Deep brain stimulation (DBS) used to be the stuff of science fiction. Today, programmable electrodes permanently implanted in a specific area of the brain are used as a treatment for severe Parkinson's disease and have also been used as an experimental treatment for major depression and other psychological disorders.
But, in true science fiction fashion, scientists didn't fully understand how these treatments worked, until now.
Dutch researchers investigating the use of DBS as a treatment for obsessive-compulsive disorder (OCD) have found that the electrodes reduce brain activity in the region where they are implanted, as well as in other brain regions connected to this area.
What the Dutch study's results suggest is that OCD is the result of overactive neural circuitry, rather than a problem of anxious thoughts. DBS helps calm the overactive circuits.
OCD is a mental disorder in which a person has unwanted and intrusive thoughts (obsessions) that often motivate actions (compulsions) designed to alleviate the obsessive thoughts.
Handwashing and compulsive checking are common expressions of OCD. For example, a person with OCD might be plagued by the thought that he has left a door unlocked and then need to continually go back to check that the door is locked. People without OCD might do this once and then move on other things. People with OCD become caught up in a cycle where their obsessive thoughts keep telling them they must check over and over that the door actually is locked.
Obsessions and compulsions have been viewed as expressions of anxiety and OCD is categorized as an anxiety disorder in the diagnostic manual used by mental health professionals. What the Dutch study's results suggest is that OCD is the result of overactive neural circuitry, rather than anxiety. DBS helps calm the overactive circuits.
In the study, 16 patients with OCD and 13 control patients without it had electrodes implanted in the nucleus accumbens region of the brain. Researchers used functional MRI and EEG scans to look at the brain activity of the two groups. Without DBS, the brain activity around the nucleus of OCD patients differed greatly from those in the control groups without OCD.
DBS is not a simple procedure. It involves both brain surgery to implant the electrodes and chest surgery to implant a battery operated pulse generator which controls the current flowing through the electrodes, similar to the way a pacemaker operates in the heart. The batteries generally need to be replaced every 3-5 years, which means more surgery.
Even for Parkinson's disease, DBS is generally only used as a last resort, when medications have proven ineffective. For OCD, only patients without other psychiatric disorders and who have failed multiple medications, as well as cognitive behavioral therapy can qualify for DBS treatment.
DBS is not a cure, for Parkinson's or for OCD, but it can help people whose symptoms have not yielded to other treatments, possibly enabling them to live a relatively normal life. As more is learned about how DBS works, it may become useful for a broader group of people.
The study is published online in Nature Neuroscience