Hand numbness or tingling has become increasingly common. Last week I explored the most prevalent neurological compression syndrome, Carpal Tunnel Syndrome, which can be one cause of these symptoms. This week I will travel further up the arm to discuss a related pathology with similar symptoms, Thoracic Outlet Syndrome. There is much controversy in the medical community as to what exactly constitutes this syndrome and how it should be diagnosed and treated, so I will give you the information that most practitioners can agree upon about the neurogenic variation of the disorder. Another version of this disorder involves vascular compression, but since obstruction of the blood vessels only accounts for approximately 5% of cases, I will focus on the much more common musculoskeletal compression of the nerves.
The Anatomy
The brachial plexus is the bundle of nerves that supplies the arm and hand with sensation and motor control. It originates in the lower vertebrae of the neck and first travels through the anterior and middle scalenes, two muscles on the front/side of the neck that flex the head forward and to the side and also elevate the first rib. It then travels through the space in between the collar bone and the first rib before moving along under the pectoralis minor muscle. This muscle runs from the third to fifth ribs up to the coracoid process (the pointy forward protrusion of the shoulder blade toward its top outer edge) and is responsible for moving the shoulder blade forward and down, like when hunching.
If the scalenes are chronically tight, they can squeeze the brachial plexus between them and/or pull on the first rib so it presses the nerve in between the rib and the collarbone. The same is true for the pectoralis minor: if it’s chronically tight, it squeezes the nerves, particularly as the arm is raised. Think about the posture we inhabit most on a daily basis: hunched over our computers and smartphones, hunched over driving or on bicycles…these postures predispose us to chronically tight anterior musculature. It is easy to see how the nerves in this region can become impinged. In addition, the shoulder joint is the most mobile joint in the body, so it’s up to the soft tissues to provide stability for this joint through muscle contraction. There are lots of nerves and tight spaces in this area, so constant muscle contraction can easily set the stage for nerve compression.
Thoracic Outlet is frequently brought on by a repetitive use injury. It predominantly affects those who habitually have their arms in the air, like painters, electricians and plumbers. Constantly tilting the head to the side, like when playing a musical instrument, can also result in this condition. Postpartum women experiencing “new mother’s neck” from holding the baby and breastfeeding are likewise susceptible. It can also be caused by traumatic injuries to the muscles in this area. For this reason, people who carry heavy loads, particularly overhead, are candidates for this condition (CrossFit, anyone?). Women are disproportionately affected, partly because the pathways through which the nerves pass are smaller and can more easily become impinged. Pregnant women often suffer from Thoracic Outlet Syndrome, but this is widely believed to be caused by edema due to increased fluid load in the body during pregnancy – the nerves are still compressed, but by fluid.
Prevention
There is no guaranteed way to prevent this condition, but some tips to help avoid it are:
- Maintain proper alignment by practicing good sitting posture, avoid hunching
- Avoid repetitive overhead movements if possible
- Stretch the muscles in your anterior neck and chest, and strengthen the muscles in your back and posterior shoulder region (here are some examples)
- Avoid carrying heavy bags on your shoulders, which can compress the nerves and blood vessels in this area
Diagnostic Testing
A simple test for this condition is the EAST test, or Elevated Arm Stress Test. 
To perform this test, sit down with the arms elevated to 90 degrees out to the sides. Bend the elbows also to 90 degrees so your hands are pointed up to the ceiling. Now open and close your fists for 3 minutes. Most people with Thoracic Outlet Syndrome are unable to complete the full 3 minutes without symptoms interfering. These symptoms include tingling or “pins and needles” sensations, numbness or shooting pains in the arms and hands. If you have a positive result with this test, you may suffer from this condition and should consult your preferred health practitioner for further testing.
Treatment
If your healthcare provider determines that your Thoracic Outlet is caused by musculoskeletal dysfunction, manual therapies will help! Massage is excellent for releasing the tight muscles. Due to the delicate nature of their placement, giving self-massage techniques for this condition would be irresponsible (you could easily compress arteries and veins if you are not precise with your positioning).
However, stretching can greatly decrease symptoms 
and these are steps you can take on your own at home. In order to stretch the scalenes, lie down face up.
Take the hand of the side you want to stretch and place it under your hip, to stabilize that arm. Take your opposite arm and SLOWLY and GENTLY pull your head over to that side, first looking straight up toward the ceiling and then facing slightly away from the pulling arm.
An easy stretch for the pectoralis muscles: 
raise your hands to your sides at 90 degrees, “goal post” style, as in the EAST test above, but while standing in a doorway. Place your arms against the sides of the doorway and allow your body to slowly move forward to the point of resistance and hold. You can also do one side at a time, as shown.
A physical therapist can recommend exercises to help with the condition, and the lifestyle changes listed under the “Prevention” section in this post should also be incorporated into treatment.
Almost all cases of Thoracic Outlet Syndrome can be linked to musculoskeletal problems arising from poor posture or repetitive movements. Being more mindful of our posture, avoiding repetitive movements, stretching and exercising are all good ways to help our bodies avoid conditions such as these.
NOTE: if symptoms are severe or chronic and accompanied by pain, they could be a sign of a more serious problem. This type of peripheral neuropathy could be caused by diabetes, kidney failure, tumors, bacterial or viral infections, neurological pathologies, chronic inflammatory disorders or nutritional deficiencies. If you think that might be the case, it’s best to partner with your health care practitioner to determine the root cause.
RESOURCES:
http://www.physio-pedia.com/Thoracic_Outlet_Syndrome
http://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/manage/ptc-20237978
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