DBS Full Storyboard. Slide 1 .
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Welcome to the Deep Brain Stimulation clinic! My name is Dr. Rita Smith. I understand that you are an up and coming medical student looking to become a neuroscientist! Well, you came to the right place. Today, I will be teaching you the basics behind a surgical procedure called Deep Brain Stimulation. Once you have mastered the information, you will assist me in performing surgery on a patient. Let’s get started!
The patient coming in today is named James Johnson. He suffers from a neurological disorder known as essential tremor that results in his hands shaking against his will. James works as a weather forecaster with a major news television station. James’ hand tremoring has gotten so bad that he is close to losing his job as people focus more on his uncontrollable hand shaking than the news. Let’s go meet James and do some preliminary testing.
Hello James, I am Dr. Rita Smith. I will be the primary surgeon working with you. The student I have with me will be helping me with the surgery after extensive training. Could you draw a circle on this paper to demonstrate the severity of your essential tremor? After the deep brain stimulation surgery, we will have you sign your name again for comparison purposes.
As you can see, James’ hand tremor is so bad that he can barely draw a circle! Thank you James’, see you at the surgery! Alright, let’s head to the lecture room to review essential tremor.
“Let’s go over some basics. James’ suffers from essential tremor. In effect, there a series of neurons in his brain that are haywire. To review neurons, read through this module: http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php?modGUI=232&compGUI=1826&itemGUI=3155
(If you think this is possible, David, we could insert the whole Mind Ilstu Neuron page into this module just to make the students go through it fully)
“A neuron (nerve cell) is the basic unit of the brain and spinal cord. Neurons are responsible for your senses of sight, smell, taste, hearing, and touch. Neurons are responsible for making you happy when you ace a test, sad when you leave those you love, and excited before a basketball game! However, damage to neurons results in a whole variety of disorders that relate to movement, the senses, and emotional distress. Defective neurons lead to mental disorders like obsessive compulsive disorder, depression, or schizophrenia. Defective neurons can also lead to motor disorders like James’ essential tremor.”
Great, now that you are familiar with neurons and how they interact in the brain, let’s return to James’ case. Essential tremor has been linked to the loss of neurons in a region of the brain called the Cerebellum. These neurons are specifically known as Purkinje cells.
In addition to loss of cells in the cerebellum, build up of protein within neurons located inside the pons has also been associated with causing essential tremor.
These disrupted neurons are unable to effectively communicate with neighboring neurons. Thus, electrical communication is broken down in essential parts of the brain responsible for normal function. In this sense, signals sent from the brain to muscles throughout the body act unusually.
Essential tremor is normally treated with medication in an attempt to restore lost communication between neurons. When essential tremor stops responding to medication, patients often begin seeking more serious measures to deal with their essential tremor. One of the newer techniques used to treat essential tremor is known as deep brain stimulation.
Deep brain stimulation, or DBS, is a surgical procedure where a device capable of electrical stimulation is lowered into the brain. This device, known as an electrode, is turned on by a battery pack that is inserted into the patients chest. When the electrode is turned on, it sends electrical pulses through the brain that ideally restore broken down electrical communication between neurons.
The electrode may be lowered into different parts of the brain to treat different diseases and disorders. Many neurologically based disorders stem from abnormal electrical activity. Therefore, electrical stimulation of different parts of the brain can lead to treatment of a variety of disorders including Parkinson’s disease, Tourette’s syndrome, Obsessive compulsive disorder, and even obesity.
Despite the enormous benefit of DBS, much of its mechanism remains unknown. In fact, when the electrode is merely lowered into the patient’s brain without electrical stimulation, the patient’s tremoring may stop. This phenomenon is known as the Honeymoon effect and suggests that deep brain stimulation has many different effects on the human brain. Therefore, it is essential that more research is done on deep brain stimulation to fully understand how it works.
Before we perform deep brain stimulation surgery on James, I want to take you through a surgery performed on a patient at the Mayo Clinic. You will be watching a series of videos of an actual DBS surgery performed by Dr. Kendall Lee on a patient with essential tremor. Let’s start off with the introduction.
