U.S. Rep. Gabrielle Giffords (D-AZ), who sustained a gunshot to the head during a Congress on Your Corner event in Tucson that killed six people, including federal judge John Roll, and injured 14 others, on Saturday, is still in critical condition but is expected to recover.

Giffords, a 40-year-old Democrat in her third term in the House of Representatives, was airlifted to a hospital in Tucson after being shot in the head at point-blank range by Jared Lee Loughner, a deranged constituent, at a Safeway supermarket in the Arizona city.

Though the chances of survival of people who get shot in the brain are pretty low, medical experts feel Giffords, who is currently on a ventilator, could survive the shooting.

CBS News Medical Correspondent Dr. Jennifer Ashton said the decompressive craniotomy surgery on Giffords that was carried out on Saturday was extremely critical to her survival. The surgery involves shaving the hair, flapping back the scalp and then drilling a large portion of the cranium skull bone.

That portion (of the skull bone) 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, Ashton said.

Ashton said the bullet path also miraculously left the central part of the brain, where critical structures including some major blood vessels are located, unharmed as it went through the rear left portion of the brain, and exited through the front left portion of the brain.

The bullet did not cross from the left to the right side of the brain - also very important, Ashton said.

According to practicing trauma neurosurgeon Dr. Sanjay Gupta, it was also important that the bullet injury was a through and through injury i.e. there was both an entry and exit wound. This helped the energy of the bullet to dissipate into space as opposed to remaining within her cranial cavity.

Most importantly, the fact that Giffords could receive very quick medical attention (she was in the operating room within 38 minutes after arriving at the hospital) and that she was healthy and young are also working in the favor of her survival.

Nonetheless, doctors are worried whether the bullet injury will impair her power of speech and recognition of speech, which is controlled by the left side of the brain. But Dr. Michael Lemole Jr, MD, who performed surgery on Giffords, said the medical team is cautiously optimistic about her recovery as even before the surgery was performed on Giffords, she could respond correctly to a simple command of Show me two fingers.

Arizona House of Representatives Medicine Arizona