While networking is always the best way to find a good lawyer, it's understandable it you don't want to discuss a brain injury case with others. Fortunately, the Internet offers a solution: many lawyers specializing in brain injuries advertise there, especially on sites like http://www.braininjury.com.
Ask a prospective brain injury lawyer for a free consultation. In most cases, they'll oblige you, because this is how they get new clients. Use to time to see how well qualified they are, and to determine whether you can work well together for however long it takes.