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Neuroradiology Case of the Week
Case 268
Ashwani K. Sharma, MD, and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: Patient
is
a 36-year-old male who presented with progressive paraparesis for past one year. There is no history of trauma or operation.
Imaging Findings: MR and post-myelography CT imaging shows classical anterior focal displacement of the cord with posterior expansion of the arachnoid space.
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Figure 1. Axial post-myelography CT shows expanded dorsal subarachnoid sac with distorted cord displaced against the back of vertebral body.
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| Figure 2. Sagittal post-myelography CT shows kink of the upper thoracic cord and adhesion to back of vertebral body. |
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| Figure 3. Sagittal T2WI MR depicts sudden anterior kink or step in the upper thoracic cord. |
Diagnosis: Idiopathic cord herniation
Discussion: Spinal cord herniation is a rare condition, which usually presents with slowly progressive myelopathy. Although most of the reported cases have been idiopathic [1] in aetiology, post-operative and post traumatic cord herniation has also been reported.
Spinal cord herniation occurs secondary to a dural defect and can be classified on the basis of etiology of dural defect, which can be idiopathic, post-traumatic or iatrogenic. Patients may present clinically as Brown-Sequard syndrome, spastic monoparesis or paraparesis [2]. In idiopathic cases, the cord herniates through a dural defect, which is usually situated on the concave side of the spinal curvature (dorsal in the cervical spine and ventral or ventrolateral in the thoracic spine) [1]. The spinal cord herniates through the damaged dura matter in traumatic cases [3], which is likely to occur in the ventral part of the dural sac. Post-operative spinal cord herniation is rare and has been reported to occur after laminectomy, surgery for intradural extramedullary tumor, decompressive laminectomy with dural openings and as a complication of fracture fixation wire.
In the past, diagnosis of cord herniation was based on myelography and CT myelography [2]. At present, MR is the most common modality used to diagnose spinal cord herniation. MR features have been well reported and include: a) acute, angular deviation of the cord; b) cord deviation limited to less than two vertebral segments; and c) the absence of posterior loculation within the subarachnoid space [2].
References:
- Miyake S, Tamaki N, Nagashima T, Kurata H, Eguchi T, Kimura H. Idiopathic spinal cord herniation: Report of two cases and review of the literature. J Neurosurg. 1998 Feb;88(2):331-5. [Medline]
- Marshman LA, Hardwidge C, Ford-Dunn SC, Olney JS. Idiopathic spinal cord herniation: case report and review of the literature. Neurosurgery. 1999 May;44(5):1129-33. [Medline]
- Spissu A, Peltz MT, Matta G, Cannas A. Traumatic transdural spinal cord herniation and the nuclear trail sign: case report. Neurol Sci. 2004 Jul;25(3):151-3. [Medline]
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