Preoperative Orbital CT Scan Findings in Patients with Nasolacrimal Duct Obstruction and its Impact on Surgical Planning

Background: External dacryocystorhinostomy (DCR) failure is sometimes due to pathologies located within the nasal cavity. Preoperative computerized tomography (CT) scan is useful in the assessment of nasolacrimal drainage and adjacent anatomical structures; however, it is not routinely performed before DCR. The present study evaluates abnormal findings in CT scans of patients with nasolacrimal duct obstruction (NLDO) and its effect on changing treatment approaches. Methods: This prospective descriptive cross-sectional study included 162 patients with NLDO. All the patients underwent a supine axial CT scan. Patients with signs of rhinosinusitis, sinus mucositis, nasal septal deviation, nasal polyps or masses, and turbinate deformities were referred to an otolaryngologist. The rest of the patients underwent external DCR. The demographics and radiologic characteristics of the patients undergoing CT scan and their effect on changing treatment approaches were evaluated. Results: The study participants included 162 patients with a mean ± SD age of 62.5 ± 14.0 years (age range of 35-93 years). The percentage of endonasal DCR in cases with an abnormal nasal cavity on CT scan was almost 30% higher compared to those without this problem (59.6% vs. 30.2%). Septum deviation and turbinate deformity led to 3.6-fold and 3.9-fold changes in the surgical approach, respectively. Conclusion: A significant association existed between the sinonasal pathologies in patients with NLDO and changing surgical approaches. It is believed that a preoperative CT scan is necessary to detect such pathologies and manage them appropriately.


Introduction
The most common cause of epiphora or dacryocystitis is nasolacrimal duct obstruction (NLDO).Dacryocystorhinostomy (DCR) is the preferred procedure to treat NLDO.This treatment is performed in two ways, external DCR and endoscopic DCR.The success rate of these two methods is almost equal (1)(2)(3).One of the causes of failure in external DCR is pathologies located within the nasal cavity which include middle turbinate abnormalities (concha bullosa, lateralization, hypertrophy), ostium problems (closed, small, or too high ostium), mucosal abnormalities (intranasal adhesions, contact granuloma, scar formation, rhinosinusitis, and pouch formation known as sump syndrome), nasal wall abnormalities (preceding maxillofacial trauma, ipsilateral septal deviation, lateral nasal wall scarring) and agger nasi over pneumatization (4)(5)(6)(7)(8).
However, a preoperative computerized tomography (CT) scan is useful in the assessment of nasolacrimal drainage and adjacent anatomical structures; although, it is not routinely performed before DCR.The importance of preoperative imaging in these patients is indicated by several reasons including the evaluation of bony anatomy surrounding the lacrimal outflow system to recognize bony erosions, knowledge of anatomical variants, diagnosis of contributing factors to nasolacrimal obstruction (such as septal deviation, turbinate malposition, and sinusitis), and recognition of malignancies or other mucosal Preoperative orbital CT scan findings in nasolacrimal duct obstruction abnormalities (9,10).
This study aimed to evaluate the abnormal findings in CT scans of patients with NLDO and their effect on changing treatment approaches.

Methods
This prospective descriptive-cross-sectional study included 162 patients, diagnosed with NLDO using conventional irrigation tests or obvious signs of NLDO (such as purulent regurgitation) from March 2019 to March 2020.Patients with a previous history of DCR, trauma, nasal and orbital surgery, lid abnormalities, ocular surface diseases, and facial nerve palsy were excluded from the study.
Data collection was performed using demographic characteristics form which included such information as patient's gender, history of sinonasal diseases, and previous facial fractures.All patients underwent detailed examinations for the eyelid, ocular surface, punctum, and tear film conditions.In addition, all the patients underwent supine axial imaging using a multi-detector (8-slice) CT scanner (General Electric, USA) with images obtained at 1.0-mm intervals.All CT images of patients were interpreted by a radiologist for the abnormalities within the nasolacrimal drainage system and around the orbit.
Demographics and radiologic characteristics of patients were analyzed on CT scans findings, which included the abnormalities of orbit, sinus, and other facial structures.Patients with abnormal findings assessed by preoperative CT scan including cases with nasal septal deviation (Figure 1), turbinate deformity (Figure 2), mucocele, nasal polyp, inflammation around the lacrimal sac, signs of chronic rhinosinusitis, soft tissue opacity in the nasolacrimal duct (Figure 3), previous fracture, and suspicious mass (Figure 4) were referred to an otolaryngologist.If the otolaryngologist recommended endonasal DCR based on examination and CT scan findings, the procedure was performed accordingly in ENT service by one surgeon.The rest of the patients underwent external DCR with silicone intubation.

