A patient comes in with hands that go numb at night, having been fitted for wrist braces that did not help. The braces did not help because the problem was never at the wrist. It was at the base of the neck, where nerves and blood vessels squeeze through a narrow corridor between the collarbone, the first rib, and the scalene muscles. That corridor is the thoracic outlet.
How to Tell It Apart From Carpal Tunnel
The distinguishing features are specific and easy to check.
Which fingers. This is the most useful discriminator. Carpal tunnel affects the thumb, index, middle, and half the ring finger — the median nerve distribution. Thoracic outlet syndrome most often affects the ring and little finger and the inner forearm, because the lower trunk of the brachial plexus takes the brunt.
What makes it worse. Carpal tunnel is aggravated by wrist position — typing, holding a phone, gripping a steering wheel. TOS is aggravated by arm elevation: blow-drying your hair, reaching into an overhead cupboard, hanging on a train handrail, sleeping with your arm above your head.
How far up it goes. Carpal tunnel symptoms rarely extend above the forearm. TOS frequently involves the shoulder, the side of the neck, and sometimes the upper back.
Other clues. A heavy, aching, easily fatigued arm. Colour or temperature changes in the hand. Symptoms that worsen carrying a bag on that shoulder.
Why It Happens
The thoracic outlet narrows for predictable reasons. Forward head and rounded shoulder posture shortens the scalenes and pectoralis minor, closing the space — the same postural pattern behind tech neck. A first rib that has lost normal motion reduces the corridor directly. Whiplash is a common precipitant, since the scalenes are frequently injured and then heal short and tight; we see this often in post-collision patients. Some people have an extra cervical rib or a fibrous band they were born with. And overhead athletes — swimmers, throwers, volleyball players — are disproportionately affected.
The Double Crush Complication
Worth knowing, because it explains why some carpal tunnel surgery disappoints. A nerve compressed at one point becomes more vulnerable to compression further along its course. Someone can genuinely have both thoracic outlet compression and carpal tunnel — and releasing only the wrist leaves half the problem in place. If your carpal tunnel release helped somewhat but not completely, this is worth investigating.
How It Is Assessed
Diagnosis is primarily clinical. There are provocative tests — positions that reproduce symptoms by narrowing the outlet — but they produce false positives often enough that no single one is conclusive. What makes the diagnosis is the symptom pattern, the aggravating positions, the examination findings at the first rib and scalenes, and the exclusion of cervical radiculopathy, which can mimic it closely. We cover that distinction in cervical radiculopathy.
Nerve conduction studies are frequently normal in TOS, which is a common source of confusion — a normal study does not rule it out.
Treatment
The great majority of cases respond to conservative care, and surgery should be well down the list.
The work has three parts: restoring motion to the first rib and the cervicothoracic junction; releasing the scalenes and pectoralis minor through soft tissue therapy; and correcting the postural pattern that is closing the space, which is where postural assessment matters. Without the third part, the first two are temporary.
Practical changes help immediately: stop sleeping with your arm overhead, switch your bag to the other shoulder or a backpack, and raise your monitor.
If Your Wrist Brace Is Not Working
That is a useful piece of information, not a dead end. It usually means the compression is somewhere else. Contact Bromberg Chiropractic in Cambridge for an examination that looks at the whole path of the nerve rather than just the end of it.
