Background: Chronic headache following traumatic brain injury(TBI) sustained in military service, while common, is highly challenging to treat with existing pharmacologic and non-pharmacologic interventions, and it may be complicated by co-morbid posttraumatic stress. Recently, a novel form of brainwave-based intervention known as the Flexyx Neurotherapy System(FNS), which involves minute pulses of electromagnetic energy stimulation of brainwave activity, has been suggested as a means to address symptoms of TBI. This study reports on a clinical series of patients with chronic headache following service-connected TBI treated with FNS.Methods: Nine veterans of the wars in Afghanistan and Iraq with moderate to severe chronic headaches following service-connected TBI complicated by posttraumatic stress symptoms were treated in 20 individual FNS sessions at the Brain Wellness and Biofeedback Center of Washington(in Bethesda, Maryland, USA). They periodically completed measures including the Brief Pain Inventory-Headache(BPI-HA), previous week worst and average pain ratings, the Posttraumatic Stress Disorder Checklist-Military version(PCL-M), and an individual treatment session numerical rating scale(NRS) for the degree of cognitive dysfunction. Data analyses included beginning-to-end of treatment t-test comparisons for the BPI-HA, PCL-M, and cognitive dysfunction NRS. Results: All beginning-to-end of treatment t-test comparisons for the BPI-HA, PCL-M, and cognitive dysfunction NRS indicated statistically significant decreases. All but one participant experienced a reduction in headaches along with reductions in posttraumatic stress and perceived cognitive dysfunction, with a subset experiencing the virtual elimination of headaches. One participant obtained modest headache relief but no improvements in posttraumatic stress or cognitive dysfunction. Conclusions: FNS may be a potentially efficacious treatment for chronic posttraumatic headache sustained in military service. Further research is needed to investigate the efficacy of FNS within a randomized, controlled clinical trial to identify the characteristics of those most likely to respond and to explore underlying mechanisms that may contribute to improvements. Background: Chronic headache following traumatic brain injury (TBI) sustained in military service, while common, is highly challenging to treat with existing pharmacologic and non-pharmacologic interventions, and it may be complicated by co-morbid posttraumatic stress. of brainwave-based intervention known as the Flexyx Neurotherapy System (FNS), which involves minute pulses of electromagnetic energy stimulation of brainwave activity, has been suggested as a means to address symptoms of TBI. This study reports on a clinical series of patients with chronic headache following service-connected TBI treated with FNS. Methods: Nine veterans of the wars in Afghanistan and Iraq with moderate to severe chronic headaches following service-connected TBI complicated by posttraumatic stress symptoms were treated in 20 individual FNS sessions at the Brain Wellness and Biofeedback Center of Washington (in Bethesda, Maryland, USA). They periodically completed measures including the Brief Pain Inventory-Headache (BPI-HA), previous week worst and average pain ratings, the Posttraumatic Stress Disorder Checklist-Military version (PCL-M), and an individual treatment session numerical rating scale (NRS) for the degree of cognitive dysfunction Data Analyses included beginning-to-end of treatment t-test comparisons for the BPI-HA, PCL-M, and cognitive dysfunction NRS. Results: All beginning-to-end of treatment t-test comparisons for the BPI-HA, PCL-M, and cognitive dysfunction NRS showed statistically significant reduction. All but one participant experienced a reduction in headaches along with reductions in posttraumatic stress and perceived cognitive dysfunction, with a subset experiencing the virtual elimination of headaches. One participant obtained modest headache relief but no improvements in posttraumatic stress or cognitive dysfunction. Conclusions: FNS may be a potentially efficacious treatment for chronic posttraumatic headache sustained in military service.Further research is needed to investigate the efficacy of FNS within a randomized, controlled clinical trial to identify the characteristics of those most likely to respond and to exploring the underlying mechanisms that may contribute to improvements.