PORT CHARLOTTE, Fla. -- Boston Red Sox prospect Ryan Westmoreland underwent brain surgery Tuesday that was successful, according to a statement from the team Tuesday night, but faces a "difficult period" in the aftermath of the five-hour operation.

The Red Sox said Tuesday that Ryan Westmoreland's five-hour brain surgery was successful. John Corneau/Lowell Spinners

A complete prognosis will not be known for a few days, a team source said, adding that the surgery "went well" for the 19-year-old Rhode Island native, who had a cavernous malformation, or angioma, removed from his brain stem.

An angioma is a congenital condition comprised of small abnormal capillaries (tiny blood vessels) that can swell and bleed. The condition, while potentially life-threatening, has a low mortality rate, but there is a risk of neurological damage that could affect a variety of functions, including movement and vision.

"Due to the complexity of this surgery, Ryan will face a difficult period initially before beginning his recovery," said the statement, attributed to Red Sox general manager Theo Epstein.

Tuesday's surgery was performed by Dr. Robert Spetzler of the Barrow Neurological Institute in Phoenix, Ariz. Spetzler is acknowledged as one of the foremost experts in the field.

Westmoreland remains in intensive care, according to the statement.

"Theo gave me a call," said manager Terry Francona, who attended both ends of split-squad exhibitions in Kissimmee and Port Charlotte. "Seems like very encouraging news, so we're obviously thrilled and thankful."

Typically it would take a few days to determine what, if any, neurological damage may have occurred, according to Dr. Joseph Maroon, the vice chairman of the Department of Neurosurgery at the University of Pittsburgh Medical Center and team neurosurgeon for the Pittsburgh Steelers.

"But [you] immediately know about paralysis, usually,'' Maroon wrote in an e-mail.

The condition was discovered, according to a team source, after Westmoreland began experiencing headaches and exhibiting other neurological symptoms, including numbness. He left the team's minor league camp on March 4, according to a statement released by the team, and was diagnosed the next day at Massachusetts General Hospital. The decision to have surgery was made after consultation with three specialists.

Westmoreland was in Arizona with his entire family, including his parents, Ron and Robin, according to a source close to the family. Chris Westmoreland, the home clubhouse manager for the Tampa Bay Rays and the player's uncle, is also among the family members present.

While the condition is relatively rare, at least three prominent members of the sports world have experienced angiomas, according to the Angioma Alliance, an organization that describes itself as a "patient-directed" network devoted to improving the lives of those who have had the condition.