A CT scan showed that he had a subdural hematoma, and emergency surgery was performed to remove it. According to his RuSPORT team, da Matta is currently recovering in the intensive care unit, where he'll be monitored 24/7.
Deer strikes are dangerous enough in regular passenger vehicles, so we shudder to think how much worse it must be in a an open-wheel racer traveling at very high speeds. According to Motorsport.com, the deer impacted on the right side of da Matta's car and landed near the cockpit.
[Source: RuSPORT, Motorsport.com]