The Spaghetti Sign: Nerve Root Redundancy in Lumbar Spinal Stenosis

Redundant nerve roots (RNRs) seen in conjunction with lumbar spinal stenosis (LSS) are well-described radiographic findings. Several studies suggest their presence may be a negative prognostic indicator of postoperative outcome. Our hypothesis was that severe RNR (informally known as the spaghetti sign [SS]) can serve as a reliable marker of LSS that would benefit from surgical decompression. We sought to evaluate a grading scale for RNR, characterize the association with stenosis, and investigate the clinical implications of RNR.

We conducted a retrospective chart review of 72 patients who underwent lumbar spine surgery from 2016 to 2018 at 1 institution. Preoperative T2 magnetic resonance imaging scans were graded by 3 reviewers for severity of stenosis (0-4), severity of RNR (0-3), and rostral versus caudal RNR. SS was defined as RNR score ≥2 (clear-cut or marked nerve root irregularity). Preoperative and postoperative Oswestry Disability Index scores were analyzed by stenosis and RNR severity.

Seventy-one (98%) patients had severe stenosis (score ≥3) and 25 (35%) had a SS. SS was 100% specific for high-grade stenosis. If patients had a SS, it was more likely rostral (P=0.02). Postoperative Oswestry Disability Index scores improved significantly, but there were no differences related to RNR score, presence of SS, or stenosis severity.

The study demonstrated that there is a significant association between SS and severe LSS and that presence of RNR is not a negative prognostic indicator for postoperative outcomes.