British Journal of Radiology (2003) 76, 132-134
© 2003 British Institute of Radiology
doi: 10.1259/bjr/60547861
Spinal cord herniation into a mediastinal neurenteric cyst: CT and MRI findings
K Aydin, MD
1
S Sencer, MD
1
A Barman, MD
1
O Minareci, MD
1
K T Hepgul, MD
2 and
A Sencer, MD
2
Departments of 1 Radiology and 2 Neurosurgery, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
Correspondence: K Aydin, Camlikyolu, B. Mehmetpasa sokak, Yavuz apt. No: 10/10 Etiler, Istanbul, Turkey
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Abstract
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Split notochord syndrome is a spectrum of congenital spinal malformations that develops due to an adhesion between endoderm and ectoderm causing the "splitting" of notochord. Neurenteric cyst is one of the components of split notochord syndrome. We report CT and MRI findings of an unusual case with thoracal spinal cord herniation into a mediastinal neurenteric cyst.
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Introduction
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Split notochord syndrome is a spectrum of congenital spinal malformations that results from the "splitting" of notochord due to a persistent connection between endoderm and dorsal ectoderm. Dorsal enteric fistula, dorsal sinus, dorsal diverticula and neurenteric cysts are the components of the spectrum [1, 2]. All forms of split notochord syndrome are frequently associated with vertebral anomalies such as anterior and posterior spina bifida, butterfly vertebrae and hemivertebrae [1, 3].
We report the imaging findings of an interesting case of thoracal spinal cord herniation into the mediastinal neurenteric cyst and discuss the pathogenesis.
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Case report
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An 8-year-old boy presented with weakness in the lower extremities and thoracic scoliosis noticed by his family when he was 2 years old. Physical examination revealed spastic paraparesis and left sided thoracic scoliosis.
X-ray examination of thoracic spine revealed a large defect in the bodies of T3 and T4 vertebrae and a well circumscribed mass located in the posterior mediastinum adjacent to the vertebral body defects. CT examination showed a dysplastic appearance with increased interpedicular distance of upper thoracic vertebrae. The bodies of T3 and T4 vertebrae were split creating a large anterior spinal defect and kyphosis (Figure 1
). There was also a cystic mass located in the posterior mediastinum. The spinal cord was displaced ventrally at the level of this anterior spina bifida (Figure 2).
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Figure 1. Three-dimensional reconstructed CT image of the thoracic vertebrae demonstrates a large bony defect in the bodies of T3 and T4 vertebrae and kyphosis just above the bony defect. The bodies of T3 and T4 vertebrae seem to be "split".
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Figure 2. (a) Axial non-enhanced CT image at the level of anterior spina bifida. Note the wide anterior spina bifida defect and the ventral displacement of spinal cord into the mediastinal cyst (arrow). (b) Axial CT image below the level of spina bifida reveals a well circumscribed posterior mediastinal cyst (arrow heads).
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MRI was performed to evaluate the relationship between the mediastinal cyst and spinal cord. On MR images the mediastinal cyst was isointense with cerebrospinal fluid (CSF) on both T2 and T1 weighted images (Figure 3). The flow of CSF from the spinal subarachnoid space into the mediastinal cyst caused a "signal void" which confirmed the direct anatomic connection between two compartments. The spinal cord at the level of the anterior spina bifida was deformed in shape and herniated into the mediastinal cyst through the bony defect (Figure 3a). There were hypointense bands extending between the ventral surface of spinal cord and superior wall of the cyst on T2 weighted images. MR images from the other levels of spine were normal. The spinal cord ended at the level of the L2 vertebra.
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Figure 3. (a) T1 weighted sagittal image (460/15/2 [TR/TE/excitation]) at midline shows the herniation of thoracic spinal cord into the posterior mediastinal cyst through the defect in the vertebrae bodies (open arrow). Note the band extends between the anterior surface of cord and the walls of cyst (arrow head). (b) T2 weighted sagittal (4000/90/2) image reveals the signal void due to cerebrospinal fluid flow in the subarachnoid space towards the lumen of mediastinal cyst (arrow) and in the cyst (open arrow). Note the hypointense band extending between the cord and superior wall of the cyst (arrow head).
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With characteristic imaging findings, the case was diagnosed as thoracic spinal cord herniation into a mediastinal neurenteric cyst. The patient's family refused the operation suggested by the neurosurgery department.
