Intradural Disc Herniation at the L1-L2 Level: A Case Report and Literature Review

Background: Why are intradural disc herniations (IDHs) (0.3% of all discs) so infrequent? One explanation has been the marked adherence of the posterior longitudinal ligament (PLL) to the ventral wall of the dura. Variability in symptoms and difficulty in interpreting magnetic resonance (MR) images with/without contrast make the diagnosis of an IDH difficult. Here, we reported a patient with an L1-L2 IDH and appropriately reviewed the relevant literature.

Case Description: A 57-year-old male presented with chronic low back and 1 month's duration of the left thigh pain. The lumbar MR with/without contrast demonstrated an IDH at the L1-L2 level, resulting in spinal cord compression. At surgery, the disc herniation was appropriately resected, the dura was closed, and an interbody fusion with pedicle screw fixation was performed. Postoperatively, the patient clinically improved.

Conclusion: IDHs are rare, being seen in only 0.3% of all cases. MR findings, performed with/without contrast, may help signal the presence of an IDH. MR findings include a hypointense structure inside the dura; the "hawk beak" sign (e.g., beak-like mass with ring enhancement at the intervertebral disc space); the Y sign (e.g., ventral dura split into ventral dura and arachnoid by disc material); an abrupt loss of continuity of the PLL; a diffuse annular bulge with a large posterocentral extrusion; and an typical crumbled appearance of disc (e.g., "crumble disc sign"). At surgery, both the extradural and intradural components of the disc must be excised.