Alex Zanardi has undergone a second neurological operation as he remains in a medically-induced coma.

The Santa Maria alle Scotte polyclinic, issuing its first update on the Italian since last Tuesday, revealed that the former F1 drivers and two-time IndyCar champion underwent a second neurological operation lasting more than two hours after which he was returned to intensive care.

"Following a CT scan, the diagnostic examination showed an evolution of the patient's state which made it necessary to resort to a second neurosurgery," reads the latest update from the hospital.

"After the operation, which lasted about two-and-a-half hours, Alex was again hospitalized in the intensive care unit where he remains sedated and intubated.

"His condition remain stable from the cardio-respiratory and metabolic point of view, severe from the neurological point of view, the prognosis remains confidential.

"The intervention, said the health director of the Aou Senese, Roberto Gusinu, "represents a step that had been hypothesized (anticipated) by the team.

"Our professionals will evaluate the evolution of the situation day by day, in agreement with the family the next bulletin will be released in about 24 hours."