Retrograde filling of a thoracic spinal artery during transforaminal injection

Transforaminal injection of steroids has been associated with infrequent but devastating neurological complications and death. Direct injection of particulate steroids into the vertebral artery or medullary arteries is the leading theory in the majority of these complications. Practice guidelines have been published to minimize the likelihood of directly encountering vulnerable arterial structures. However, retrograde flow into a vertebral or medullary artery has not been considered in the literature.

This case demonstrates retrograde flow into a common arterial trunk with subsequent antegrade flow of intravenous contrast into a thoracic spinal artery during thoracic transforaminal injection.

Antegrade flow of particulate steroids through direct cannulation of a vertebral or medullary artery has been advocated as one explanation for complications involving brain or spinal cord infarction. The possibility of retrograde flow into a common arterial trunk with subsequent antegrade flow into vulnerable arteries should also be considered as a possible mechanism by which embolic spinal cord or brain injury may occur.

Retrograde flow into medullary or vertebral arteries without direct cannulation can occur, and provides an alternative mechanism of potential injury to the spinal cord or brain during transforaminal injections.