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Posted on Fri, 7 March 2014
An interesting topic came up recently about nerve vulnerabilities in the area around the collar bone. It's not an area we immediately consider but upper wraps and 3rd ropes or halter neck arrangements run in this territory. So, is it an issue? The question was prompted by this illustration on Fetlife which makes it appear that the brachial plexus could be at risk. If you aren't on, the image below is very similar to the one below. In short, the brachial is the bundle of nerves that branch off from the spinal cord down the arm comprising the radial, median and ulnar nerves but I'll provide a fuller explanation further on. 
Of course, the images show a dissection designed to show off the brachial plexus as clearly as possible. To achieve this, the clavicle (collar bone) and the tissue surrounding the nerves has been removed. Consequently, the casual observer might be forgiven for assuming that the brachial plexus is exposed in this region. In fact, most of the nerves are buried deep inside and protected by the clavicle until they emerge in the armpit area and inner upper side of the arm as you can see here. Biodigital Human is a great resource for visualising how everything is laid out internally as it allows you to not only rotate the body in 3D but also to add and subtract components like muscles, blood supply and nerves. We are already well aware of the risk of nerve injury in the armpit/inner upper arm area from overly tight cinches or rope bulk, e.g. knots or twists.
GirlOnFire provided this explanation of this nerve bundle and the vulnerabilities:
"The Brachial Plexus (the bundle of nerves that innervate the arm) leaves the spinal cord at the neck and pass between the Antirior and Middle Scalene muscles before travelling inferior(underneath) to the clavicle and supirior(above) to the 1st rib and then inferior to the Pectoralis Minor muscle. In theory the clavicle should protect/maintain the space for the brachial plexus (the subclavian artery and vein also pass through this space) in fact protecting it at this particular point. However each person is built slightly different so if the space is perhaps slightly narrowed(costoclavicular syndrom) or if the bottom has extra movement of the clavicle due to laxity or injury to the ligaments of the Acromioclavicular(AC) or Sternoclavicular Joints then the nerves and/or blood vessels passing beneath the clavicle could become compressed. Another possibility that would create much greater risk for nerve damage in this area is the presence of a Cervical rib. A cervical rib is an extra rib above the 1st rib. While this is rare (1 out of 500 people) it is possible for a bottom to have this and not know about it. I mentioned that the Brachial Plexus passes between the anterior and middle scalene muscles. This is actually a common place for the nerves to become compressed (Thoracic Outlet Syndrome) if these muscles are tight or over developed. Another possibility is for the nerves to become compressed by tight pectoralis minor muscle (or other key muscles along the nerve path however I'm getting off topic). I would say the most common nerve problem with rope over the clavicle would be compression to the Supraclavicular nerves which travel over top of the clavicle. These are sensory nerves that supply the skin over the upper chest and shoulder."
I have heard back from a highly knowledgeable gentleman, who is a neurosurgeon and is no stranger to tying up girls. As you'll see, he offers a very similar opinion:
"This image, even if anatomically correct, is misleading because we have the impression that the brachial plexus is in front of the chest . This is why in the comments some think upper wraps may cause nerve compression on the chest. What we don't see is the third dimension where we would observe the curvature of the ribs, the plexus is not in front of the ribs, but more lateral between the ribs and humerus, in the armpit (under the thumb of the examiner in this picture. The brachial plexus is anterior (in front) in his upper part , which is the neck region the goes laterally below the collar bone. Furthermore, on this anatomic preparation as you noticed the collar bone was removed but also, scalene muscles and pectorals major and minor muscles. The collar bone also very effectively protects the plexus (brachial plexus injuries are very seldom caused by seat belt in high energy car crashes, and this is always an "upper palsy" which means the upper roots only were injured, above the clavicle, in the neck region ). Then the only potential problem there is at the armpit (upper cinch) as you know. Compression of the plexus between first rib (or an accessory cervical rib) and collar bone may occur in some people, the pathology is known as the "thoracic outlet syndrome", but may not cause real nerve injury: at most numbness in predisposed people."
In summary, we need to be aware that some people might suffer from thoracic outlet syndrome and of the possibility of compressing the supraclavicular nerves which run over the collar bone. The latter is most likely to happen with halter neck arrangements such as the 3rd rope in a gote. As this is a sensory nerve, the symptoms would be limited to loss of sensation in the upper chest and shoulder and would not affect movement like a radial compression might.
As with all nerve issues, it is wise to heed any warning signs, if you are lucky enough to have any, however slight. Nerve compression is often signified by twinges or mild electric shock-like feelings travelling along the path of the nerve. Attention to such signs can avoid or minimise the severity of an injury if fast action is taken. By this, I mean removing the pressure. As this is most likely to happen during a suspension, the best solution is to get at least one foot on the floor so the person tied can support themselves. If this isn't practical, choose the safest way possible to remove the pressure. This could be by simply supporting their weight or an advanced rigger might change of suspension orientation or the main load-bearing point, e.g. transferring the suspension from gote to hip harness. If you aren't confident that you can solve the problem fast in the air, don't mess around. Seconds can count. I have seen a preventable injury when a rigger failed to act quickly enough thinking he could sort it by adjustments.
