Wilderness Medical Society snowmass 2005 Page 52
3
· All brains swell
· Total volume change of 2.4±1.4% > 32
hrs
· Inverse to SaO2%
· Swelling CBF
· Swelling AMS (AMS 14-24h, scan at
32h)
· SIENA: Structural Image
Evaluation, using
Normalization of Atrophy
· Measures atrophy /
general brain change
· Proven for a range of MRI
slice thicknesses and
sequences
· Accuracy
0.2%
of brain
volume
h Brain Swelling in AMS by SIENA
%
C
h
a
n
g
e
B
r
a
i
n
V
o
l
u
m
e
But Is It Edema?
· DWI, T2WI and Flair suggest not
· Are techniques sufficiently sensitive?
ADC and Brain Swelling in
AMS
h
diffusion
i
diffusion
p<0.01
h
ADC =
h
movement
of free water, usually
interpreted as
consistent with
vasogenic edema
i
ADC = restricted
diffusion, usually
interpreted as
cytotoxic edema
