Another Day in the Frontal Lobe (18 page)

What this means is that because a blind person has no visual input, the parts of the brain normally involved in visual processing are freed up for other purposes, as when an old school shuts down and lies dormant for a while, but is then turned into something else, like apartments. The good real estate doesn’t go to waste, especially in an active, dynamic community. (It might remain dormant in the setting of an unstimulated economy, though, to extend the metaphor.) The active learning and reading of Braille, then, allows new life to inhabit a dormant space in the brain.

A skeptic can be persistent, though, and he might look at a study like this and assume: okay, so the visual cortex is activated by reading Braille—granted, that is surprising—but the activation is probably just some sort of epiphenomenon, not really functionally relevant to the reading process.

Wrong again. Another study was designed to prove that activation of the visual cortex was critical in blind Braille readers, and not just some sort of an afterthought.
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  They used transcranial magnetic stimulation (TMS)—a cool and somewhat sneaky technique that can stimulate the brain via a magnetic force through the scalp and skull—to sort this out. While blind individuals were reading Braille out loud, they placed the TMS device over various parts of the head (with the subjects’ permission, of course). When the TMS device was placed over the occipital lobes specifically, where the visual cortex resides, subjects made a significant number of errors in their reading and would even perceive missing, faded, or extra dots in the Braille text.

These studies are a great demonstration of what is called “cross-modal plasticity”—a type of plasticity or flexibility of the human brain in which one part of the cortex can shift its purpose, when necessary, to accept a different type of sensory input. It also may explain the common observation that people who are blind tend to have certain other heightened sensitivities. With one sensory modality shut down, there is more brain volume available for other sensory functions (hearing, touch, smell). There is similar evidence that the auditory cortex is used for sign language in the deaf.

(By the way, TMS has been used in other very interesting ways. An article in
The New York Times Magazine
described its experimental use in enhancing creativity. A nonartist was asked to draw a dog before, during, and after stimulation, and the differences between the drawings were quite remarkable, with the “stimulated” drawings clearly having more of a lifelike animated feel compared to the unskilled childlike baseline.
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)

One more thought on the topic of blindness. Apparently, Braille can be read using just one finger, the index finger, or three fingers at a time, the middle three. Unlike memory, the representation of tactile sense along different parts of the body actually
is
typically neatly defined along a gyrus, in the somatosensory cortex. There is a different area that represents the face, hands, feet, and so on, mapped out as a so-called homunculus: a map of the human body in which certain more sensitive parts—index finger, lips—are given greater representation, as opposed to the less finely sensitive back, for example.

What’s amazing here is that, for blind people who use all three fingers simultaneously, the cortical map of these fingers becomes somewhat “smeared” and overlapping rather than distinct.
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  As a result, if you were to touch one of the three fingers individually, such a person might not be able to tell you which of the three is being touched. All three fingers have fused, in a sense, both in terms of their representation along the cortex and in terms of their sensory function, working as one unit.

In talking to patients, we sometimes use a term like “silent region” or “relatively silent region” to make them feel more comfortable with the fact that we’ll have to go through their right frontal lobe, for example, to accomplish our surgical goals, as in placing a shunt catheter into the ventricle. (Some patients fixate on this concern excessively whereas others don’t even question it—“whatever you have to do, Doc, no problem.”) In truth, there
are
areas that are “relatively silent,” but mainly in the sense that injury to those areas is well compensated functionally, even to the point of being undetectable in everyday living.

If you brought up the idea of a “silent” area to scientists like Drs. Just or Carpenter, which I have, they would argue. Functional brain imaging studies haven’t found any areas that are nonfunctional, regions that never “light up.” In other words, you can forget the old adage that we use only 10 percent of our brains. I remember hearing that “fact” from a misinformed friend in elementary school, but I don’t know where the idea originated. Regardless, you can delete the 10 percent fallacy from your brain and use the room for something else.

The study of traditionally mushy topics, like emotion—strongly tied to the frontal lobes—used to be considered a bit risky for serious neuroscientists to take on, but this area of inquiry has definitely been gaining in credibility over the past ten years or so. (Studies on this topic may help explain some of the 90 percent of the brain that some of you had assumed to be useless.) I feel particularly lucky when my random browsing—even in the more popular press—lands me good material in this department.

Interestingly, because Buddhism is so strongly focused on cultivating the mind, the study of well-seasoned Buddhist monks has been quite fruitful. Put aside the robes, the chanting, and the shaved heads for a moment. Look past whatever cultural trappings might distract (or attract) you. Consider these guys Olympic athletes—gold medal athletes of the mind. They practice meditation techniques and other mind-related exercises just as athletes practice a sport. As a result, they can develop enviable strengths that put the average harried, anxiety-prone, modern brain to shame.

