Advances in Neuroimaging of Traumatic Brain Injury and Posttraumatic Stress Disorder

Article excerpt

Abbreviations: A[beta] = amyloid-[beta]; ACC = anterior cingulate cortex; ACR = anterior corona radiata; AD = Alzheimer disease; ADC = Apparent Diffusion Coefficient; ADNI = Alzheimer's Disease Neuroimaging Initiative; ANT = Attention Network Task; ASL = arterial spin labeling; BOLD = blood oxygen dependent level; CA = cornu ammonis; CAPS = Clinician-Administered PTSD Scale; CBF = cerebral blood flow; CBT = cognitive-behavior therapy; Cho = choline; CNS = central nervous system; Cr = creatine; CT = computed tomography; DG = dentate gyrus; D-MRI = diffusion magnetic resonance imaging; DTI = diffusion tensor imaging; EPI = echo-planar imaging; FA = fractional anisotropy; FDG = fluorodeoxyglucose; fMRI = functional magnetic resonance imaging; LDFR = long-delay free recall; mI = myo-inositol; MR = magnetic resonance; MRI = magnetic resonance imaging; MRS = magnetic resonance spectroscopy; MRSI = magnetic resonance spectroscopic imaging; NAA = N-acetylaspartate; OIF/OEF = Operation Iraqi Freedom/ Operation Enduring Freedom; PCS = postconcussion syndrome; PET = positron emission tomography; PIB = Pittsburgh Compound B; PTSD = posttraumatic stress disorder; PW-MRI = perfusion-weighted magnetic resonance imaging; QA = quality assurance; rCBV = regional cerebral blood volume; ROI = region of interest; RT = reaction time; SNR = signal-to-noise ratio; SPECT = single photon emission computed tomography; SWI = susceptibility-weighted imaging; TBI = traumatic brain injury; UCSF = University of California, San Francisco; UF = uncinate fasciculus.

TRAUMATIC BRAIN INJURY AND POSTTRAUMATIC STRESS DISORDER: "INVISIBLE WOUNDS"

Improved diagnosis and treatment of traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) are needed for our military and veterans, their families, and society at large. According to a RAND Corporation study based on screening questionnaire data, nearly one out of five Operation Iraqi Freedom/Operation Enduring Freedom (OIF/OEF) servicemembers (300,000) are estimated to experience symptoms of PTSD or depression and more than 320,000 OIF/OEF servicemembers have sustained a TBI [1]. Similarly, 23 percent (907/3,973) of a returning brigade combat team were clinician-identified to have a history of TBI [2].

The majority of cases of TBI in civilian and combat-related settings are categorized as "mild," a category based primarily on the characteristics of the acute sequelae following the injury. The criteria for the classification of mild can vary, but the Department of Defense/Department of Veterans Affairs March 2009 Clinical Practice Guideline has adopted the following criteria: (1) brief loss of consciousness (30 minutes or less), (2) brief alteration of consciousness (up to 24 hours), (3) posttraumatic amnesia for 0 to 1 days, or (4) Glasgow Coma Score (best score within the first 24 hours) of 13 to 15 (15 = normal), and (5) a normal-appearing brain on computed tomography (CT) scan [344].

In contrast to civilian TBIs due to falls, sports, etc., nearly 70 percent of combated-related TBIs are a result of blast "plus" injuries, i.e., the effects of blast plus another modality [3]. In mild TBI, the underlying pathology is not well understood and the lesion(s) may be subtle, scattered, varied, and, as indicated above, not detected on conventional brain CT studies. Further diagnostic challenges are posed by virtue of the varied and nonspecific post-concussion symptoms (e.g., concentration problems, irritability, headaches) that are also found in PTSD, depression, sleep disorders, or in otherwise healthy persons. However, improving the sensitivity of neuroimaging to subtle brain perturbations and combining these objective measures with careful clinical characterization of patients may facilitate better understanding of the neural bases and treatment of the signs and symptoms of mild TBI.

For combat-related PTSD, the clinical manifestations include not only intrusive recurrent memories and hypervigilance but also nonspecific symptoms, including insomnia, concentration difficulties, irritability, impaired decision-making abilities, and memory problems. …

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