Coronal magnetic resonance imaging of three-dimensional fast-field echo with water-selective excitation improves the sensitivity and reliability of identification of extraforaminal lumbar disc herniation

Abstract

Objective: The complete view of the nerve root, including the extraforaminal zone, can be displayed by coronal magnetic resonance imaging (MRI) of three-dimensional (3D) fast-field echo with water-selective excitation (CMRI). However, its sensitivity, specificity, and reliability for the diagnosis of extraforaminal lumbar disc herniation are unclear. We compared the sensitivity, specificity, and reliability of conventional MRI, CMRI, and 3D MRI for the identification of extraforaminal lumbar disc herniation.

Methods: This study involved 140 patients (68 with extraforaminal lumbar disc herniation and 72 with paramedian disc herniation). Their mean age was 44.57 ± 14.59 years. Conventional MRI, CMRI, and 3D MRI of all patients were evaluated by five experts. The reliability, sensitivity, and specificity of the three imaging techniques for identification of extraforaminal lumbar disc herniation were compared using kappa statistics and the chi-squared test.

Results: CMRI showed higher agreement (0.843) than conventional MRI (0.671) and 3D MRI (0.771) for the identification of extraforaminal lumbar disc herniation. CMRI demonstrated higher sensitivity (95.6% vs. 91.2%) than conventional MRI (85.3% vs. 70.6%) and 3D MRI (92.6% vs. 86.7%) regardless of whether performed by junior or senior surgeons.

Conclusions: CMRI is helpful for identification of extraforaminal disc herniation by junior and senior orthopedic surgeons.

Keywords: Extraforaminal herniation; magnetic resonance imaging; reliability; sciatica; sensitivity; specificity.

Figure 1.

(a) T2-weighted MRI in the sagittal plane was used to aid in localization of L5/S1, (b) T2-weighted images in the axial plane revealed a mass in the extraforaminal region of L5/S1, (c) CMRI confirmed that the extraforaminal disc (red arrow) compressed the nerve root of L5 and (d) Three-dimensional MRI also clearly showed that the extraforaminal disc compressed the nerve root of L5. MRI, magnetic resonance imaging; CMRI, coronal magnetic resonance imaging of three-dimensional fast-field echo with water-selective excitation.

Figure 2.

(a) T2-weighted MRI in the sagittal plane was used to aid in localization of L3/L4, (b) The junior surgeon did not find the extraforaminal disc herniation (yellow arrow) in the axial plane of the T2-weighted images, (c) However, the junior surgeon accurately diagnosed the extraforaminal disc herniation (blue arrow) using CMRI and (d) Three-dimensional MRI also clearly showed that the extraforaminal disc (red arrow) compressed the nerve root of L3. MRI, magnetic resonance imaging; CMRI, coronal magnetic resonance imaging of three-dimensional fast-field echo with water-selective excitation.

Figure 3.

(a) T2-weighted MRI in the sagittal plane was used to aid in localization of L5/S1, (b) Neither the junior surgeon nor senior surgeon found the extraforaminal disc herniation in the axial plane of T2-weighted images, (c) However, both accurately diagnosed the extraforaminal disc herniation (red arrow) using CMRI and (d) The extraforaminal disc herniation (red arrow) was not found using 3D MRI because the imaging details were lost after the original images were reconstructed using 3D maximum-intensity projection and volume-rendering techniques. MRI, magnetic resonance imaging; CMRI, coronal magnetic resonance imaging of three-dimensional fast-field echo with water-selective excitation.