The Exposed Brain



The Exposed Brain
by Edison McDaniels, MD

This is a picture of a craniotomy, one of the most ancient of all surgical procedures.

Man has been trephining the skull, that is opening a hole through the skull, for thousands of years. The purpose of those early operations is not readily apparent, though there are numerous examples of those skulls which show the patient (victim?) survived. Many more most have died during the attempt or in its aftermath.

Modern day brain surgery dates only from the early 1900s, with a few surgeries having been accomplished ten or so years before that. Many of those early patients, if not most, died as well. The road to the modern craniotomy is paved with broken skulls and enough spilled blood and spinal fluid to fill more than one olympic sized swimming pool. Perhaps many more.

Modern brain surgery, although still risky, is a remarkable undertaking. Advances in neuroimaging (see my article “A Game of Shadows” at and anesthesia have made brain surgery very safe today. Death in surgery is a very rare thing, and most patients survive with little or no deficits. There are virtually no parts of the extra-axial space, the complicated 3-D anatomic space surrounding the brain, into which a neurosurgeon’s knife cannot venture. There are areas of the brain itself which still elude our reach, but only in the most extreme circumstances, such as intrinsic tumors of the brainstem. Today, neurosurgeons routinely remove blood clots, clip aneurysms which would have killed even 20-30 years ago, excise once inoperable tumors, and selectively obliterate brain tissue to cure such ills as Parkinson’s disease and obsessive-compulsive disorder. Other neuro specialists, including therapuetic radiologists and interventional neuroradiologists, treat with radiation and endovascular therapies what were once dreaded operative diseases, such as vascular malformations, many aneurysms, and certain tumors.

What does a modern day brain surgery look like? Through the magic of photography, let us glimpse one moment in the exposure of the living, pulsating human brain.



The picture is of an exposed living brain. It’s a still photo, so one needs to imagine the brain actually pulsating with the rhythms of life, both the beating heart at perhaps eighty beats per minute, and the breathing, which in the operating room is controlled at a rate sixteen to twenty breaths per minute. These rhythms are very noticeable to the surgeon, and the surgeon learns to time his activity to them in a more or less subconsious fashion.

Blood tends to pool constantly during brain surgery, along the dependent areas of the exposure. You can see this in the lower left portion of the image. Note also the bloody sponges, which have slowly taken up the oozing blood. Along the border of the sponges are skin clips. These clips attach to the edge of the skin along the line of the incision and have only one purpose: to stop the otherwise copious bleeding from the scalp blood vessels. The scalp is quite vascular and it is very possible to bleed to death from an otherwise simple scalp laceration (as did the actor William Holden, who bled to death in his hotel room after stumbling and striking his head on the corner of his nightstand).

Accumulating blood is removed with a sucker. The sucker is a hollow tube, a straw actually, attached to a suction device. It provides a constant low level of suction that can be used to remove accumulating debris from the operative field. This debris includes not only accumulating blood, but also spinal fluid, bone dust (from drilling the skull), brain itself (sometimes, one will have to remove good brain in making a path to a tumor or other target; surgeons refer to this as ‘taking brain’), and tumor. The sucker is finely controlled by the surgeon using his nondominant hand, and comes in various shapes and configurations. One becomes very adept at its use, as a wrong swipe here or there can be quite costly.

The surgeon’s dominant hand might hold any number of devices. In this picture, it holds the yellow bipolar forceps. This is a cauterizing device. By pressing a foot pedal, the surgeon can send a gentle pulse of electricity between the tips of the bipolar. This brief pulse cauterizes whatever is between the tips of the bipolar. In the picture, the bipolar is cauterizing the edge of the dura mater. The dura mater, latin for tough mother, is a leathery membrane that encases the entire central nervous system (brain and spinal cord) in a protective envelope. Anatomically, it rests just under the bone of the skull, tending to adhere to the inner aspect of the skull in the aged. Sometimes, especially after a blow to the head which fractures the skull, bleeding can occur in the potential space between the skull and the dura (a potential space is one that normally does not exist and only arises under duress—not good). This accumulating blood is called an epidural hematoma and can be life-threatening. It’s what killed the actress Natahsa Richardson after she fell and suffered a ‘minor’ head injury on a ski slope. A craniotomy almost certainly would have saved her, though apparently the severity of the injury was not recognized. When it is, the only reasonable course in many cases is a craniotomy. Fortunately, the prognosis is excellent in most cases—if the surgery is timely.

