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Year : 2000  |  Volume : 10  |  Issue : 3  |  Page : 187-188
Posterior fossa enterogeneous cyst: CT and MRI


Department of Radiodiagnosis and Imaging, Christian Medical College and Hospital, Vellore, Tamilnadu, India

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How to cite this article:
Singh S. Posterior fossa enterogeneous cyst: CT and MRI. Indian J Radiol Imaging 2000;10:187-8

How to cite this URL:
Singh S. Posterior fossa enterogeneous cyst: CT and MRI. Indian J Radiol Imaging [serial online] 2000 [cited 2019 Sep 17];10:187-8. Available from: http://www.ijri.org/text.asp?2000/10/3/187/30596
Sir,

I would like to report CT and MRI appearances of a posterior fossa enterogenous cyst in a patient in whom an initial radiological diagnosis of cystic meningioma, epidermoid inclusion cyst and cystic astrocytoma was considered.

A forty-years-old man presented with bi-occipital headache associated with visual obscuration, unsteadiness of gait, vertigo and tinnitus of one-year duration. Examination showed bilateral papilledema and horizontal gaze evoked nystagmus. Mild hypotonia of the left upper and lower limbs with cerebellar signs was also noticed. Tandem walking was impaired. The provisional clinical diagnosis was of a posterior fossa mass. The CT scan showed a 7 x 5 x 4.5 cm thin peripherally enhancing extraaxial hypodense mass lesion in the left side of the posterior fossa [Figure - 1]. There was mild hyperostosis of the adjacent skull vault. On MRI, the T2W and proton density-weighted images showed a homogeneous high signal intensity lesion with an ill-defined peripheral isointense rim [Figure - 2]a,b. On T1W images, the lesion was hypointense with a peripherally enhancing rim [Figure - 2]c. The adjacent tentorium also showed mild thickening and enhancement. There was compression of the cerebellum with midline shift, upward displacement of the tentorium and mild dilatation of the lateral and third ventricles. The radiological diagnosis of cystic meningioma/ epidermoid inclusion cyst /cystic astrocytoma with predominant exophytic component was considered.

A left retromastoid suboccipital craniectomy showed a cystic extradural lesion with dark fluid containing shiny crystals suggestive of epidermoid /dermoid cyst. The cyst was excised in toto and histopathology revealed the presence of an enterogenous cyst. There was no evidence of recurrence.

Enterogenous cyst results from a dysembryogenetic error that occurs in the third week of fetal life [1],[2],[3]. It is a rare, slowly growing mucin-producing epithelial-lined neurenteric cyst of endodermal origin [1],[3]. In a few patients, it may be associated with congenital anomalies of the axial skeleton; localized expansion of the spinal canal, hemivertebra, spina bifida and vertebral fusion [2]. Histologically, the diagnosis is confirmed on specimens stained with periodic acid-Schiff, alcian blue, mucicarmine and immunohistochemical staining of carcinoembryonic antigen and by electron microscopy [1],[2],[3]. The cervical followed by the lower thoracic spinal canal are said to be their favorite sites [2]. Intramedullary enterogenous cysts of the cervical spinal cord are very rare [2]. Few case reports of an enterogenous cyst in the cerebellopontine angle cistern orbit, intraventricular and retroperitoneal locations have been published [1],[2],[3]. A case report of a well-differentiated papillary adenocarcinoma arising in a supratentorial enterogenous cyst has also been described [4].

The CT and MRI findings in enterogenous cysts are non-specific and a definitive diagnosis is established on histopathological evaluation of the specimen. On CT scan, hypodense, non-enhancing, cystic, irregular, extra-axial mass lesion [1],[2],[3] and on MRI, a sharp edge lesion that is hypointense on T1W and hyperintense on T2W images with signal intensity similar to CSF have been described [3],[4]. MRI also allows the evaluation of any CSF pulsation in the cystic lesion and, in the presence of a cystic neoplasm, any signal changes in the adjacent parenchyma [4]. A case report of widespread craniospinal dissemination associated with the incomplete resection of an enterogenous cyst has been described [1],[2]. Recurrence of enterogenous cyst has been reported and hence patients should be monitored for a possible recurrence. In our patient a provisional diagnosis of enterogenous cyst was not considered due to its rarity especially in the posterior fossa.

 
   References Top

1.Nalm-ur-Rahman, Jamjoom A, al-Rajeh SM, al-Sohaibani MO. Spinal intradural extramedullary enterogenous cysts. Report of two cases and review of literature. J Neuroradiol 1994; 21: 262-6.   Back to cited text no. 1    
2.Rao MB, Rout D, Misra BK, Radhakrishnan VV. Craniospinal and spinal enterogenous cysts-report of three cases. Clin Neurol Neurosurg 1996; 98: 32-6.   Back to cited text no. 2  [PUBMED]  
3.Ito S, Fujiwara S, Mizoi K, Namiki T, Yosimoto T. Enterogenous cyst at the cerebellopontine angle: case report. Surg Neurol 1992; 37: 366-70.   Back to cited text no. 3  [PUBMED]  
4.Ho LC, Olivi A, Cho CH, Burger PC, Simeone F, Tihan T. Well-differentiated papillary adenocarcinoma arising in a supratentorial enterogenous cyst: case report. Neurosurgery 1998; 43: 1474-77.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]

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Correspondence Address:
Surendra Singh
Department of Radiodiagnosis and Imaging, Christian Medical College and Hospital, Vellore, Tamilnadu
India
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Source of Support: None, Conflict of Interest: None


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