Originally Posted by mike53
Try searching for "hypermobile ulnar nerve"
It certainly sounds like it.
In a study of 200 people, I was surprised that the ulnar nerve moved from its normal location in back of the elbow, to a position in front of the elbow (by moving medially over the tip of elbow) in 20% of people. http://www.jhs-euro.com/cgi/content/abstract/25/1/85
That's pretty common. And the movement of the nerve would certainly fit with the sensation the OP is describing.
That study also found that while the ulnar nerve was about 3x2 mm in men, in those with a hypermobile ulnar nerve the nerve was usually somewhat larger.