12.24.2010

Review: The Mind's Eye, by Oliver Sacks

For those of us whose vision is relatively unimpaired, the world appears a coherent place. We see words on a page or the face of a loved one sitting across the table from us and can easily recognize both as what they are. This is enabled by complex visual circuitry in the brain, which is divided into discrete areas, each responsible for “seeing” different things. There are groups of neurons that specialize in faces, others in words, and yet others that are responsible for detecting movement. The brain then combines these different pieces together (just how is not fully understood) to form a coherent whole.


Read more on the National Post website

posted by Maria Schamis Turner @ 10:39 AM   0 Comments

12.13.2010

Alzheimer's disease and deep brain stimulation

Just published on dana.org, my article on deep brain stimulation for Alzheimer's disease:

Alzheimer’s Disease a New Target for Deep Brain Stimulation

posted by Maria Schamis Turner @ 5:05 PM   0 Comments

12.09.2010

Notes from a surgery

The day starts with morning traffic. Although he is running a few minutes late, neurosurgeon Dr Rolando Del Maestro does not seem fazed. He stops to pick up his surgical garb—it’s all automatic now, like a vending machine: swipe the card, open the drawer, and take out a fresh set of scrubs—then he heads into the operating room. It’s a little after 8 am.

Besides Del Maestro, there are at least 10 other people in the OR, not including the patient. These include a neuronavigation technician, a surgical resident or two, scrub nurses, circulating nurses, a nursing resident, and the anaesthesiologist. Everyone has a critical role to play or, because this is a teaching hospital, is there to learn. There are two surgeons working today, Del Maestro and research fellow Dr Alessandro Perin.

The nurses are responsible for getting the room ready for the surgery. “It’s like preparing supper,” explains Elizabeth Coté, the head nurse. “We prepare the whole environment, and all the equipment, to make sure nothing inadvertent happens. Then we invite the doctor to sit down to the meal.”

The room is cool. The temperature is kept intentionally low, both to keep bacteria proliferation down and to prevent the surgical team from getting too hot in their scrubs. You don’t want to be dripping with sweat during a surgery.

*

Today’s patient is anxious. An anxious patient means general anaesthetic because it is safer and easier for everyone if he is asleep. Someone of a different temperament could be awake for this same procedure. Sedated, but awake. Being awake during surgery has advantages. The surgeon can get direct feedback during the operation, testing the patient’s cognitive and motor functions as the surgery progresses. But if the patient is too uncomfortable with the idea, like today’s patient, it’s not worth it.

The patient has already gone through pre-op with the residents. Now it’s time to get ready for the surgery. Before he goes under, the patient wants to know if they will be removing the tumour from his brain with a saw. The team explains that a saw is used only to open the skull, the tumour itself will be removed with a Cavitron ultrasonic aspirator. The Cavitron breaks the tumour into fragments using high frequency sound waves. The fragments are then vacuumed up by a suction tube.


Del Maestro, Perin, and the residents review the patient’s MRI scans and discuss the surgical plan. The MRI scans show a large tumour – the reason for today’s surgery. The doctors suspect a glioblastoma, the most common of the primary brain tumours. These are tumours that initiate in the brain, that have not metastasized there from elsewhere in the body. Unlike other types of cancers, the risk factors for these types of tumours are unknown.

The tumour is located at the junction of the parietal, occipital, and temporal lobes of the right-hand side of the brain. That it is in the right hemisphere of the brain is good news for the patient. He is right-handed which means his speech functions are controlled by the dominant left hemisphere and won’t be affected by the surgery. Also, the tumour is close to the surface of the brain, which makes access a little easier. It is also close to one of the most important veins in the brain, which the surgeons must be very careful not to damage.

The MRI scans provide a map of the brain, allowing the surgeon to plot a trajectory through the brain to the tumour. But they do not tell the whole story. The surgeons also need the bone data, that is, the exact positioning of the skull over the brain so they know the best way to enter. They get this information through a probe attached to a machine known as a neuronavigation system. They run the probe over the patient’s head and it sends information about the skull to the neuronav, which then matches it with the MRI images.

Despite all of this technology, there is still room for error. The brain is held in place by the skull, and once the skull has been opened, the brain can shift. And swelling, in reaction to the tumour, can put pressure on the brain and cause it to herniate through the opening, which in turn could lead to major impairments.

The surgical team is well aware of all of the potential complications and dangers of the procedure they are about to perform, but they look relaxed. For them, this is just part of the job.

*

Once the patient is asleep he has to be properly positioned on the operating table. This involves not only positioning the head to give the surgeons access to the tumour site, but also making sure that the patient will not suffer bed sores or injury from being in an awkward position. This kind of surgery usually takes from four to six hours but if there is major bleeding or any other complications during the procedure, it can take up to twelve.

The surgical team then gets to work. The patient is draped in surgical sheets until the only part of him showing is the piece of his head where the surgeon will enter the brain. The patient’s head is shaved very carefully just around where the incision will go. It has been shown that shaving a greater area increases risk of infection.

Opening the skull takes time. Although there are automatic instruments available, Del Maestro prefers to do things by hand. “I do many operations on patients who are awake,” he says. “Automatic instruments really shake the skull.” First, he drills holes into the skull with a hand-operated drill. Once the holes are drilled, a Gigli saw—a long wire with a blade and two handles—is used to cut through the skull between the holes. The section of skull is then removed while the rest of the operation is performed.

It takes over an hour to get through the skull and the dura, the layer that lies between the brain and the skull, and expose the tumour. It will take hours more to remove the tumour. The surgeons look through a microscope as they work, so they can better see what they are doing. Del Maestro and Perin take turns sitting on a stool as they aspirate, suction, and mop up the blood with surgical patties, swabs designed to absorb fluids and protect the surrounding normal brain tissue. At the end of the day, a nurse will count all of the used patties removed from the patient to make sure that nothing has been left inside.

During the operation, a sample of the tumour is sent to the pathology lab to confirm the diagnosis. Dr Perin takes the residents to see the pathologist while Del Maestro stays behind and continues the surgery. The diagnosis is confirmed as a very malignant glioblastoma multiforme.

It’s going on 4:30 pm by the time the surgical team is ready to close the surgery and replace the skull flap, approximately another hour and a half of work. For many in the OR, this will mean a 12-hour workday, having started their shifts at the hospital at six that morning. Del Maestro has not left the room during the whole procedure. Not to pee, not to eat. “You get used to it,” he says. This is a discipline that requires physical stamina. (According to a resident, at a similar surgery the previous week the entire surgical team had been on call the night before, which meant they hadn’t had much sleep.)

The surgery has gone well. If everything goes smoothly with recovery, the patient will go home within three days. This does not mean the end of his medical treatment. He will most likely undergo chemotherapy and radiation following his recovery from surgery.

As for the surgical team, in a couple of days they will start all over again: another patient, another operation.

posted by Maria Schamis Turner @ 8:40 AM   0 Comments