Paradiscal extraforaminal technique for lumbar sympathetic block: report of a proposed new technique utilizing a cadaver study.

Knowledge of the relationship of the lumbar sympathetic chain to the vertebral bodies is needed to perform sympathetic block and sympatholysis. This information should be correlated with fluoroscopy to determine the best method to perform this technique clinically. Twenty cadavers were dissected to demonstrate the lumbar sympathetic chain. In five cadavers, a 17 G Hustead needle was introduced inferior to the transverse process in the concavity of the body of L2 vertebra utilizing an extraforaminal (paraforaminal) approach and images were obtained in both the anteroposterior and lateral views. Needles were placed by utilizing either the loss of resistance technique (just piercing the psoas muscle) or by placing the needle posterior to the anterior border of the vertebral body. The cadavers were then dissected to demonstrate needle position in relationship to the lumbar sympathetic chain. Each lumbar sympathetic chain was located on the anterolateral aspect of the vertebral body at the medial attachment of psoas major to the vertebral body. When needles were inserted using the loss of resistance technique, dissection revealed needle tips considerably anterior to the ganglia and missing it. When the needle was placed just on the anterior border of the vertebral body, the tip was close to the sympathetic chain. In all of the dissections, lumbar segmental vessels were found in the concavity of the vertebral body ventrodorsally and closely related to the sympathetic chain. The chain varies in both size and location of the ganglia. In the majority of cases, lumbar ganglia were 3 in number. We believe the extraforaminal technique of lumbar sympathetic block is superior to the paramedian approach considering that there should be a reduced chance of passing through viscera and a lower incidence of genitofemoral neuralgia. However, with the extraforaminal technique, two important possible complications need to be highlighted. Chances of injury to the segmental lumbar vessels and the anterior ramus are present. Therefore, the extraforaminal technique needs to be modified. We advocate the extraforaminal paradiscal technique for lumbar sympathetic block. The initial target point for entry should be the lateralmost tip of the transverse process. Advancement of the needle should be extraforaminal with minimal chance of injury to the nerve or the anterior ramus. Final target point should be paradiscal. The needle tip should be positioned just posterior to the anterior border of the vertebral body. Loss of resistance technique should not be utilized and is potentially dangerous. Use of at least two needles is advisable (L2 and L3 vertebral body). Care should be taken to avoid the lumbar vessels. A transdiscal technique recently advocated may also avoid some of the complications with the paramedian technique, but chances of discitis, nerve root injury, accelerated disc degeneration, disc herniation and rupture of the anterior annulus have to be considered when using this technique.