TORIE-DTI: Transient white matter changes under sevoflurane anesthesia

Cognitive dysfunction after surgery under general anesthesia is a
well-recognized clinical phenomenon in the elderly. Physiological effects
of various anesthetic agents have been studied at length. Very little is
known about potential effects of anesthesia on brain structure. In this
study we used Diffusion Tensor Imaging to compare the white matter
microstructure of healthy control subjects under sevoflurane anesthesia
with their awake state. Fractional Anisotropy, a white mater integrity
index, transiently decreases throughout the brain during sevoflurane
anesthesia and then returns back to baseline. Other DTI metrics such as
mean diffusivity, axial diffusivity and radial diffusivity were increased
under sevoflurane anesthesia. Although DTI metrics are age dependent, the
transient changes due to sevoflurane were independent of age and sex.
Volumetric analysis shows various white matter volumes decreased whereas
some gray matter volumes increased during sevoflurane anesthesia. These
results suggest that sevoflurane anesthesia has a significant, but
transient, effect on white matter microstructure. The role of white matter
in the loss of consciousness under anesthesia will need to be studied and
MRI studies with subjects under anesthesia will need to take these results
into account.