Alrighty, I had a similar issue for 2+ years
Good to see you are going down the avenue of seeing a neurologist, ticks potential variables off the list of things that could be wrong with you.
I had the same issue with a hollow lat, pec atrophy, albeit my pec atrophy was pec minor.
Eventually my index/pinky finger became weak, as did the muscles that I use to externally and internally rotate my arm/shoulder.
What was wrong with me?
Well… apparently I had been repeatedly dislocating my shoulder for years. I was always of the opinion my dislocations were sublaxations as I was always able to pull on my arm, thus leading to my shoulder re-locating within it’s socket, or the shoulder would pop out for a few seconds followed by excruciating pain before popping back in
With each subsequent time this happened, the side affected would get weaker. My issue was likely an injury to and/or chronic compression of axiliary nerve + brachial plexus mediated by accumulativd damage to my shoulder that took place over years because I have lax connective tissue.
I eventually required fairly extensive recomstructive surgery because I kept ignoring pain/weakness as I didn’t want to stop training… I didn’t want to believe something was wrong.
Do you have any shoulder issues? Can you cross the arm on your affected aide over to the other side of your body?
If you perform cable internal rotation for reps do you have any pain? During external or internal rotation, do you feel one side of your shoulder girdle/rotator cuff complex contracts harder than the other?
Can you contract your traps (lower and upper) equally on both sides
Just going by what happened to me… your pathology may have nothing to do with your shoulder. Biggest irritance for me was weakness and eventually substantial atrophy in pec minor and lat.
Labral and RC tears can be degenerative as opposed to acure in nature. If the above describes you an MRI WITH contrast or MR arthrogram (latter is best with contrast injected into joint) is gold standard for diagnosing pathology of shoulder tendons and cartilage. These tears can irritate nerves surrounding, particuarly axiliary nerve which is the nerve that innervates lattisimus dorsi. Especially if imaging identifies paralabral cyst