For a long time, the science told us that there was no connection between the brain and the immune system. The brain was supposedly a privileged organ, whose cells did not need immune protection. All that changed in very recent history, due to a discovery that happened almost by accident. There was in fact a channel in the brain that had previously been compressed and then missed largely because of the way brain banks stored their specimens.
It was a ground-breaking, textbook-rewriting discovery when Antoine Louveau first stumbled on this lymphatic vessel system in the brain. Previously, this vessel system had been tucked away, hidden from the prying eyes of the researchers. The knowledge that there was in fact a lymphatic system containing immune cells in the brain at all was highly significant.
“Usually when you have an immune response in the brain it’s considered to be a bad thing,” said Louveau. “What we’ve known from several years now, is that there are immune cells in your brain under normal conditions and this is actually good for your brain. The big question we still had was how those cells get in and get out of that system. The system we discovered is actually the way those cells get out of the brain and do what they are supposed to do [2].”
So healthy brains could contain immune cells and this was not a bad thing! This was big news. Still, for chiropractors at least, there was a missing link. What did this new discovery mean for us?
Enter Dr. Amy Haas. Amy started off on a different path to chiropractic, “But the universe has its ways of getting you where it needs you to be,” she says. After completing a Bachelors, Masters and PhD in Biochemistry as well as a postdoctoral fellowship in the Department of Pathology at the esteemed Harvard Medical School, a series of injuries that were not healed through traditional approaches saw her turn to chiropractic for help. The experience was so profound she left her career as a scientist to become a chiropractor.
Despite moving on from the world of science, she can’t help but keep a watchful eye on the world of research and constantly ask, “How does this apply to chiropractic?” Here, her unique perspective borne of classical scientific research training and chiropractic training is put to work linking both worlds.
One result of this pursuit is a hypothesis paper recently published in the Journal of Vertebral Subluxation Research, and it presents one postulate on how chiropractic can impact lymphatic drainage – and it has a lot to do with the Atlas, Axis and the Cervical spine.
“Early on, when I was in college we were originally taught that the brain is an immunologically privileged organ. There’s a blood brain barrier, and the immune system has no access to the deep brain tissue.” We are now seeing that is completely wrong. “Could this have just a little bit of bearing on chiropractic?” she muses.
“The immune system really does have access to the deep tissues of the brain, because it has to! The immune system cleans up cellular debris and messes. A cell dies, who’s going to clean it up? The immune system! Logically, the immune system has to be there in some way, shape or form. In the past 20 years or so, the field of neuro-endocrine immunology has exploded. It has really shown that the nervous system, the endocrine system and the immune system not only share chemical modulators, such as interleukins, they have a lot of cross talk.
The results of lymphatic drainage could indeed be profound – with scientists like Louveau speculating that faults in lymphatic drainage could actually be the starting point for many neurodegenerative diseases. This potentially makes Dr. Amy’s hypothesis on the link between chiropractic care and lymphatic drainage a very significant one.
According to Dr. Amy’s hypothesis paper, the link lies in the area of cerebral spinal fluid and the pressure gradients that may kick in when a person is subluxated. The circulation of cerebral spinal fluid will be no new concept to chiropractors. Produced in the choroid plexuses of the ventricles of the brain, it provides immune and mechanical protection to the brain and spinal cord before returning to the vascular system via the dural venous sinuses.
“CNS Lymphatic drainage is a bit of an interesting subset because it drains into the deep cervical lymph nodes. Essentially, [if there are lymphatic drainage issues] it’s a plumbing problem. Drainage from the deep cervical lymph nodes is dependent on a pressure gradient,” explains Haas. “While extracranial lymphatic drainage is assisted via muscle contraction, the cranium is a closed compartment; you don’t have any muscle contraction. Therefore drainage has to depend only on a pressure gradient. Anything that backs up that pressure gradient will slow the transfer of fluid.
So how can chiropractic have any impact on this pressure gradient? Haas puts her Harvard-trained scientist hat back on to explain the anatomical ties.
“Lets say for example you have an atlas subluxation; you rotate the atlas and you can put pressure on the internal jugular vein. That has been shown by research and I cited in the paper [3]. An atlas subluxation may impinges drainage through the internal jugular vein. That may in turn increase the CSF pressure because it can no longer drain quickly and freely via the cervical lymph nodes and the internal jugular vein. When the CSF pressure is increased just a little bit, that will affect the lymphatic drainage through the channels adjacent to and lining the dural sinuses because that also has to be pressure dependent. When the dural sinuses are become compressed by fluid pressure, you can no longer see the channel [the lymphatic vessel in the brain]. It is not a solid channel. That is a channel that is very changeable. So that brings up the possibility (at this point an unproven hypothesis) that if an atlas subluxation were to slow the drainage of the venous blood out of the cranial cavity, then you develop a pressure gradient.
When you work backwards in that plumbing problem, the pressure gradient could slow the process of lymphatic drainage just by virtue of pressure. And furthermore lymphatic drainage is postulated to be the mechanism by which the glymphatic system in the deep brain tissues gets rid of cellular debris from deep brain tissues. Louveau postulates that interference of proper drainage through the CNS lymphatic system could be the root cause of many neurodegenerative disorders [1]. That is exactly what caught my eye. Louveau is a PhD scientist in a completely non-chiropractic realm saying if you don’t properly drain waste out of the brain you could end up with Parkinson’s.
If this hypothesis were to be proven, we could have on our hands a breakthrough in evidence for chiropractic care. Adjusting the atlas and cervical vertebrae can have a profound impact on the entire system, this we know, but to link (through research) lymphatic drainage and chiropractic care, we could potentially quantify a way that chiropractic care could impact neurodegeneration.
Still a poignant question remains: Is it only upper cervical specific adjustments that have the potential to impact CSF pressure and lymphatic drainage? Although the relevant research has not yet been performed, Haas believes the answer is unlikely to be a divisive one.
“My personal belief is that there are multiple methods by which the chiropractic adjustment can have its many diverse effects on normal physiology, and on guiding abnormal physiology towards normal physiology; whether that’s is at the neurochemical level, whether that’s at the stress level, whether that’s at the endocrine level, the nerve root hypothesis, whether its glucose metabolism [etc]. There are so many different mechanisms that can affect the nervous system. So I don’t want to say its just one technique or another. I think it’s different in every person. I’m not keen on saying, ‘upper cervical is the only way to go,’ because I think in truth it’s a bit more complicated than that.”
What I will say is that this series of observations does suggest that adjustments that will restore the position and motion integrity of the atlas and therefore may help open up the drainage from the cranial vault.
While the discovery of the immune vessel in the brain was an event that had great bearing on our understanding on immune function and neuro-anatomy, Haas’s work brings an important perspective for chiropractors.
The evidence base for chiropractic has built up significantly over the last two decades, but still the ability to draw connections between non-chiropractic research and our own profession is an important one. We look forward to seeing more from Dr Amy.
References
[1] Louveau A et al. “Structural and functional features of central nervous system lymphatic vessels.” Nature 523, 337–341 (16 July 2015)
[2] Staff Interviewer University of Virginia, (2016), “Antoine Louveau, PhD speaks to Lymphatic Brain Discovery” UVA Link,
[3] Haas, A (2017), “Lymphatic Drainage of the Brain: Implications for Chiropractic,” A. Vertebral Subluxation Res. February 13, 2017
