2149. Regional FA Values and Loss Of Consciousness In Mild Traumatic Brain Injury
Authors* Denotes Presenting Author
Alex Asturias *;
Touro University Nevada
Touro University Nevada
Imgen; University of Nevada, Las Vegas
Imgen; Mountain View Hospital
Recent studies have described a significant association between loss of consciousness (LOC) and worse clinical outcomes, including increased symptom presentation, after mild traumatic brain injury (mTBI). Diffusion tensor imaging is the most sensitive modality for detecting microstructural alterations in white matter which may be associated with neurological sequelae of mTBI, with changes in fractional anisotropy commonly reported as a marker of white matter abnormality. We hypothesized that in a large and diverse group of civilian subjects diagnosed with mTBI, significant decreases in WM FA may be present in those who experienced LOC as compared with those who did not.
Materials and Methods:
Whole brain DTI performed in the chronic phase (avg=175 days from trauma) and clinical data were obtained retrospectively for 168 subjects diagnosed with mTBI, 36 with LOC. The mean age was 40 years, similar in those with and without LOC. Patients with hemorrhages and contusions (complicated mTBI) were excluded. Single shell whole brain DTI was obtained in 90 directions using a 3T Siemens Magnetom Verio scanner (thickness = 4.0 mm, resolution = 1.79688 mm, b-value = 1000 TR = 4200ms and TE = 95.0ms). Data were then processed with DSI studio with analysis of 80 WM tracts as defined by the Human Connectome Project 842 tractography atlas. Two-way ANOVA and t-tests were used to assess for differences in FA values in subjects with mTBI and without LOC, controlling for familywise error rate using the false discovery rate (reported as q-values) for the t-tests.
Assessment of isolated right and left tract FA values and LOC revealed a statistically significant (q=<0.001) association between lower FA of the right extreme capsule and LOC, but a smaller difference between LOC and non-LOC in the left extreme capsule (q=0.194). FA in both right and left tracts was observed in the LOC group compared to no LOC group for the corticothalamic pathway (p=0.038), fornix (p=0.041), frontopontine tract (p=0.035), parietopontine tract (p=0.002), middle longitudinal fasciculus (p=0.023), CN II (p=0.039), and CN III (p=0.011).
Significantly lower regional FA values were observed in WM tracts in subjects with mTBI who experienced LOC as compared with those who had no LOC. Significant differences were observed in the corticothalamic pathway, the fornix the frontopontine tract, the parietopontine tract, and the middle longitudinal fasciculus as well as CN II and CN III. As LOC in patients with TBI has important clinical implications, imaging findings associated with LOC may have important diagnostic and prognostic value.