Just my 2 cents...

the justification on mobility aid is not tied to a "diagnosis" but instead is dependent on needs. In other words, if you can't walk unassisted for X feet/minutes you need (and qualifiy if your medica records have notes about it) a set of crutches/walker/wheelchair/powerchair etc.

Heck, even Medicare uses this justification. For example my neuro documents I have ataxia (balance) and endurance limitations. My right hand is fused in a few joints, blah blah blah. I was approved for a K0005 level chair with no problem and am only highly probable MS. The main point is that they are interested in what you can do, what you cannot do and (more importantly) what you can do again if you have equipment X, Y or Z. Its all about Atvities of Daily Living

If you need it just tell your doctor. Most are usually happy to document the need so that you can get what you need. Good Luck and chin up!