Ependymal cysts (EC) are benign fluid-filled sacs lined by columnar or cuboidal cells that arise from cerebral parenchyma and are most commonly found supratentorially near the lateral ventricle, juxtaventricular, or temporoparietal regions [1], [2]. Previous cases have also identified infratentorial EC of the brainstem, cerebellum, and subarachnoid spaces [2]. EC is often misinterpreted due to conflicting nomenclature in the literature and their elementally indistinguishable radiological nature from other intraventricular simple cysts, such as arachnoid and choroid plexus cysts [3]. Choroid plexus cysts can be distinguished from EC due to their enhancing nature and bilateral pattern. Ependymal and arachnoid cysts are more difficult to differentiate due to their non-enhancing nature, but arachnoid cysts are isolated to the subarachnoid space, while EC can be identified in periventricular regions [4]. EC are also thin-walled, well-defined, do not contrast enhance, and are isoattenuating to CSF. In magnetic resonance imaging (MRI), EC does not exhibit diffusion restriction and follows the CSF signal on all sequences. They may be hyperintense to CSF in the case of high protein content [2]. To confirm the diagnosis of an ependymal cyst, gross histopathological examination is essential. EC should show an immunoreactive response towards staining for the glial fibrillary acidic protein (GFAP) and S-100 markers commonly expressed by normal ependymal epithelium [1], [2].

EC are typically seen in young adults with a male preponderance [1]. These are asymptomatic, however, neurological deficits can arise when its mass effect compresses adjacent intracranial structures [5]. In the literature, nearly all confirmed ependymal cyst cases reported some form of headache, whereas dizziness, seizures, or associated hydrocephalus are also common depending on location and severity [1], [3], [5]. Past studies have shown that EC are commonly treated through various endoscopic and microsurgical techniques including cyst fenestration and excision. Other treatment methods such as stereotactic aspiration and placement of a cystoventricular shunt have been utilized successfully to treat EC [5]. Regardless of the treatment plan utilized, cases reported have shown high survival rates [3]. In this paper, we present the first-ever reported case of a symptomatic medullary ependymal cyst treated with surgery, along with a comprehensive review of the literature on EC of other parts of the brain stem (Table 1) [6], [7], [8], [9], [10], [11].