In this video, a patient is questioned about how and why he chose deep brain stimulation for treatment of his essential tremor.
The patient first experienced essential tremor as a teenager when he was trying to solder wires in a stereo. The patient mentions how hard it is to go through life with essential tremor. For example, he cannot shave well or type on a keyboard.
In this video, you will see the mounting of a head frame. The purpose of the head frame provides a coordinate system that will be used when looking at MRI images taken of his brain.
You will see the patient have local anesthesia injections to the skin on his head so that the head frame can be properly mounted.
At the end of the video, you will see a localizer box put over the head frame.
This next video shows the MRI images taken of the patients brain. As you will see, the localizer box that was attached via the head frame provides coordinates that aids the surgeon to find the tremor cells. Take a look at the image below. The dots on the side of the head arise due to the localizer box.
You will also hear Dr. Kendall Lee point out the location of the tremor cells in the MRI images.
These images provide Dr. Kendall Lee with a great idea of where the target tremor cells are for electrical stimulation. Equally important, Dr. Lee mentions that the MRI provides an idea to where blood vessels are located. Note the white dots scattered throughout this image. These are each blood vessels. If a blood vessel is hit during surgery, the patient may have a stroke and die.
The next video demonstrates how the MRI images taken of the patient’s brain are used to plan out the surgery. They make it possible to know exactly where the tremor cells are in the brain. In this surgery the target area for stimulation with the DBS electrode is the VIM thalamus.
As you head from Dr. Lee, there are many different variables involved in mapping the exact trajectory of the electrode. These variables take into account blood vessel avoidance and location of the tremor cells. Once this trajectory is mapped out, the electrode will be positioned in such a way that the electrode perfectly reaches its target, in this case, the VIM thalamus.
Pay close attention to this video. Since the electrode will be lowered over the top of the head, a pathway must be planned so that the electrode reaches its destination without damage to the brain.
Dr. Lee highlights some of the blood vessels and adjusts the electrode, represented by the red line, so that the electrode misses all of them but still reaches tremor cells in the VIM thalamus.
As Dr. Lee mentioned, the most important part of the surgery lies in the mapping of the electrodes trajectory. The number one priority of surgery is to avoid hitting a blood vessel with the electrode that could result in death of the patient.
This next video introduces some of the instruments used in the DBS surgery.
Dr. Kendall Lee starts by showing the X-Ray tube that allows images to be viewed of the brain while the DBS electrode is lowered into the brain. This is important just to make sure that the electrode is being lowered at the right trajectory.
Also, take note of the electrophysilogy rig described by Dr. Lee. After you watch the video, I will talk more about its purpose.
The purpose of the electrophysiology rig is of upmost importance. Since region of the brain being sought is small, it is hard to know when it has been reached by the electrode. Although preliminary mapping was done using MRI images, it is hard to locate the exact location of the neurons. Thus, the electrophysiology rig is used. As the electrode is slowly lowered into the brain, the tip of the electrode records neuron activity. Once the electrode reaches the tremor cells in the VIM thalamus, the monitor on the electrophysiology rig will show haywire cell firing, indicating that the electrode is located exactly at the tremor cells.
The patient is now submitted to a tremor test. This is similar to the tremor test we performed on James earlier. At the end of the surgery, Dr. Kendall Lee will ask the patient to once again do the tremor test to the effectiveness of the DBS surgery.
Dr. Lee will nowshave the patient’s head and have the area scrubbed to ensure sterilization/ This is a critical part to any surgery as it reduces chances for bacterial infection.
Dr. Lee prepares the drill. The patient is covered with a tarp with only his head exposed. Dr. Lee will determine the perfect angle for implanting the electrode relying on the trajectory plan mapped-out earlier. It is imperative that all the angles are exactly right to make sure a blood vessel is not hit when the electrode is lowered.
Next Dr. Lee makes an incision where the electrode is to be lowered and drills a hole into the skull. During this procedure, the patient is awake with only local anesthesia in the area where the hole is drilled. Once again, Dr. Lee double checks the angles throughout the drilling process.
Dr. Lee uses a tool to break through the dura mater over the drilled hole. The dura mater is a tough membrane right beneath the skull and covering the brain. This must be broken or else it will deflect the electrode.
