MRI Evaluation of Lacrimal Drainage After External and Endonasal Dacryocystorhinostomy

Purpose: External and endonasal dacryocystorhinostomy (EX-DCR and EN-DCR, respectively) affect the tear drainage mechanism. This study evaluates the preservation of "lacrimal pump" function in both procedures. Methods: Cases of successful EN-DCR (4 patients) and EX-DCR (4 patients) were included. All patients underwent MRI of the rhinostomy areas, at least 6 months postoperatively. The vertical diameter of rhinostomy (both osseous and soft-tissue apertures) was measured in T(1)-oriented images, whereas the signal intensity levels were examined for 3 regions of interest (ROIs) in T(2)-oriented (true fast imaging steady state pulse) images with instillation of normal saline to the conjunctival fornices, both before and after blinking (activation of the "lacrimal pump"). ROI I corresponded to the globe (control), ROI 2 corresponded to the inferior conjunctival fornix, and ROI 3 corresponded to the rhinostomy site. Results: Signal intensity in ROI 3 (rhinostomy) was significantly increased after blinking in both EX-DCR and EN-DCR cases. The increase was significantly higher in the latter. Signal intensity changes in ROI 3 were significantly correlated with rhinostomy size in both groups, whereas the respective correlations with the postoperative interval were not statistically significant. Conclusions: Findings imply that the "lacrimal pump" is active following DCR and may be better preserved in the EN-DCR than in the EX-DCR group. Persistent epiphora after patent DCR may thus be attributed to a defective "pump" function and treated accordingly.