Clinical relevance of blast-related traumatic brain injury.

The global war against terrorism has created new challenges for neurosurgeons, craniofacial surgeons and maxillofacial surgeons; United States military operations in Iraq and Afghanistan have resulted in the greatest incidence of head trauma since the Vietnam conflict. The more frequent use of improvised explosive devices (IED), in conjunction with increased survival from improved body armor and battlefield medicine, has contributed to the increasing number of craniomaxillofacial injuries and consequent head trauma [28]. IEDs usually contain an explosive that, during detonation, is converted into a gas that rapidly expands and forms a high-pressure wave [4]. This blast overpressure wave travels at supersonic speeds and causes primary blast injury. The subsequent blast wind that follows the initial blast wave can propel objects, leading to further harm [7, 29]. The effect of a primary blast wave on the brain remains poorly understood despite the various models and computer simulations used to predict different mechanisms of injury [5, 27]. Because 59% of the service members in Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) suffered from TBI [21], a better understanding of mechanisms underlying primary blast injury and the establishment of guidelines of care are warranted. Persistent and debilitating symptoms are often associated with mild traumatic brain injury [24], underscoring the need for improved diagnostic and therapeutic modalities. Diffuse axonal injury (DAI) is widely hypothesized to be a principle mechanism of damage and the cause of persistent cognitive defects after traumatic brain injury (TBI). Angular forces can cause shearing or stretching of axons, leading to impaired axonal transport and swelling [9]. However, further elucidation of the pathological mechanism behind blast injury and determining the ideal diagnostic method to identify this condition may help lead to greater protection for military personnel and treatments for those already suffering from this disease. The majority (85%) of reported TBI cases are undetectable with imaging (computed tomography (CT) and magnetic resonance imaging (MRI) are usually insensitive to its characteristic small lesions [1, 13]) and are classified as mild [2, 25] based on the Department of Defense (DoD) screening criteria. The DoD defines mild TBI as loss of consciousness, amnesia, mental status alteration at time of injury, and/or focal neurological deficit or peri-injury confusion/disorientation in a patient with a Glasgow Coma Scale (GCS) score of 13–15 [18]. Once diagnosed, mild TBI is a treatable disease typically associated with a very favorable prognosis [15]. As a result, the recently published results by Mac Donald and colleagues have created a sense of cautious optimism regarding the use of diffusion tensor imaging (DTI) in detecting structural brain damage in blast-exposed patients suffering from mild TBI. In their study, Mac Donald et al. enrolled 63 patients, ages 19–58, from a screened population of 122 service members. The primary goal was to establish whether or not traumatic axonal injury is a primary feature of human blastG. Appelboom : J. Han : S. Bruce : E. S. Connolly Jr. Department of Neurological Surgery, The Neurological Institute, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA