Speculation on Brain Injury of Rep. Gabrielle Giffords
If reports are true—namely that the bullet that hit Arizona Congresswoman Gabrielle Giffords entered her left forehead, missed her ventricles and language areas, and exited her left occiptal or parietal area*—then the bullet path (confined to the left hemisphere) seems subcortical (ie, below the surface of the brain) and fairly superior (ie, high or close to the top of the head).
Guessing her consequent deficits is probably a fool's task, even for a neurologist, but damage to the visual cortex may have been averted if the bullet exit wound was superior enough. Otherwise, transection of subcortical motor and sensory tracts and injury to the some portion of the frontal cortex by the bullet seem likely. Nevertheless, early reports indicate that Giffords (before a chemical coma was induced) had preserved motor function, along with basic comprehension of simple commands.
Injury-associated brain edema (swelling), which can lead to midline shift and deadly brain herniation, is being addressed (as expected) surgically with removal of a large portion of Giffords's skull and by ventilatory settings and drugs, say news reports.
According to a 2009 review by Maiden on gunshot wounds, the extent of brain damage is dependent on the bullet type, shape, construction, velocity, and mass and the nature of the injured tissue. He also writes, "[B]ullets which display greater yaw [side-to-side movement] will be associated with increased temporary cavitation [of tissue]." Cavitation of the brain could place strain and traction on adjacent tissue; although early brain swelling may make this issue an academic point, I would argue. A ballistics tutorial, including a discussion of yaw and what it means to tissue injury, is provided through the website of the University of Utah Health Sciences Library.
Reports indicate that Giffords was shot in the head with a 9-mm handgun at a range of about 4 feet. The 22-year-old alleged (and apparently seriously troubled) perp shot 19 other people, 6 of whom have died so far.
* It's not entirely clear from news reports whether the bullet entered Giffords's forehead or the back of her head.
From http://www.nlm.nih.gov/visibleproofs/education/medical/index.html: Postmortem image of coronal brain section showing path of a fatal bullet that entered the right temporal area and lodged in left frontal lobe.
Update: According to the LA Times, the bullet entered the back of Giffords's head.
01/12/11 update: Although Dr. G. Michael Lemole, Jr, Giffords's treating neurosurgeon, reports that the congresswoman is scratching her nose—a excellent clinical sign—he does not say (importantly) which hand she used.
However, according to an MSNBC report, Giffords is moving both of her arms and that she "previously raised two fingers with her left hand and gave a thumbs-up when responding to doctors' verbal commands [emphasis added]." (With a left hemispheric injury, paralysis or paresis of the right arm and/or leg would be expected.) In addition, Dr. Peter Rhee, trauma chief at the University of Arizona, indicated (in a sort of groan-inducing fashion) that Giffords has a "101 percent chance of surviving."
In short, Giffords is extremely lucky in her extreme unluckiness.