Effect of general anaesthesia on the magnetic resonance imaging signal from the brain.

Magnetic resonance images of the brain were obtained in 10 female patients before and 2-6 h after a standard general anaesthetic. The longitudinal magnetic relaxation times (T1) showed a non-significant decrease, whereas the transverse magnetic relaxation times (T2) increased in all scans, with significant increases in the pons and corpus callosum. This suggests that general anaesthesia may be associated with structural changes in the brain at a molecular level.