Incidental maxillary sinus findings on cranial computerized tomographic scan in a tropical setting

Abstract

Background

Abnormalities in the maxillary sinuses are occasional findings on routine CT scans of the head.

Aim

To study the incidental findings in the CT scans of the maxillary sinuses in patients with indications other than sinuses-related diseases.

Setting

Jos University Teaching Hospital, Jos, Nigeria.

Materials and Methods

Images of patients who underwent CT scan of the head over a 5-month period (January 2015- May 2015) were retrospectively reviewed with the exclusion of those whose indication for the scan was trauma or sinus related disease.

Results

A total of 121 CT scan images were reviewed comprising 72 males and 49 females with a male to female ratio of 1.5 to 1.0. Their age range was between 5 and 90 years with a mean of 47.5 ± 20.4 years. The mean age of males was 48.7± 21.2 years while that of females is 45.7± 19.1years. The weight of the patients ranged between 12kg and 109kg with a mean weight of 64.7 ± 16.6kg. The most frequent indications for cranial CT scan were cerebrovascular accident (57; 47.1%), suspected space occupying lesion (23; 19.0%) and persistent headache (5; 4.1%). In all, 93(76.8%) patients had normal scan while 28 (23.2%) patients were observed with sinus pathology. Maxillary mucosal thickening with associated fluid level constituted 11 (9.1%) of the pathologic findings, and this was found bilaterally in 4(3.3%) patients. Seven (5.8%) patients had maxillary mucosal thickening only, with this occurring bilaterally in 4(3.3%) patients and 10 (8.3%) patients had polypoid masses, with bilateral polyps in 1(1.2%) individual. There was no statistical significance with the patient’s weight in relation to the sinus findings.

Conclusion

Incidental maxillary sinus pathologies on cranial CT scan are not infrequent. Vigilance is necessary during routine review and reporting of CT scans of the head for appropriate inclusion and interpretation of these findings towards optimal patient’s care.

Introduction

Computerized tomographic (CT) scan has replaced plain radiographs as the definitive imaging technique for detecting disease of the paranasal sinuses1. It is known that CT provides information about the extent of sinus diseases even in atypical sinus infections, malignancy and in the management of routine complications of rhinosinusitis, providing a guide to the sinus surgeon2. Its role is essentially ancillary however, as the diagnosis of sinus disease such as rhinosinusitis is primarily clinical3.

Reports are available from around the world about the incidental findings of paranasal sinus abnormalities on CT imaging done as a result of ailments other than sinus diseases with some of these showing correlation or non-correlation of the findings with the clinical history of the patients2,4.

There has been an increase in the availability and usage of the diagnostic CT scanner in West Africa generally and Nigeria in particular. A study in the South-West region of the country had reported a prevalence of 35% for incidental abnormal sinus findings on CT scan5. Our study aims to determine the baseline prevalence of incidental findings in maxillary sinuses on cranial CT scans done for pathologies other than sinus diseases in Jos, North Central Nigeria.

Materials and Methods

A retrospective study, involving 121 patients who had cranial CT examinations from January 2015 to June 2015 at the Radiology Department of the Jos University Teaching Hospital, Jos, Nigeria was carried out.

The initial sample group included 252 patients who were referred for cranial computed tomographic scans within the study period for varying indications including head injury. The referrals were mainly to access for or to exclude intracranial pathology. Patients referred primarily for suspicion of sinus disease and all those with head injury were excluded from the study. GE Bright Speed 4 Slice CT scanner was used for the study. The protocol used contiguous axial 2.5 mm sections for the skull base including the petrous temporal bones and 5 mm sections for the rest of the cranium up to the vertex. The obtained serial axial images of the cranium in supine position were examined in each patient focusing on the maxillary sinuses. Image manipulation other than would be done in a routine cranial investigation was not employed as the study was on incidental findings. Coronal and sagittal reconstructed images were reviewed where necessary. All scans were evaluated by two radiologists and consensus reached on the findings. The findings were carefully recorded. Other retrieved information from CT documentation included age, gender, weight and indication for the cranial CT scan. The patients were grouped according to the following age brackets (in years): less than 10, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, and 70 and above.

