Cerebrospinal fluid flow extends to peripheral nerves further unifying the nervous system, 2024, Alexander P. Ligocki et al

Abstract
Cerebrospinal fluid (CSF) is responsible for maintaining brain homeostasis through nutrient delivery and waste removal for the central nervous system (CNS).

Here, we demonstrate extensive CSF flow throughout the peripheral nervous system (PNS) by tracing distribution of multimodal 1.9-nanometer gold nanoparticles, roughly the size of CSF circulating proteins, infused within the lateral cerebral ventricle (a primary site of CSF production). CSF-infused 1.9-nanometer gold transitions from CNS to PNS at root attachment/transition zones and distributes through the perineurium and endoneurium, with ultimate delivery to axoplasm of distal peripheral nerves.

Larger 15-nanometer gold fails to transit from CNS to PNS and instead forms “dye-cuffs,” as predicted by current dogma of CSF restriction within CNS, identifying size limitations in central to peripheral flow. Intravenous 1.9-nanometer gold is unable to cross the blood-brain/nerve barrier.

Our findings suggest that CSF plays a consistent role in maintaining homeostasis throughout the nervous system with implications for CNS and PNS therapy and neural drug delivery.
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Yet another new finding that counters long-held beliefs (that CSF stays in the brain). Doctors are supposed to learn continuously, but it's also important for them to unlearn false facts.

 

Except that it is complete garbage.
The first sentence is entirely incorrect. CSF does not supply the CNS with nutrients or remove waste. Blood vessels do that.

The passage of 1.9 nanometer gold into peripheral nerve axoplasm tells us nothing about nutrition or waste removal in nerves (nothing to do with macromolecular transit). If you put particles in CSF it is not surprising that some get into axoplasm and pass distally but it says nothing whatever about normal physiology.

 

Testing done on mice.