Thresholds for Mechanical Injury to the in Vivo White Matter 99SC19
In vivo, tissue-level, mechanical thresholds for axonal injury
in the guinea pig optic nerve were determined by comparing
morphological injury to estimated in vivo tissue strain. The right
optic nerve of adult male guinea pigs was stretched to one of seven
ocular displacement levels. Morphological injury was detected three
days post-stretch with neurofilament immunohistochemical staining
(NF68). A companion set of in situ experiments was used to
determine the empirical relationship between ocular displacement
and optic nerve stretch. Logistics regression analysis, combined
with sensitivity and specificity measures and receiver operating
characteristic (ROC) curves were then used to predict strain
thresholds for axonal injury.
From this analysis, we determined three Lagrangian strain- based
thresholds for morphological damage to the guinea pig white matter.
The threshold intended to minimize the false positive rate was a
strain of 0.34, and the threshold that minimized the false negative
rate was 0.14. The threshold criteria that balanced the specificity
and sensitivity measures was 0.21. With this threshold data, one
may gain new insights into the occurrence of DAI in man.