Psychological depression is more than an emotional state. Good evidence for that comes from emerging new uses for a technology already widely prescribed for Parkinson’s patients. The more neurologists and surgeons learn about the aptly named deep brain stimulation, the more they are convinced that the currents from the technology’s implanted electrodes can literally reboot brain circuits involved with the mood disorder. Thomas Schlaepfer, a psychiatrist from the University of Bonn Hospital and a leading expert in researching deep brain stimulation, describes in the interview that follows the workings of the technique and why it may help the severely depressed.
Can you explain what deep brain stimulation is and what it is currently used for?
Deep brain stimulation refers to the implantation of very small electrodes in both hemispheres of the brain, which are connected to a neurostimulator, usually placed under the skin on the right chest. This device is in size and function very similar to a heart pacemaker. It allows stimulations of different pulse width and frequency. Depending on the chosen stimulation parameters the electrodes in the brain are able to “neuromodulate” –to reversibly alter the function – of the surrounding brain tissue. Deep brain stimulation has gained widespread acceptance as a successful treatment for tremor associated with Parkinson’s disease. More than 80,000 patients worldwide have been treated with this method. Some see deep brain stimulation as a much less invasive and fully reversibly alternative to historical neurosurgical interventions, which require tiny amounts of brain tissue to be destroyed in order to have clinical effects.
2. Are there other possible uses for the technology?
Further neurological indications that are either already clinically used or under research are essential tremor, primary dystonia, treatment resistant cluster headache and certain other pain syndromes. Deep brain stimulation has only recently, in the last decade, been actively researched as a putative treatment for very treatment resistant psychiatric disorders. Since 1999, data on DBS treatment in patients with refractory obsessive- compulsive disorder have been published as small case series or case reports. Five research groups from Europe and the United States reported individual case studies on OCD. Overall there seems to be a very positive efficacy signal in this patient group. In the same time frame three groups started to actively look at the efficacy of deep brain stimulation in three different targets—the subcallosal cingulate cortex, the anterior limb of the capsula interna and the nucleus accumbens—have been published. Interestingly the overall response rate of 50 to 60 percent (response is defined as a decrease of at least 50 percent in from the baseline depression score) has been reported, a surprisingly high rate given the extreme treatment resistance of these patients, who underwent up to 60 courses of psychotherapy, electroconvulsive therapy and psychopharmacology.