The dura mater is perhaps a few millimeters thick and can be quite vascular. Here, the bipolar is cauterizing a bleeding point on the edge of the dura. The sucker is clearing the field of the blood so the surgeon can see what he is doing and so the bipolar can work properly. Note also that the dura mater is thick enough to hold stitches. It is often tacked up to the bone during the surgery (B in the images). The tack-ups help prevent oozing of blood from the epidural space. At the conclusion of the surgery, the dura mater will be closed with a row of closely approxiamated stitches. It will also be tacked up to the over lying bone flap, so as to prevent any accumulation of blood under the bone and above the dura. Such bleeding, an iatrogenic epidural hematoma, would necessitate a return to the operating room and reopening of the craniotomy to evacuate the accumulated blood. This is one of many potential complications of a craniotomy. It is one of the chief things neurosurgeons watch for in the first hours after a cranitomy.

Note the cut edge of the skull in our image. A large circular piece of skull has been removed to gain the exposure shown. The removal of the bone is the actual craniotomy. Drilling the skull is one of the more dramatic moments in any craniotomy, especially to the uninitiated. How is it done?

A Civil War era trephine for opening the skull.

A Civil War era trephine for opening the skull.

Drilling the skull is surprisingly easy. In the old days a trephine was used. This is a T-shaped handheld instrument with a circular base of sharp teeth. When pressed to the skull, the user presses his weight down on the T-shaped handle and simultaneously turns it, like a cookie cutter. Nowadays, at least in the United States, such a trephine is rarely used.

Another way to open the skull is with a pneumatic drill. These drills have a failsafe that causes them to stop when the bone is drilled through. The surgeon drills several holes spaced at intervals around the desired exposure area, then simply connects the dots with a saw. Today the saw is often pneumatic itself. However, another very good option is to pass a thin wire under the bone between the holes and saw through the bone with a to and fro action. This is called a gigly saw and has been used for decades. It carries the advantage of removing very little bone along its path, which makes for a better fit when the bone is replaced.

Replacing the bone is easy today. It is usually screwed in place with several tiny plates and screws. In the past it was wired or sutured.  

Craniotomy implies the bone will be returned to its proper anatomic position at the end of the operation. A craniectomy implies the bone will not, or has not been, returned to its normal position (it has been left out). Most elective operations are craniotomies. Many emergent procedures involve a craniectomy, since brain swelling or the threat of brain swelling sometimes prevents replacement of the bone flap. A decompressive craniectomy is a procedure done for uncontrolled brain swelling wherein a large portion of the overlying skull is purposely removed in an effort to control increased pressure in the head. This is often a last ditch effort to control such swelling.

Patients who have had a craniectomy will require further surgery to replace the missing bone flap if they survive. Sometimes, if the defect is especially large, they will need to wear a helmet in the interval between recovery and replacement surgery (called cranioplasty). What do we use to replace a missing bone flap? Usually, in the United States, it is a custom designed acrylic prosthesis that fits the defect more or less exactly. Such a procedure has a significant risk of infection however, and patients need to be watched for signs or symptoms of infection around the prosthesis for many months.

The patient in our image does not appear to have any brain swelling. The architecture of the surface of the brain is well preserved. Notice the large blue veins coursing over the surface of the brain, as well as the fine, spidery, red branching vessels, the arteries. The surface of the brain is composed of peaks (gyrus, or gyri for plural) and valleys (sulcus, or sulci for plural). Some surgeons prefer to operate through the depth of a sulcus in order to minimize brain tissue injury, others are more adept at going through the gyrus. When such a decision is crucial, as when working around the motor strip (which controls movement on the opposite side of the body) the brain can be mapped intra-operatively. This requires special equipment however—and an awake patient!

An awake craniotomy is possible because the brain itself does not feel any pain, despite the presence of billions of nerve cells. With awake surgery, the patient is gently sedated and the scalp is numbed with local anesthetics. Once the incision and the bone work are done, the dura mater is opened. There are many pain fibers in the dura mater, and so the patient is kept sedated until the dura mater has been incised and tacked up. Only then is the patient awakened to respond to the surgeon’s questions. The exposed brain in the image could well belong to an awake patient.

Note the glare in the image. This is caused by a thin and wispy web of issue over the brain, the arachnoid mater. The arachnoid is a flimsy membrane, generally not tough enough to hold stitches. Coursing under it, in the subarachnoid space (a true space, not a potential space) is the elusive cerebrospinal fluid, CSF. The CSF bathes the entire brain and spinal cord. It may provide nutrients and acts as a shock absorber. Infection in the CSF is called meningitis and can be life threatening.

The vessels over the brain also couse through the subarachnoid space. A subarachnoid hemorrhage is caused by the rupture of one of these vessels, often as a result of an aneurysm (a weak spot in a blood vessel). A ruptured aneurysm is a dire circumsance, fatal half the time. However, if the patient survives the initial hemorrhage, clipping the aneurysm via a craniotomy is one option. Coiling the aneurysm through an endovascular approach is another.

