Incidence of Inadvertent Intercostal or Epidural Spread During Thoracic Sympathetic Ganglion Block

Clinically, sympathetic blocks (SB) have been used widely to relieve the symptoms of SMP or to differentiate between SMP and sympathetically independent pain. In order to an SB has a diagnostic value, it requires the successful disturbance of the sympathetic activity for a proper duration of time.

For the diagnosis of SMP using an SB, it is essential achieving complete interruption of the sympathetic activity while preserving the sensory and motor function. The sympathetic trunk at lumbar region runs on the anterolateral surface of the vertebral column from L1 to L4 levels, and deep to the medial aspect of the psoas major muscle. Therefore, the investigators can hardly find epidural contrast spread during lumbar SB due to an anterior location of lumbar sympathetic ganglion to the lateral vertebral body. However, frequent psoas muscle injection can be encountered due to a close proximity of lumbar sympathetic ganglion.

In contrast to lumbar sympathetic ganglion, the thoracic sympathetic ganglion is not separated from somatic nerves by muscles and connective tissue. Moreover, the upper thoracic ganglion runs on the posterior surface of vertebral column with close proximity to adjacent epidural region.

This difference of thoracic sympathetic ganglion leads to a frequent epidural and intercostal spread if the investigators perform thoracic SB. Such spread to epidural and intercostal space lowers the diagnostic value of thoracic SB. In addition, serious adverse outcome can be encountered if neurolytic agent is injected into epidural or intercostal space for the purpose of thoracic sympathectomy. Considering the diagnostic value and safety of thoracic SB, evaluation of actual incidence of occurrence of intercostal and epidural spread is important.