<p>You are right, you would not want to make this your main common app essay. But here is the thing… admission offices don’t want to read extensive additional essays, either. This is something you should mention briefly in the additional information section, and also if you have a school guidance counselor you could discuss with them whether they could include a comment in it in their recommendation. But I don’t think an “essay” with anecdotes is the right thing to do. A short, factual statement that you have had a pain-related medical condition that disrupted your high school career, but is now being effectively managed is the sort of thing you want to say. They don’t want a lot of medical details… but you probably want to tell them enough so they know it is a physical health problem and currently well managed (assuming that is true).</p>
<p>But that said, be sure you have some good match and safety schools on your list. Top tier colleges may shy away from a student who hasn’t been in a normal school environment for a few years due to medical issues. So make sure you have a good range of schools on your list so you have good options next spring.</p>