Presentation
Subtotal resection of a filum terminale mass 6 months ago, now presenting with vague low back pain radiating to the left lower limb with painful straight leg raise test.
Patient Data
Evidence of previous laminectomy at L3 and L4.
Large irregular fluid collection at the level of previous surgery, following CSF signal intensity on all sequences, demonstrating a thin rim of enhancement after contrast administration with enhancing perilesional postoperative changes. It appears to be communicating with the thecal sac via a tiny defect in the dorsal dural coverings opposite L3, through which a few cauda equina nerve fibers are herniating.
Small homogenously enhancing filum terminale mass at the level of L4, consistent with the patient's known residual intradural tumor. A fatty filum terminale is incidentally noted.
Normal conus termination.
Degenerative disc bulge with a small central annular fissure at L5/S1.
Small defect in the dorsal dural coverings opposite L3, with cauda equina nerve root entrapment (red arrow)
Case Discussion
Postoperative pseudomeningoceles represent extradural fluid collections of CSF content communicating with the subarachnoid space through small dural tears. Chronic CSF leakage may lead to paraspinal pseudocyst formation with surrounding reactive changes.
Pseudomeningoceles may very rarely occur following lumbar laminectomy, with an incidence of around 1-2%.
Nerve root herniation may occur within the cystic cavity, and this, in turn, may lead to radicular symptoms and potentially irreversible nerve damage.
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