Localizing the L5 Vertebra Using Nerve Morphology on MRI: An Accurate and Reliable Technique

Area of Science:

• Radiology
• Neuroanatomy
• Spinal Imaging

Background:

• Determining lumbar vertebral levels on MRI can be challenging without full spine imaging.
• Lumbar nerve root counting postmortem shows high accuracy for vertebral body numbering.
• Axial MRI nerve morphology offers potential clues for lumbar vertebral numbering.

Purpose of the Study:

• To assess the accuracy of L5 vertebra localization using nerve morphology on MRI.
• To compare nerve morphology method with full spine imaging reference standard.
• To evaluate interrater and intrarater reliability of the nerve morphology method.

Main Methods:

• 108 full spine MRIs were analyzed, noting transitional states.
• L5 nerve origin and iliolumbar ligament location were documented.
• Five blinded raters assessed lumbar MRIs twice using nerve morphology; reliability was measured using kappa statistics.

Main Results:

• The L5 nerve originated from the L5 vertebra in 98.1% of cases.
• High agreement (98.1%) with the reference standard was maintained in variations.
• The nerve morphology method demonstrated strong inter- and intrarater reliability.

Conclusions:

• Exiting L5 nerve morphology accurately localizes the L5 vertebra on MRI.
• This neuroanatomic method is crucial for preprocedure planning without full spine imaging.
• The method shows superior agreement and reliability compared to prior techniques.