Rep. Gabrielle Giffords remained in critical condition on Tuesday afternoon after sustaining a gunshot wound to the head on Saturday, but the head of the trauma center that’s treating her told the press, “She has 101 percent chance of survival.”

Details about the congresswoman’s recovery remain sparse and speculative, however. Giffords was meeting with constituents outside a grocery store in Tucson, Arizona on Saturday, when twenty-two-year-old Jared Loughner, who is now in custody, went on a rampage, shooting nineteen and killing six. Giffords was shot at near point-blank range, with the bullet entering the back-left side of her head and exiting just above her left eye.

[Update, 1/20: According to a January 11 report from The Associated Press: “Doctors now think that Rep. Gabrielle Giffords may have been shot in the front of the head, not the back. After she was wounded last weekend, doctors said the bullet traveled the length of the left side of the congresswoman’s brain, entering the back of the skull and exiting the front. At a briefing today, Dr. Peter Rhee said it now looks like she was probably shot in the front, with the bullet going out the back, although they can’t say for certain. He said that’s based on consultations with two specialists who came to Tucson, Ariz.”

In addition, a security-camera video, described by The New York Times on Wednesday, shows the gunman shooting Giffords just above the eyebrow at a range of about three feet.]

A number of science journalists have since attempted to explain how Giffords was able to survive the blow, and what doctors are doing to bring about her recovery. Physician correspondents such as CNN’s Sanjay Gupta, CBS’s Jennifer Ashton, and NBC’s Nancy Snyderman all used plastic models of brains to demonstrate how the bullet travelled through the left hemisphere of Giffords’ brain without crossing through the middle to the other side, which would have caused much greater injury (ABC’s Richard Besser did so without props). It is also fortunate, they added, that the bullet exited Giffords’s head rather than remaining inside.

According to an informative post by Scientific American’s Mike Orcutt:

The most important predictors for how well a victim will recover from a gunshot wound to the head are the type of bullet and its travel path once inside the brain, and Giffords was fortunate on both counts, says Dr. Keith L. Black, chairman and professor of neurosurgery at Cedars-Sinai Medical Center in Los Angeles. The bullet, reportedly fired from a 9 mm semi-automatic handgun, entered the left side of the back of her head and traveled through her brain, exiting through her forehead. This “through and through” course indicates that the bullet was probably not of the variety designed to expand or break into smaller fragments once inside the body, which would have caused a much more severe injury. Further, the Congresswoman would have sustained much more damage had the bullet ricocheted off the inside of her skull, or if it had remained lodged in the brain matter where it could “migrate around” and cause additional harm, says Black.

As the projectile moved forward, it remained in the left hemisphere, avoiding crossing through the middle to the other side, which, according to Black, could have caused catastrophic injury. The bullet’s trajectory was also high enough to apparently avoid certain crucial structures on the left side of the brain, including areas responsible for language processing—a notion reinforced by reports that the Congresswoman has been responsive to commands.

Another post at Scientific American went into even greater detail on why, “as past cases demonstrate, a shift of inches or a varied assault type can change everything for an individual patient, determining whether key brain regions are shattered or spared.” (The outlet has been vigorously reporting on the shooting, creating a page full of news and archived articles titled “How Can Science Help Make Sense of the Tucson Massacre?” which includes, among other items, an interesting post about what psychologists have to say about the connection between violent political rhetoric and acts of violence.) About 90 percent of people shot in the head do not survive, according to a detailed article by WebMD, a site that publishes health news and information, which interviewed five prominent experts in dealing with brain injuries.

Giffords also benefited from rapid treatment, entering into surgery at Tucson University Medical Center’s Level 1 trauma center (the highest of five classes) approximately thirty-eight minutes after being shot. According to Scientific American’s post:

Once in surgery, neurosurgeons removed bone fragments, worked to stop the bleeding, and then performed an operation called a decompressive hemicraniectomy. The procedure, which has become popular in the past decade or so, especially in the context of battlefield brain injuries, entails the removal of a portion of the skull to allow the brain to swell. Brain swelling creates increased pressure inside the cranium, and if part of the bone is not removed the pressure disrupts a vital differential between blood pressure and the pressure in the brain. When it comes to swelling, explains Black, “minutes count,” and that the pressure in her brain was relieved so quickly was essential to her relatively positive prognosis.

“Since surgery, [doctors] have used short-acting drugs to put Ms. Giffords in a medical coma that they lift periodically to check on her neurological responses,” The New York Times’s Lawrence Altman, a licensed physician, reported Monday. Scientific American followed up with a Q&A with Emery Brown, an anesthesiologist at Harvard Medical School, which explained that, “Shutting down function can give the brain time to heal without the body performing radical triage by shutting off blood flow to damaged section.”

Time and the Orlando Sentinel also used the Q&A approach, talking to neurosurgeons in their respective areas. And the Boston Globe’s health blog weighed in with a post that provided additional details about the benefits and risks of both craniectomies and medically induced comas.

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