A cavernous malformation is a vascular issue which, according to an audio report on the Mayo Clinic Web site, is a group of "abnormal, thin-walled blood vessels." Typically, cavernous malformations don't cause symptoms and are often only discovered if doctors are looking for something else via a brain MRI exam.
If the malformation bleeds, it can cause stroke-like symptoms, seizures, numbness, vision changes or other neurological problems.
"Typically, a stroke might be more dramatic, while symptoms from a cavernous malformation come on more gradually," Mayo Clinic neurosurgeon Dr. David Piepgras said in the audio report. "Most people who have cavernous malformations, we can't tell them why they occur."
While the severity of Westmoreland's condition and the location of the malformation is unknown, it is serious enough to require surgery. The course of treatment is often just observation, with surgery becoming an option if symptoms persist.
According to the Mayo Clinic site, the malformation can often be removed entirely without causing new issues because it is so distinct from the brain tissue around it. If it is not completely removed, it can grow back. The risk involved depends on the size and location of the malformation.
"What's most critical is where it's located," said Dr. Ronald Woosley, a neurosurgeon at the St. John's Neurology Center in Tulsa, Okla. "Some are in a very accessible area, some are not.
"It's like going into a piece of jello and taking out a piece of tissue that has a different consistency than the brain. Usually you can eradicate the lesion and have a cure, so it doesn't bleed again. You remove it completely, you shouldn't have any problems with it again in terms of it re-bleeding and causing any symptoms."
The choice of Spetzler to perform the surgery is a good one, according to Woosley. His colleague tends to be aggressive in treating cavernous malformations, opting for surgery when perhaps others would be more conservative, and he's had good success in operating on lesions such as these, even ones which are in more inaccessible areas of the brain.
Also working in Westmoreland's favor are his fitness and age. The younger a patient, said Woosley, the better chance the brain tissue will regenerate and maintain function.
Westmoreland, the No. 27 prospect on MLB.com's Top 50 Prospect list, was selected in the fifth round of the 2008 First-Year Player Draft. A five-tool player, Westmoreland was a New York-Penn League All-Star in 2009, hitting .296/.401/.484 (average/on-base/slugging) and going a perfect 19-for-19 in stolen-base attempts during his pro debut. He had shoulder surgery after being drafted and broke his collar bone after crashing into the outfield wall in late August.
"He's sort of the classic five-tool player," Red Sox farm director Mike Hazen said about Westmoreland this past offseason. "He's a tremendous kid and a very hard worker, so there's a lot to like, a lot to get excited about. But he's 19 years old and he's in low [Class] A, so he's got a little bit of a ways to go from a development standpoint. But there's a lot to be excited about with just the package of the person and the player."