A rare case of extradural neurenteric cyst with supratentorial and infratentorial extension

Abstract

Dear Editor, Neurenteric cysts are rare benign endodermal lesions of the central nervous system like the Rathke cleft and colloid cysts. Intracranial neurenteric cysts are rare, with less than 100 cases reported in literature, most of which are found in the posterior fossa. We discuss a rare case of an extradural neurenteric cyst with supratentorial and infratentorial extension, and review the embryogenesis and differential diagnosis based on imaging and histopathological features. A 20-year male presented with suboccipital headache and painless, progressive diminution of vision of both eyes of 2 months’ duration. He was counting fingers close to face, and bilateral papilledema was noted. Evaluation with CT scan and MRI of the brain revealed an extradural lesion in the left posterior fossa with extension into the temporal region across the tentorium (Fig. 1a). He underwent a left retromastoid suboccipital craniectomy which was extended into the temporal region. The cyst was completely extradural in location, easily separable from the overlying bone and underlying duramater, except in the region over the transverse sinus where it was adherent to the duramater. Near total excision of the cyst wall was performed, leaving behind a part of the wall which was not separable from the duramater overlying the transverse sinus. The cyst contained thick, yellowish fluid (Fig. 1b), which was sterile on pyogenic culture with no cholesterol crystals or macrophages on microscopic examination. The patient had an uneventful post operative recovery period. At 6 months follow-up, his vision in the right eye improved to finger counting at 2 m, while that in the left eye remained unchanged. On fundoscopy, bilateral optic atrophy was noted. CT scan performed at 6 months showed no evidence of recurrence of the lesion (Fig. 1d). Histopathology sections showed a cystic lesion lined by a single layer of ciliated tall columnar epithelium (Fig. 1e). There was focal squamous metaplasia. Other connective tissue or glial elements were not identified. Immunohistochemistry with cytokeratin showed intense cytoplasmic positivity (Fig. 1f) in lining cells, whereas glial fibrillary acidic protein was negative (Fig. 1g). The precise embryological origin of the intracranial neurenteric cyst is not known. Since the endoderm does not extend cranially farther than the clivus, the possible explanation for an intracranial neurenteric cyst is displacement of the endoderm from its normal location (nasopharyngeal, respiratory tract, or intestinal tract) to an ectopic position in the embryo. Harris et al. has attributed the occurrence of posterior fossa neurenteric cyst to disturbance in early gastrulation after the onset of primitive streak regression [3]. Graziani et al. proposed that neurenteric cyst, colloid cyst, and Rathke cleft cyst originate from Seessel’s pouch, an endoderm diverticulum found behind esophageal membrane that usually regresses and disappears [2]. The evidence in support of this theory is that intracranial neurenteric cysts are not associated with other developmental malformations unlike spinal neurenteric cysts that are associated with occult spinal dysraphisms. The authors declare that this case report has not been presented at any conference or accepted for publication in any journal before. R. S. Reddy (*) :M. Vijayasaradhi Department of Neurosurgery, Nizam’s Institute of Medical Sciences, Hyderabad, Andhra Pradesh, India 500082 e-mail: rajesh_jipmer@rediffmail.com