Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 4, 2010, pp. 676-677

Neurology India, Vol. 58, No. 4, July-August, 2010, pp. 676-677

Letter To Editor

Cerebellopontine angle endodermal cyst: A rare occurrence

Batuk Diyora, Koichiro Yoshida, Tsukasea Kawase, Tetsuo Kanno, Ando Motomi

Department of Neurosurgery, L.T.M.G. Hospital, Sion, Mumbai

Correspondence Address:Department of Neurosurgery, L.T.M.G. Hospital, Sion, Mumbai, bddiyora@hotmail.com

Date of Acceptance: 31-Jan-2010

Code Number: ni10185

PMID: 20739829

DOI: 10.4103/0028-3886.68699

Sir,

Endodermal cysts are rare congenital lesions of central nervous system (CNS) and usually occur in the posterior cranial fossa. ^[1] Endodermal cyst in the cerebellopontine angle is very rare. ^[2],[3] Imaging provides the anatomical details, but improved immunohistological techniques provide the definitive diagnosis. The cyst needs complete removal and recurrence is common with incomplete removal.

A 66-year-old female presented with progressive gait ataxia of four months duration. Neurological examination revealed right cerebellar signs. Computed tomography (CT) revealed non-contrast enhancing low-density cystic lesion in the right CP angle [Figure - 1]. Magnetic resonance (MR) imaging also revealed non-contrast enhancing cystic lesion in the right CP angle, which was homogenously hypointense on T1- weighted image and homogenously hyperintense on T2-weighted images [Figure - 2] and [Figure - 3]. Patient had right sub-occipital craniectomy and complete excision of the cyst by microsurgery. Frozen section study suggested epithelial nature of the cyst. Cyst content was creamy white colloid fluid. Histopathological examination showed non-ciliated columnar epithelial cells with focal pseudo stratified arrangement [Figure - 4]. Immunohistochemical studies revealed that the cells were positive for carcinoembryonic antigen and epithelial member antigen but negative for S-100 protein and glial fibrillary acidic protein. She had uneventful postoperative recovery and resolution of cerebellar signs.

The cysts in posterior cranial fossa.can be epithelial, mesenchymal or mixed in origin. ^[3] Epithelial cysts are rare CNS cystic lesion and are of two types, endodermal (neurenteric) and neuroepithelial (ependymal and choroidal). Endodermal cyst is lined with endodermal epithelium. Enterogenous, neuroenteric, foregut, bronchogenic and respiratory cyst are the other names according to the epithelial lining of the cyst wall. ^[4] The first report, three cases, of intracranial endodermal cyst was by Small. ^[5] Pathogenesis of the posterior fossa endodermal cysts is yet to be understood. Endodermal - ectodermal adhesion, split notochord or neurenteric band, disorder of gastrulation and persistence of the neurenteric canal are the possible explanations for the location of these lesions in the posterior fossa. Cyst content varies and includes clear, mucinous fluid, browny necrotic material, milky white liquid, viscous yellow fluid and cheesy grumous material. Differential diagnosis includes the arachnoid cyst, epidermoid cyst, neuroepithelial cyst, cystic schwannoma and inflammatory cysts such as cysticercosis. Steady-state free precession (SSFP) imaging is useful in differentiating lesions such as epidermoid from simple or complex benign cyst. Diffusion weighted MR can distinguish arachnoid cyst and epidermoid cyst. ^[6] Immunohistochemical stains are useful for the differential diagnosis, endodermal cysts are positive for cytokeratine and carcinoembtyonic antigen (CEA) in endodermal cyst and negative in neuroepithelial cyst. ^[3],[7] The treatment of choice for intracranial endodermal cysts is fenestration of the cyst and removal of the cyst wall. Since recurrence of endodermal cyst after fenestration alone has been reported, complete removal of the cyst wall is recommended. ^[8]

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