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Lumbar Dorsal Root Ganglia Location: An Anatomic and MRI Assessment.

Michael P Silverstein, MD1,2, Lynn J Romrell, PhD3, Edward C Benzel, MD,2,4 Nicolas Thompson, PhD,5 Sandra Griffith, PhD,5 Isador H Lieberman, MD, MBA6

1Department of Orthopaedic Surgery, Cleveland Clinic Foundation, Cleveland, OH. 2Center for Spine Health, Cleveland Clinic Foundation, Cleveland OH. 3Department of Anatomy, College of Medicine, Florida State University, Tallahassee, FL. 4Department of Neurological Surgery, Cleveland Clinic Foundation, Cleveland, OH. 5Department of Quantitative Health Sciences, Cleveland Clinic Foundation, Cleveland, OH.  6Scoliosis and Spine Tumor Center, Texas Back Institute, Plano, TX.



The dorsal root ganglion (DRG) is a key structure in the mechanism of symptomatic radicular pain, weakness and change in sensation. DRG localization can assist in the decision making process of which areas require decompression, and type of procedure that should be performed to treat radicular symptoms. In this study we determine dimensions of lumbar foramina, DRG and its relationship to the neuroforamina through anatomic and magnetic resonance imaging (MRI) evaluation Agreement between MRI and anatomic assessment of DRG location will be determined.


Sixteen embalmed cadavers, 10 females and 6 males, aged 68 to 106 years had an MRI of the thoracolumbar spine followed by dissection. Measurements made included foraminal height and width, DRG size and nerve root take off angle. The center of the DRG and its relationship to the foramina were measured and the probability of agreement between anatomic and MRI assessment were made.


The greatest width of the DRG was 6.5mm bilaterally at L5 (range 3.2-6.5mm). The nerve root take off angle was largest at L5 on the left (range 50.5o-58.8o) and L4 on the right (range 50.5o-57.2o). The center of the DRG was found bilaterally in the medial zone of the foramen of L1-4 and lateral zone at L5. Foramina size increased from L1 to L5 in the ventral to dorsal and cephalad to caudal direction. Pedicle width increased from L1 to L5. The estimated overall probability of agreement between anatomic and MRI DRG location was 86.3% (95% confidence interval = 77.5% − 92.0%).


The percentage of agreement between MRI and anatomic evaluation of lumbar DRG location significantly exceeded our pre-defined threshold of 70% (p = 0.0013).

Clinical Relevance

Our results aid in surgical decision-making as true anatomic position can be directly correlated to what's seen on MRI.

lumbar spine, dorsal root ganglia, MRI, lumbar foramina, cadaver
Volume 9 Article 3