In previous work, researchers in the Center for Brain Circuit Therapeutics located brain networks via which they could treat depression and addiction with TMS. TMS is a technique that uses magnetic fields to stimulate nerve cells in the brain. In the current study, the researchers aimed to identify a target network for PTSD too.
To do so, they examined 193 patients who had sustained penetrating traumatic brain injuries from the Vietnam Head Injury Study. While some veterans with head injuries involving shrapnel went on to develop PTSD within 20 years of the war, many did not. Of particular note, fewer patients with shrapnel-related head injuries developed PTSD than veterans without brain damage.
To understand why this may be, the researchers examined each patient's brain circuitry data, which included mapping of the exact location and neurological effects of damage. In doing so, they deduced that a circuit likely exist that protects against PTSD when damaged.
To test this hypothesis, the researchers mapped where the brain damage occurred and where each lesion connected. They then compared the data to 180 veterans without brain damage, some of whom had PTSD and some not. Ultimately, they found that circuit connectivity correlated with the incidence of PTSD.
Next, the researchers investigated whether this circuit could be a good treatment target. After examining previous trials using TMS for PTSD, they found that stimulating the identified circuit tended to yield positive outcomes for PTSD.
During the study, a patient with severe PTSD requested TMS treatment. After a careful process of informed consent, clinicians targeted the circuit found in the study to treat the patient, which ultimately improved his symptoms.
Limitations to the research include the fact that the treatment was only tested on one patient. This means that it remains unknown how the findings may translate to others in a clinical setting. To gain FDA approval, the researchers will need to conduct a randomized controlled trial targeting the circuit.
"While more work remains to be done, we've taken an important step here to identify a therapeutic target for a condition in patients who desperately need better treatments," said co-author of the study, Michael Fox, MD, PhD, Associate Professor of Neurology at Harvard Medical School, in a press release.
Sources: Science Daily, Nature Neuroscience