Deep Brain Stimulation for Cervical Dystonia (Spasmodic Torticollis)
New Brain Stimulation for Dystonia
Erwin B. Montgomery Jr. MD
Professor (University) of Neurology
Adjunct Professor, Department of Biomedical Engineering
Adjunct Professor, Department of Communicative Disorders
Affiliate Scientist, National Primate Research Center
University of Wisconsin-Madison
June 27, 2007
Deep Brain Stimulation (DBS) continues to demonstrate remarkable effectiveness for relieving dystonia of all types. However, DBS is not without risk. Our research focuses on ways to make brain stimulation safer and more effective. For example, research in animals has shown us that DBS of the subthalamic nucleus (STN) and globus pallidus (GPi), parts of the brain thought to be affected in dystonia, actually directly or indirectly stimulate the motor cortex on the surface of the brain. Likewise, recordings of brain cell activity in humans with dystonia corroborate the findings in laboratory animals. Consequently, we are now offering a method to directly stimulate the motor cortex for patients with dystonia.
The new procedure is called epidural motor cortex stimulation (EMCS). Epidural means that the electrodes are placed beneath the skull but on top of the dura which is a thick tough membrane that covers and protects the brain. Because the brain is not actually penetrated with electrodes, as is the case in DBS, the risks of EMCS are much less than DBS. There is very little risk of stroke or bleeding inside the brain compared to DBS. With STN or GPi DBS, the target structures lie deep within the brain. The brain must be punctured with the electrodes in order to reach the GPi or STN. This is not the case with EMCS.
There is a chance of seizures from the EMCS that is greater than with DBS. However, seizures occurred only during programming sessions where the stimulation was turned up too high. There have not been any cases of patients continuing to have seizures after programming or when the stimulator is turned off. We are confident in our understanding of the risks of EMCS because this procedure has been used many times in patients for the treatment of pain. There have been well over two hundred patients who have received this type of brain stimulation for pain.
The numbers of patients who had EMCS for dystonia are few but the results have been very encouraging. There have been many more patients with dystonia who had GPi DBS. Consequently, for most patients, we recommend GPi DBS. This may change as we gain more experience with EMCS. However, there are some patients who may not be candidates for the more dangerous DBS surgery, for example patients that are older or who have other medical illnesses, particularly problems with thinking or memory or psychological problems. There are other patients who just would prefer the EMCS because of the lower risks despite the fact that our experience with EMCS is more limited.
The decision to undergo any treatment for any illness requires balancing the risks versus the benefits. In the case of EMCS, the risks are well understood based on the larger experience of cortical stimulation for pain, Parkinson’s disease and dystonia. However, we cannot be as confident about the benefits of EMCS, compared to GPi DBS, because only a relatively few patients have had EMCS. Every patient is different in their balancing the risks versus benefits.
Does this mean that EMCS is experimental? We do not believe that it is experimental or investigational. It is important to point out that the electrodes and impulse generators used in EMCS have been approved by the federal Food and Drug Administration (FDA) for other conditions. The electrodes, made by Medtronic Neuromodulation Inc., used in EMCS are approved for stimulating the spinal cord for patients with pain. The impulse generator, also made by Medtronic Neuromodulation Inc., is approved by the FDA for GPi DBS in patients with dystonia. We are using FDA approved devices for other purposes; what is known in medical practice as “off-label” use. Many “off-label” uses of medications and devices are considered routine standard care and insurers often cover “off-label” uses.
Unlike GPi DBS surgery, patients undergoing EMCS are asleep during the surgery. In GPi DBS surgery, the patient’s cooperation is necessary to map the precise location to place the permanent DBS lead. In addition, the patient’s head has to be held still. For some patients, this means attaching a metal halo-like device using sharp pins that pierce the skin to hold onto the skull. This is not necessary for EMCS. Prior to placement of the permanent DBS lead, a temporary microelectrode is used. This electrode has a microscopic tip that allows the physician to record electrical impulses generated by individual neurons. Each part of the brain has a unique pattern of electrical impulses. The physician uses these patterns to identify the location of the electrodes in the brain. The physician often will move the arm or leg to activate the neurons during DBS surgery. The physician often stimulates in the operating room and needs to know what the patient is experiencing. That is why patients generally need to be awake during GPi DBS.
EMCS surgery also maps the proper location for the permanent electrodes. In this case, an array of electrodes is placed over the dura that is over the area of the motor cortex. Electrical pulses are used to stimulate the nerves at the wrist and in the lips. These stimuli create a response over the motor cortex of the brain that can be recorded and analyzed. When the right patterns of electrical responses are found, the physician knows where the motor cortex is. At this point, the electrodes placed over the dura are used to electrically stimulate the motor cortex. This results in twitches in the muscles that can be observed. Fortunately, the patient does not need to be awake during the mapping. Also, the surgery is shorter in duration compared to most GPi DBS surgeries.
