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Research testimonial from Dr. Jennifer Andrews

A Knee Jerk Response: Improving deep brain simulation surgery for Parkinson’s disease by measuring spinal reflexes

Deep Brain Stimulation (DBS) involves the electrical stimulation of the brain through surgically implanted electrodes. It is a very effective treatment for people with Parkinson’s Disease (PD) and can improve both motor function and quality of life compared to medication alone in properly selected patients. Placing the small DBS electrodes into precise targets in the brain requires a lengthy neurosurgical procedure, often with an awake patient! Getting the electrodes to precisely the right “sweet spot” deep in the brain continues to be a challenge, and on occasion, electrodes may be misplaced. Locating the sweet spot often requires trial-and-error and it can be exhausting for a patient to remain awake throughout a long surgery.Developing an objective way to identify the best location for the DBS electrodes in each patient could avoid electrode misplacement, shorten the DBS implantation procedure, and improve outcomes for people with PD.

Researchers from the University of Alberta have taken a new approach to solving this problem. The approach is based on work first started in the lab of renowned neuroscientist, the late Dr. Richard Stein. Under the guidance of Dr. Stein and clinical neurophysiologist Dr. François Roy, then PhD student Jennifer Andrews examined a number of different spinal reflexes in people with PD. Of particular interest was the Hoffmann reflex (H-reflex), a reflex induced by painless electrical stimulation of a nerve behind the knee. The H-reflex is similar to the knee jerk reflex, in which the doctor taps the tendon just below the knee and observes a characteristic kicking motion of the lower leg. The team found that the H-reflex is altered in people with PD and appeared to return to normal when DBS is turned on and a patient’s motor function is improved.  The team was then joined by University of Alberta neurosurgeon, Dr. Tejas Sankar–who performs all DBS implantation surgery in Edmonton–and Dr. Fang Ba, a neurologist who follows most PD patients in Edmonton who undergo DBS. Together, they carried out a study to see if changes to the H-reflex measured during DBS surgery could be used to determine the sweet spot in the brain where the final DBS electrode should be placed. Indeed, they recently found that the H-reflex returns closest to normal at the exact site in the brain where–when stimulation is applied–the patient shows the most improvement of their Parkinson’s symptoms on the operating table. These results were published in the journal Brain Stimulation, and the group is now studying whether the H-reflex can be used in patients undergoing DBS while fully asleep. Further to this, they are also exploring whether the H-reflex could be used to help with DBS programming after electrode implantation. Currently, DBS programming is a trial-and-error process that requires multiple visits to the neurologist’s office over many months.

Much of the work on these projects was conducted by Dr. Jennifer Andrews and would not have been possible without generous funding from the Parkinson Association of Alberta to carry out a post-doctoral fellowship in Dr. Sankar’s lab. Dr. Andrews–who is currently studying medicine at the University of Alberta–has published 4 papers (and counting!) based on this work, in journals such as Brain Stimulation, The Journal of Clinical Neurophysiology, and Experimental Brain Research. In the coming years, Dr. Andrews looks forward to a career as a physician-scientist where she hopes to continue to advance research in PD with the ultimate goal of improving patient outcomes.

Dr. Jennifer Andrews
University of Alberta
Centre for Neuroscience

Photo of Dr. Jennifer Andrews