Dorsal Arachnoid Cysts/Webs and Spinal Cord Herniation: Diagnostic Challenges and Imaging Insights

Purpose or Learning Objective: Dorsal arachnoid cysts/webs and spinal cord herniation are rare thoracic spinal cord abnormalities. They can lead to significant neurologic morbidity if left untreated. Distinguishing between these conditions based on clinical and radiologic features remains challenging. This presentation aims to:

1. Recognize key radiologic features of spinal cord herniation and dorsal arachnoid cysts.

2. Describe clinical presentations.

3. Understand the role of imaging in diagnosis and surgical planning.

4. Evaluate the usefulness of imaging in disease progression, monitoring, and postsurgical assessment.

Methods or Background: Spinal cord herniation results from the protrusion of the spinal cord through a dural defect into the epidural space, causing tethering and displacement of the cord. It may be congenital or secondary to trauma, infection, or surgery. Dorsal arachnoid cysts can also be congenital or acquired due to adhesions and are often incidental findings. We retrospectively reviewed cases of spinal cord herniation and dorsal arachnoid cysts/webs from the Radiology Information System in a tertiary spinal and major trauma center. Spinal cord herniation demonstrates a female predominance, typically between 21 and 78 years of age (mean: 51 years). Most patients with spinal cord herniation present with Brown-Séquard syndrome. In contrast, most dorsal arachnoid cysts are asymptomatic and detected incidentally.

Results or Findings: On retrospective review over 3 years, 111 cases were reported as either dorsal arachnoid cysts, webs or spinal cord herniation. Most of the cases were reported as dorsal arachnoid cysts or webs. Spinal cord herniation was reported in only nine cases with an imaging differential of dorsal arachnoid cysts/webs. Magnetic resonance imaging is the primary imaging modality for spinal cord herniation, showing anterior displacement of the spinal cord, a characteristic “C-sign” deformity, and chronic compression signal changes in the cord. Spinal cord herniation is most common between T4 and T7. Computed tomography myelography confirms ventral dural defects and altered cerebrospinal fluid dynamics. Arachnoid cysts appear as nonenhancing extramedullary cerebrospinal fluid collections displacing the spinal cord or nerve roots. Myelography reveals contrast filling defects and subarachnoid space effacement. The “scalpel sign” has been described in dorsal arachnoid webs. Imaging findings differentiating these entities are illustrated using examples in this study.

Conclusion: Both spinal cord herniation and dorsal arachnoid cysts/webs cause focal spinal cord deformities but require distinct management approaches. Improved awareness and early recognition by radiologists can facilitate accurate diagnosis and timely intervention, reducing the risk of delayed treatment and neurologic morbidity.

Publikationsverlauf

Artikel online veröffentlicht:
02. Juni 2025