Deep brain stimulation: challenges to integrating stimulation technology with human neurobiology, neuroplasticity, and neural repair.

By the year 2040, neurodegenerative diseases , such as Alzheimer's disease, Parkinson's disease, ALS (Amyotrophic Lateral Sclerosis), and similar disorders, will overtake cancer as the second most common cause of death (1). What this means, from a practical standpoint, is that one in three of us will get a neurodegenerative disease. And if that's not bad enough, the other two of you will be paying for that individual's treatment. So it's important to pay some attention to this area. Of course, the incidences of these sorts of diseases also increase as the population ages. We are going to be facing an epidemic of neurodegenerative disease in the near future. The good news is that we have 30 or 40 years of warning. So it's time to start seriously thinking about this topic. Let us now turn specifically to Parkinson's disease. Neurosurgeons have been interested in treating Parkinson's disease for some time (2). In fact, before the advent of drugs, neurosurgery was the mainstay of therapy. If you had Parkinson's disease in the 1940s and '50s, you were treated by a neurosurgeon, not by a neu-rologist. And if one looks at the number of papers published on surgery for Parkinson's disease across time and specifically for pallidal surgery, one sees that in the 1950s, there were quite a number of papers. Then in 1960s, lev-odopa was introduced and we entered the " ice age " of functional neurosurgery. With the introduction of levodopa and the realization of its striking clinical benefits, neurosurgical interventions all but disappeared for 30 years. Only now are we seeing a renaissance of neurosurgical procedures for the treatment of Parkinson's disease that began in the late 1990s (3,4). The first of several reasons for this is that for many patients, the drugs are simply not doing the job. Existing pharmacological interventions have shortcomings that have taken some time to become apparent. Although patients initially respond to the drugs such as levodopa, with time and chronic use, they are less effective and complications of their use arise. This means that patients continue to be disabled despite the best available pharmacological therapies. Second, there have been very important advances in technology. We can now operate better, and we have more effective operative procedures to offer our patients. But the third and perhaps the most important reason is that we now have a very strong scientific rationale for tackling different …