OBJECTIVE Mineralized or desiccated colloid cysts pose some unique challenges to endoscopic removal. The extrusion of the solid matrix into the intraventricular compartment has not been previously reported and, as such, no guidance exists regarding its predilection, prevention, and fate. METHODS Postoperative imaging studies in a registry of patients undergoing endoscopic removal of colloid cyst were reviewed to detect any solid matrix within the ventricular compartment. Preoperative images and operative notes were used to determine if any features were predictive. Serial postoperative images and clinical notes were used to characterize the implications of these findings. RESULTS From a review of 94 patients, 10 (10.6%) patients had evidence of an extruded intraventricular solid fragment (median follow-up 4 months; range 0.5-115 months). Of the evaluable patients, 7 of 9 patients had T1-weighted hyperintense and T2-weighted hypointense cysts on preoperative scans. Seventy-eight percent of the extrusions were on the same side as the endoscopic entry. Three patients demonstrated early fragment migration, but not after 8 months of radiological follow-up. All evaluable patients demonstrated improvement in their hydrocephalus, and none suffered a complication attributable to the intraventricular extruded fragments. CONCLUSIONS Intraventricular extruded colloid fragments can occur after endoscopic resection, with the possible risk demonstrated as cyst hypointensity on preoperative T2-weighted images. The finding does not seem to result in any clinical morbidity, and radiographic involution is the rule. Migratory capacity, however, does exist and justifies a more frequent imaging surveillance schedule and consideration for removal.
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