The findings in any or both maxillary sinuses were classified as normal, mucosal thickening with fluid level, mucosal thickening only, and polypoid mass. Mucosal thickening was taken as any thickening of more than 1 mm in at least one wall of the maxilla. A horizontal interphase delineating an opacity within a maxillary sinus signified a fluid level. A polyp was defined as homogenous opacity with a convex margin within the sinuses.

Data was analyzed descriptively using Statistical Package for Social sciences. (SPSS) version 15 and results were presented in tables and figures.

Results

The CT images of a total of 121 patients (242 sinuses) were reviewed. The age range of patients was between 5 and 90 years with a mean age of 47.5 years (± 20.4). The age group with largest number of patients was 50-59 consisting of 27 (22.3%) patients (Table 1).

Table 1. Age and sex distribution.

Age group	<10	10- 19	20- 29	30- 39	40- 49	50- 59	60- 69	70+
Male	4	7	4	7	8	17	10	15
Female	0	4	6	8	9	10	6	6
Total	4(3.3%)	11(9%)	10(8.3%)	15(12.4%)	17(14%)	27(23.3%)	16(13%)	21(17.3%)

The mean age of males was 48.7± 21.2 years while that of females is 45.7± 19.1years. The weight of the patients ranged between 12kg and 109kg with a mean weight of 64.7 ± 16.6kg. The most frequent indications for cranial CT scan were cerebrovascular accident (57; 47.1%), suspected space occupying lesion (23; 19.0%) and persistent headache (5; 4.1%). In all, 93(76.8%) patients had normal scan while 28 (23.2%) patients were observed with sinus pathology. Maxillary mucosal thickening with associated fluid level constituted 11 (9.1%) of the pathologic findings, and 4(3.3%) had same occurring bilaterally. Seven patients (5.8%) had only maxillary mucosal thickening while 4(3.3%) patients had same bilaterally. Polyps were detected in 10(8.3%) patients, and polys were found bilaterally in one patient (1.2%).

The findings were seen in both sexes (Fig 1) and age groups (Fig. 2). Several patients had more than one finding (Table 2). There was no statistical significance of the weight of the patients in relation to the findings (p =0.09).

Discussion

The paranasal sinuses among other functions assist in the humidifying and heating of inhaled air. Sinus mucosal inflammatory disease are often ignored by individuals especially where the symptoms are not overwhelming, and where there are still some spaces left for inhaled air to traverse in either or both sides.

The maxillary sinuses are the largest of the paranasal sinuses and expectedly constitute most of the findings as host of pathologies on conventional X-rays and axial imaging, be it computed tomography scan or magnetic resonance imaging. Previous work4,6 on various population subsets have reported the prevalence of incidental sinus abnormality on axial imaging to range from 16% to 40%. The high sensitivity of the CT scan in detection of mucosal inflammation makes it possible to recognize incidental findings more so in the maxillary sinuses because of their configuration in a supine patient during a cranial CT scan and their pneumatization from early childhood. It is possible that ‘incidental’ mucosal findings that do not represent true sinus disease could be detected on CT scan and over-diagnosis on a radiographic basis due to the sensitivity of the CT scan has been reported7. However, Bolger et al8reported that the incidence rate on CT might not be reflective of the true rate of sinus mucosal abnormalities, due to the undocumented concurrent use of antibiotics for other reasons. Symptomatic sinus patients were much more likely to have positive sinus CT scan findings than asymptomatic patients9.