There is evidence from brain imaging studies, for example, that the ratio of activation between the right and left frontal lobes (specifically the prefrontal cortex, in front of the motor and premotor areas that control movement) is tied to happiness and a sense of well-being. Too much right-sided activation is associated with a tendency toward depression and anxiety. This ratio goes a long way in explaining the concept of a set point for emotion, different for different individuals, in which we may temporarily swing one way or the other depending on the circumstances (marriage versus divorce), but tend to settle back to our baselines before too long.

This knowledge, by itself, may be cause for depression, especially in those who fear their ratio may be shifted to the right, but the good news is that there is also evidence that this ratio can be improved with practice (no drugs!). Richard Davidson, a neuroscientist at the University of Wisconsin, had the chance to study not only nearly a couple hundred regular volunteers, but also a senior Tibetan monk.
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  The monk’s brain activation was the most heavily shifted to the left out of all the other research subjects. With this knowledge as inspiration, non-monk volunteers were taught brain-strengthening meditation techniques similar to those used by Tibetan monks, and were able to shift their ratios over time, concurrently noting that they felt better overall, less prone to being derailed or unraveled by the common annoyances of daily life.

Most people I know, though, would complain that they have neither the time nor the energy required to train their brains to become stronger, happier, smarter. Spending several hours a week meditating or playing mind games in the name of self-improvement sounds like a good idea, but “it’s not going to happen,” most would say.

What we really need are the right implants…

After a year of poring through journals, pondering the complexities of cognition with smart Ph.D.s, and daydreaming, I believe that I can see the future of brain surgery. It’s exciting and a bit frightening. But these thoughts will have to wait. I’m heading back to the OR.

SIXTEEN

Focus

The patient on our operating room table was just a baby. She was the sixteen-month-old daughter of Latin American immigrants. For months, she had been having anywhere from one to ten seizures a day. That’s why we were looking at the surface of her brain, preparing to remove a small piece of it. We needed to get rid of the abnormal brain tissue that had become an irritant, the focus of her epilepsy.

The problem was, we couldn’t tell exactly which small piece to remove. We had a clear idea going in—based on her EEG (brainwave test) and the abnormal spot we could see on her MRI—but things weren’t as clear as we expected once we elevated the overlying portion of skull and dura and took a look at her cortex. It looked absolutely normal.

The other problem was that we had to be exact here, even more exact than usual. The abnormality was small and in a very unfortunate location: the part of the motor cortex that controls fine motor functions of the hand. This is not a “relatively silent” region. This is high-priced real estate. Luckily, given her extreme youth and the enviable plasticity of an infant brain, we had high hopes for a nice recovery. Still, we wanted to be as precise as possible in removing this thing, so as to leave all the surrounding brain perfectly intact for her future.

We bring out all our technology in a case like this, no cutting corners, so we had our high-tech 3-D image-guidance system up and running. This system, which is registered to correspond to a patient’s preoperative MRI with near millimeter accuracy, is designed to give us extra confidence in homing in on the right spot. That was another problem, though. The system seemed to be off for some reason—several millimeters off—and our typical troubleshooting tricks couldn’t correct the glitch. Its inaccuracy rendered it useless to us. We couldn’t trust it. Technical difficulties like this do arise on occasion, as every neurosurgeon knows, and are generally more of an annoyance than a crisis. Usually, we can see the abnormality with our eyes. This wasn’t a usual case.

So we continued to stare. We went back and forth between the convoluted gyral surface of her brain and the MRI images hanging up on the light box. The images teased us: they revealed the bright spot in her brain that we knew was the culprit, the seizure focus. If we could just match them up…her brain to the images…this thing was supposed to be right there on the surface. I knew that sometimes a lesion could be hiding just a millimeter or two underneath the surface, and you can’t always discern that level of distinction from a scan. Maybe that was the issue.

We were confident we’d be able to figure it out, though. This wasn’t a crisis, and it wasn’t rocket science. But we were, maybe, just a little worried. The room was more still and quiet than an OR should be.

Then, a breakthrough. The senior professor of neurosurgery standing next to me, teaching me the ropes, a surgeon I look up to, not only because of his height but more because of his expertise, had an idea. He put his finger on the brain and gently slid it around over the surface. He looked at me, nodded, and smiled. (A surgical mask does not hide a smile.) Putting your fingers on or in the brain is typically frowned upon. It’s sort of a low-class move akin to eating non-finger food with your fingers in a classy restaurant. This professor frowned upon it, too, in general, but he was savvy enough to know exactly when to go against etiquette.

