Seve Ballesteros is back in intensive care after undergoing further surgery at La Paz hospital in Madrid.
Five-time major winner Ballesteros underwent scheduled surgery for the placement of a cephalorachidian fluid VP shunt.
At the same time, the surgical team treating the 51-year-old performed a cranioplasty to repair a bone defect.
His condition is reported as stable and he will remain in the intensive care unit.
Ballesteros was diagnosed with a brain tumour after losing consciousness at Madrid Airport in October.
He underwent a lengthy operation on 24 October to reduce pressure on his brain and remove remaining tumour tissues following two previous operations.
On 18 November he had recovered sufficiently to leave intensive care, although a hospital statement did warn there was a long way to go.