Abstract

This study compares the effectiveness and extent of spread of two different volumes, 1 ml and 2 ml, of a local anesthetic/radiopaque dye combination (referred to here as the injectate) in selective sacral nerve root blocks. With 1 ml of injectate, a selective sacral nerve root block was obtained in seven of nine patients, and with 2 ml of injectate, in eight of nine patients, as measured by urodynamic testing or scoring of pain relief. The three patients who did not have a successful block in this study were effectively blocked at another sacral nerve on a later date (outside of the study) when injected with 1 ml of injectate. The group that received 2 ml of injectate had significantly larger spread of injectate than the 1 ml group. One milliliter of injectate can produce a selective sacral nerve root block. Increasing the volume of injectate increases the spread and thus the possibility of involving other nerve roots. This could then cause difficulty in the interpretation of the results of the block.