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Scientist and Mechanic
The brain is soft. Some of my colleagues compare it to toothpaste, but that’s not quite right. It doesn’t spread like toothpaste. It doesn’t adhere to your fingers the way toothpaste does. Tofu—the soft variety, if you know tofu—may be a more accurate comparison. If you cut out a sizable cube of brain it retains its shape, more or less, although not quite as well as tofu. Damaged or swollen brain, on the other hand, is softer. Under pressure, it will readily express itself out of a hole in the skull made by a high-speed surgical drill. Perhaps the toothpaste analogy is more appropriate under these circumstances.
The issue of brain texture is on my mind all the time. Why? I am a neurosurgeon. The brain is my business. Although I acknowledge that the human brain is a refined, complex, and mysterious system, I often need to regard it as a soft object inhabiting the bony confines of a hard skull. Many of the brains I encounter have been pushed around by tumors, blood clots, infections, or strokes that have swollen out of control. Some have been invaded by bullets, nails, or even maggots. I see brains at their most vulnerable. However, whereas other brain specialists, like neurologists and psychiatrists, examine brain images and pontificate from outside of the cranium, neurosurgeons boast the additional manual relationship with our most complex of organs. We are part scientist, part mechanic.
The scientist in me revels in the ethereal manifestations of the brain: the mind, consciousness, memory, language. The mechanic in me is satisfied by the clear fluid that rushes out of the end of a tube I insert into a patient’s brain to relieve excessive pressure. In everyday surgical practice, the science may take a backseat to the handiwork, and that’s okay. If you have an expanding blood clot in your head, you want a skilled brain mechanic, and preferably a swift one. You don’t care if your surgeon published a paper in Science or Nature.
I’ll give you an example of a most straightforward and manual case. I was paged to the emergency room a few years ago during my training and received the following brief report over the phone: “carpenter coming in with a nail stuck in the left frontal region of his head . . . neurologically intact.” What is going through my mind at this point? Do I hark back to my studies of frontal lobe circuitry and mull over the complex neural networks involved in language and memory? No. I’m thinking concrete, surgical thoughts: nails are sharp; the brain is full of blood vessels; the nail may have snagged a vessel on the way in. These thoughts are instantaneous, of course. I spell out the simple logic here purely for effect.
What I encountered in the ER was a young man, in his thirties, sitting up on an emergency room gurney. Perfectly awake and alert, arms crossed in repose and still in his construction boots, he smiled nervously when I walked in. Was he the right patient? He looked too good.
He was the right one. The carpenter explained that he and his friend were both on ladders along the side of a house. His friend was working a few rungs above. They were driving heavy-duty nails into the siding with automatic nail guns. His friend’s hand slipped upon firing in one of the nails, and the nail entered the left frontal region of my patient’s head below. For the first few moments after impact, the carpenter doubted what had happened. Although he noticed a stinging sensation within a split second of his friend’s slip of the hand, and heard the loud expletive coming from the same direction, there was no trickle of blood and he felt nothing unusual as his fingers frantically searched the top of his head. He wasn’t sure if it went in. His friend knew otherwise.
Upon close inspection of his scalp, past his short crew cut, I could see the flat silver head of the nail, not quite flush with the scalp, but a bit deeper. Apart from the nail, he looked great. I performed a quick five-minute neurological exam and found nothing wrong. I sent him down the hall for a CT scan. The nail entered his brain perfectly perpendicular to the surface of the skull. It had been driven a good two inches into his left frontal lobe. Luckily, it didn’t snag any sizable blood vessels along the way. There was no evidence of bleeding within the brain. Unlike the more common gunshot wounds we see, this was a respectably neat and clean penetrating injury.
At this point, my biggest fear—bleeding in the brain from entry of the nail—had been put to rest. Now, do I take a breath and mull over any complex scientific issues at this point? Am I exercising my formidable brainpower as a brain surgeon? When people say, “it doesn’t take a brain surgeon,” they refer to the assumption that we are the smartest ones around. Have I demonstrated this superior intelligence so far? Again, my thoughts return to the practical and concrete. We need to get the nail out of this guy’s head. It didn’t cause any bleeding on the way in. We need to avoid bleeding on the way out.
I walked out to the waiting room. His wife was there and so was his friend, who was pale and despondent, looking down at the floor. I tried to cheer them up a bit. Yes, the nail entered his brain, but his brain function, as far as we could tell, was normal and the nail caused no bleeding. Without looking up, the friend opened his hand and offered me a large silver nail that had been warming in his palm, the same type embedded in my patient’s head. “I don’t know . . . it might help you guys to have one of these . . . so you know what you’re dealing with.” I hadn’t been able to tell from the scan that the nail had two copper-colored barbs sticking out from the shaft at acute angles. I’m not a carpenter, but I figured that the purpose of the barbs was to ensure a strong hold. I thanked him and pocketed the nail in my white coat. On my way back to the ER, I ran my fingers over the pointy barbs and thought about the issue of bleeding again. Avoiding and controlling bleeding are elementary and pervasive themes in surgery—not quite the stuff of rocket science, but critical nonetheless.
After calling on the appropriate team, including the supervising neurosurgeon and anesthesiologist, I took him to the OR, shaved a small patch of hair around the nail head, and made a short linear incision in his scalp, down to the skull. There are no how-to entries in our textbooks regarding removing nails from heads, so we improvised using common sense. We drilled out a disc of frontal bone from his skull, with the nail head at the center of the disc. Slowly, we lifted this piece of bone up away from the surrounding skull, bringing the firmly embedded barbed nail with it. Although we could see a small jagged tear in the covering of the brain and a puncture wound on the surface of the brain itself, there was no blood oozing from the hole, and we considered ourselves lucky. (“Better lucky than good” is a favorite slogan among surgeons.)
Then, using large tools fit more for our patient’s line of work, we clipped off the barbs and pounded the nail through the disc of skull, backward. After soaking the bone in an antibiotic solution, we neatly plated it back in place with miniature titanium plates and screws and sewed his scalp back together. Actually, rather than suture, we used surgical staples from a staple gun to close the final layer of his scalp, unaware, at the time, of the subtle irony in that move. Within less than twenty-four hours, the patient was on his way home, joking the entire length of the hall with the friend who nailed him in the head.
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.
From the Hardcover edition.