1478. Anatomical correlation between radicular pain and rostral take-off from the thecal sac.

Authors: Nikolay L. Martirosyan, MD; Mauricio Avila, MD; Travis Dumont, MD (Tucson, AZ)

Introduction. Lumbar radiculopathy is a common presentation of degenerative spine diseases. The degree of nerve root compression may determine the intensity of radiculopathy. We hypothesize that anatomical variation of nerve root take off from thecal sac may correlate with the intensity of S1 radiculopathy. Methods. 11 patients (mean age of 62 years) who underwent decompressive surgery for bilateral S1 radiculopathy were included in this study. Preoperative MRI of the lumbar spine was used to predict the level of nerve root take off. Patients underwent bilateral L5/S1 medial facetectomy and foraminotomy. Once nerve roots were decompressed and visible, we noted the difference between right and left nerve root take off from the thecal sac. Roots either noted to be symmetrical, or one side was rostral to another (at root axilla). Pain dominance assessed compared to root sleeve anatomy. Results. Of 11 patients 6 (55%) had left the side, 2 (18%) had right side dominant and 3 (27%) had equal intensity bilateral radicular symptoms. Preoperative MRI findings did not provide an accurate prediction of the nerve root take off. S1 root take-off was on the left in 4 cases, right in 3 cases, and symmetric in 4 cases. Pain dominance correlated with more rostral root take-off in 8 cases. In the 3 cases where pain dominance did not correlate to rostal root take-off, there was MRI dominance of disk/osteophyte complex. Conclusions. In our study, 73% of patients had dominant S1 radiculopathy on the same side as more rostral nerve root take off. A rostral lumbar nerve root take-off may be more stretched and cause increased compression in lateral recess. Clinical and anatomical studies needed to further investigate this association.