Abstract
Over the last century the pattern of diseases and injuries among military combatants has shifted dramatically due, in large part, to advances in medical technology and disease prevention. Respiratory and infectious maladies were the top reasons for hospital admission during World Wars I and II, and the Korean War. During Operation Iraqi Freedom and Operation Enduring Freedom, musculoskeletal disorders and combat injuries have emerged as the leading causes of medical evacuation (1). Neurological disorders, including headache, rank third (1).
Existing data indicate that the impact of headache disorders on the US military is substantial. Annually, 2.5% of males and 9.5% of females in the military will have a medical encounter for headache (2). An estimated 19% of US soldiers experience migraine headaches while deployed to a combat zone, impairing their ability to perform duties and contributing to sick call visits (3). Headaches are especially common among returning soldiers who have had a deployment-related concussion, with up to 97% reporting headaches and 37% having headaches that meet criteria for chronic post-traumatic headache (4).
An observational study by Cohen et al. in this issue provides valuable new information about headaches as a cause of medical evacuation among US military personnel deployed to a combat zone. The medical records of 958 personnel who were medically evacuated for headaches from Operation Iraqi Freedom and Operation Enduring Freedom to Landstuhl Regional Medical Center in Germany between 2004 and 2009 were reviewed to determine the prevalence of various headache subtypes, demographics, treatment patterns, and return to duty rates. This is the first study specifically examining headache as a cause of medical evacuation from a war zone.
A majority of study subjects were males (87%) and members of the Army (78%), with a mean age of 29.6 years. The most common headache disorders among military medical evacuees were post-concussive headache (34%) and migraine (30%). This is not surprising given the high prevalence of migraine and concussion in military personnel involved in combat operations in Iraq and Afghanistan. The results of the study confirm migraine and post-concussive headache as causes of unit attrition in the modern era of military conflict.
The outcome of each study subject was based on their disposition from Germany, which usually occurred within 2 weeks of arrival. A positive outcome occurred if the individual returned to duty (RTD) in the combat zone. RTD is a meaningful outcome and the investigators should be commended for assessing it. Overall, 34% of those evacuated for headaches subsequently returned to duty. Nearly 40% of migraineurs returned to duty whereas only 19% of personnel with post-concussive headache returned. The authors identified multiple features associated with a lower likelihood of returning to duty to include continuous headache (as opposed to episodic), traumatic brain injury, physical trauma, and psychiatric comorbidity. The identification of prognostic factors in this study will help to inform decisions regarding medical evacuation of military service personnel with headache disorders. Moreover, the findings highlight the importance of both physical and emotional trauma as factors influencing the prognosis of headache in deployed military personnel.
Notably, the study by Cohen et al. was conducted prior to the implementation of current US military policy which mandates immediate evaluation of all US military personnel exposed to potentially concussive events. Personnel with persistent symptoms after concussion and those with three or more concussions in a 12-month period are sent to higher centers of care within the combat zone for further evaluation and treatment by multidisciplinary teams that include neurologists, neuropsychologists, behavioral health specialists, and rehabilitative specialists. Early identification and management of symptoms after concussion should improve outcomes of post-traumatic headache in theater. The data ascertained by Cohen et al. will serve as a useful baseline for measuring the effectiveness of the in-theater concussion care program with regard to headache outcomes.
Another significant observation made by Cohen and colleagues was that 34% of headache cases used opioids, which was strongly associated with a negative outcome. The reasons for the relatively high use of opioids were not reported but could potentially be related to concurrent non-headache pain conditions such as orthopedic disorders or refractoriness of headaches to other headache abortive medication classes. Unfortunately the treatments used for specific headache disorders were not reported. The frequency of headache abortive medication use was also not reported, precluding a determination of the number of cases at risk for medication overuse, a risk factor for chronic daily headache and medication overuse headache.
While this study helps to fill a major gap in our understanding of the epidemiology of headaches in the military, there are several limitations. We do not know how many personnel were treated for headaches within the combat zone during the study period. It is therefore not possible to calculate the medical evacuation rate among all headache cases treated in theater. Also, the cases included in the study can reasonably be assumed to be more complicated or more refractory compared to cases that were not medically evacuated, thereby limiting the generalizability of the findings. Another limitation is the uncertainty of the diagnostic criteria that were used to define the specified headache disorders. While a neurologist was consulted in almost all cases, it is unclear if headache classification was standardized or was conducted in accordance with the International Classification of Headache Disorders (ICHD). This is particularly important when one considers that post-concussive headaches often phenotypically resemble migraine, creating the potential for diagnostic uncertainty (4,5). Additionally, outcomes were determined after a short period, typically within 2 weeks of arriving in Germany. Determining long-term outcomes of headache in this population using validated measures of headache-related functional disability, headache impact, and quality of life are important goals of future research.
The observation by Cohen and colleagues that psychiatric comorbidities were associated with a failure to return to duty reminds us that headaches do not occur in isolation but rather in the context of other conditions and individual factors. Anxiety, depression and other psychiatric conditions occur more frequently among migraine sufferers in the general population and post-traumatic stress disorder has been associated with chronic migraine (6,7). This study reinforces the importance of identifying and addressing psychiatric conditions in all headache patients.
The fact that 40% of military personnel evacuated for migraine headaches were subsequently able to return to duty after receiving specialty care at Landstuhl predicts that optimizing migraine care within the combat theater will eliminate a substantial number of medical evacuations. A wide variety of migraine treatments are available in the combat zone, including triptans and all of the major classes of migraine prophylactic medications. The new data reported by Cohen et al. allows for a rough estimate of the evacuation rate for migraine: 318 cases of migraine were evacuated over a 5-year period involving deployment of roughly 150,000 troops per year with a 1-year migraine prevalence of 19%. Thus, perhaps only 0.2% of migraine cases actually resulted in medical evacuation, with the vast majority of cases being managed in theater.
The findings by Cohen and colleagues that post-concussive headache is the most common headache disorder resulting in medical evacuation from a combat zone and is associated with a low likelihood of returning to duty underscore the tremendous need to identify effective therapies for post-traumatic headache. There are no randomized controlled trials of treatments for post-traumatic headache in civilian or military populations. Treatments for post-traumatic headache are the same as those utilized for primary headache disorders. Although the US military has devised and implemented consensus treatment guidelines for post-traumatic headache, these have not been validated by studies in military personnel. Expanding the evidence for treatments of post-traumatic headache is a critical goal of future research and is a necessary step for optimizing headache outcomes in deployed troops.
Disclaimer
The views are those of the author and are not the official position of the United States Department of Defense or US Army.