Intradural lumbar disc herniations at the L1–L2 level: A case study and literature review

History

A 65-year-old female had a 2-month history of low back pain and intermittent neurogenic claudication. Over the course of a few days, she developed perineal hypoesthesia accompanied by paraparesis and urinary retention. On examination, she had a positive Laségue’s sign on the right at 30°, right-sided quadriceps weakness, bilateral lower extremity hyporeflexia (loss of patellar and Achilles responses), and loss of pin appreciation in the perineal region.

Preoperative imaging

The lumbar MR (T2-weighted sagittal and axial images) showed marked dural compression at the at the L1–L2 level with caudal migration to L2, combined with a positive “hawk- beak” sign. The lesion itself at L1–L2 did not enhance with contrast, but there was enhancement of the surroundings tissues [Figure 1].

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Figure 1:: Pre-operative T2-weighted MRI sagittal (a) and axial (b) images show a “hawk-beak like” appearance at L1-L2 level, suspecting an intradural herniated disc (yellow asterisk).

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Surgical intervention

At surgery, consisting of a L1–L2 laminectomy, no significant epidural lesion was present. However, when the dura was opened, a large IDH/fragment was encountered measuring 2 × 1 cm. This was carefully teased away under the operating microscope from the surrounding nerve roots of the cauda equina and ventral dura [Figure 2]. Further, the ventral dura had to be sutured closed; fibrin glue was also applied, with care being taken to avoid creating a significant mass. Postoperatively, due to the dural repair, the patient was kept on bed rest for 48 h. One week postoperatively, the lumbar MR confirmed adequate decompression of the spinal canal without any residual disc [Figure 3]. Upon discharge, 13 days postoperatively, the patient fully recovered.

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Figure 2:: Intraoperative description of the IDH removal. After the L1-L2 laminectomy, a dural incision is made. The roots of the cauda equina (black arrow) appear dislocated by a voluminous migrated intradural disc fragment. (black asterisk) (a) With the use of disc pounches a removal of the voluminous IDH is performed. (b) Microsurgical discectomy is completed with the use of a Cushing’s buttoned nerve hook (black asterisk) through the ventral dural defect (c), achieving a macroscopic complete disc removal and decompression of the nerve roots (black arrow). (d).

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Figure 3:: Post-operative T2-weighted MRI sagittal (a) and axial (b) images show an optimal decompression of the conus medullaris and of the roots of the cauda equina with absence of further disc fragments.

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Noncontrast and contrast MR findings for IDH

On T1- and T2-weighted MR images, IDHs are homogeneously isointense. Notably, Hidalgo-Ovejero et al.[5] found that gas within the spinal canal was associated with IDH.

Gadolinium-enhanced MR scans demonstrate a positive “Hawk-Beak” sign (e.g., a “Beak-Like” appearance at the level of the lesion sharply compressing the dural sac, especially on T2-weighted axial images). Hida et al.[4] further described, at the level of the intervertebral disc space, the positive “Beak- Like” mass, plus the abrupt loss of continuity with the PLL, and focal ring enhancement. In the case presented, the L1–L2 MR documented all three findings consistent with an IDH at the L1–L2 level.