Anatomic Variations of the Lacrimal Sac Relative to Middle Turbinate Axilla and Skull Base in Chinese Patients with Nasolacrimal Duct Obstruction: A CT-Dacryocystography.

OBJECTIVE

The middle turbinate axilla (MTA) is a crucial anatomical landmark for localizing the lacrimal sac (LS) during endonasal dacryocystorhinostomy (En-DCR). Despite being a standard surgical procedure, En-DCR may lead to severe complications, such as cerebrospinal fluid (CSF) leakage, which is closely associated with anatomical variations between the LS and the anterior skull base (ASB). This study aimed to investigate the anatomical location of the LS relative to the MTA and ASB in Chinese patients with nasolacrimal duct obstruction (NLDO) and analyze the influencing factors.

METHODS

This cross-sectional study enrolled 227 Chinese patients who were diagnosed with NLDO and underwent computed tomographic dacryocystography (CT-DCG). Anatomical distances between LS and MTA, as well as LS and ASB, were measured using CT-DCG images.

RESULTS

The mean distances from the superior and inferior edges of the LS to the MTA were 9.94 ± 4.70 mm and - 0.23 ± 4.15 mm, respectively. Male patients showed significantly more superior-anterior displacement of the LS compared to female patients (P < 0.001), while patients with chronic dacryocystitis (CD) had an inferior and posterior LS position relative to those with simple NLDO (P = 0.005, P = 0.001). The mean distance from the intersection (Point P) of the superior and posterior boundaries of the LS to the ASB (MP) was 18.35 ± 4.48 mm, which was shorter in females and those with frontal sinus aplasia (P = 0.001; P < 0.001). A subgroup (28/227, 12.3%) with a critical anatomical feature was identified, where the distance from Point Q (10 mm posterior to P) to the ASB (NQ distance) was ≤ 10 mm. This subgroup had a higher prevalence of complete supra-MTA LS positioning (71.4% vs. 41.2%, P = 0.003).

CONCLUSION

Preoperative CT-DCG provides essential anatomical insights into the spatial relationship between the LS and MTA in Chinese patients with NLDO. The LS position varies significantly by gender and disease type, with males showing more superior-anterior and CD patients more inferior-posterior positioning relative to the MTA. Special attention should be paid to patients with frontal sinus aplasia or LS entirely above the MTA to minimize the risk of CSF leakage during En-DCR.