, who lost both his legs in a horrendous accident in CART in 2001, was placed in a medically induced coma by his neurosurgeons after an initial operation performed upon his admission to the clinic's intensive care unit.
On Monday, the Siena University Hospital issued a bulletin in which it confirmed that Zanardi had undergone a second surgery following the results of a CT scan.
"As part of the diagnostic and therapeutic evaluations carried out by the team which is treating the athlete, a CT scan was performed," read a statement from the hospital.
"This diagnostic examination showed an evolution of the patient’s state which made it necessary to resort to a second neurosurgery.
"After the operation, which lasted about two and a half hours, Alex Zanardi was again hospitalised in the intensive care unit where he remains sedated and intubated.
"The intervention carried out represents a step that had been hypothesised by the team," said the University's health director, Roberto Gusinu.
"Our professionals will evaluate the evolution of the situation day by day."
In accordance with Zanardi's family, the next health bulletin will be issued in about 24 hours.
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