Take a smooth-bottomed stream and throw a handful of rocks into it. Watch what happens to the surface of the water.
It goes from flowing evenly to churning. The disturbance you can see on top is caused by something underneath that the water now has to move around.
That's turbulence, and it's the right mental image for something that happens inside the head after the upper neck is disrupted.
How Is Cerebrospinal Fluid Supposed to Flow?
Cerebrospinal fluid is produced inside your brain, circulates around the brain and down the spinal cord, and is reabsorbed and drained back out. It nourishes the tissue, carries away metabolic waste, and helps regulate pressure inside your skull.
That circulation has a rhythm to it. It isn't static. It's driven partly by the beat of your heart, so it moves in gentle pulses, and it depends on traveling across surfaces that are smooth and passages that are properly shaped.
Those surfaces and passages are formed by structures — bone, membrane, ligament — that are supposed to sit in specific positions relative to one another.
Head position and head movement are part of that system rather than incidental to it. In healthy adults, phase-contrast MRI has shown that rotating the head measurably changes cerebrospinal fluid flow rate and stroke volume at the craniocervical junction (Xu et al., 2016). The geometry of that junction is not a bystander to fluid movement. It participates in it.
What Does a Misalignment Do to That Flow?
When the craniocervical junction is disrupted, the structures forming the fluid pathway no longer sit where they belong.
Now the fluid that should glide along an even surface has to travel across a bump, around a corner, or through a passage that has narrowed on one side. Instead of moving smoothly, it tumbles. The pulse from each heartbeat, which should be absorbed and smoothed by an evenly shaped channel, instead breaks up into turbulence.
The larger the misalignment, the more turbulent the flow becomes.
There's a specific version of this worth describing, because it produces a symptom people recognize immediately. The deep muscles at the base of your skull connect to the membrane surrounding your brain and spinal cord — the dura — through a connective tissue structure called the myodural bridge. That connection was first described in detail in cadaveric dissection, running from the rectus capitis posterior minor muscle to the dorsal spinal dura at the atlanto-occipital junction (Hack et al., 1995). Functionally it works like a rope: when those muscles contract, they pull on the membrane and hold it away from the spinal canal.
If that connection is disrupted, the membrane loses some of that support. When you extend your head backward, the membrane can fold inward toward the spinal canal instead of staying taut, creating an obstruction the fluid then has to pass over.
People with this describe a whooshing or thumping inside the head, often timed to their heartbeat, often worst in extension, and often painful.
Why Does Tissue Answer Repeated Irritation by Hardening?
Here is the principle that connects turbulence to something more serious, and it's one you already understand from other parts of your body.
If I punched you in the same spot on your arm every day for a few weeks, that tissue would change. It wouldn't stay soft. The bone underneath would thicken. The tissue around it would toughen. Your body would lay down denser, more resistant material specifically to withstand the repeated insult.
That's the same reason a guitarist develops calluses on their fingertips and a laborer develops them on their palms. Repeated mechanical irritation produces adaptive hardening. It isn't a malfunction. It's a sensible response to a mechanical problem.
Your body applies that logic broadly. It does not have a separate rulebook for the nervous system.
Can That Principle Be Applied Inside the Central Nervous System?
Now put those two ideas together.
Turbulent fluid flow is a repetitive mechanical insult. It isn't dramatic — no single pulse does damage — but it repeats with every heartbeat, continuously, for years.
My working position is that nervous tissue subjected to that responds the way tissue generally responds. Instead of remaining soft, pliable, and able to transmit signals cleanly, it begins to harden. Over a long enough period, that adaptive hardening comes to resemble the plaque and degenerative change associated with neurodegenerative disease.
I want to mark clearly what is established here and what is mine. The association between impaired cerebrospinal fluid dynamics and neurodegeneration is well documented. Glymphatic dysfunction has been described in animal models of traumatic brain injury, Alzheimer's disease, and stroke, alongside human imaging evidence of reduced clearance in Alzheimer's (Rasmussen et al., 2018), and failure of that clearance system has been proposed as a shared final pathway across the dementias (Nedergaard & Goldman, 2020).
