New clue to brain bleeding after stroke treatment

October 17, 2011

The only medication currently approved for stroke treatment – tissue plasminogen activator (tPA), which dissolves blood clots – is associated with an increased risk of bleeding in the brain, particularly among patients with hyperglycemia (high blood sugar). A study led by Raymond A. Swanson, MD, chief of the neurology and rehabilitation service at the San Francisco VA Medical Center, provides a possible reason: high blood sugar fuels the formation of superoxide, a toxic form of oxygen, which in turn damages tissues, weakens blood vessels and promotes excess bleeding.

The study, which used an animal model of stroke, was published on October 14 in the online Early View section of Annals of Neurology.

“A stroke is usually caused by a blood clot lodging in a brain artery and cutting off ,” said Swanson, who is also professor and vice chair of neurology at the University of California, San Francisco (UCSF). “If you can administer tPA in time and dissolve the clot, then blood flow is restored.” However, he said, “there’s a risk that when the clot is dissolved and blood suddenly flows back into the affected area of the brain, there will be bleeding. And that is a huge problem, because the bleeding can cause more damage, or even death.”

The risk of bleeding after tPA treatment increases in patients with hyperglycemia, Swanson said, “but whether this increase is actually caused by the hyperglycemia has been difficult to ascertain.”

To investigate the question, Swanson and his research team mimicked strokes in two groups of rats by temporarily stopping blood flow to a section of their brains. They then gave the rats tPA as blood flow was restored. One group of rats was hyperglycemic. That group had bleeding in the brain at three to five times the rate of the non-hyperglycemic rats, at rates directly proportional to blood sugar level.

“I think this supports the idea that hyperglycemia contributes to bleeding in the brains of stroke patients who have been given tPA,” Swanson said.

Swanson suspected that the bleeding was caused by superoxide, the production of which is fueled by . To test that hypothesis, the scientists blocked superoxide production in a subset of the hyperglycemic rats. Those rats did not show excess or damage.

Based on their findings, the authors suggest that clinical guidelines for tPA be reconsidered. “We should ask whether stroke patients who are hyperglycemic should be excluded from tPA treatment,” said Swanson.

The authors also suggest that treatment targeting the production of superoxide could potentially negate the harmful effects of hyperglycemia in .

Related Stories

Recommended for you

New insights on how cocaine changes the brain

November 25, 2015

The burst of energy and hyperactivity that comes with a cocaine high is a rather accurate reflection of what's going on in the brain of its users, finds a study published November 25 in Cell Reports. Through experiments conducted ...

Can physical exercise enhance long-term memory?

November 25, 2015

Exercise can enhance the development of new brain cells in the adult brain, a process called adult neurogenesis. These newborn brain cells play an important role in learning and memory. A new study has determined that mice ...

Umbilical cells help eye's neurons connect

November 24, 2015

Cells isolated from human umbilical cord tissue have been shown to produce molecules that help retinal neurons from the eyes of rats grow, connect and survive, according to Duke University researchers working with Janssen ...

Brain connections predict how well you can pay attention

November 24, 2015

During a 1959 television appearance, Jack Kerouac was asked how long it took him to write his novel On The Road. His response – three weeks – amazed the interviewer and ignited an enduring myth that the book was composed ...

No cable spaghetti in the brain

November 24, 2015

Our brain is a mysterious machine. Billions of nerve cells are connected such that they store information as efficiently as books are stored in a well-organized library. To this date, many details remain unclear, for instance ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.