PMC

The classification of Pfirrmann grade. On T2-weighted image, grade I—the structure of the disk and disk height are normal, with a bright white signal intensity. Grade II—the structure of the disk is abnormal and the disk height is normal, with a white signal and a clear distinction between nucleus and anulus. Grade III—the structure of the disk is abnormal and the disk height is normal or slightly decreased, with an average gray signal intensity and an unclear distinction between nucleus and anulus. Grade IV—the structure of the disk is abnormal and the disk height is normal or moderately decreased, with a dark gray signal intensity and a lost distinction between nucleus and anulus. Grade V—the structure of the disk is abnormal and the disk space is collapsed. The distinction between nucleus and anulus is lost

T2-weighted images illustrating 4 Pfirrmann disk grades. Midsagittal images show a grade II disk (A) with high signal intensity in the central region and lower signal intensity in the peripheral region, clearly distinguishing the nucleus pulposus region from the annulus fibrosus; a grade III disk (B) with lower signal intensity in the central region and less clear distinction between the nucleus pulposus region and annulus; a grade IV disk (C) with homogeneously low signal intensity and with no distinction of the nucleus pulposus region and annulus; and a grade V disk (D), which is collapsed.

Graph illustrating the location of the intervertebral disk extrusion of all dogs, dogs without and with muscle signal alteration. Dogs with a disk extrusion caudal to L1 had a higher risk for muscle signal changes (OR = 2.8, P = 0.03) than dogs with a disk extrusion cranial to L1.

A 75-year-old man with a posterior epidural disk migration.
A, Sagittal T2-weighted (TR/TE, 4000/119.8) fast spin-echo MR image of the lumbar spine at the midline plane reveals a mass lesion (arrow) with isointensity relative to the intervertebral disk at the posterior epidural space at the L2–3 level, compressing the dura (arrowheads).
B, Right parasagittal T2-weighted image shows a disrupted outermost annulus fibrosus (white arrow) of the intervertebral disk at L2–3. By comparison, the intact outermost annulus fibrosus (black arrows) is shown as a delicate dark line along the margin of the disk at adjacent L1–2 and L3–4 levels.
C, Axial T1-weighted (TR/TE, 600/10.42) fast spin-echo MR image obtained at the level of the migrating disk fragment shows an irregularly shaped mass lesion (arrows), with an isointense signal intensity relative to the intervertebral disk at the right posterior epidural space, which is contrasted by high-signal-intensity epidural fat.
D, Axial gadolinium-enhanced T1-weighted (TR/TE, 466.7/10.22) MR image with fat saturation at the disk fragment level shows a rim enhancement of the epidural disk material (arrows).
E, The same pulse sequence MR image obtained at a higher level than that in D at the intervertebral disk shows a tractlike enhancement (arrows) from the site behind the ruptured annulus fibrosus to the right posterior epidural space, indicating the route of disk migration.
F, Photomicrograph of the surgical specimen shows increased vasculature (arrows) and focal mild lymphocytic infiltration at the edge of the degenerated fibrocartilage (asterisk) (H&E, original magnification ×100).