Castan had been out of action since September after being substituted during a Serie A game at Empoli when suffering from acute dizziness.
Tests revealed the Brazilian had a cavernoma blood vessel malformation.
A statement from Roma on Wednesday read: “The operation, which began at 8:30am and finished at 12pm, was carried out using a surgical microscope and neuronavigator, whilst the player’s neurophysiological activity was constantly monitored.
“The cavernoma itself, which measured 3cm, was completely removed.
“This was confirmed by an MRI scan carried out immediately after the operation.
“Castan has now woken up and is breathing unaided, and has been informed of the operation’s successful outcome.
“He will remain in intensive care for the next 24 hours, after which a prognosis will be formed. “
The 28-year-old started in 36 league games for Roma last season, helping the team finish runners-up to Juventus in Serie A.