Or maybe it said that you have a "vessel anomaly." Anomalous is the adjective, and anomaly is the noun. Either way, it just means there is something that is unusual. Evidently, you have a blood vessel in your head that is unusual in some way. It is not necessarily good or bad, unless the doctor stated or implied that it is. If you can post more information directly from the report, feel free.
I'm thinking the word may have been "anomalous," which just means unusual. It doesn't mean good or bad. It just means you have something that is unusual. Structures that are unusual can still be normal. Can you post any more detail from the report? For instance, if you have the actual written report, there should be a section toward the end that says IMPRESSION, or something like that.