I followed his lead, running my own finger over the pristine surface of this baby’s brain. The lesion was obvious to the touch, a hardened knot embedded within soft normal brain. Then we laughed, partly because we were now safe to consider the whole situation funny, and partly because we were relieved. We got back to work and everything went smoothly from then on. And the baby did beautifully, as babies tend to do.

I spent my second research year—my sixth year of residency—as a fellow in epilepsy surgery. There are only a few places in the country that offer formal fellowship training in this subspecialty field. Despite the small number of spots, though, and the fact that the field is a fascinating one, the competition is not overly intense. A choice spine surgery fellowship tends to be the hot item now, partly because of all the new and improved “toys” available for implantation in the spine to treat painful degenerative conditions, and partly because these new implants—as a realist would be quick to point out—can enhance not only a patient’s life, but also the bottom line. In the future, epilepsy surgery may become more popular as new technology brings new possibilities, implants, procedures, and demand, similar to the transformation that occurred in spine surgery.

I was lucky to work with one of the real masters and thought leaders in the field. He had a kind of dual identity: as a neurosurgeon and as a Harley-Davidson biker. He acted more like the former but looked a bit of both. Tall and thin, bald, and with a prominent white beard and mustache, he wore cowboy boots to work every day. In the winter he wore a black leather vest underneath his suit jacket and, in the warmer months, suspenders. He used an old-fashioned pocket watch rather than a wristwatch. He did wear ties, and had a soft spot for ones adorned with seahorses because the hippocampus, a part of the brain often involved in epilepsy, was named after the scientific term for this sea creature whose tail curls in on itself in a similar way.

This professor was the consummate academic neurosurgeon—like neurosurgery founder Harvey Cushing—intellectually curious and entrenched in basic research. He was busy and in demand, even overcommitted at times: seeing patients in the clinic, operating, running a department, serving on committees, working on the next research grant, attending international conferences. He didn’t get to ride his motorcycle (or “donorcycle” as we tend to call them in the head injury business) as much as he wanted or as much as you might have assumed. Somehow, though, he kept it all together.

Epilepsy surgery intrigued me for many reasons. For one, you can sometimes actually cure people of their epilepsy. I still find that incredible. “Cure” is not a word we get to use often enough in medicine. Also, it is the branch of neurosurgery most concerned with the mind and cognition, which is what led me to neurosurgery in the first place. Collaborations with neuropsychologists are routine, for every case, to assess language, memory, and other functions. In removing a seizure focus, you want to preserve the patient’s mind as much as possible—obviously—and a detailed array of cognitive tests can help us figure out if that’s going to be possible. Maybe this small subspecialty, then, would be my ticket to lifelong career satisfaction, with its blend of interesting science, interesting surgery, and devotion to the mind. For one full year, it would be my sole concentration.

Epilepsy surgery is the purest form of brain surgery. By that I mean that you’re actually operating on the brain itself, not around the brain, underneath it, or through it, as is otherwise often the case. In epilepsy, there’s something wrong with the substance of the brain, usually an area of the cortex, and in surgical candidates we have to try to fix it, by finding and removing the abnormal region. I also like the imaging. Epilepsy surgeons (and their very close allies, epilepsy neurologists) rely on multiple different types of images—MRI, PET (positron emission tomography), SPECT (single photon emission computed tomography)—and try to correlate the imaging findings to every other piece of data, hoping to localize the seizure focus. As a very visual person, I enjoy examining interesting images, especially when the brain is the subject.

Most intriguing and rewarding, though, were the patients. As a fellow concentrating only on epilepsy surgery candidates, I got to know them better than I had during other years of my training, which were more frenetic. Each patient went through a complicated, time-consuming, and often tedious workup. I often saw them over multiple visits, before and after surgery. It was lower volume but higher intensity—more my style.

Some patients were highly functional, with careers and families of their own. At the other extreme, some were on the fringes of society or even institutionalized, a combination of seizures and mental deficiency having devastated their lives and even their families’ lives. It is a peculiarity of our profession that we do some of the most high-tech, interesting, labor-intensive, and expensive work on some of the most compromised individuals. Thinking back on our epilepsy conferences, I wonder in what other scenarios would you find a dozen intelligent people (neurosurgeons, neurologists, fellows, neuropsychologists, neuroradiologists, nurses) gathered around a conference table, focusing great time, energy, and resources on a single patient who may never comprehend what is being done to them? What might be accomplished, in addition, if the same group lent some of their collective brainpower to, say, improving public education or homeland security?

