The operation was to reduce swelling on his brain but Toomey will remain sedated for "a few days" as his condition continues to be monitored closely.
Lisa Hancock, CEO of the Injured Jockeys Fund, said in a statement on behalf of the Toomey family: "Brian Toomey underwent surgery yesterday (Sunday) to reduce swelling and resultant pressure on his brain.
"The surgery went well and Brian remains in a stable condition in an induced coma. It is anticipated he will be kept sedated for the next few days as his progress continues to be monitored."
Toomey was riding Solway Dandy when he was injured last week.