Sensitivity of Computed Tomography Compared With that of Magnetic Resonance Myelography in the Presurgical Diagnosis of Foraminal or Extraforaminal Entrapment at the Lumbosacral Junction.

STUDY DESIGN

This is a retrospective analysis.

OBJECTIVE

To investigate and compare the sensitivities of computed tomography (CT) and magnetic resonance myelography (MRM) in the presurgical diagnosis of foraminal or extraforaminal entrapment of the L5 nerve.

SUMMARY OF BACKGROUND DATA

CT is more clinically available than MRM. Foraminal or extraforaminal entrapment at the lumbosacral junction may cause L5 radiculopathy but is difficult to diagnose. Asymmetric enlargement of the anterior primary division (APD) of the L5 nerve on preoperative CT and dorsal root ganglion (DRG) swelling and abnormal L5 nerve course on MRM coronal images have been examined in cases of foraminal or extraforaminal L5 nerve entrapment, but have not been compared directly.

MATERIALS AND METHODS

Ninety-five patients (mean age 63 y; 28-85 y) with L5 nerve entrapment at the lumbosacral junction who underwent preoperative CT and MRM, and microsurgical decompression by a single surgeon (K.-H.M.) from January 2010 to June 2014 were included. Symptomatic sites were diagnosed by confirming L5 nerve entrapment intraoperatively. Two spinal surgeons independently compared the bilateral APD diameters of the L5 nerve on CT and the L5 nerve courses and DRG swelling on MRM coronal images.

RESULTS

The interobserver agreement of asymmetric APD swelling on CT and abnormal nerve course and DRG swelling on MRM were excellent (κ=0.808, 0.811, and 0.849, respectively), and the sensitivities were 81%, 84%, and 82% on the right, and 86%, 92%, and 90% on the left sides, respectively. There was no statistically significant difference in the sensitivity between APD swelling on CT and an abnormal nerve course or DRG swelling on MRM on the right (P=1.000 and 0.789) and left (P=0.727 and 1.000) sides, respectively.

CONCLUSIONS

CT has comparable sensitivity to MRM for the presurgical diagnosis of L5 nerve entrapment at the lumbosacral junction.

LEVEL OF EVIDENCE

Level II.