New research has shown how a technique that measures patterns of brain activity can be used to diagnose and monitor obsessive-compulsive disorder (OCD) in people who undergo deep brain stimulation (DBS). The findings have been reported in Nature Medicine. OCD patients usually spend inordinate, disruptive amounts of time on repetitive tasks and compulsions that may seem nonsensical; or they experience pervasive, intrusive thoughts. It's thought that around two or three percent of the global population experiences OCD, which can take a major toll on quality of life and well-being.
Medications can help some OCD patients, but it's thought that around one-third of people with OCD do not experience relief from available treatments. DBS has been used since the early aughts to alter neural activity in parts of the brain that have been associated with OCD. Patients receiving DBS have often not benefited from medications. But around two-thirds of treatment-resistant OCD patients get relief from their symptoms with DBS therapy, which is an FDA-approved procedure that is also used for movement disorders such as Parkinson's disease.
"Recent advances in surgical neuromodulation have enabled long-term continuous monitoring of brain activity in OCD patients during their everyday lives," said first study author Dr. Nicole Provenza, an assistant professor at Baylor College of Medicine and McNair Scholar. "We used this novel opportunity to identify key neural signatures that can act as predictors of clinical state in twelve individuals with treatment-resistant OCD who were receiving DBS therapy."
DBS devices operate under a similar principle as pacemakers for the heart; they help control electrical activity, but in this case, in the brain. Electric leads extend out of the devices from a generator that is usually implanted in the upper chest, to bring electrical impulses to specific parts of the brain. The aim is to restore normal function to dysfunctional brain circuits. One drawback is that it can be challenging to determine the correct doses for DBS therapy recipients with OCD as opposed to those with movement disorders.
When DBS is applied to movement disorders, patients can experience relief from tremors right away, the researchers explained. But with OCD, it takes time for the treatment to work, so it's challenging to know what dose was best for a patient months after it is applied. The researchers were searching for a biomarker that could show when symptoms were relieved, or not.
One hallmark of OCD is pathological avoidance, in which people use rigid routines or behaviors to deal with perceived threats in their daily life that are hard to control. The investigators focused on that behavior, and looked at low-frequency brain oscillations in the theta (4–8 Hz) to alpha (8–12 Hz) range in OCD patients. Previous work has linked this range to human cognition.
DBS devices can stimulate the brain as well as record brain activity. The researchers wanted continuous monitoring, so the DBS system was implanted. The investigators could assess activity during symptomatic states.
The 9 Hz (theta-alpha border) ventral striatum neural activity was found to have a significant circadian rhythm that changed over 24 hours. Neural activity was predictable before DBS, then after activation, the pattern changed.
"In summary, we have identified a neurophysiological biomarker that can serve as a reliable indicator of improvements in mood and behaviors in OCD patients after DBS treatment. We anticipate these findings to transform how patients are monitored throughout DBS therapy," said senior study author Dr. Sameer Sheth, a professor and Vice Chair of Research in the Department of Neurosurgery at Baylor College of Medicine, among other appointments.
Sources: Baylor College of Medicine, Nature Medicine