disabling tremor. In order to locate the target, the neurosurgeon applied low frequency stimulation to the planned target as well as surrounding structures and observed the patient’s symptoms while the patient was awake. Dr. Benabid noticed that the patient’s tremor would often respond positively to this stimulation prior to the lesion even being made. He postulated that the application of stimulation may alleviate symptoms without requiring the destruction of tissue. DBS for movement disorders was born. Word of this procedure reached Dr. Kim Burchiel, who traveled to Grenoble in 1989 to observe DBS for himself. Dr. Burchiel was amazed by the results, and in 1991 performed the first DBS surgery in the United States, at Oregon Health & Science University. He has performed the procedure ever since, with 2016 marking the 25th anniversary of DBS in the U.S. DBS can be life-changing, but the procedure is not as widely applied as it could be, and for several reasons. One hurdle is the procedure itself. Most neurosurgeons continue to perform DBS while the patient is awake. In 2010, Dr. Burchiel began using intraoperative computed tomography imaging to identify the target, thus allowing the patient to be under general anesthesia for the procedure. Target identification via intraoperative imaging was a huge step forward in terms of surgical precision, minimizing risks and patient comfort. Equally important to the procedure is the management of the post-DBS patient. This involves programming the neurostimulator, which is analogous to finding the right dose. The DBS electrode is placed in a specific nucleus in the brain: for Parkinson’s disease this can be either the globus pallidus pars interna (GPi) or the subthalamic nucleus (STN). For Essential Tremor, the target is the ventral intermedius nucleus of the thalamus (VIM). Within the specific nucleus, the programmer can activate electrodes in certain patterns with varying degrees of charge density in an attempt to best alleviate symptoms, without inducing side effects. The job of the programmer PHYSICIAN ASSISTANTS is equal parts science and art. It requires both understanding the neuroanatomy of the target and the adjacent structures, and finely tuned physical exam skills. Both are necessary to understand how the stimulation affects the patient’s body. DBS does not cure or slow down the disease process, whether it is Parkinson’s disease, Essential Tremor, or any other known disease. Nevertheless, DBS is a powerful tool for improving some of the more troublesome motor symptoms, and this can have a huge impact on a patient’s quality of life and sense of self. There is nothing more rewarding than turning on the neurostimulator to see a patient who has experienced tremor, stiffness or abnormal extra movements suddenly experience something quite different: a sense of calm. w ww.theOMA.org Spring 2016 23
OMA Medicine in OR Spring 2016
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