Increasing attention has been paid recently to the study of spontaneous brain 
activity; moreover, particular attention has been paid to the concept of a 
default-mode network of brain function. Although the functional significance of 
the default-mode network remains a matter of debate, it has been suggested to be 
a candidate for the network subserving basic functions related to consciousness. 
We report the case of a 29-year-old man with encephalopathy and a reversible 
lesion of the entire corpus callosum. Despite resolution of corpus callosum 
lesion on magnetic resonance imaging (MRI) within 1 week, the patient 
persistently presented disturbance of consciousness. Resting-state functional 
MRI revealed that the posterior cingulate cortex/precuneus was functionally 
disconnected from other brain regions within the default-mode network. Our case 
report suggests that assessment of the functional connectivity in the 
resting-state default-mode network could be a useful marker of consciousness 
disturbance even in the presence of a reversible brain lesion.