Transcript of interview with Dr. David Clarke

Pauline Dakin, national health reporter for CBC News, chats with Dr. David Clarke, neurosurgeon with the Halifax Brain Repair Centre, about the brain surgery of U.S. congresswoman Gabrielle Giffords who was shot through the head at a shopping mall in Tucson, Ariz., on Jan. 8.

Dakin: I think people are wondering how can a bullet go through the brain without actually killing someone?

Dr. Clarke: Often times with a bullet injury to the brain it is fatal. Some of the things that would predict that someone's not going to survive such an injury would be the type of weapon used, and obviously a high-velocity bullet would cause more damage to the brain; and also location, where the bullet enters, the trajectory of the bullet and the damage that it causes along the way.

Dakin:Lets break that down, did this bullet come out cleanly?

Dr. Clarke: I dont know the details of this particular case (referring to Gabrielle Giffords).In some ways the fact, if in fact it did go in and then go out of the skull, that can be viewed as both a positive and a negative thing. It can be viewed as positive in the sense the bullet did not ricochet within the skull and that can sometimes be a source of tremendous damage. It also suggests the bullet was of significant velocity to go through the skull in two locations. So in that sense it obviously was a high velocity impact.

Survival stories

James "the Bear" Brady had served just three months as press secretary to U.S. President Ronald Reagan when he suffered a shot to the head on March 30, 1981. Deranged gunman John Hinckley Jr. fired six shots at the president and his entourage outside the Washington Hotel, wounding Reagan, Brady, a police officer and a secret service agent.

Doctors removed large sections of Brady's right frontal lobe and smaller sections of the left frontal lobe. With intensive physical therapy, Brady's recovery was deemed remarkable. He remains paralyzed on the left side of his body.

"I'm the 50 per cent man," Brady told CBS News in 2006, 25 years after the shooting.

Along with his wife Sarah, Brady became a crusader for stricter gun control. In 1993, the Brady Bill, which requires a five-day waiting period and background checks for handgun purchases, was signed into law. However, a 1997 Supreme Court decision deemed the associated checks unconstitutional.

Brady in 1996 received the Presidential Medal of Freedom and in 2000 the White House Press Briefing Room was renamed in his honour.

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Mary Jo Buttafuoco in 1992 was shot in the face by her husband's mistress, a 16-year-old teen named Amy Fisher.

Buttafuoco was left paralyzed on the right side of her face. She would also later complain of headaches, hearing loss and double vision. In a 2009 memoir, Buttafuoco also described an addiction to painkillers and her difficult recovery.

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Musician Marc Cohn in 2005 suffered a gun shot to his right temple during a carjacking in Denver.

The bullet did not penetrate his skull and he was released after being held in hospital for one day. Denver police said the bullet was slowed by the van's windshield.

We know that when bullets enter the skull a bullet can cause damage by a number of mechanisms. One, the bullet can tear up, if you like in a simplistic way, brain tissue and drag fragments of other tissue such as bone along the way as it travels through the brain. Secondly as we mentioned, the bullet can ricochet in the skull and therefore it can exaggerate the damage that would otherwise occur along a straight path.And thirdly and very significantly, as the bullet enters the skull it causes a high energy, high-pressure wave throughout the brain and that's why we can often see in many gunshot wounds to the head, injury at quite a distance from the actual route of the bullet.

Dakin: This bullet, for example, which went through the left to the back to the front and exited over the eyebrow, what do we know about this part of the brain?

Dr. Clarke: If we work backwards to forwards in terms of the trajectory of the bullet, in the back of the brain is the area that's responsible for processing vision, vision that comes from the right side as you look out. Moving forward, we also know that sensory information from the right side of the body is processed in the left hemisphere, as well as the vision just behind that area.

Then we know the motor function, ability to move the arms, legs, face is also controlled in the left hemisphere for the right side of the body.So there are a number of important things. On top of that, with the left hemisphere we worry about speech, the ability to either understand what someone is saying to us, and or the ability to say what your want to say. So these are very important functions.

Dakin: The surgeons in this case are saying that a squeeze of the hand is a very hopeful sign. Does it mean that the speech area or the understanding area could remain intact?

Dr. Clarke: It's early to prognosticate in terms of those specific kinds of functions but it's obviously an encouraging sign if there's some appropriate response to some commands. That lets us know those pathways are intact.

Dakin: How much trauma can the brain cope with?

Dr. Clarke: It depends on the location of the injury and the extent of damage. There is damage that occurs at the time of injury, so the things we talked about, the pathway of the bullet, other fragments of material such as bone that can be brought into the brain as well, where the bullet goes, the pressure wave that's sent, and then there's also injury that can happen over the next several days where there can often be swelling of the brain in response to the injury. It's as if you hit your thumb with a hammer, sometimes the swelling of the thumb is worse two to three days after.

Dakin: Can the brain regenerate?

Dr. Clarke: We know that in some limited way at least the brain does have the ability to regenerate some new cells and that is the basis of stem cell therapy for example. On the other hand, once these cells are injured oftentimes they are not able to recover. What will be important over time is to see is the extent of recovery of the injured part of the brain and also the extent to which the areas around that injured part of the brain can compensate for some of that lost function.

Dakin: What do you do when you see a gunshot wound like this one?

Dr. Clarke: The initial treatment, the emergency treatment which is really trying to control the swelling and bleeding that occurs after a gunshot wound are the foci of attention in the initial phase. And then in the subsequent number of days, again, brain swelling is an important part of managing these patients so often times we'll leave a part of the bone of the skull out to allow the brain to swell. Oftentimes we'll put a little catheter or tube inside the brain to monitor the pressure. There are some medications and things we can use to help to control that pressure. But sometimes that can be overwhelming and sometimes people can survive the surgery and not survive the subsequent days of swelling.And then as we move into a more chronic phase of things, then the focus turns to the rehabilitation phase of things.

Dakin: What kinds of surgery take place?

Dr. Clarke: Depending on the case there can be multiple goals of the surgery. One may be to remove the skull so as to allow the brain to expand as it swells. Sometimes there may be significant injury to the brain with bleeding that may have to be dealt with at the same time. So sometimes it also involved going inside the brain along the path of the bullet, finding where that bleeding is and stopping it, removing the collection of blood and sometimes any dead tissue that's of no function.And bone fragments as well maybe. We have to balance the risk of trying to remove as much as we can with at the same time not wanting to compromise a brain that may have the ability to recover.

Dakin: Have you dealt with many gunshots to the head?

Dr. Clarke: I think any neurosurgeon in Canada has dealt with gunshot wounds to the head and they are not pleasant things to deal with. However, the volume of gunshot wounds we see in Canada certainly pales in comparison with that seen by our colleagues in the States.

Dakin: How common is it to survive a gunshot wound to the head?

Dr. Clarke: First of all I think it's still early to talk about how she [Giffords] specifically will do and whether she will survive. I think it's encouraging she survived thus far and we'll see how she'll do over the days and weeks to come. Again the issues we talked about, trajectory of the bullet and so forth, are very important. When both hemispheres are involved we know that predicts a very poor outcome and often times fatal. Certainly to have a bullet come into the skull and out again and to survive that would be remarkable. I think uncommon.