Neurenteric Cyst: Magnetic Resonance Imaging Findings in an Adolescent.

Intracranial neurenteric cysts are uncommon congenital space-occupying lesions that may be misinterpreted for other more frequent nonneoplastic cysts and cystic tumors. We discuss the imaging findings of this lesion in a 16-year-old female who presented with chronic headaches.

CASE PRESENTATION

A 16-year-old female presented with chronic headaches for 5 years with neurological examination revealing no sensory or motor deficits. The patient was referred for magnetic resonance imaging of the brain that showed lobulated lesion appearing hypointense on T2-weighted/fluid-attenuated inversion recovery (FLAIR) images and hyperintense on T1-weighted images in the midline anterior to the pontomedullary junction and extending from the midline into the left cerebellopontine angle [Figures 1–4]. The lesion measured 2.8 cm × 1.3 cm × 1.5 cm and showed no obvious enhancement on the administration of contrast. There was no diffusion restriction on diffusion-weighted (DW) images while magnetic resonance spectroscopy (MRS) exhibited an N-acetylaspartate (NAA) like peak at 2.02 ppm. The same lesion was appearing hyperdense on computed tomography scan done at some other center. Midline suboccipital craniectomy was done with near-total removal of the lesion. Histopathology revealed the cyst wall comprised endothelium-lined structures of partially ciliated cuboidal to columnar cells with pseudostratification in places as well as squamous metaplasia, which was suggestive of neurenteric cyst. Immunohistochemical analysis was negative for periodic acid-Schiff stain and glial fibrillary acidic protein.

Figure 1

Sagittal T2-weighted image demonstrates a mass in the midline anterior to the pontomedullary junction. The cyst is hypointense to brain parenchyma and cerebrospinal fluid

Figure 4

Axial T1-weighted demonstrates a hyperintense mass at the level of the pontomedullary junction. It is hyperintense to cerebrospinal fluid and the surrounding brain parenchyma

Axial T2-weighted scan shows a mass anterior to the pontomedullary junction

Axial T2-weighted scan shows the mass extending from the midline into the left cerebellopontine angle

These space-occupying lesions (SOLs) are rare, congenital, benign, malformative endodermal lesions involving the craniospinal axis with spine being the more common location. As in our case, the majority of intracranial neurenteric (NE) cysts are located in the posterior fossa. They are classically located in the midline anterior to the brainstem and may extend to involve the cerebellopontine angle.[1] While the exact source is undetermined, NE cysts possibly develop at the time of notochordal development during the phase of existence of the NE canal. The notochord and foregut are unable to split, causing primitive endodermal cells to be assimilated into the notochord. These migrant alimentary cells eventually turn into a cyst. These lesions generally measure <2 cm, and on macroscopic examination, they are smooth, thin-walled, and translucent structures. Contents of these cystic lesions vary from clear to mucoid or xanthochromic. Histopathological analysis of the cyst wall exhibits endothelium-lined structures of partially ciliated cuboidal to columnar cells. Pseudostratification may also be seen in the epithelium at random intervals and characteristically has ciliated and goblet cells. These lesions comprise only endodermal components and very much bear a resemblance to gastrointestinal tract mucosa.[2]

Typical imaging characteristics of an NE cyst comprise a circular and/or lobulated, mildly hyperintense SOL located anterior to the medulla and showing no enhancement in postcontrast images. The signal intensity of these cysts on MR sequences varies with the protein content with typical appearance of a T1 isointense to slightly hyperintense and T2-weighted/FLAIR hyperintense signal. However, in the present case, this cyst had hypointense signal on T2-weighted images which has been postulated to be due to elevated protein concentration within the cyst, squamous metaplasia, and voluminous keratinous debris. Uncommonly, these lesions may show mild restriction on DW images as well as rim enhancement in postcontrast images.[3] The differential diagnosis of these cysts comprises arachnoid cyst, epidermoid cyst, Rathke and colloid cysts with the last two being other subtypes of endodermal cysts. The epidermoid has greatest similarity to the NE cyst as it is hyperintense on T1-weighted images and is often located along the midline. However, epidermoid cysts typically show restriction on DW images. On the other hand, arachnoid cysts have the same signal intensity as cerebrospinal fluid at all sequences and have no NAA peak at 2.02 ppm on MRS because of lack of neuronal elements. Rathke and colloid cysts can be distinguished from NE cysts on the basis of site.[4]

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Conflicts of interest

There are no conflicts of interest.