I remember many patients. There was the pleasant, heavyset teenager who traveled all the way from Turkey with his family for epilepsy surgery. Just like the baby with the hidden lesion, this patient also happened to have an abnormality in the area of the brain that controls the hand and arm. His English was decent but he had a habit of referring to his arm as “my armie,” which I found endearing.

Based on his MRI, we knew he probably had a condition called focal cortical dysplasia, which means that a portion of his cortex did not form properly during his brain development. Otherwise, he was a perfectly normal and healthy teenager. Cortical dysplasia is often associated with seizures. His seizures were mainly focal in nature, involving only his hand and arm on one side, rarely progressing to the type of seizure that would involve the entire body, the kind associated with unconsciousness. In other words, he remained fully alert during his seizures.

We did his surgery “awake,” which means we performed an “awake craniotomy.” This sounds a bit more dramatic than it really is because the patient is awake for only a certain critical portion of the operation. He is not awake during the scalp incision or the drilling of the bone flap or the closure at the end—the potentially painful parts. The anesthesiologist allows the anesthetic medications to wear off once the brain is already exposed, and puts the patient back to sleep after we complete the necessary awake testing. The brain itself has no pain fibers (a detail that I think is now common knowledge), so the procedure is better tolerated than you might expect.

With our young Turkish patient awake, brain exposed, we talked to him as we systematically explored the abnormal area of his cortex with a fine two-pronged electrical stimulator. We figured out which parts of his brain corresponded to his hand and arm and, as we feared and expected, the dysplastic cortex was mixed right in. This would be a balancing act: remove enough tissue to decrease his seizure frequency but not so much that his hand and arm function would be compromised. A complete cure of his epilepsy would be a real bonus; we weren’t counting on it.

At the tail end of the stimulation the patient started to have one of his typical seizures, right there on the operating room table. We were alerted to this by the anesthesiologist, as we were on the other side of the drapes, unable to see the patient’s hand. “Cold irrigation, please,” my mentor asked of the scrub nurse, who promptly handed over a syringe full of cold, clear saline solution. Usually, we’re careful to use nice warm saline on the brain and the rest of the body, but cold saline on the brain can actually stop a seizure in its tracks—a detail that is probably not common knowledge.

With the seizure aborted, we continued working. We removed the small area that we felt we could get away with removing, and did multiple subpial transections, or MSTs, on the portion that we had to leave in place. This is a technique in which we make small fine cuts in the surface of the brain. The theory here is that these cuts can prevent a seizure from spreading horizontally through the cortex, while allowing function within the remaining vertical columns of brain tissue. It sounds good, but it tends not to work out quite so perfectly. In this young man’s case, his seizures did decrease in magnitude and frequency, but were not cured, and he was left with a slight hand weakness that required some time to recover from. All in all, though, the trip from Turkey and the neurological trade-off were definitely worth it.

When brain tissue is removed in a case like this, it’s not treated like just some inflamed gallbladder or gangrenous toe, walked over to the pathology department in a plastic bag in the hands of a candy striper. This particular professor would send out a call to his entire research posse and, within minutes, fully fledged Ph.D.s toting special containers, complex preservative solutions, and dry ice would show up in the OR, wearing flimsy disposable white “bunny suits” over their street clothes. They would line up, quietly and respectfully, and would each receive a small piece for their own special projects. It always reminded me of Halloween. “Trick or treat!” was the only thing missing.

In the future, a patient such as our Turkish teenager might be fitted with some form of an electrical stimulator implanted over the cortex that would predict and then prevent a seizure, obviating the need for any actual brain removal, which, if I take a step back and think about it, does seem a bit primitive.

There is one type of electrical stimulator for epilepsy already on the market. It’s called a vagus nerve stimulator. The thin, coiled, insulated leads are implanted around the vagus nerve in the neck, which lies sandwiched between the jugular vein and the carotid artery. The nerve originates in the brain stem, so when a segment of the nerve in the neck is stimulated, electrical impulses are able to travel in a retrograde fashion up to the brain, with the nerve as a conduit. A little battery pack is implanted under the collarbone area, just like a pacemaker. Typically, the device is not curative, but it can function as a valuable adjunct to medication, without the typical side effects of medication.

My mentor was skilled at talking to patients, including kids. He really wanted them to understand the plan. Once, we sat down in the clinic with a seven-year-old boy who was scheduled to undergo implantation of one of these vagus nerve stimulators the following week. His seizures were mainly “complex partial” in nature. This type of seizure—the most common type that we operate for—can be quite bizarre to watch because the patient loses awareness but not necessarily the ability to do things. A patient may, for example, remain staring with his eyes open but demonstrate strange “automatisms” like repetitively smacking his lips and blinking. When it ends, the patient typically awakens with no memory of what just occurred.