Ependymal cysts are rare, benign neuroepithelial lesions that primarily occur in the brain parenchyma but can also be found in the subarachnoid space, spinal canal, brainstem, pontine cerebellar angle, and rarely in the ventricle of the brain (Boockvar et al., 2000). The majority of cysts are clinically asymptomatic and are detected during routine imaging. However, patients may exhibit symptoms upon excessive cyst enlargement that causes compression of the brain parenchyma and affects cerebrospinal fluid circulation. The extent of symptoms can vary with the size and location of the lesion. In such patients, surgical intervention may be necessary to reduce hydrocephalus (Ho and Wu, 2009). Currently, there is limited research on ependymal cysts, they can be difficult to differentiate from other benign intracranial lesions by imaging alone, so they are often misdiagnosed (Ciricillo et al., 1990). Therefore, the final diagnosis should only be made after observation of a cystic lesion using imaging, histopathological confirmation of an ependymal cyst postoperatively, and positive glial fibrillary acidic portein (GFAP) staining using immunohistochemical analysis (Inoue et al., 1988).

The majority of patients exhibit good outcomes following treatment of benign ependymal cysts, with only one study to date reporting patient death, cause of death is the neurosurgical procedure itself (Paulla Galdino Chaves et al., 2022). Although the origins of ependymal cysts remain unclear, it has been proposed that they may arise from ectopic displacement of ventricular cells during embryonic development (Friede and Yasargil, 1977). During embryonic development, the abnormal ependymal cysts in the primitive rhombencephalic vermis expand into the brain parenchyma and then gradually enlarge as the patient grows, eventually compressing the brain parenchyma or affecting cerebrospinal fluid circulation, and leading to the development of the corresponding symptoms (Sharpe and Deck, 1977). Headache is the most common clinical manifestation of ependymal cysts. Oversized cysts often lead to obstruction of cerebrospinal fluid circulation, and some patients may show symptoms of obstructive hydrocephalus, such as headache, nausea, vomiting, blurred vision, drowsiness, and seizures (Czervionke et al., 1987). The development process of these lesions is biased towards a benign progression, before cystic lesions were discovered during casual imaging, a number of patients didn’t perceive the presence of early lesion, which has led to a minimal number of reports about them in the literature, and there is less research in this field can also be attributed to this. Data on past patients in the literature can be found in Supplementary Table 1 (van Lindert et al., 1998; Shin et al., 2000; Roberti and Magram, 2005; Kumar et al., 2006; Endo et al., 2009; Fonoff et al., 2010).

Differentiation of ependymal cysts from other benign cranial lesions such as arachnoid, endothelioid, or endothelial cysts can be difficult using imaging alone (Ciricillo et al., 1990). Computed tomography (CT) scans show that these round lesions are similar in density to cerebrospinal fluid, and the MRI imaging of the fluid in cysts shows signals similar to cerebrospinal fluid-like signal. This can also be used to rule out the presence of other lesions, such as gliosis or soft tissue masses.

Due to the rarity of these lesions, no standardized treatment protocols have been developed to date. Surgical intervention is deemed necessary in patients presenting with symptoms such as headaches and blurred vision, with the most common surgical approaches include being open total resection, partial resection communicating ventricular shunts, cyst deroofing and opening, and stereotactic suction (El Damaty et al., 2017). The surgical approach of choice varies with the location of the cyst, and some articles have suggested the use of neuronavigation for intraoperative localization of the lesion in order to minimize the damage to the brain parenchyma (Prieto et al., 2013). These treatment measures typically aim to relieve compression of the brain tissue and restore cerebrospinal fluid circulation, with the majority of cases involving the removal of the capsule wall and connection of the capsule cavity to the ventricular system. This approach reduces brain tissue damage during total cystectomy while also allowing the cystic fluid to be recycled and metabolized through the ventricular system, preventing postoperative lesion enlargement. However, some patients have experienced cyst recurrence, after undergoing partial resection communicating ventricular shunts or stereotactic suction. To avoid this, a concomitant ventriculoperitoneal shunt is recommended for patients with poor connection of the capsule chambers to the ventricular system. Most patients exhibit improvement in symptoms after surgery, with only one patient dying due to surgical complications to date (Paulla Galdino Chaves et al., 2022). However, the recurrence rates of these cysts remain unknown due to limited long-term follow-up evidence.

Ependymal cysts have a translucent or light gray membrane, do not communicate with the ventricular system or the subarachnoid space, and contain a clear fluid (similar to cerebrospinal fluid) that is actively secreted by the epithelial cells leading to progressive growth of the lesion and gradual worsening of symptoms such as intracranial hypertension and cerebral edema (Boockvar et al., 2000). Histopathological examination shows that the cystic wall is divided into the inner and outer layers, with the former consisting of a single layer of cylindrical cells (similar to ventricular cells) containing ciliated structures and the latter directly connecting to the brain tissue or glial cells (Friede and Yasargil, 1977). Immunohistochemical staining shows positive GFAP, which, in conjunction with the imaging findings, allows definitive diagnosis.

Ependymal cysts in the cerebellum are clinically rare and difficult to distinguish from other benign neurological cysts. Therefore, the diagnosis should be made taking clinical signs, imaging findings, and positive immunohistochemical GFAP into consideration. The appropriate surgical approach should be selected based on the location of the lesion and its adjacent structures. Future studies should aim to carry out long-term follow-up of these patients to estimate recurrence rates at a later stage.

The original contributions presented in this study are included in this article/Supplementary material, further inquiries can be directed to the corresponding authors.

Written informed consent was obtained from the participant/patient(s) for the publication of this case report.

CH: Data curation, Writing – original draft, Writing – review and editing. YL: Conceptualization, Supervision, Writing – review and editing. FL: Resources, Writing – review and editing. QZ: Writing – review and editing.