Neurenteric cyst of the ventral cervicomedullary region.

Neurenteric cysts are rare, benign, endodermally derived tumors of the central nervous system. Intracranial neurenteric cysts are rare with posterior fossa being the most common location among them. Neurenteric cyst of the craniocervical region is very rare. Authors report a rare case of neurenteric cyst located in the ventral cervicomedullary region. The pertinent literature is reviewed regarding this uncommon entity.

Introduction

Neurenteric cysts are rare endodermally derived lesions. They are most commonly located within the spinal canal and are usually associated with bony malformations.[1] Intracranial neurenteric cysts are rare and most are located in the midline posterior fossa.[2] Uncommon locations include craniocervical region, cerebellopontine angle, fourth ventricle, and supratentorial parenchyma.[3-6] Authors here report a rare case of neurenteric cyst located in the ventral cervicomedullary region which was excised via a lateral suboccipital approach.

Case Report

A 20-year-old male patient presented to our outpatient services with complaints of neck pain for 4 months and intermittent vomiting for 2 months duration. General physical examination was unremarkable. Neurological examination revealed left upper limb weakness (power 4+/5, Medical Research Council grading). Rest of the examination was normal.

Gadolinium-enhanced magnetic resonance imaging (MRI) revealed a well-defined lobulated lesion in the ventral cervicomedullary region from medulla to upper border of C2 vertebra. The lesion was heterogeneous in appearance; the anterior part measured 2.8 × 1.6 cm and was hypointense and hyperintense on T1- and T2-weighted images, respectively; while the 1.7 × 1.1 cm sized posterior part was iso to mildly hyperintense on T1 and heterogeneously hyper intense on T2-weighted sequences [Figure 1a and b]. The anterior part of the lesion was isointense, whereas the posterior part was hyperintense on fluid attenuation and inversion recovery (FLAIR) sequences. There was mild restriction on diffusion-weighted sequences. On post-contrast study, rim enhancement was evident in the posterior part of the lesion [Figure 1c]. Preoperative diagnosis was neurenteric cyst. Surgery was performed in prone position. A midline suboccipital craniectomy (with bone removal more on left side), left-sided C1 posterior arch removal, and partial C2 hemilaminectomy were performed. Intraoperatively, there was a well-defined, intradural, extra-medullary encapsulated, relatively avascular, lobulated lesion containing easily suckable, cheesy material located anterior to medulla extending up to C2 vertebral level. Vertebral artery, lower cranial nerves, and posterior inferior cerebellar artery were well visualized and preserved. Tumor decompression was followed by near total excision of the cyst wall in view of adherence of the cyst wall focally to surrounding vital structures. Postoperative course was uneventful and he was discharged on 7th postoperative day and is currently on regular follow-up. At the last follow-up of 3 months, patient was well with no deficits. Postoperative MRI showed a very small residual lesion [Figure 2].

Figure 1

(a) Sagittal T1-weighted magnetic resonance imaging showing the anterior hypointense and posterior hyperintense part of the lesion extending from medulla to upper border of C2 (b) Sagittal T2-weighted magnetic resonance imaging showing the lesion to be hyperintense (c) Sagittal T1-weighted post-contrast magnetic resonance imaging showing an isolated rim enhancement of posterior part of the lesion

Figure 2

Postoperative sagittal T1-weighted post-contrast magnetic resonance imaging showing a very small residual lesion in the lower brainstem

Histopathology

Hematoxylin and eosin photomicrographs showed epithelial lining thrown into folds along with irregular bundles of collagen. Higher magnification images show a prominent columnar epithelial lining with goblet cells focally thrown into papillary formations (×100), pseudostratification, and absence of cilia (×400). Overall features were consistent with an endodermal (neurenteric) cyst of Hind-gut type [Figure 3a and b].

Figure 3

Hematoxylin and eosin section photomicrographs showing prominent columnar epithelial lining with goblet cells focally thrown into papillary formations (×100) (a) pseudo-stratification and absence of cilia (×400), (b) Overall features were consistent with an endodermal (neurenteric) cyst of Hind-gut type

Discussion

Neurenteric cysts are benign, endodermally derived, epithelial-lined benign cystic lesions of central nervous system and constitute around 0.01% of central nervous system tumors.[2] Described in 1934 by Puusepp et al. as intestinoma, different terminologies have been used in the nomenclature including endodermal cyst, epithelial cyst, enterogenous cyst, enterogenic cyst, bronchogenic cyst, and enteric cyst among several others.[7] As the term neurenteric is used in cases of endodermal type cysts of the neural axis, the term neurenteric cyst has gained increasing popularity. Although many theories have been proposed to account for the embryogenesis of these lesions, the most widely accepted theory has been that proposed by Bremer et al. (1952), which postulates that these are due to abnormal persistence of neurenteric canal or formation of an accessory neurenteric canal with a split notochord and displacement of endodermal cells.[8]

