The widely-reported story of a man who emerged from a minimally conscious state following surgery to implant a “brain pacemaker”1 has led to the mistaken belief that such devices are of recent origin. This is certainly not the case in that implantable brain stimulation devices have been approved for use in the management of Parkinson’s disease for many years and are currently being investigated in the management of conditions ranging from severe depression to Tourette syndrome.
What is a “brain pacemaker?”
The term “brain pacemaker” is a creation of the news media and was used to call attention to the similarities between the device and the much more common cardiac (heart) pacemaker. The term used in the medical literature is “deep brain stimulation” (DBS).
In neurology, the practice of applying short bursts of electric current to specific areas of the brain is known as “deep brain stimulation.” In general terms this involves the implantation of one or more very thin electrodes into a previously-identified area of the brain while the patient remains awake, but sedated (see Image 1). Once this has been accomplished, the electrode is then attached to an implantable battery pack and the output of the battery pack is tested until the desired effect on the patient’s is obtained.
It must be noted that 1) the maximum effect of DBS is usually not immediate but occurs over a course lasting from a few weeks to even months and 2) that, at this time, the combination of DBS and pharmacologic therapy seems to be superior to DBS alone. These findings seem to hold true regardless of the medical condition present.
Parkinson’s disease and other movement disorders
Deep brain stimulation has been approved for management the management of Parkinson’s disease symptoms (such as trembling, stiffness, and gait disturbances) since 2002. There are now over 40,000 Parkinson’s disease patients worldwide that have undergone the DBS procedure.2
According to information provided by the Parkinson’s disease Foundation3 many patients report that they are 50% improved when compared to their pre-surgical status, even after 5 years.
Although there are fewer cases reported in which DBS has been used to treat non-Parkinson movement disorders the current view is that DBS, again combined with medication, holds the promise of improvement in selected cases.
Epilepsy
There have several reports, involving small numbers of patients, which indicate that DBS in conjunction with medical therapy may be of value in the treatment of epilepsy that is otherwise resistant to medical therapy.
On July 19, 2007 Medtronic announced4 that the initial phase of the SANTE (Stimulation of the Anterior Nucleus of the Thalamus in Epilepsy) clinical trial had concluded. In this study 110 epilepsy patients have had a DBS device implanted and will now be monitored for 13 months for signs of clinical improvement in the number and severity of seizures, complications of surgery, and other factors.
The findings of the SANTE study are expected to be reported by year’s end, 2008.
Tourette syndrome
Despite sensational news reports to the contrary, the use of DBS in Tourette syndrome has been limited to only a handful of patients. The Tourette Syndrome Association, and most physicians involved in the management of Tourette syndrome, stress that DBS is at best an experimental procedure and that much more research in this area is required before DBS can be considered as a treatment option.
Depression
Deep Brain Stimulation has been infrequently employed in the management of severe depression that has not responded to intensive medical therapy. As of this writing there have been too few studies published to allow the medical community to draw any conclusions regarding the clinical utility of DBS in the treatment of depression.
In summary, the clinical utility of Deep Brain Stimulation in most diseases is still under active investigation and, with the exception of Parkinson’s disease, must remain within the realm of experimental therapies.
Notes and References
1. Schiff, ND; Giancino, JT; Kalmar, K and Victor, JD et al (2007): Behavioural improvements with thalamic stimulation after severe traumatic brain injury, Nature 448, 600-603.
2. Unless otherwise noted, the number of patients treated by deep brain stimulation is taken from the Medtronics.com web pages. This is because Medtronics is the world leader in implantable neurological stimulation devices and also provides medical devices that are used in many investigational applications of DBS.
3. Ford, Blair (2005): Deep Brain Stimulation for Parkinson’s disease, New York: Parkinson’s disease Foundation, pp 20-23.
4. See “Medtronic Completes Implants in SANTE Trial of Deep Brain Stimulation for Epilepsy” at http://wwwp.medtronic.com/Newsroom/
5. See http://www.tsa-usa.org/Medical/images/Askthe/AsktheExpertmdSummer2004b.pdf
