I had high hopes for this possibility.
http://www.urmc.rochester.edu/news/story/index.cfm?id=4235
Complications involving the brain’s unique waste removal system – the
existence of which has only recently been brought to light – may thwart
efforts to identify biomarkers that detect traumatic brain injury
(TBI). That is because proteins that are triggered by brain damage are
prevented from reaching the blood system in levels necessary for a
precise diagnosis.
Tens of millions of dollars have been invested by the U.S. government
and the private sector in recent years in an effort to develop a simple
blood test that can help physicians quickly and accurately gauge the
extent of neurological damage after a blow to the head. However, a new
study conducted in mice and published today in the Journal of Neuroscience appears to indicate that these efforts may face significant hurdles.
“These findings show that a blood-based biomarker for TBI is unlikely
to be effective for routine clinical use,” said Maiken Nedergaard,
M.D., D.M.Sc., co-director of the University of Rochester Medical Center
(URMC) Center for Translational Neuromedicine
and lead author of the study. “Both the injury itself and the clinical
approach to TBI can impair the ability of the brain to remove waste,
resulting in variable and – for the purpose of detection and diagnosis –
unreliable protein levels in the blood.”
More than 1.5 million Americans, both children and adults, suffer
concussions every year. Furthermore, it is estimated that more than
300,000 U.S. military personal have been victims of TBI since 2000.
Readily visible symptoms – such as headache, nausea, dizziness, and
sleep problems – don’t reflect the extent of the injury. Consequently,
there is an urgent and compelling public health need to develop a method
that can determine the severity of TBI and help predict which of these
individuals may be at risk for long-term cognitive problems.
It is only within the last few years that researchers have begun to
understand how the brain deals with waste. In 2012, scientists at the
University of Rochester revealed that the brain possesses its own unique waste removal system, which has been dubbed the glymphatic system.
The glymphatic system consists of a plumbing network that piggybacks
on the brain’s blood vessels and pumps cerebral spinal fluid through
brain tissue to flush away waste. The waste flows out of the brain, into
the lymph nodes, and eventually makes its way to the general blood
circulation system and, ultimately, the liver.
It is known that during the shock of brain injury, certain proteins
are shaken free from the brain’s cells. This has led to the speculation
that by measuring the levels of these proteins after they have made
their way into the blood system, physicians may be able to ascertain the
existence and severity of injury.
The Rochester team of researchers performed a series of experiments
on mice with TBI and tested the animal’s blood for three proteins (S100
beta, glial fibrillary acidic protein, and neuron specific enolase) that
are considered strong candidates for a blood-based biomarker for TBI.
It turns out that the glymphatic system is very delicate and small
alterations can disrupt function, impairing the ability to remove waste
products, such as the proteins associated with TBI, from the brain. An
earlier study showed that the blows to the head themselves can disrupt the function of the glymphatic system.
The current study shows that treatments for these conditions may also
impair the brain’s ability to remove waste. Just like a water pump, the
glymphatic system requires pressure to function properly. Efforts to
relieve the stress on the brain from swelling after an injury by using
drugs like acetazolamide or employing a surgical procedure that drains
CSF can “depressurize” the system and impair clearance of waste.
Furthermore, people under observation in hospitals for TBI are often
subjected to frequent neurological evaluation by physicians, disrupting
their sleep. In other instances, patients are given sedatives to induce
sleep after TBI. Because the glymphatic system primarily functions while we sleep, these variations in clinical care can skew protein levels found in the blood.
During experiments that replicated these conditions in mice with TBI,
the researchers were not able to detect reliable changes in protein
levels in the blood.
“This study shows that even small changes can modulate the brain’s
ability to clear waste,” said Benjamin Plog, an M.D./Ph.D. student in
Nedergaard’s lab and a co-author of the study. “Consequently, we need to
recalibrate our efforts and begin to think about measuring brain damage
in a manner that takes into account the level of impairment to the
glymphatic system. “
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