Turbulence as the specific mechanical driver of that hardening is my clinical reasoning, extended from how tissue behaves everywhere else in the body. It is a hypothesis I find persuasive, not a demonstrated finding, and I'd rather say so plainly.
One observation does support it. Lesions tend to appear specifically where turbulence and pressure are greatest — which is what you'd predict if repeated mechanical irritation were driving the change, since the tissue taking the most insult should show it first.
What Is the Second Half of the Problem?
Turbulence is one contributor. Reduced clearance is the other, and they usually travel together.
Cerebrospinal fluid is how your brain removes metabolic waste. That clearance runs through a paravascular route — the glymphatic system — that moves fluid through brain tissue and carries interstitial solutes, including amyloid beta, out with it (Iliff et al., 2012). It depends on the fluid actually moving through and out, primarily through the jugular vein at the front of the upper neck. If drainage is restricted, waste that should be carried away instead accumulates.
The more time passes with poor drainage, the greater the accumulation, and the faster degenerative change proceeds. That drainage route, and what narrows it, is worth understanding on its own — [brain fog is often the first way people notice it](post-brain-fog-may-be-a-drainage-problem.html).
So a disrupted craniocervical junction can contribute along two paths at once: turbulent flow producing repeated mechanical irritation, and restricted drainage allowing waste to build up. Neither one announces itself. Both operate quietly over years.
Why Take This Seriously Early?
The first symptoms are mild enough to dismiss. [Brain fog](condition-brain-fog.html). [Pressure in the head](condition-pressure-in-the-head.html). Difficulty holding concentration. A headache that pounds with the pulse.
Those get attributed to stress, poor sleep, or aging, and none of those explanations are unreasonable on their face. But they're also the earliest signs of a process that has a much more serious endpoint if nothing changes.
The alternative to waiting is to work backwards. Rather than waiting until degeneration is severe enough to appear on imaging or produce a formal diagnosis, you can ask why the brain's environment is degraded in the first place — and examine the structures that determine whether fluid flows smoothly and drains completely.
The structural version of this problem is addressable. Restoring alignment at the craniocervical junction restores the shape of the pathway, which reduces turbulence and reopens drainage. It doesn't undo damage already done. It removes the thing that was driving it.
Waiting does not preserve any options. It only lets the process continue.
Have Head Pressure, Fog, or Pulsing Symptoms Gone Unexplained?
If you have pressure in the head, brain fog, or a whooshing that keeps time with your heartbeat, the shape and drainage of your fluid pathway is worth examining — particularly if it started after a [whiplash or head injury](condition-concussion-and-mtbi.html).
Assessing that pathway directly is the work we do at Cerebral. If you'd like a real evaluation, we're here.
References
- Xu Q, Yu SB, Zheng N, et al. Head movement, an important contributor to human cerebrospinal fluid circulation. *Scientific Reports*. 2016;6:31787. https://www.nature.com/articles/srep31787
- Hack GD, Koritzer RT, Robinson WL, et al. Anatomic relation between the rectus capitis posterior minor muscle and the dura mater. *Spine*. 1995;20(23):2484–2486. https://pubmed.ncbi.nlm.nih.gov/8610241/
- Iliff JJ, Wang M, Liao Y, et al. A paravascular pathway facilitates CSF flow through the brain parenchyma and the clearance of interstitial solutes, including amyloid β. *Science Translational Medicine*. 2012;4(147):147ra111. https://pubmed.ncbi.nlm.nih.gov/22896675/
- Rasmussen MK, Mestre H, Nedergaard M. The glymphatic pathway in neurological disorders. *The Lancet Neurology*. 2018;17(11):1016–1024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6261373/
- Nedergaard M, Goldman SA. Glymphatic failure as a final common pathway to dementia. *Science*. 2020;370(6512):50–56. https://pubmed.ncbi.nlm.nih.gov/33004510/