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Discussion
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During the second week of normal embryonal development, the embryo consists of dorsally lying ectoderm and ventrally lying endoderm, which is in contact with the yolk sac. During the third week of gestation, a midline primitive streak appears at the caudal end of ectoderm. Proliferating ectodermal cells from the primitive streak migrate laterally between ectoderm and endoderm to form the mesodermal layer. The cephalic end of the primitive streak thickens and forms Hensen's node. Proliferating cells from Hensen's node migrate cranially in the midline to form the notochord. The notochord separates endoderm from ectoderm in the midline and forms the vertebral column with surrounding mesoderm [1, 4].
The embryologic mechanism for the development of split notochord syndrome was first discribed by Saunders in 1943 [5]. In the pathogenesis of split notochord syndrome, an adhesion occurs between endoderm and ectoderm in the route of notochord and notochord splits around the adhesion creating a defect in the vertebral column. Adhesion between endoderm and ectoderm also results in a potential connection between yolk sac (gut) and dorsal ectodermal surface (skin). This connection persists as a tractus in the dorsal enteric fistula, which is the most severe form of split notochord syndrome or may obliterate at any point creating a dorsal enteric sinus, diverticula and neurenteric cysts [5–8].
The location of neurenteric cysts may be pre-vertebral, intraspinal or post-vertebral. The posterior mediastinum is a frequent location for pre-vertebral neurenteric cysts. Neurenteric cysts are lined by gastrointestinal or respiratory epithelium. Anterior and posterior spina bifida, butterfly vertebrae and hemivertebrae frequently accompany the neurenteric cysts [1, 3]. Prevertebral neurenteric cysts may be connected to the meninges or spinal cord by a tube or a fibrous neurenteric band via an anterior spina bifida and dura defect [2].
In this case, the CT and MR appearance of the posterior mediastinal cyst, which has direct communication with the subarachnoid space through a wide anterior spina bifida, is characteristic for neurenteric cyst. Particularly on CT images, the split appearance of vertebral bodies is highly suggestive for the diagnosis of split notochord syndrome. An unusual feature in this case is the herniation of thoracic spinal cord into the mediastinal cyst. To our knowledge, there is no reported case of spinal cord herniation into a mediastinal neurenteric cyst in the literature. Although pre-vertebral neurenteric cysts generally do not cause neurological symptoms, it seems that tethering and herniation of spinal cord were responsible for the neurological symptoms and signs in this case [1, 2].
The sponteneous herniation of thoracic spinal cord into extradural arachnoid cysts has been reported. Anterior displacement of the thoracic spinal cord with an acute angle as seen in this case has also been described in spontenous cord herniation. The pathogenesis of sponteneous cord herniation has been ascribed to a congenital dural defect [9]. In this case, tubular connection between subarachnoid space and neurenteric cyst provides a route for the cord herniation. The adhesion of nerve roots to the walls of cyst or CSF pulsation force may be the reason for tethering and herniation of cord within the mediastinal cyst.
In conclusion, we reported the CT and MRI findings of a mediastinal neurenteric cyst with spinal cord herniation, which has previously not been reported in the literature. Although it is very rare, spinal cord herniation may be the cause of neurological symptoms in cases with pre-vertebral neurenteric cysts.
Received for publication July 2, 2002.
Accepted for publication September 16, 2002.
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References
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- Barkovich AJ. Pediatric Neuroimaging. New York: Raven Press, 2000;621–714.
- Alrabeeah A, Gillis DA, Gianmantonio M, Lau H. Neurenteric cysts—a spectrum. J Pediatr Surg 1988;23:752–4.[CrossRef][Medline]
- Brooks BS, Duvall ER, El Gammal T, Garcia JH, Gupta KL, Kapila A. Neuroimaging features of neurenteric cysts: analysis of nine cases and review of the literature. AJNR 1993;14:735–46.[Abstract]
- O'Rahilly R, Meyer DB. Timing and sequence of events in the development of the human vertebral column during the embryonic period proper. Anat Embryol 1979;157:167–76.[CrossRef][Medline]
- Saunders RL de CH. Combined anterior and posterior spina bifida in a living neonatal human female. Anat Rec 1943;87:255–78.[CrossRef]
- Burrows FGO, Sutcliffe J. The split notochord syndrome. Br J Radiol 1968;41:844–7.[Abstract/Free Full Text]
- Bentley JFR, Smith JR. Development of posterior enteric remnants and spinal malformations: the split notochord syndrome. Arch Dis Child 1960;35:76–86.
- Razack N, Page L. Split notochord syndrome: case report. Neurosurgery 1995;37:1006–8.[Medline]
- Wada E, Yonenobu K, Kang J. Idiopathic spinal cord herniation: report of three cases and review of the literature. Spine 2000;25:1984–8.[CrossRef][Medline]
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Abstract
Introduction