Before patients have EMCS, they undergo a functional MRI (fMRI) scan during which they will open and close the hand. This results in activation of the motor cortex that can be seen on the MRI. The MRI images are used in the operating room to help plan the surgical incisions. The patient usually is admitted to the hospital early on the morning of surgery after not having anything to eat or drink from the night before. The patient is taken to the operating room where the patient undergoes general anesthesia. Then an incision in made in the scalp and a window of skull bone a few inches in diameter is temporarily removed. The arrays of electrodes are placed over the dura that covers the brain, and the mapping is done as described above. Once the proper location of the permanent epidural electrodes is determined, the electrodes are sewn into position on the dura. The window of skull bone is replaced and fixed into position. The incision is closed and the patient wakes up and goes to the recovery room. Patients are typically in the hospital for three days.
After one week following the implantation of the epidural stimulating electrodes the patient returns to the operating room. Under general anesthesia an incision is made over the head behind the ear. The connector from the epidural electrodes is attached to an extension wire that is tunneled under the skin to connect to the impulse generator that is placed under the skin over the chest. The patient is typically in the hospital for less than 24 hours.
About one month after the implantation of the epidural electrodes the patient is seen in the outpatient clinic for the stimulator to be turned on and programmed. The patient may make periodic visits to the clinic for further programming until the patient’s symptoms are brought under control. The patient then makes less frequent visits to check the impulse generator battery and to make any further stimulator adjustments as needed.
The impulse generator battery may last two to four years; however, battery replacement is relatively simple. The patient undergoes general anesthesia. An incision is made over the impulse generator under the skin over the chest. The old impulse generator is removed and a new impulse generator is placed. The patient typically is in the hospital for less than 24 hours.
Together with Dr. A. Leland Albright, Professor (University) of Neurological Surgery, we are developing methods to make EMCS more effective. This research is combined with our continued efforts to better understand how the basal ganglia of the brain works normally to control movement and then what goes wrong in patients with dystonia. Already that work has demonstrated that current theories about how the basal ganglia works and what happens in disease are wrong and those entirely new approaches to research and understanding are necessary. This research is supported in part by grants from the Spasmodic Torticollis/Dystonia Association.
There have been dramatic discoveries related to dystonia with the discovery of many genes that may cause the disease. We hope that one day these discoveries will lead to prevention or, at least, a means to stop, or slow, the progression of symptoms. However, until that day arrives, there will be many patients with disabling symptoms that need more effective and safer treatments and this will take more research. Unfortunately, with the excitement of genetic discoveries and similar work on the causes of dystonia, it is possible to overlook the importance of understanding what goes wrong in the brain in patients already with advanced dystonia in order to develop new and better theories. There is the danger that these important areas of research will be underfunded.
P.S. Howard…attached is the x ray of
your brain (below). Erwin
From: howard thiel [mailto:firstname.lastname@example.org]
Sent: Tue 7/3/2007 10:17 AM
To: Montgomery (Erwin)
THIEL: Subject: Your article on the new operation. I’ve just finished reading your article you gave me the other day. Very, very interesting…and revolutionary, and I believe the people at the symposium and, later, after our October magazine, all members, will be very interested in this procedure.
I have a few questions for now, probably more, as I read it over more and more.
In the regular DBS you have mentioned you try and insert the lead into the GPi (internal) to correct the movement of the patient. Do you get at all close to the GPi with this new operation, I’ll call EMCS? In other words, are these two parts synonymous and can one be operated on without the other?
MONTGOMERY – the GPi and STN are deep in the brain and that is why the brain is punctured and that is where the risk comes from.
THIEL: I take it the halo is no longer used. I would think that that piece of information should be somehow incorporated into the piece somewhere. What do you think?
MONTGOMERY – no halo
THIEL: Is this new procedure your “development” or “invention”, for lack of a better word at this juncture?
MONTGOMERY – my contribution is the basic animal research, which your organization helped to fund in part, that demonstrated that GPi and STN probably work by activating the motor cortex thus providing an important rationale for EMCS. Also, we have an invention to make EMCS work even better.
THIEL:Are there are any renderings, drawings, etc that could show the difference in the brain as to where these two parts are – the GPi and the STN?
MONTGOMERY – I will try to dig some up or get some made
My mom and I wanted to thank you for hosting such a great symposium this year. This was our third year and we are looking forward to next years. E. Mathews