Anatomical and experimental studies of nerve root infiltration.

Cervical or lumbar nerve root infiltration is a valuable and reliable technique when the localization of the symptomatic level cannot be assessed by any other diagnostic procedure. In order to obtain the morphological basis for this technique, anatomical and experimental studies were carried out with 6 mongrel dogs and 7 human cadavers. In the spinal canal a membranous structure, the epidural membrane, interposing between the dura and yellow ligament can be found. There is a fibrous covering around the nerve root in the intervertebral foramen, which is called the epiradicular sheath. The epiradicular sheath is formed by a lateral extension of the superficial layer of the posterior longitudinal ligament blended with the epidural membrane enveloping the dura. When epidurography is performed on dog cadavers both at the cervical and lumbar levels, the contrast material is located between the dura and epidural membrane. When cervical nerve root infiltration is performed on dog and human cadavers, the contrast material spreads under the epiradicular sheath. Based on these anatomical and experimental studies it can be concluded that selective infiltration of each nerve root with the contrast material and/or local anesthetic is possible by the existence of the epiradicular sheath. And the epiradicular sheath is responsible for the fact that the contrast material is located around the nerve roots in a tubular fashion.