RECOVERY OF THE RODENT BRAIN AFTER CARDIAC-ARREST - A FUNCTIONAL MRI STUDY

Recovery of the cerebral cortex after 10 min of cardiac arrest was stu died in rat using noninvasive MRI techniques. The apparent diffusion c oefficient (ADC) of brain water was imaged to document reversal of the metabolic impairment. Perfusion-weighted imaging and blood oxygen lev el dependent (BOLD) imaging were performed to assess functional recove ry. To this purpose, rats were anesthetized with alpha-chloralose, and somatosensory cortex was activated by electrical stimulation of the c ontralateral forepaw, In sham-operated controls, cortical ADC was 862 +/- 10 mu m(2)/s, and stimulation of forepaw led to a focal increase o f signal intensity in somatosensory cortex by 71 +/- 22% in perfusion- weighted images and by 6 +/- 1% in BOLD images. One hour after success ful resuscitation following 10 min of cardiac arrest, ADC did not diff er from control but functional activation was completely suppressed. A fter 3 hours of reperfusion, functional activity began to reappear but the recovery of the BOLD signal progressed faster than that of the pe rfusion-weighted signal, The differences in the recovery of ADC, BOLD, and perfusion imaging are related to differences between metabolic an d functional recovery on one hand and between blood flow and oxygen ex traction on the other, The combination of these MRI methods thus provi des detailed qualitative information about the progression of brain re covery after transient circulatory arrest.