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Neuroradiology Case of the Week
Case 321
Wade C. Hedegard, MD
Clinical
Presentation: A 2-year-old female presented with neck pain, stiffness and hypotonia.
Imaging Findings: CT scan showed a large, hypodense cystic mass. It is non-calcified and is displacing the cerebellar vermis, brainstem and spinal cord posteriorly (Fig. 1).
MRI shows the large cystic lesion in the posterior fossa extending from the belly of the pons down to the level of the C3 vertebral body. It measures 2.9 x 1.8 x 4.2 cm and is displacing the medulla and upper cervical cord posteriorly. It is hypointense on T1 sequences (Fig. 2) and hyperintense on T2 sequences (Fig. 3). It demonstrates signal intensity equal to that of CSF on DWI, with no restricted diffusion (Fig. 4). The lesion does not enhance with contrast administration (Fig. 5).
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| Figure 1: Axial non-contrast CT image. |
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Figure 2: Sagittal T1-weighted MR image.
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Figure 3: Sagittal T2-weighted MR image.
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| Figure 4: Axial diffusion-weighted MR image. |
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| Figure 5: Sagittal T1-weighted post-contrast MR image. |
Diagnosis: Intracranial neurenteric cyst
Discussion: Neurenteric cysts, also known as enterogenous cysts, are rare lesions that may occur within the spinal cord as well as intracranially. Approximately 80% are located within the spine and only 10-15% within the brain. Please see Neuroradiology Case 240 for further discussion of intraspinal neurenteric cysts. When they are found in an intracranial location, they typically occur along the midline as intradural extramedullary masses in the posterior fossa. Very rarely they may be found as intramedullary lesions. The craniocervical junction (anterior to the brainstem) as well as the cerebellopontine angles are common locations.
Neurenteric cysts are benign, congenital disorders that arise during notochord development from an abnormal persistent connection between the endoderm and neuroectoderm. The vental midline adhesion prevents normal induction and formation of the notochord, leading to it splitting around the area of endodermal/neuroectodermal connection and forming a cyst. Pathologic examination reveals a thin-walled, fluid containing cyst. The cyst wall is made up of fibrous connective tissue overlying a single layer of columnar or cuboidal epithelium.
Neurenteric cysts may be asymptomatic and found incidentally. Conversely, they may cause headaches, visual disturbances, cranial nerve palsies or ataxia. Imaging characteristics are not entirely specific but usually include a well-defined lobulated midline cystic mass. Neurenteric cysts are typically non-calcified and do not enhance. The differential diagnosis of a posterior fossa neurenteric cyst is an arachnoid cyst, neuroepithelial cyst, epidermoid cyst, cystic schwannoma, or cysticercosis. Treatment is complete removal of the cyst.
References:
- Osborn AG: Diagnostic Neuroradiology. St. Louis:Mosby, 1994:648-649.
- 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 Am J Neuroradiol. 1993 May-Jun;14(3):735-46. [Medline]
- Castillo M: The Core Curriculum: Neuroradiology. Philadelphia:Lippincott Williams & Wilkins, 2002:335.
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