Blood biomarkers reveal impact of tumor-removal surgery on brain cells

Surgery to remove brain tumors comes with risks, one being that it may cause damage to the surrounding brain tissues. Researchers have found that biomarkers found in the blood are a useful new tool for tracking damage on a cellular level, providing more detailed information than currently used techniques.

Although it’s an extraordinary organ, the human brain is extremely fragile, with a consistency not unlike that of Jell-O. Given the brain’s fragility, surgery to remove a brain tumor can sometimes result in residual damage to tissues and lead to the development of neurological deficits.

Ordinarily, damage to the brain tissue is assessed by way of postoperative magnetic resonance imaging (MRI). While, in this circumstance, MRI can identify bleeding in the brain or areas that have reduced or inadequate blood flow (ischemia), it may not be able to tell doctors what’s going on at a cellular level.

Researchers from the University of Gothenburg in Sweden have now developed a blood test that can check for biomarkers that indicate the presence of damage in a way that MRI can’t.

“MRI scans can’t always provide sufficiently detailed information about the degree of cell injury,” said Isak Michaëlsson, the lead author of the study. “In the long run, the new biomarkers could bridge this knowledge gap and offer more accurate and objective assessments of impairment due to brain tumor surgery.”

The researchers looked at biomarkers that are well-known to researchers studying neurodegenerative diseases like Alzheimer’s disease and other dementias and in patients with traumatic brain injuries. The markers they measured are neurofilament light (NfL), glial fibrillary acidic protein (GFAP) and tau protein.

NfL is a marker for damage to nerve cell (axonal) fibers and has been identified as a biomarker of multiple sclerosis. GFAP indicates injury to the glial cells, the brain’s support cells, and tau shows impairment of nerve cells (neurons). Modified tau proteins clump together to form the tangles that are a hallmark of dementia.

The researchers recruited 34 adult patients scheduled to have surgery to remove a glioma, a type of malignant tumor that originates from glial cells and primarily occurs in the brain. NfL, GFAP and tau biomarkers were measured the day before surgery, immediately afterwards, and on postoperative days one, three, five, and 10.

They found that there were increased levels of all three biomarkers postoperatively on day one and that NfL continued to rise, peaking at day 10. There was a correlation between the increased levels of GFAP, tau and NFL on day one and the amount of ischemic brain tissue seen in postop MRI scans. The researchers found that patients with new neurological deficits (those not caused by the tumor) after surgery had higher GFAP and NfL levels than those without new deficits.

The researchers say that their study’s findings show that using biomarkers may be a novel way of evaluating the injury caused by brain surgery. And, they say, it might be a way of identifying patients who need rehabilitation to treat the neurological deficits that have arisen after surgery.

“It’s also conceivable that high levels of these markers might be signs of damage that could cause brain fatigue or other cognitive problems for the patients in the somewhat longer term,” said Michaëlsson. “If so, the markers could be used to identify patients at an early stage so that they get the right kind of rehabilitation.”

The study was published in the journal Neurosurgery.

Source: University of Gothenburg

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