In this world of brain plasticity and the excitement it engenders, we may sometimes forget the complexities of the rest of the body and maybe also, the rest of the nervous system.
The T6 area in the clinic
What is it about the T6ish area? The middle of the back is a very popular place to experience pain and tightness. About 30 years ago, as neurodynamics thinking emerged, I was intrigued with this area. A repeated clinical pattern exists where many people with positive straight leg raises (SLR) or slump tests often complain of pain around the T6 area. Additionally, if someone had a positive SLR or passive neck flexion, suggesting some alteration of meningeal biomechanics, palpation around the T6 area often revealed tenderness and stiffness, usually unbeknown to the owner of the back. People, post whiplash, often have this finding and indeed whiplash sufferers who complain of pain in the mid thorax may have a worse prognosis (Maimaris, Barnes et al. 1988). Many clinicians reading this blog are well aware that if you gave the mid-thorax a bit of a wriggle and shake, the whole body movement can improve and SLR and slump test findings will often improve, sometimes markedly.
Intriguingly, some science on neuromeningeal biomechanics emerged at the time of developing neurodynamic theories. With an extrapolation from a 24 human cadaver study by Louis (1981), supported by earlier work by Breig (1978) and painstaking monkey dissections by Smith (1956), the year I was born! I came up with the image below from “Mobilisation of the Nervous System (1991). The spinal canal could be around 9 centimetres longer in flexion than extension – somehow the contained cord and meninges have to adapt. Check out the T6 area – it doesn’t move that much in relation to the surrounding canal – kind of like if you pull a piece of elastic from both ends, there is a bit in the middle that doesn’t move much in relation to its surrounds.
If there was something special about the area then you would expect that the anatomy would express something about the function. While there has been minimal study (and few would bother today), the major blood vessel for the thoracic cord and meninges comes in just under T6 – so it’s probably not a good place to have a lot of sliding around, and in addition, the canal here is quite narrow and the dura mater is thicker than anywhere else along the neuraxis. Maybe it is designed to be like the middle of a piece of elastic?
Pause a moment and marvel– the spinal cord in the thorax may only be a little over a centimetre in diameter with the surrounding canal maybe around 1.4 centimetres and also containing meninges and cerebrospinal fluid (CSF) whose freshness is necessary for cord nutrition. This tiny area has a lot of work to do in representing the low back, pelvis and legs. I think it is best to add the cord into modern concepts of representation and neuromatrix which are often all brain based.
I think that no matter what, if central sensitisation is considered, then the physical health of the nervous system including the cord should be entertained. Is the T6 area a place that is perhaps biomechanically more at risk than other parts of the nervous system especially when you consider what humans do with their bodies these days? Physical problems with physiological consequences could result in significant nociception from the meninges, peripheral neurogenic contributions from sinuvertebral nerves innervating the meninges, and nerve roots plus mechanically induced contributions to sensitisation. The slump test, especially in long sitting may be useful to check it out and I am sure the area loves inputs such as yoga, dance, martial arts and just a good old roll around on the floor.
In conclusion, there is a place in the biopsychosocial framework for T6.
Tell us your T6 stories
– Breig, A. (1978). Adverse Mechanical Tension in the Central Nervous System. Stockholm, Almqvist and Wiksell.
– Louis, R. (1981). “Vertebroradicular and vertebromedullar dynamics.” Anatomia Clinica 3: 1-11.
– Maimaris, C., M. R. Barnes, et al. (1988). “‘Whiplash injuries’ of the neck: a retrospective study.” Injury 19: 393-396.
– Smith, C. G. (1956). “Changes in length and position of the segments of the spinal cord with changes in posture in the monkey.” Radiology 66: 259-265.