Hands and arms falling asleep when lying down

[Tuna Salad]

Good day

I have been experiencing my hands and arms falling asleep whenever I lie down.  It has been progressing from occassionally to everytime.  In the past it would wake me from sleep, and now it occurs within 5 mins of lying down.  My BP bilateral when this is happening is 108/55 with good peripheral pulses and cap refill.  

Could someone please explain the physiology of why this happens upon assuming a supine position, and provide a differential diagnosis.  Thank you,

K.

[catmando]

I have the problem that when I lie supine my face goes to sleep, especially around my eyes and across my nose.  I also have chronic severe headaches that can only be controlled bythe drug lyrica.  This seems to mean that they are caused by the inflammation of the nerve endings in my head.  I have had MRI's, CAT's, epidural blocks, facet blocks, and recently an occipital nerve block in case it is occipital nueralgia.  So far no one can give me a clear diagnosis.  I also have moderately severe arthritis in my facet joints, neck, and shoulders.
Has anyone run across any of these symptoms in their search?