CASE 8356 Published on 29.04.2010

Transdural spinal cord herniation

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Arora A, Bhutani R, Gupta R, Mahajan H

Patient

39 years, male

Clinical History
A 39-year-old man presented with a 2 year history of progressive loss of temperature sensation and dysesthesia in the right thigh and weakness in the contralateral lower limb.
Imaging Findings
A 39-year-old man presented with a 2-year history of progressive loss of temperature sensation and dysesthesia in the right thigh and weakness in the contralateral lower limb. Neurological assessment revealed pyramidal signs in both the lower limbs, spasticity in the left lower limb and bilateral plantar extensor response. In addition he had wasting of left thigh muscles. MRI of the thoracic spine revealed a ventrally displaced spinal cord at D4 level with obliteration of the anterior subarachnoid space. There was anterior kink of the spinal cord noted suggesting adherence to the dorsal aspect of the D-4 vertebral body. On the basis of the MR findings, a diagnosis of transdural idiopathic spinal cord herniation was considered. Patient underwent D3-D5 laminectomy and reduction of the herniation. Intra-operatively herniation of the cord through a small dural defect was recognised. Successful reduction and closure of the dural defect with graft material was performed.
Discussion
Spontaneous or idiopathic spinal cord herniation is a rare condition that is seldom recognised. It most commonly occurs in the thoracic region. The thoracic spinal cord prolapses through a ventral or lateral dural defect causing anterior displacement and focal kinking of the thoracic spinal cord. The commonest presentation is a Brown-Sequard syndrome.

The etiopathogenesis remains unclear; however various proposed theories include: congenital dural defects, minor trauma leading to focal dural tear, rupture from prolapsed disc, and duplication of the dura. The negative epidural pressure and CSF pulsations contribute in progressive herniation of the cord through the dural defect. This results in myelopathy and progressive neurological symptoms. Other factors that may contribute to progressive myelopathy include tethering and distortion of the cord, and cord ischemia.

MRI is the imaging modality of choice. Dorsal spine MRI shows ventral displacement of the thoracic spinal cord with disappearance of the anterior subarachnoid space and enlargement of the posterior subarachnoid space. An anterior kink of the thoracic spinal cord is best observed on the Sagittal MR images, most commonly between D4 to D7 vertebral level. Associated cord atrophy may be present at the level of herniation. It is important to exclude a cystic lesion posterior to the spinal cord, such as an arachnoid cyst, because on imaging it can mimic cord herniation. Phase-contrast MR imaging has shown to be helpful in differentiating the two, by showing an absence of CSF flow anterior to the herniated cord and a normal CSF flow pattern dorsal to the cord in patients with spontaneous cord herniation.

Reduction of the herniated cord and microsurgical repair of the dural defect is usually successful in achieving recovery of function or at least arresting its progression. It is important to be aware of the imaging findings, since this cause of paraparesis is potentially curable if diagnosis is made early.
Differential Diagnosis List
Idiopathic ventral transdural herniation of the thoracic spinal cord
Final Diagnosis
Idiopathic ventral transdural herniation of the thoracic spinal cord
Case information
URL: https://www.eurorad.org/case/8356
DOI: 10.1594/EURORAD/CASE.8356
ISSN: 1563-4086