Statistical analysis
Data were analyzed using SPSS software (version 21.0).Descriptive statistics were presented with mean ± standard deviation and 95% confidence interval.However, the analytic statistics were presented with chi-square test and fisher's exact test.A chi-square test was used to compare the approaches of surgery according to CT scan findings.The multivariant logistic backward LR method was used for multiple variant analysis.A p-value less than 0.05 was considered statistically significant.
The percentage of turbinate deformity in females was almost twice that of males (47.7% vs 23.7%, P = 0.009).Soft tissue opacity in the nasolacrimal duct was observed in 10.7% of females; however, none of the males had this finding.No difference was found between genders in other abnormal CT scan findings.
Given the logistic regression model (backward LR method), the variables leading to the change of surgical approach in patients with NLDO included septal deviation (P = 0.001), and turbinate deformity (P = 0.001).Septal deviation and turbinate deformity led to 3.6-fold and 3.9-fold changes in the surgical approach respectively.The rate of endonasal DCR in patients with a history of nasal and sinus diseases was seven times more than that in those without such a history.

Discussion
Pathologies located within the nasal cavity are a cause of external DCR failure.Although a preoperative CT scan is useful in the assessment of nasolacrimal drainage and adjacent anatomical structures, it is not routinely performed before DCR (4)(5)(6)(7)(8)(9)(10).The present study evaluates abnormal findings in CT scans of patients with NLDO and its effect on changing treatment approaches.
A total of 162 patients were enrolled in this study and the majority of them were female (63.6% female vs 36.4% male) which was consistent with previous studies (11,12).Dimensions of the bony nasolacrimal canal, middle nasolacrimal duct, and lower nasolacrimal fossa were smaller in females.In addition, acute angle between the bony canal and the nasal floor in females predisposes them to chronic inflammation of the nasolacrimal drainage system and consequent NLDO.All these anatomical differences can justify the greater prevalence of NLDO among females (13)(14)(15)(16)(17). Furthermore, the results of the present study showed that turbinate deformity was more common in females, which might be another reason for the higher prevalence of NLDO in females.
In this study, abnormal CT scan finding on the same side of NLDO was detected in 71 % of the participants which was similar to the results of the study conducted by Yazici et al (70%) (18).This rate was lower than that obtained in the studies performed by Kallman et al (87%) and Habesoglu et al (95.1%) (19,20).However, a lower rate (57.3%) of abnormal CT scan findings has been reported by Choi et al (10)which may be due to racial and anatomical variations in different countries.
It should be noted that the most common abnormal finding in this study was nasal septal deviation (37%) of the normal population.Czyz et al showed that air was present more fully in the upright rather than supine position (16,17).In the present study, all CT scans were performed in a supine position which can justify the lower percentage of soft tissue opacity in NLD (6.8%).Nasal septal deviation as the most common CT scan finding in this study was observed in 37% of the cases which was comparable to that in studies conducted by Kallman et al and Habesoglu et al (39%) (19,20), though less than that in the studies performed by Habesoglu et al, Sefi et al and Yazici et al (64.6%, 65%, and 70% respectively) (18,21).On the other hand, the rate of patients with nasal septal deviation in Choi et al and Kaplama et al studies was lower than that in the current study (11.9% and 27.4% respectively) (10,22).The nasal septal deviation was the first and second abnormal CT scan findings in the studies carried out by Kaplama et al and Habesoglu et al, respectively (19,22).These differences can be explained by racial and anatomical differences, different imaging indications, and different criteria for the interpretation of abnormal CT scan findings.
