Page 59 - NNS 2014 Program & Abstract Book

evaluated in primary and secondary auditory (A1; A2) and visual (V1;
V2) cortices using 2 · 2 (Group · Cue/distracter congruency) mixed
measures ANCOVA analyses with simple effects performed to follow-
up on significant interactions. No differences existed between groups on
median reaction time and accuracy. Functional results indicated in-
creased sensory response in V1 (trend) and V2 (significant) for mTBI
patients in response to increasing stimulus frequency. In contrast, trend
evidence of a reduced sensory response was present in A1 for patients.
A similar pattern was observed for ARMs in visual (mTBI > HC) and
auditory cortex (HC > mTBI) during congruent trials. These findings
suggest a potential correlation between the greater incidence of vi-
sual symptoms during semi-acute mTBI in contrast to self-reported
normal auditory functioning. The current research supports the use
of ARMs derived from a multisensory cognitive control task as a
putative central nervous system biomarker for identifying neuro-
sensory deficits in mTBI, potentially even in the absence of mea-
surable behavioral deficits.
Key words
fMRI, mTBI, multisensory, neurosensory deficits
A2-08
MANGANESE ENHANCED MRI FOLLOWING TRAUMATIC
BRAIN INJURY
Chemello, J., Watts, L.T., Long, J.A., Shen, Q., Duong, T.Q.
University of Texas Health Science Center, San Antonio, US
Manganese is a calcium analog and MRI contrast agent. The purpose
of this study was to evaluate the utility of manganese-enhanced MRI
(MEMRI) in hyperacute, acute, and subacute phases of experimental
moderate TBI. MnCl2*4H2 O was infused at a rate of 1.8 mL/hr for 30
minutes before TBI via tail vein at doses of 87.5 mg/kg (n = 4) or
29.17 mg/kg (n = 4). Anesthetized male rats underwent a 6mm cra-
niotomy over the left primary forelimb somatosensory cortex and
were impacted using a cortical impactor (impact velocity: 5 m/s;
250us dwell time; and 1mm depth) mimicking a moderate TBI. Ad-
ditional MnCl2 was given on days 1, 6 and 13 after TBI (24 hrs before
subsequent MRI). MRI was performed 1–3 hrs and 1, 2, 7, and 14 days
after TBI to acquire T2 maps and manganese enhanced T 1-weighted
images. We found the 87.5 mg/kg dose yielded some mortality and
negatively affected behavioral performance. The 29.17 mg/kg dose
was well tolerated, had no negative effects on behavioral perfor-
mance, and yielded good MRI signal contrast. On day 0, T2 MRI
showed mild hyperintensity immediately underneath the impacted
area. In contrast, MEMRI showed marked hyperintensity in and
around the impacted area, extending beyond the impacted site. The
sources of MEMRI contrast is likely due to disrupted BBB and/or
spreading depolarization following TBI on day 0. T2 MRI showed the
largest change on day 2. On days 2, 7, and 14, MEMRI in the im-
pacted area was heterogeneous with hypointense and hyperintense
regions compared to normal tissue suggesting regions with enhanced
and reduced calcium activities. Heterogeneous contrasts in the area
surrounding the lesion on days 7 and 14 could be due to functional
reorganization of neurons or glial scarring. MEMRI provides novel
and useful MRI contrast to study TBI. MEMRI detects earlier and
more sensitive changes than T2 in the hyperacute phase. MEMRI
could be sensitive to BBB permeability, spreading depolarization,
functional reorganization, and glial scarring. Future studies will need
to cross validate these findings with immunohistology.
Key words
contrast agent, manganese, MRI, TBI
A2-09
MRI REVEALS WIDESPREAD DISRUPTIONS IN CBF AND
VASCULAR REACTIVITY FOLLOWING FOCAL TBI
Long, J.A., Watts, L.T., Chemello, J., Shen, Q., Duong, T.Q.
University of Texas Health Science Center, San Antonio, US
The goal of this study is to investigate cerebral blood flow (CBF),
Diffusion, T2, and vascular responses to 5% CO 2 inhalation in a mild
TBI model in rats. Rats (n = 8) underwent a 6mm craniotomy over the
left primary motor/somatosensory cortex and were impacted using a
pneumatic cortical impactor (impact velocity 5.0 m/s, 250 ls dwell
time, and 1mm depth) mimicking a moderate TBI. CBF, Fractional
Anisotropy (FA), Apparent Diffusion Coefficient (ADC), T2, and 5%
CO2 responses were longitudinally monitored on 0, 2, 7, and 14 days
post-TBI. TBI induced widespread, severe heterogeneous perfusion
disruptions beyond the impact ROI in the acute phase (first 3 hours).
In the lesion, CBF dropped to 20% of normal 1–3 hrs post-TBI, in-
creased to 140% of normal on day-2 (hyperperfusion), and returned
toward normal on day-7 and 14. CBF actually decreased with CO2
inhalation. CO2 responses varied between both cortices at 1–3 hrs and
day-2. ADC increased, T2 increased, and FA decreased 1–3 hrs and
day-2 post-TBI. In the perilesional regions, CBF dropped to 60% of
normal 1–3 hrs post-TBI, remained depressed on day-2, and returned
toward normal on day-7 and 14. CO2 response was attenuated at 1–
3 hrs and day-2, and recovered by day-7 and 14. ADC, FA, and T2
values did not change. In summary, CBF and CO2 response distur-
bances were extensive while T2, FA and ADC changes were limited
only to the area of impact. For FA, ADC, and T2 to change, CBF must
reduce to 20% of normal for a substantial duration. No changes in
these MRI parameters were detected if CBF dropped to 60% of nor-
mal up to 14 days post-TBI. Multimodal MRI offers complementary,
clinically relevant information to probe tissue condition following
TBI and can provide useful information to further characterize TBI.
Key words
cerebral blood flow, MRI, TBI, vascular reactivity
A2-10
RESTING-STATE BRAIN ACTIVITY IN MILD TBI PATIENTS
WITH HIGH VERSUS LOW POST-TRAUMATIC STRESS
DISORDER SYMPTOM SEVERITY
DeGraba, T.J.1, Popescu, M.1, Popescu, A.1, Balbir, A.1, Bleiberg, J.1,
Riedy, G.1, Balkin, T.2, Merrifield, W.1
1National Intrepid Center of Excellence, Bethesda, USA
2Walter Reed Army Institute of Research, Silver Spring, USA
The objective is to use magnetoencephalography (MEG) to identify
electrophysiological patterns that characterizes the presence and se-
verity of symptoms from post-traumatic stress disorder (PTSD) in
military service members with mild traumatic brain injur (mTBI) in
resting state brain activity.
Service members (n = 23) injured in Iraq and Afghanistan, diag-
nosed with mTBI were evaluated for PTSD, PTSD Check List-
Military (PCL-M) score ‡ 50, during intake at the National Intrepid
Center of Excellence four-week interdisciplinary intensive outpatient
program. Resting-state 5min MEG recordings were acquired in two
subject groups: Group 1 comprised participants with high PTSD
symptom severity scores (n = 12, mean 61.8 – 8.0); Group 2 comprised
participants with low PTSD symptom severity scores (n = 11, mean
39.5 – 6.5). Independent component analysis was used to remove
A-27