DN> Thoracic outlet syndrome is caused by pressure on the brachial plexus
DN> (not ulnar nerve), as well as on the subclavian artery and vein.  The
DN> symptoms are thus both vascular and neurologic.  Poor posture (droopy
DN> shoulders) is one of the things that can cause it.

True neurologic TOS (as opposed to vascular TOS, or vague symptoms
attributed to TOS) is also extremely rare.  Gilliatt has estimated
the prevalence of true neurologic TOS to be about 1 per *million*.
The cause of TN-TOS is a cervical rib, or a fibrous band running
from an elongated transverse process of C-7 to the first rib, with
chronic compression of the lower trunk or medial cord of the
brachial plexus.  The symptoms are numbness along the ulnar border
of the forearm and hand, sometimes up to the axilla (C-8, T-1), plus
weakness and atrophy of C-8 and T-1 innervated muscles (i.e., all
intrinsic hand muscles).  I doubt that "droopy shoulders" has
anything to do with TN-TOS.
---
 . SLMR 2.1 .