Catheter-tract recurrence after Ommaya reservoir-assisted cyst decompression followed by stereotactic radiosurgery for cystic brain metastasis: A case report.

Background: Cystic brain metastases pose a therapeutic challenge for stereotactic radiosurgery (SRS) because of their large volume. Stereotactic cyst aspiration with Ommaya reservoir placement followed by SRS has emerged as a minimally invasive strategy to facilitate effective irradiation; however, catheter-tract recurrence remains rarely reported. Case Description: A patient with esophageal squamous cell carcinoma presented with a large cystic metastasis in the right frontal lobe. An Ommaya reservoir was inserted via a right frontal approach using Kocher's point without ventricular penetration. Cyst aspiration resulted in marked volume reduction. Staged Gamma Knife radiosurgery was subsequently performed, targeting only the reduced cystic lesion and mural enhancement, while excluding the catheter tract from the radiation field. Initial follow-up imaging demonstrated good local control. However, several months later, a new enhancing lesion developed linearly along the catheter tract. Surgical resection confirmed viable metastatic squamous cell carcinoma. No histological features of radiation necrosis were identified. Conclusion: Although rare, catheter-tract recurrence can occur after Ommaya reservoir-assisted cyst decompression followed by SRS. This finding should be regarded as a clinical caution rather than a contraindication to this treatment strategy. Awareness of this potential complication may help optimize procedural planning, radiation targeting, and postoperative surveillance.