A simple craniotomy, as for an epidural hematoma, can be done in 60-90 minutes. Clipping an aneurysm might take three hours. Complicated tumor surgery can take 12-24 hours. These types of operations are usually done at university medical centers, with residents to assist the surgeon with the opening and closing portions of the craniotomy.

As a neurosurgeon, and a fiction writer, I’ve incorporated craniotomies into my stories several times. By way of bringing the reader into the operating room and closer to the action, I have included a scene from one of my novels below. For a graphic and dramatic depiction of a neurosurgeon in action, I refer the reader to my short story, THE CRUCIBLE, available for free at the Summerset Review website. Click the image at the end of this posting to go to the story directly.


What follows is an excerpt from NOT ONE AMONG THEM WHOLE, an audacious novel I wrote about surgeons amid the chaos and carnage of a battlefield hospital during the Battle of Gettysburg. While the scene is fictitious, it effectively portrays a trephination during the Civil War era. A trephination is not quite a craniotomy, but before one can master the rudiments of a craniotomy, one most know the trephine. Such an operation was uncommon during the Civil War, but not unheard of. At least twenty are known to have been done. 

Josiah Boyd is a tobacco chewing surgeon, Tobias Ellis his assistant surgeon, and Tiny is their hospital aide. This is a graphic scene, as is the novel itself. The trephination:

The wind howled around them, but the rain stopped abruptly. Boyd looked up from the soldier on the table, toward the cloudy sky. He didn’t pray though, knowing beyond any doubt that God had long ago abandoned him. He was not a prayerful man.

He could have been the last physician in a land besieged by plague.

He spat tobacco gruel and tried to concentrate on the problem at hand. From the corner of his eye, he saw Tobias Ellis watching him. The assistant surgeon stood directly opposite, waiting to take his cues. To Ellis’s left was a skeletally thin negro stretcher bearer named Abel. Abel’s job was to hold a lantern, to fan Boyd, to hold an umbrella, whatever might be needed. Tiny, Boyd’s long-time assistant, stood at the head prepared to administer the chloroform whenever the word was given.

The right side of Spencer’s head was discolored the blue of days-old bruised skin. Boyd smoothed the blond hair back and saw the small hole where the bullet had pierced him. Another hole just behind and above the ear where it had exited. “I guess that’s as good a place as any to cut,” he said with a lack of enthusiasm. “Sleep ‘im.”

Tiny let go a few drops of chloroform into the mask and Spencer’s heel stopped moving. The lack of movement was eerie, like he was dead. But he was only playing at dead, for every now and again he swallowed or suffered a slight cough. Boyd waited what he thought was a full minute, probably longer as he was in no hurry to get the thing started. Once started however, he was most certainly in a hurry to get it ended.

“Give me a knife.”

Tiny wiped the blade on his apron and slapped it hard into the surgeon’s outstretched palm.

Boyd sucked hard at the wad in his cheek, putting the cold edge of the steel against Spencer’s temple. He ignored the hair and pressed the blade into the skin, cutting not quite to the bone, and dragged it upward over a distance of two inches. He made a second incision at right angles to the first, the effect of which was to fashion an ‘X.’ The incisions were half in, half out of the hairline so that if Spencer survived, the marks would be forever obvious to all.

The skin parted and a brisk stream of bright blood jetted out, as if proof of life. The stream pulsed twice more in quick succession, each striking Assistant Surgeon Ellis in the belly. Ellis was quick to act though, knew the import of blood after more than a year of watching it spill. He put a stubby finger over the artery and halted the flow.

“Ligature,” Ellis said, and tied off the exposed ends of the temporal artery and vein with lengths of silk thread Tiny handed him.

Done smartly, Boyd was impressed with the assistant surgeon’s hands.

Boyd deepened the cut through the muscle over the side of Spencer’s head, running the knife over the same path as before, this time sinking the knife all the way to the skull. The wound filled to overflowing with the dark red of venous blood.


Ellis continuously swabbed the wound with a lint sponge, but the effort did little good until Boyd inserted a couple of curved metal tongs under the skin on each side of the X-shaped incision. “Here,” Boyd said, indicating Ellis should take control of them.

The assistant surgeon tugged the retractors apart from each other, opening the wound as wide as the split skin allowed. Boyd wiped again at the blood, then leaned back to spit and wiped his hand across his forehead.

“Hold that lantern up now.”

“Yassah,” Abel said and came around the table to a spot behind Boyd.

The long shadows of morning leaned lazily against the exterior of the church. The spot was the same a priest had given last rites the day before, though not a man among them had been present for that solemn observance.

