Mild traumatic brain injury (mTBI), also known as a concussion, is prevalent in military personnel and has been deemed the ‘signature injury’ of the conflicts in Iraq and Afghanistan. Cognitive complaints, headaches, nausea, and dizziness, among others, are common and expected symptoms following mTBI. These symptoms resolve within 7-10 days in most individuals, though 90 days is often referenced as the duration of ‘normal’ recovery after a mild TBI. However, 15-30% of individuals do not recover along this timeline and experience persistent post-concussive symptoms.
Psychological factors have been shown to play a substantial role in the persistence of post-concussive symptoms beyond 90 days. Because post-traumatic stress disorder (PTSD) is also highly prevalent in combat Veterans and highly comorbid with mTBI in this population, it has been difficult to tease apart the etiology of persistent cognitive symptoms in the comorbid group and determine if remote history of concussion is contributing to current behavioral symptoms or if the presentation is driven by mental health factors.
Traditional structural neuroimaging techniques are largely insensitive to the subtle damage resulting from mTBI. Newer magnetic resonance imaging (MRI) acquisition methods such as Diffusion Tensor Imaging (DTI) have shown more promise in identifying changes in white matter integrity following mTBI. However, even this advanced technology produces equivocal results, and lacks the sensitivity or specificity to identify the underlying cause of any white matter changes. Therefore we will utilize a new approach for assessment specifically of myelin abnormalities, multicomponent-driven equilibrium single-pulse observation of T1 and T2 (mcDESPOT), to calculate myelin volume on Veterans with a history of mTBI, PTSD, or both.