Neurenteric cysts associated with the spinal cord are the most common and are typically situated in the ventral intradural extramedullary location in the lower cervical and thoracic spines. Approximately, 50% of them are associated with bony malformations including scoliosis, spina bifida, Klippel–Fiel syndrome, syringomyelia, and others.[9] Intracranial neurenteric cysts are uncommon and very rarely they have been associated with bony malformations. The first case of intracranial neurenteric cyst was reported by Small (1962) and around 81 cases of intracranial neurenteric cysts have been reported in the literature since then.[210] Among these, the most common locations include midline posterior fossa, anterior to the brainstem which account for about two-third of cases. Craniocervical junction, cerebellopontine angle, cerebellum, and fourth ventricle are other reported locations in the posterior fossa.[3-5] Supratentorial location is, however, very rare.[6] In a review of intracranial neurenteric cysts by Tucker et al.[2] and Bejjani et al,[11] these lesions are known to occur in all ages, most commonly in the third and fourth decades. Most reported reviews show a slight male predilection but recently, report by Tucker et al. has shown equal male and female distribution.[2] The presenting features depend upon the location of the cyst. Most patients present either with mass effects or with features of aseptic meningitis due to spill-over of cyst contents.[211] Major differential diagnosis at any site includes arachnoid cyst, dermoid cyst, and epidermoid cyst.[2] Complete excision is the treatment of choice. Subtotal excision is advisable if the cyst wall is adhered to vital structures.

Imaging

Lesions are commonly hypodense on computed tomography (CT) scan and hence, are often undetectable. On MRI, these lesions have a variable appearance but the most common one is of a well-defined, lobulated, T1 hypointense, T2 hyperintense lesion with no perilesional edema. Most are small sized, often <2 cm. On FLAIR sequences, they are hyperintense, show mild restriction of diffusion images and on post-contrast images, show no/minimal rim enhancement. They, however, are known to possess variable imaging features. Calcification is very rare. These lesions are avascular as documented by angiographic studies previously. In our case, there was a more heterogeneous appearance on all MRI sequences with rim enhancement of the posterior component. Other cystic lesions including arachnoid cyst, epidermoid cyst, dermoid cyst, and other endodermal lesions such as colloid cyst should be kept as differential diagnosis while interpreting these lesions on MRI.[1112]

Pathology

According to the Wilkins and Odem classification of spinal neurenteric cysts which is based on histopathological findings, three different types can be described: Types A, B, and C.[13] Of these, type A is the most common, whereas type C is the rarest and most complex variety. Most reported intracranial neurenteric cysts are of type A or B. None of them has been a type C variety.[11] On light microscopy, findings are of cyst lining composed of columnar epithelium with goblet cells. Two types: Mucin-producing cell-rich and poor types are recognized. However, there appears to be no correlation with the type and recurrence.[12] The contents of the cyst can also vary ranging from thin fluid to mucoid and cheesy contents. Immunohistochemical studies are generally not required. These cysts show positivity for epithelial membrane antigen (EMA), cytokeratin, carcinoma embryonic antigen (CEA), and CA 19-9 while they are uniformly negative for glial fibrillary acid protein (GFAP), vimentin, and S-100 markers. These help in differentiating them from arachnoid cysts, ependymal cysts, and cysts of neuroectodermal origin.[21415]

Treatment

The surgical approach depends upon the location of the lesion. As these lesions are benign and have minimal adherence to the surrounding structures, total surgical excision is the treatment of choice. However, in cases of adherence of the cyst wall, subtotal excision or marsupialization is advisable. Recurrence is uncommon and occurs usually at the site of the primary lesion. Long-term follow-up with radiological studies is necessary as delayed recurrences can occur. Signs of aseptic meningitis and increasing levels of CA 19-9 in cerebrospinal fluid (CSF) have been depicted as possible indicators of recurrence.[1415] Re-surgery is advisable for recurrent lesions. No adjuvant treatment is effective and hence is not required. Although considered benign, malignant transformation is possible, but very rare.[1516]

Conclusion

Intracranial neurenteric cysts are rare, benign lesions of central nervous system. Craniocervical region is an uncommon location for neurenteric cyst. They need to be considered in the differential diagnoses when presented with the classical imaging appearance as described. Complete surgical resection is the treatment of choice. Subtotal excision is advisable in cases where cyst wall is adhered to the surrounding structures. Long-term follow-up is necessary to look for delayed recurrences.