As with most studies on the subject, there was a preponderance of normal finding in the maxillary sinuses in this study, accounting for 76.8% of the patients. We found a total of 28 patients (23%) with maxillary sinus abnormality. Eleven patients (9.3%) were found with maxillary mucosal thickening associated with a fluid level. The presence of an air-fluid level implied acute sinus disease and mucosal thickening in a normal sized maxillary sinus suggested chronic sinusitis10. Opacified maxillary sinus (partial or complete) had been described in other studies and might have either fluid or solid material as its content11. Maxillary mucosal thickening with air fluid level indicated an acute on chronic process. While this constituted the most frequent findings in this study, we did not encounter a patient with completely opacified sinus. The finding was at variance with the findings of other researchers especially in the developed western countries2,4,12. Dust mite, mold and dander which persist in tropical climates are potential allergens and a major cause of perennial allergic rhinitis13. Swings of temperature changes between fair extremes of hot and cold in a dry climate as obtained in the middle belt region of Nigeria especially on the Jos Plateau could be contributory14.

Seven patients had maxillary mucosal thickening (bilateral in four cases) constituting 5.8% of the study population. Irritation of the maxillary sinus mucosa resulting from acute and chronic infections is thought to be the cause. Odontogenic factors have also been implicated and reported to be the main factor in 10–12% of cases of maxillary sinusitis15. Mucosal thickening may be flat and fairly uniform or exuberant and irregular, partially filling the air space. Mucosal thickening in the maxillary sinuses was the most frequent incidental finding by Silva et al16 in a retrospective study of the paranasal sinuses in brain CT scans of 70 patients aged between 0 and 12 years in Sao Paulo, Brasil.

Polypoid mass as an incidental finding was seen in 10(8.3%) patients in this study. We used the definition of polyps by Lim and Spranger12 as homogenous round opacities with distinct demarcating boundaries at the base, different from any partial opacification without clear distinct boundaries. These were regarded as extensions of thickening in an inflamed sinus mucosa following irritation from recurrent infections. They had been defined previously on CT scans as mucous retention cysts with a reported incidence of 12.4–22%17,18. Hiari et al19 studied incidental paranasal sinus inflammatory changes on MRI in a Jordanian population and observed that polypoidal changes seen were restricted to the maxillary sinuses.

All patients in which trauma was the indication for the CT scan were excluded from the study to avoid the ambiguity of maxillary densities either with fluid levels which may represent a hemosinus in acute trauma or with ‘polypoid’ appearance of clotted blood in a delayed case of trauma.

There is paucity of the finding of polypoid mass in individuals between their first and third decades of life. This may not be unrelated to the fact that their formation involves mucosal irritation and repeated infection over time as has been described above. Similar observation has been previously documented12.

The 50-59 years age bracket was observed with the highest number of participants comprising 27 patients in this study. These more often constitute the senior cadre of the working population whose age group is often associated with conditions necessitating more frequent medical attention. Cardiovascular disease is common amongst the middle aged and its investigation may involve requests including a CT scan of the brain. The most frequent indication for cranial CT scan in the study population was cerebrovascular accident.

The Lund-Mackay grading system20 as a measure of abnormal findings seen in the paranasal sinuses on cross-sectional imaging like CT scan has been widely accepted. It involves scoring for each sinus cavity including the osteomeatal complexes on each side based on the degree of opacification. The objectives of our study were nonetheless with a focus on the maxillary sinuses using routine head CT scans and no application of the scoring method was employed.

The limitation of this study was that 4-slice CT scanner was used because it was the only one available. Higher degree CT machines should have made resolution better.

Conclusions

In conclusion, Incidental maxillary sinus pathologies on cranial CT scan are not infrequent. Vigilance is necessary during routine review and reporting of CT scans of the head for appropriate inclusion and interpretation of these findings towards optimal patient’s care.

Figure 1. Incidental maxillary sinuses findings.

Table 2. Distribution of findings.

	total	Unilateral		Bilateral	<10	10- 19	20- 29	30- 39	40- 49	50- 59	60- 60	70+
		L	R
Normal	93				3	9	8	9	14	21	11	18
Mucosal thickening with fluid level	11	2	5	4	0	2	0	3	2	3	1	0
Mucosal thickening only	7	2	1	4	1	0	2	2	0	0	1	1
Polypoid mass	10	3	6	1	0	0	0	1	1	3	3	2

Figure 2. Findings in relation to age groups.