The doctor added there is a risk Nicolaescu might develop other blood clots, but his condition is currently stable and he is on blood thinning medication.
The Romanian director was operated Tuesday after a minor head injury, which had caused a blood clot to form on the brain.
"Unfortunately, the illness cannot be detected immediately, because there are no symptoms. The formation of this clot has nothing to do with stress, effort or physical activity. It is an illness specific to the elderly," the doctor said.
He added Nicolaescu is stable, conscious and can move, but further developments are unpredictable.
Nicolaescu will remain committed to hospital for at least another ten days, the doctor said, adding he does not think another surgery will be necessary.