Once or twice the white skull chanced into a fleeting view, but for the most part Boyd worked blindly and by feel.


The instrument was six inches long and resembled the gnawed clean bone of a chicken leg the way it flared at one end. The other tip was flat and blunt and he scraped this back and forth against the hard skull, detaching whatever muscle was there and confirming the need for the trephine. Dark blood and gray matter slowly percolated up through the bullet hole in the skull. All the while a steady stream of blood oozed from the skin edges, enough to be a nuisance but not so much the man would bleed out. Ellis pulled the skin edges taut with the retractors and the bleeding slowed to a trickle.

Boyd pushed a naked finger against the skull and felt around, rolling the digit under the skin and making a small pocket. He tried not to think too much about what he was doing, hoping only that he was making a difference.


Three minutes had passed since the incision. Boyd was exhausted.

Tiny passed the T shaped trephine to the surgeon. It had an ebony cross bar handle and a metal shaft that ended in a hollow conical drill with a flange of teeth. The whole thing was built compactly, no more than five inches long, and was solidly built, so that one could put his weight behind the turning of it; a human skull is hard, not meant to be penetrated.

He gripped the handle in his palm, the shaft between the middle and ring fingers.

Boyd knew the drilling would require muscle and backbone, though he was hesitant having never done this before—at least not in a living person where the drill could potentially plunge brainward. He thought for a moment about that word. Brainward. Like rightward or leftward, though it didn’t seem a direction one wanted to test all that often. But he was committed now, and so he leaned over the open head and pressed the teeth of the drill against the bone. He tested the unyielding nature of it, gaining confidence. Boyd simultaneously pushed down and turned the handle the way one might work a stuck door latch. The teeth bit the bone and stopped. He tried a second time using more force. The teeth moved slightly, then popped out of the skull and skittered across Spencer’s forehead, leaving a pattern of tiny bleeding nicks.

Hardy’s words haunted him: You ever trephined a man still this side of the grave?

He hadn’t pressed hard enough, that’s all. He replaced the thing and turned the drill, learning the art and work of it. It sank deeper into the bone and Hardy was at him again: I’m telling you it can’t be done without killing him.

He ignored the thought and pressed forward. The work was tedious and the minutes passed like days. At one point Spencer stirred and Tiny poured a few more drops of chloroform into the mask. Ellis too strained, holding the retractors and the head both. The assistant surgeon swallowed at the sight of the drill poking out of the head but didn’t falter when the thing skittered. 

Boyd turned the drill in small jerks, a quarter arc at a time. Simple brute force, with no way to build momentum. Despite the cool morning, sweat dripped from the tip of his nose. After every few turns, he leaned over and spat, sometimes on the floor and sometimes on the trouser leg of the man beside him.

From the post-mortem trephination he’d done and the several skull fractures he’d seen, Boyd recollected the skull to be about a quarter-inch thick. But a quarter-inch came and went and the drill was still anchored in firm bone. Several times he took the trephine out and tapped the cut skull with a mallet and chisel. Finally, on the fourth such occasion, he felt it give. He tapped again and the bone popped free and floated up, a clot of blood welling up with it.

Ellis grinned at Boyd, still holding the retractors in place. “Hot damn.”

The blood was thick and almost black. Several large chunks pushed out and slid down the side of Spencer’s head. Boyd pushed his little finger into the hole and twirled it, feeling the inside of the smooth skull and dislodging several additional pieces of clot. There didn’t look to be any fresh bleeding though, and after a few minutes he considered how he would end the operation. He decided not to put the bone back in place, there being no good way to secure it. In the case of a fracture the bone would simply be discarded and he saw no reason to deviate from that. Ellis removed the retractors, and Boyd proceeded to stitch the skin with a needle and silk thread. The entire operation had taken just under thirty minutes. When done, the right side of Spencer’s head was dimpled where the bone was missing. They wrapped his head with a length of muslin and waited for the chloroform to wear off.

Boyd spat in the dirt again and stepped back from the table. He picked up the trephine, stared at it a moment or two, then set it back down. Leaning against a wall, he closed his eyes and slept standing up for several minutes.

Another half hour passed before Spencer Hardy began to come out of his stupor. As he did so, he crossed his legs and reached up to grab his head. This was more movement than he’d done in a day and those present cheered.

Boyd at least was satisfied. He slumped to the bloody grass and slept.

Edison McDaniels, MD is a board certified neurosurgeon and practices in the American South. Follow him on twitter @surgeonwriter and read his fiction at Amazon in paperback and on kindle.

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2 thoughts on “The Exposed Brain

  1. Wow, this was remarkable to read. Both the facts and fiction. Thanks for making it so clear for lay-folk like me. Wonderful writing.

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