Traumatic brain injury (TBI), especially mild TBI (mTBI), has become the “signature injury” of recent warfare, including the involvement of military service personnel in the wars in Afghanistan and Iraq [1]. Among the leading factors contributing to this are various mechanisms of concussion and exposure to explosive blasts [1–3]. It has been estimated that from 30 to 90 % of individuals with TBI may develop some form of headache [4]. In one cohort of US military service members returning from Afghanistan or Iraq, 19.6 % met criteria for a deployment-related concussion; among those, 97.8 % reported having headaches during the final 3 months of deployment; and more than 1 in 3 met criteria for posttraumatic headache, that is headache with onset within 7 days after head trauma (or regaining consciousness following head trauma) [5]. Such headaches have been associated with greater frequency of headache attacks and increased prevalence of chronic daily headache [5, 6]. Some evidence suggests mTBI may result in more severe headache patterns relative to more severe cases of TBI, but this remains controversial [7, 8]. In any event, chronic daily headache is a persistent and potentially debilitating sequela of military service related TBI.

Many returning service personnel also experience posttraumatic stress disorder (PTSD) [9]. Although not included in the diagnostic criteria for PTSD, individuals with PTSD are at increased risk for experiencing chronic headaches [1, 10]. Further, symptoms of TBI and PTSD often overlap and/or co-occur in the same individual [11, 12]. There is some evidence suggesting the combination of the two may be associated with overall more severe symptom presentations across shared symptom domains [10, 13]. There is also evidence to suggest TBI and PTSD may share some underlying mechanisms [10, 11]. Furthermore, treatment for chronic headache is complicated by the presence of co-morbid PTSD [8, 10].

Treatment of chronic headache associated with TBI remains highly challenging. The forms of headache most typically manifesting as chronic posttraumatic headache correspond closely to symptom patterns seen in migraine and tension-type headaches [4, 7]. Treatment recommendations typically are extrapolated from the broader headache literature on these more common forms of headache [4, 7, 14]. However, despite typical pharmacologic and non-pharmacologic interventions, many individuals remain highly symptomatic and are vexing to clinicians [8]. While relaxation-based (surface electromyography or temperature/thermal) biofeedback has demonstrated some efficacy in treating the more common types of headaches in the general population, it is far from universally effective [15]. Further, variations of biofeedback incorporating electroencephalograph (EEG) information have also been suggested [16]. However, EEG biofeedback (sometimes also known as neurofeedback or neurotherapy) requires considerable time and effort on the part of both patient and clinician in order for the patient to learn voluntary control over the production or inhibition of specific EEG frequencies or frequency ranges [17].

Recently, a form of brainwave-based intervention known as the Flexyx Neurotherapy System (FNS) has been suggested for addressing mixed symptom presentations of TBI and PTSD [18]. As a novel variant of EEG biofeedback, FNS falls within the bio-energy domain of complementary and alternative medicine. Rather than requiring patients to acquire skills to change patterns of EEG activity, FNS instead involves off-setting stimulation of brainwave activity by means of an external energy source, specifically, the conduction of electromagnetic energy (EM) stimulation via the connecting EEG cables [19]. FNS has been further adapted by utilization of two-channel, versus one-channel only, EEG monitoring. The procedures also do not require active effort on the part of the patients; rather, patients remain relatively passive while their EEG activity is monitored and the information obtained interacts with parameters pre-set within the software to initiate subtle, minute pulses of EM stimulation. The present investigation focuses on a subset of service members from a larger investigation who were experiencing chronic daily headaches after sustaining service-related TBI and for whom the majority also had PTSD. These individuals were all highly symptomatic and had not benefited significantly from typical pharmacologic or psychotherapy interventions.

These findings suggest FNS may be a potentially useful and safe treatment for chronic daily headache following TBI, and that improvement in headache may also be associated in most persons with significant reductions in co-morbid posttraumatic stress symptoms and perceived cognitive dysfunction. However, contrary to the general trend, one of the nine participants in this study did not report any symptom improvement; and another did not report improvement in posttraumatic stress symptoms or cognitive dysfunction, although he did experience some reduction in headache intensity ratings down to low moderate/mild levels. Hence, it is likely that there are subgroups of patients with varying degrees of potential to respond to this intervention. Also, given the small sample size and lack of a randomized controlled clinical trial, we cannot rule out placebo responding or attention or other nonspecific effects contributing to the positive outcomes [23]. Further, the durability of effects is unknown, since we did not have extended follow-up information at this stage of the investigation. In addition, the manner in which chronic headache is influenced by or influences comorbid posttraumatic stress symptoms and features of cognitive dysfunction remains to be clarified. However, the findings provide preliminary support to justify future research within the design of a randomized, controlled clinical trial to more rigorously investigate the efficacy of FNS for treatment of posttraumatic headache and to better identify the characteristics of those most likely to respond favorably.

Chronic headache remains a challenging and often vexing problem following TBI and which, particularly in military personnel with comorbid PTSD, may result in limited response to typical pharmacologic and non-pharmacologic treatments. Neurotherapy in the form of FNS as described here may be of potential efficacy in at least a subset of persons with persistent posttraumatic headache pain. Future research is warranted to better investigate the potential of FNS for symptom relief in terms of chronic headache pain; to examine the durability of any salutary effects; to identify the characteristics of those individuals most likely to obtain positive outcomes with FNS; to better understand the interactions with posttraumatic stress or other emotional dysfunction; and to explore the mechanisms underlying improvements across the domains of headache pain, cognitive dysfunction, and posttraumatic stress symptoms.