In this study, septum deviation and turbinate deformity caused 3.6-fold, and 3.9-fold changes in the surgical approach, respectively.Habesoglu et al and Kallman et al reported a higher prevalence of sinonasal pathologies in patients with NLDO compared to those in the control group.Moreover, they reported a higher rate of nasal septal deviation in these patients compared to those in the control group (18,20).In the study performed by Habesoglu et al (20), it has been reported that the incidence of inferior turbinate hypertrophy and maxillary sinusitis was higher in patients with NLDO compared to the control group, which was in line with the results obtained in the study conducted by Sefi et al (21).The results of the studies conducted by Yazici et al, Lee et al, and Taban et al were indicative of the correlation between the side of the septal deviation with the side of NLDO (18,23,24).On the other hand, based on the results of the previous studies, DCR failure may be due to the untreated existing sinonasal pathologies, such as nasal septum and concha bullosa pathologies (20,23).The high percentage of nasal and sinus pathologies in the present study and the role of these conditions in the development of NLDO and the rate of recurrence following DCR could be the reason for changing the surgical approach in a significant number of patients.
In the present study, chronic sinusitis did not lead to a change in the surgical approach.The reason for this difference might be the presence of sinusitis in sinuses not adjacent to the nasolacrimal duct or the resolution of sinusitis by medical treatment.Habesoglu et al showed that maxillary sinusitis was more common in patients with NLDO; however, they did not find any relationship between the presence of ethmoidal sinusitis and NLDO (20).The sinuses were not evaluated separately in this study, therefore, no association was found in this regard.Abnormal CT scan finding was detected in 71% of patients in the present study.The percentage of endonasal DCR was almost 30% higher in cases with an abnormal nasal cavity on CT scan than those without these problems (59.6% vs. 30.2%)which highlights the importance of performing CT scans for surgical planning.Numerous studies supported the performance of CT scans before surgery in all cases of acquired nasolacrimal obstruction.However, some arguments oppose this.Moreover, a CT scan can recognize bony anatomy surrounding the lacrimal outflow system, anatomical variants, factors contributing to nasolacrimal obstruction (such as septal deviation, turbinate malposition, and sinusitis), and malignancies or other mucosal abnormalities (9,10,22) which some of them cannot be detected by only examination.However, there are some limitations regarding the application of CT scans.Intrinsic tumors of the lacrimal outflow tract may not be evident on a CT scan.The positive predictive value of the test is low for neoplasia as the cause of lacrimal outflow obstruction.Radiation exposure and cost are other concerns in this regard (25,26).It is worth mentioning that there are several ideas about the importance of imaging in a patient with NLDO.
Regarding the limitations of the present study, one can refer to the limited number of patients.Moreover, the effect of sinonasal surgery was not evaluated on the surgical outcome, which should be considered in future studies.

Conclusion
Based on the obtained results, a significant association was observed between the sinonasal pathologies in patients with NLDO and changing the surgical approach.Therefore, a preoperative CT scan seems to be necessary to detect and manage secondary NLDO.

Table 1 .
Summary of CT scan findings * Some patients had more than one finding.

Table 2 .
(10)uency distribution of type of surgery according to CT scan findings in patients with lacrimal duct obstruction Preoperative orbital CT scan findings in nasolacrimal duct obstruction followed by turbinate deformity (35.8%) and periocular inflammation (23.5%).In a study carried out by Choi et al, soft tissue opacity in NLDO was reported as the most common (85.9%) abnormal CT finding, which could be attributed to the upright position of patients during CT scans since a high percentage of patients without NLDO (81.7%) showed this abnormality(10).Loftus et al and Czyz et al reported NLD opacity in approximately 70%