Assessing the relationship of agger nasi pneumatization to the lacrimal sac: a dynamic computed tomography-dacryocystography analysis.

BACKGROUND: An understanding of the anatomical structure is crucial for completing successful endoscopic dacryocystorhinostomy (DCR) surgery. This study aimed to precisely delineate the spatial relationship between the lacrimal sac and the agger nasi cell (ANC) and evaluate the impact of ANC on surgical strategies in endoscopic DCR.

METHODS: This retrospective cross-sectional study included 110 Han Chinese patients diagnosed with unilateral primary acquired nasolacrimal duct obstruction (PANDO) from January 2021 to June 2023. This study was conducted in Eye, Ear, Nose, and Throat Hospital of Fudan University and involved inpatient participants who were scheduled for DCR surgery under general anesthesia. Patients were consecutively enrolled. The patients underwent preoperative computed tomography-dacryocystography (CT-DCG), and contrast-enhanced images were used to locate the positions of the lacrimal sac and the common canaliculus. A dynamic approach was adopted to analyze the multiplanar CT imaging, facilitating a detailed assessment of the morphology of the lacrimal drainage system and potential overlap of the lacrimal sac. Patient ages and measured values are presented as the mean ± standard deviation, which were measured three times by the same observer and averaged for statistical analysis.

RESULTS: The prevalence of ANC in this study was 90.9% (100/110). Dynamic examination revealed that only 42.7% (47/110) of ANCs appeared as discrete cells, while the majority were connected to nearby sinus openings. Spatial analysis showed that in 57 out of 110 cases, ANCs were situated below the common canaliculus and not posterior to the lacrimal sac, indicating an overlap rate of 51.8%. Notably, our dynamic approach identified five critical cases of overlap below the level of the common canaliculus, which might have been missed by prior studies that used different methodologies.

CONCLUSIONS: More than half of the ANCs exhibited overlap with the lacrimal sac, suggesting a significant proportion may necessitate opening during endoscopic DCR procedures. ANCs are often interconnected with adjacent nasal sinuses, necessitating careful consideration in the decision to open the ANCs during surgery. The dynamic evaluation employed in CT-DCG effectively assessed the extent of ANC coverage over the lacrimal sac.