Our understanding of the human brain is experiencing a watershed moment.
The sewerage gates are open.
In 2024, scientists discovered the first direct evidence of an internal 'waste disposal system' hidden deep within the human brain and spinal cord.
Now, just a few years later, researchers in Australia think this system could be driving the symptoms of a debilitating health condition affecting millions worldwide.
Their preliminary research is published in Frontiers in Neuroscience.
Chronic fatigue syndrome, sometimes known as myalgic encephalomyelitis (ME/CFS), has been neglected by the medical system for decades, and still has no known cause or cure.
Historically, health experts assumed that when patients complained of extreme fatigue, 'brain fog', or persistent flu-like symptoms, it was all in their minds, as no other explanation could be found.
In recent years, however, scientists have found 'unambiguous' biological markers of ME/CFS in the genes, spinal fluid, blood, and gut microbiome of patients.
What's more, many of these clues are linked to the immune system or inflammation, indicating systemic health issues.
Researchers at Griffith University in Australia now suspect that a broken brain sewage system may be at the very root of the problem.
"This study is the first to demonstrate impaired glymphatic function in ME/CFS using MRI, providing a mechanistic explanation for the inflammatory changes reported by other Australian and international teams," says neuroimmunologist Kiran Thapaliya.
"This suggests that dysfunction in the brain's natural cleaning system may be a key driver of this condition."
The research is small and preliminary, but the hypothesis is logically sound.
The glymphatic system is a new frontier in human physiology, and neuroscientists are only just beginning to sift through its muck and mire.
Today, most of our knowledge of this system is based on research in mice, but it appears that the brain's recycling efforts are most active during sleep.
This seems to be when toxic products or dead cells are flushed out of the mammalian brain, riding on 'waves' of cerebrospinal fluid. These pulses of liquid appear to be pumped by some obscure plumbing network that is still coming to light.
"Dysfunction in the brain's natural cleaning system may be a key driver of this condition." – neuroimmunologist Kiran Thapaliya
In humans, researchers are starting to associate issues of the glymphatic system with cognitive decline, memory issues, musculoskeletal problems, and psychosis.
This is the first study to investigate a link with ME/CFS.
In preliminary investigations, Thapaliya and colleagues scanned the brains of 31 participants with ME/CFS and compared them with those of 27 healthy controls.
Directly imaging the glymphatic system is no simple feat, which is why the waste disposal network has eluded us for so long.
Typically, a 'tracer' needs to be injected into a person's cerebrospinal fluid (CSF) in an invasive procedure, so that it can be imaged as it flows through the system's secret passageways.
But researchers at Griffith took a different route.
They used a non-invasive technique that instead merely estimates glymphatic function. It does so by measuring the diffusion rate of CSF into tiny channels surrounding small blood vessels in the brain.
This is less direct and precise, but it can be used non-invasively to assess MRI scans. Already, this technique has hinted at changes to glymphatic flow in patients with Parkinson's disease, Alzheimer's, blood pressure issues, and multiple sclerosis.
Researchers in Australia have now found that the brain scans of CFS/ME patients also show signs of reduced glymphatic function.
What's more, this dysfunction is observed only in the brain's right hemisphere, not the left.
"This kind of hemispheric asymmetry," the study authors note, "… has been previously reported in patients with temporal lobe epilepsy, Parkinson's disease, and in amyotrophic lateral sclerosis (ALS)."
Interestingly, the worse a CFS/ME patient's sleep issues or impaired concentration (aka 'brain fog'), the greater the signs of glymphatic dysfunction in their right hemisphere.
Sonya Marshall-Gradisnik, director of the National Center for Neuroimmunology and Emerging Diseases at Griffith, explains that these brain scans reinforce "the notion that sleep plays a critical role in maintaining brain health."
"We hope the results can pave the way for better diagnosis through the use of non-invasive procedures, and importantly, future treatment for patients," she adds.
Unfortunately, the study's findings cannot reveal why glymphatic dysfunction may be occurring only in the right hemisphere, or how that might be driving CFS/ME symptoms.
But if the brain's waste clearance system is not efficiently removing toxic products, it may potentially exacerbate inflammation in the central nervous system, leading to neurological symptoms.
This is roughly the same argument for why the glymphatic system may be disrupted in those with Alzheimer's or Parkinson's disease.
Far more research is needed to understand the glymphatic system in human brains, and how its disruption may lead to different diseases.
Related: Scientists Mapped The Human Brain's Sewage System For The First Time
With its discovery, however, the field of neuroscience may never be the same.
The brain's trash is turning out to be a neurological treasure.
The study is published in Frontiers in Neuroscience.
This article was fact-checked by Michael Irving and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.