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How Giffords Survived Being Shot in the Brain

Doctors say more than 90 percent of gunshot wounds to the brain prove fatal, and more than two-thirds of victims die before receiving hospital care.

But Rep. Gabrielle Giffords survived an assassination attempt Saturday in which she was shot in the brain.

How has she seemingly beaten the odds?

CBS News Medical Correspondent Dr. Jennifer Ashton says the surgery on Giffords on Saturday was "critical to her survival. It's called a decompressive craniectomy. … The hair gets shaved. The scalp gets flapped backwards, and a large portion of the cranium skull bone is drilled away. (That area of the skull left open, with the brain covered by a synthetic material and then scalp, so that the brain can swell and not have any vital blood supply or tissue compromised) That portion remains in a refrigerator for up to, potentially, two-to-three months, and (that area of the brain) is left open so the brain can swell and not impair other parts of the brain."

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Controlling the swelling's impact is also critical, Ashton told "Early Show" co-anchor Erica Hill Monday.

The bullet's path once it entered Giffords' brain was also key, Ashton pointed out, noting, "The bullet went through the rear left portion of the brain, and exited through the front left portion of the brain. … Critical structures, which tend to be located deeper and more centrally in the brain, were miraculously spared, as were some major blood vessels that also are in the midline, and the bullet did not cross from the left to the right side of the brain - also very important."

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The left side of the brain, Ashton says, is, basically, "the speech center. We know the left side of the brain controls the right side of the body, so interpreting speech and being able to speak all potentially could be affected by any type of injury to the left side of the brain. That's why it's so encouraging to the doctors that, when she's asked to perform a simple command, like, 'Show me two fingers,' she's able to show two fingers. It will be important to know whether she's raising those fingers on the right side of her body or the left side."