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 –]. 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.\nThese 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.[] 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.[]\nTypical 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.[] 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.[]\nNil.\nThere are no conflicts of interest.
A 17-year-old female patient presented with neck pain since two weeks which was aggravated by exercise and neck movements. She developed weakness of limbs for one week which started in left upper limb and then evolved to involve all four limbs. She also complained of numbness in both upper limbs and urgency of micturation. On neurological examination, tone was mildly decreased in both upper limbs and increased in both lower limbs. Power was 2/5 in left upper limbs and 4/5 in other limbs. Deep tendon reflexes were absent in upper limbs and exaggerated in lower limbs. Pain and touch sensation decreased by 30% below C2 level and vibration sense lost below T2 level.\nMRI [] showed a well circumscribed extra-axial cystic lesion of 3 × 1.8 × 2.4 cm size noted anterior and to the right of medulla extending through foramen magnum into upper cervical canal. It was hyperintense on T1 and T2 weighted images with no diffusion restriction. On right side hypoglossal nerve was displaced laterally by lesion.\nShe underwent suboccipital craniectomy and total excision of the lesion via right lateral approach. Histopathology showed a cyst wall is lined by cuboidal and columnar epithelium with goblet cells (arrow) suggestive of a neuroenteric cyst.\nPostoperatively, patient's power improved to 4/5 in all 4 limbs.