So I've been dealing with this issue for a few years. One of the few things that has actually helped (but not made the problem go away) is stretching areas like my anterior scalenes and pec minors. I do other stretches and exercises, but I don't know how effective they are.

I have noticed due to that generally now I only get numbness when I am asleep, and my arm has to be both above my shoulder and bent. Also I 'think' I have to be sleeping on my stomach.

If I am awake and put my arm above my head and bend my elbow, I get no numbness (I used to before I started stretching my pec minor, but now I tend to have trouble causing numbness in that position when I'm awake).

If I wake up with my ulnar nerve numb and my arm bent above my shoulder, and I straighten my elbow (still above my head) the numbness goes away in about 10 seconds.

If I wake up with my arm numb above my head, and I bring my arm below my shoulder it doesn't matter if I keep my elbow bent or straight, the numbness goes away.

Another contributing factor is if the bottom of my forearm is resting on the bed. Sometimes I've found if I take my arm (still bent above my head) and rest my forearm on a pillow instead of the mattress (the pillow is softer than the mattress), the numbness will go away. Sometimes not though. So if the bottom of my forearm is resting on something soft is also a contributing factor, but not as strongly.

This isn't what happens 100% of the time, but I can say that 75%+ of the time, the numbness comes from arm above the head and bent (with whether my forearm is resting on something soft also contributing, but not as much). Sometimes I'll get it with arm straight, etc. but by and large I need to be sleeping on my stomach, arm over my head and bent.

Why does bending my elbow seem to contribute? Is it that I am stretching the nerve too much? Like I said, I need 'both' my elbow bent and my arm above my head to get ulnar nerve compression in my sleep.

Part of the problem is I have sleep apnea and haven't been treated yet. I can't sleep on my back because of this issue, and I always wake up on my stomach I guess because I breathe easier in that position. I saw an ad for a $200 at home apnea test, and a used APAP is about $400 so I can try that out. Maybe if I can get my apnea treated and am able to sleep on my back that will help keep this issue under control.

Has anyone else found sleep apnea to aggravate TOS (because you invariably end up sleeping on your side or stomach after you fall asleep)?

As far as my symptoms of arm bent, above my shoulder being the main cause of numbness, what could that imply? What areas might be too tight? I once had a massage therapist tell me that meant the pec minor was too tight, but before I started stretching the pec minor I could recreate the numbness during the day with my arm above & bent. Now that I've stretched that muscle a bit I usually can't get ulnar nerve numbness during the day from that position.

Does both the arm above the head and elbow bent position cause nerve compression? Like I said, I was told the arm above the head can compress the nerve at the pec minor, maybe I can handle one compression but not both the elbow and pec minor. I don't know. This condition sucks, there are so many things that can contribute.