New study shows Cerebrospinal fluid flow is more important than previously thought

As Chiropractors, we are intimately acquainted with the importance of Cerebrospinal fluid and its dynamics. From infancy, as we care for little nervous systems, we work on spinal tension so that this liquid gold can circulate the brain and spinal cord of the infant under care. As these infants grow into adulthood, it remains vital. Chiropractors who use the Sacro-Occipital technique particularly focus on the sacrum at the base of the spine, and occiput at the top of the spine, ensuring that CSF flow can continue to bathe the brain and spinal cord in this cushioning substance that also carries nutrients to the central nervous system.

So, we know it’s essential. The brain and spinal cord are obviously vital to the goings on inside the two major components that run the whole body. But a recent study shows that it’s the peripheral nerves, too, that benefit from CSF. But before we get to that – here’s the background.

Cerebrospinal fluid (CSF) is primarily produced by the choroid plexus and is made by tissue lining the brain’s ventricles (hollow spaces). It provides physical cushioning while delivering nutrients and removing waste for the central nervous system (CNS) tissues. [1-10] CSF flows continuously, and humans produce approximately 0.5L per day. Cerebrospinal fluid flow is essential for maintaining nervous tissue homeostasis.

Nerves also have layers similar to those around the brain and spinal cord, with a fluid-filled space that may be connected to the CSF system. While some studies have suggested that CSF might flow into the peripheral nervous system (PNS), it’s still mostly believed to be confined to the brain and spinal cord. [2, 10, 11-15] This  new study demonstrates that CSF can also flow from the central nervous system (CNS) into peripheral nerves, suggesting a more interconnected nervous system than previously understood. The findings suggest that CSF may play a role in maintaining the health of peripheral nerves, leading to new treatments for nervous system disorders.

The Study

The study, recently published by ScienceAdvances, traced CSF flow from the central nervous system (CNS) to peripheral nerves in mice. Gold nanoparticles were infused into the brain and were found in distal nerves (those far from the centre of the body). The distribution of nanogold was influenced by size, time, and concentration. CNS structures were labelled quickly, while delivery to distal sciatic nerves peaked between 4 and 6 hours. Electron microscopy confirmed nanogold movement from the brain to the axoplasm of distal peripheral nerves. Knowing that mice studies are one of the most commonly used scientific methods to map how human bodies might behave, these findings support a continuous CSF flow system from the CNS to the distal ends of peripheral nerves, likely crucial for nerve function.

The Findings

Interest in the CSF system has grown with a series of discoveries in recent years, with research revealing previously unknown roles for CSF in the health and homeostasis of CNS tissues. [5, 6, 16, 17-19]. This particular study had a number of potentially significant findings for basic science and chiropractic alike:

• Ventricular infusion of gold nanoparticles demonstrates CSF flow to peripheral nerves – The researchers injected gold nanoparticles into the CSF of mice to track its movement and determine if it could flow into peripheral nerves. The nanoparticles were small enough to pass through the blood-brain barrier and enter the nerves. Researchers discovered that CSF can flow into peripheral nerves.
• Differential probe deposition patterns reveal size dependence of CSF solute transport – The size of nanoparticles affects their movement in the CSF and their ability to enter peripheral nerves. Researchers found that smaller nanoparticles (1.9-nm) can enter peripheral nerves, while larger nanoparticles (15-nm) are mostly restricted to the CNS. 
• Nanogold infused into the CSF transits the length of peripheral nerves – The study found that the concentration of gold nanoparticles injected into the CSF affects their distribution in peripheral nerves. Higher concentrations of nanoparticles were found to travel further along the length of the nerves. This suggests that the flow of CSF into peripheral nerves may be influenced by the concentration of substances within the CSF. This literally means that CSF may effect everything from the brain to the fingertips.
• CSF flow from CNS to peripheral nerves is contiguous and continuous – The flow of the CSF into peripheral nerves is slow and takes time. It was discovered that the distance from the injection site affects the time it takes for the CSF to reach the nerves.
• Nanogold transits from CNS to PNS at the RAZ – CSF can flow into PNS at the subarachnoid angle or the RAZ. This was shown by the presence of gold nanoparticles in the peripheral nerves after they were injected into the CSF. The researchers also found that the nanoparticles accumulated in the endoneurium, a layer of connective tissue surrounding the axons of peripheral nerves.
• Nanogold efflux from the CNS post-ICV infusion follows established patterns for CSF outflow – Gold nanoparticles injected into the CSF are cleared from the nervous system, the same as other substances. The nanoparticles were observed in the cervical lymph nodes, spleen, kidneys, and bladder, following the typical pathway for CSF elimination. However, it took longer for the nanoparticles to be cleared from the nervous system after they were injected into the CSF, compared to when they were injected intravenously. This suggests that the flow of CSF may be slower than the flow of blood.
• Electron microscopy demonstrates CSF-infused nanogold delivery to peripheral nerve layers including delivery to axoplasm of peripheral nerves – The study used electron microscopy to examine the distribution of gold nanoparticles in peripheral nerves. They found that nanoparticles were present in various parts of the nerves, including the axoplasm, perineurium, and endoneurium. Nanoparticles were also found in association with different cell types, such as Schwann cells, fibroblasts, and macrophages. These findings suggest that CSF can flow through peripheral nerves and interact with different cell types.

The study found that CSF can flow from the CNS into peripheral nerves. This suggests that the nervous system is more interconnected than previously thought. While the study’s discussion geared towards potential implications on pharmaceutical delivery, the study is still significant for chiropractic. We now know that supporting the flow of CSF around the brain and spinal cord may also affect the organs and other nerves outside what we know as the central nervous system.

The interconnectedness of the whole body is very much central to the chiropractic philosophy. Nothing is disconnected. The body is a self-regulating, self-healing system that does wonderful things when we remove subluxation and let the brain and body communicate well together. We now have a better idea of how CSF fits into that picture.

References

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