Small meningiomas, small unruptured aneurysms, cavernomas that have not bled, arachnoid cysts and many Chiari malformations are found on scans done for other reasons and cause no symptoms at all. For these, the risk of an operation can be higher than the risk of leaving the condition alone, and the right plan is an interval MRI at an agreed time, with a clear description of what would change the advice.
Being told to watch can feel like being told to wait. It is not. It is an active plan with a review date, and it can be revisited whenever symptoms change or the scans do.