Background

Metastatic spread of intracranial ependymoma (EPN) has significant implications for both treatment strategy and prognosis. Metastases are CSF-borne and typically nodular. However diffuse leptomeningeal enhancement can be present on presentation and early postoperative MRI scans and is often interpreted as evidence of metastatic spread. Due to the relative rarity of EPN, studies reporting the significance of leptomeningeal enhancement in EPN are limited to case reports.

Objective

To report incidence, distribution and significance of leptomeningeal enhancement at presentation and after first resection in a large multicentre intracranial EPN cohort.

Methods

Retrospective analysis of cases referred to the Ependymoma Management Advisory Group from February 2016 to March 2022. Preoperative and postoperative MRI as well as follow-up studies when available were reviewed.

Results

160 cases (72 females, 88 males) of posterior fossa (n=118) and supratentorial (n=42) EPN were included. For posterior fossa EPN, preoperative scans were available for 112 cases, of which 19 (17%) demonstrated preoperative leptomeningeal enhancement, typically thin linear enhancement over the pons, medulla, cervical cord along the anterior, posterior surface or circumferentially, and over the conus. Of these 11 (58%) had leptomeningeal enhancement on early postoperative studies. In 93 cases of posterior fossa EPN with no preoperative leptomeningeal enhancement, 25 (27%) demonstrated leptomeningeal enhancement after surgery. 20 follow-up studies were available in cases of posterior fossa EPN with pre- or postoperative leptomeningeal enhancement, and persistent enhancement was seen in only 6 cases. No leptomeningeal enhancement was demonstrated in supratentorial EPN preoperatively or postoperatively.

Conclusions

Leptomeningeal enhancement is a common finding in posterior fossa EPN, seen in 17% of cases preoperatively and in just over a quarter of cases on the postoperative scans. In the majority of the cases it is a transient imaging finding and should not be interpreted as definite evidence of metastatic spread. Leptomeningeal enhancement is not a feature of supratentorial EPN.