Unless you are 100% sure of things like sleepwalking or even enuresis (could have just been infection) you have to really try to verify. Something that may have occurred years ago would be hard to verify.
There is a very good reason that the SAs and DODMERB want you to disclose everything. They are not only qualifying you to attend an SA but also to serve in the military, where you will be subject to conditions that the average civilian will never face.
Something that happened once years ago could in fact recur, lead to a different medical condition, etc. in the future. You aren't in a position to make that decision.
If that condition or some related condition resurfaces, you could face not being physically qualified for commissioning or not being able to do the military job you want (e.g., pilot). Worst case, you slip through and someday that condition ends up endangering your life or the life of your shipmates/soldiers/airmen, etc.
If your condition truly is "no big deal" TO THE MILITARY then you will more than likely receive a waivern and rest easy knowing that you are fully qualified (usually) at least of the time you enter an SA. If the military considers it a big deal, better to find out now than later. It will eventually come to light and, more often than not, at a time much worse than now.
For future applicants, DO NOT LIE and don't try to play doctor or DODMERB. If you are unsure whether something in your past rates mentioning on the DODMERB, contact Larry Mullen for advice.