Scientist and Mechanic, Part 2

Another Day in the Frontal Lobe
by Katrina S. Firlik, M.D.

(Page 2 of 2)

When I recounted this story to my family and friends after dinner one night, they all nagged me with the same question: "How could he be normal? This went into his brain." Finally, here's where the scientist in me gets to pontificate a bit, settling into a fast-paced question-answer session in the comfort of my own home with a captive audience. I am not just a mechanic, after all, and the brain is not just tofu.

How could he be normal? First of all, his brain function was considered normal based on our typical bedside examination, which is, admittedly, a bit coarse. His speech was fluent. He answered simple questions appropriately. I asked him to remember three objects over a five-minute time span, and he did. His pupils reacted when I flashed a light in his eyes and his eyes moved symmetrically. He had no drooping of his face. The strength in his arms and legs was normal and so was his sensation. His reflexes were fine. He was capable of rapid and coordinated hand movements. In other words, his five-minute neurological examination was perfectly satisfactory.

But the frontal lobes harbor quite sophisticated functions, more sophisticated than the relatively simple ones I tested. The frontal lobes make up the largest section of the brain and are the most recently evolved. Compare the forehead of an ape to the forehead of a human. One slopes, the other bulges. We can thank, or blame, our frontal lobes for much of what we consider to be our personality and intelligence. Damage to the frontal lobes can be subtle, including changes in insight, mood, and higher-level judgment ("executive function," in the professional lingo). I'm not going to detect such changes in the ER during my five-minute exam before he is whisked off to the CT scanner. I'm just the neurosurgeon here. We would need to consult a neuropsychologist to help us evaluate these more complex brain functions.

"So why didn't you send this poor guy for more sophisticated testing?" my dinner audience asks in a confused and mildly accusatory tone. Why did I simply proclaim him "fine" and send him on his way? I explain that the foreign object was a nail, not a jackhammer. A relatively minuscule portion of brain was violated. The large frontal lobes, in particular, can be quite forgiving, especially when only one side is involved. It's not unusual to see a frontal lobe tumor, for example, grow to impressive citrus fruit proportions before the patient even detects a problem. In fact, the patient often does not detect a problem at all. It is frequently a spouse or friend who insists on the doctor appointment, explaining: "He's just not right, but I don't know what it is."

There is a redundancy and resilience to certain brain functions. What is compromised in one portion can sometimes be compensated for in another. (A remarkable ability referred to as "plasticity.") Even if the brain doesn't compensate directly, the patient often can cope indirectly, without even realizing it. If a person develops minor difficulty with memory, for example, he may start to write more things down, thereby maintaining the otherwise seamless flow of his existence. There are limits, though, to the power of plasticity. Damage to a single frontal lobe is frequently well tolerated (the opposite frontal lobe can compensate to some degree), whereas damage to both sides is often irreversibly devastating.

Getting back to our carpenter, we were confident that the very narrow swath of injured brain in only one frontal lobe would be inconsequential. Even if a faint cognitive deficit could be identified with detailed and time-consuming neuropsychological testing, would the patient really care? Would he, or anyone else, even notice the problem? Would his life as carpenter, husband, or friend be affected? Doubtful. On a more cold-blooded and practical note, would the patient or the hospital be willing to pay for these tests? His insurance would certainly balk at the cost and question the necessity. Besides, given my confidence in the resilience of his frontal lobes, my biggest concern was not sluggish thought but sluggish carpentry. What if he gives up the automatic nail gun altogether?

And with this final thought, the mechanic in me reclaims the front seat, as the scientist heads again to the back.

It doesn't necessarily take a brain surgeon to think like a brain surgeon, especially when it comes to the fundamentals. Consider this elementary notion: there is a limited amount of room inside the skull. Another central truth, directly related to the first, is: the brain is not the only thing inside the skull. The brain, in fact, makes up about 80 percent of the intracranial contents. The other 20 percent is split about evenly in volume between blood and cerebrospinal fluid. Once you master these central tenets, a good deal of seemingly complex neurosurgical decision-making becomes transparent.

Neurosurgeons learn to care just as much about the 20 percent as they do about the 80 percent, even though everyone else is blinded by the mystique of that 80 percent. I get plenty of wide-eyed questions about the brain, but no one ever cares to ask about the cerebrospinal fluid, a real nonissue as far as the public is concerned. Neurosurgeons care about the cerebrospinal fluid because if there's too much of it, the brain could be rendered next to useless.

In learning to think like a neurosurgeon, you have to take these thoughts one step further: given the rigid, fixed-volume container of the skull, and the 80/10/10 balance of its contents, what can be done if the equation is disrupted? This tips us more into the realm of mechanic than scientist.

Consider what would happen if you were punched in the eye. The area around the eye becomes swollen and is free to swell as much as it needs to. Aside from the social and cosmetic downsides of having a puffy, swollen eyelid and face, the swelling itself is usually not dangerous. It's not constrained. It goes down after several days, and the skin and underlying soft tissues recover nicely.

A swollen brain is another matter. There's not much room for it to swell. Swelling within a fixed container leads to elevated pressure, and unchecked pressure can lead to a cascade of events — namely a last-ditch shifting of delicate intracranial contents — that can be fatal. So as neurosurgeons, we do whatever we can to maintain a normal pressure within the skull when things go awry, such as in a serious head injury.

Although this is "brain surgery," the options we have for treating high pressures within the head are relatively simplistic and mechanistic: drain off cerebrospinal fluid from within the skull, shrink the brain tissue itself with a temporary dehydrating agent, or constrict the blood vessels in the brain via hyperventilation (although this one can be dangerous in situations when the brain needs all the blood flow it can get). If these options fail, there are more extreme measures, as a last resort: remove a portion of relatively "unimportant" brain tissue to create more room, or remove a section of skull to allow the brain to continue to swell. The decision as to which of these extreme measures you choose is largely a matter of who your mentor was and what he or she preferred to do.

Copyright © 2006 by Katrina Firlik. Excerpted by permission of Random House, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

About the Author

Katrina Firlik was the first woman admitted to the neurosurgery residency program at the University of Pittsburgh Medical Center, the largest — and one of the most prestigious — neurosurgery programs in the country. She is now a private practitioner in Greenwich, Connecticut, and a clinical assistant professor at Yale University School of Medicine. She lives in New Canaan, Connecticut, with her husband, a neurosurgeon turned venture capitalist.