[A study of cerebral circulation following cervical sympathetic ganglion block].

Cerebral circulation following cervical epidural block or stellate ganglion block at the transverse process of the 6th cervical vertebra (C6-SGB) was evaluated by single photon emission computed tomography of inhaled Xenon-133. Cerebral blood flow before and 15 min after both blocks was measured in eight patients after cervical epidural block and ten patients after C6-SGB. Cerebral blood flow decreased slightly following cervical epidural block, but it was not a statistically significant difference. Cerebral blood flow following C6-SGB could be separated into two groups; in one it increased and in the other it decreased slightly. In conclusion, cerebral circulation is not influenced by cervical epidural block, but it is probably affected by C6-SGB. The manner in which C6-SGB increases cerebral blood flow seems that local anesthetics reached the superior cervical ganglion and block it. C6-SGB without superior cervical ganglion block does not influence cerebral circulation, and it only dilates extracranial vessels.