The electrode is lowered into the brain. The patient is awake throughout this process because Dr. Lee will at times ask the patient questions. There are no pain receptors in the human brain, so this will cause no discomfort.
The electrode that will be lowered first into the brain is used to locate the tremor cells. It is imperative to find the exact location of the tremor cells to a degree that cannot be accomplished merely through MRI imaging. This is done by lowering a test electrode into the brain that records neuron firing. The test electrode is not capable of electrical stimulation, but can measure electrical signals in the brain. As the electrode is lowered past normal cells and then to the tremor cells, the electrophysiology rig will show abnormal peaks indicating that the tremor cells have been found.
Dr. Lee also has the patient do tremor tests throughout the lowering of the test electrode. Dr Lee will mention a phenomenon known as the microthalotomy effect where just the placing of the electrode, without electrical stimulation, into the malfunctioning brain area will lead to reduced tremor.
Dr. Lee first remove the testing microelectrode from the patients brain. Then, Dr. Lee will put in the DBS electrode capable of electrically stimulating the tremor cells.
Note that Dr. Lee will mention that as the DBS electrode is lowered into the brain, the patient may feel numbness at the corner of his mouth. This is a good sign because it means that the DBS electrode is hitting the right place.
Throughout the lowering of the DBS electrode, Dr. Lee will have the patient do tremor tests on pen and paper. Pay close attention to these tests.
In the last video, you saw Dr. Lee implant the DBS electrodes so that they can directly stimulate the tremor cells. In this next clip, you will see surgeons implanting the battery pack under the patient's chest. This battery back will connect to the DBS electrodes via wires under the skin, and will provide the voltage needed to electrically stimulate the tremor cells.
You will see Dr. Lee create a tunnel under the patients skin so that the battery can connect to the DBS electrodes under the skin.
This clip may bother you if you are sensitive to small amounts of blood.
Two videos ago, you heard Dr. Lee mention that the patient's tremor went down when the DBS electrode was merely lowered into the brain. This phenomenon, known as the microthalotomy effect, is only apparent for a short while. If the tremor comes back in a few days, then Dr. Lee will begin programming the DBS electrode to stimulate the tremor cells in the patients day.
To wrap up the surgery, Dr. Lee discusses the future of DBS. Dr. Lee will mention various disorders capable of being treated by DBS. Electrical stimulation of completely different parts of the brain can yield different benefits.
Dr. Lee will will discuss how DBS can be used to control brain communication in a very detailed manner. Dr. Lee will mention how DBS, a form a neuromodulation, can be used to treat a whole variety of disorders and diseases.
Let's review quickly. First, the stereotaxic head frame was put onto the patient's head. Local anesthesia was injected where the screws secure the head frame to his skull. Then, a localizer box was put on the head frame that served a role in mapping out a coordinate system which could easily locate different areas of the brain. The patient's brain had MRI images taken of it to locate the blood vessels and also to plan a trajectory that the electrode will be lowered.
Next, the information gathered from the MRI was put into a computer system to find at what angles the electrode should be lowered at to avoid hitting any blood vessels that could cause a stroke and also reach the desired tremor cells.
Once the trajectory was found, the skull was shaved and sterilized, a hole was drilled into the skull at which the electrode was to be lowered. A testing electrode was slowly lowered into the brain that could measure electrical signals of the cells. Once the testing electrode was lowered far enough, it began showing abnormal cell firing on a monitor which indicated that the electrode had reached the desired tremor cells responsible for the patient's essential tremor. Then, the testing electrode was replaced with a DBS electrode capable of electrically stimulating the tremor cells.
Finally, a battery pack was implanted in the patients chest and the lead from the DBS electrodes were connected to the battery pack underneath the skin.
Let's get back to our patient, James Johnson, who also suffers from essential tremor.
We will head down to the surgery room where he is waiting and get started right away his surgery. The trajectory at which the electrode will be lowered has already been determined by our computer system. Your role today will be in assisting me with prepping the skull for drilling, drilling the hole into the skull, and then lowering the electrode.
Are you ready? Follow me.