Cross-sectional observational study on accessory ostium of the maxillary sinus : Journal of Clinical and Scientific Research

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Cross-sectional observational study on accessory ostium of the maxillary sinus

Rajendiran, Devendiran1,; Nagabooshanam, Mohanbabu2; Venugopal, Ravikumar3

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Journal of Clinical and Scientific Research 12(2):p 88-92, Apr–Jun 2023. | DOI: 10.4103/jcsr.jcsr_107_22
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The association between chronic sinusitis and accessory ostium (AO) is still a controversial subject as previous studies have given variable results with wider range.


Present study was designed to study the prevalence of AO in those with chronic sinusitis and those without the disease; 83 chronic rhinosinusitis (CRS) patients and 83 subjects without the disease were examined by diagnostic nasal endoscopy for the presence of accessory maxillary ostium.


Of the 83 CRS patients, 29% had an AO, whereas only 11% without the disease had it (P < 0.001). Most of the AOs were on the left side, especially in the posterior nasal fontanelle, in both groups. One unexposed subject and 5 patients had AOs on both sides. Double ostia were seen in 2% of CRS patients. However, symptoms such as facial pain, headache, purulence on examination, halitosis and post-nasal drip were found to have no specific association with the presence of AOs.


The presence of an AO can be considered an indicator of the maxillary sinus disease, along with the other criteria for chronic sinusitis.


Chronic rhinosinusitis (CRS) is a sinonasal disease, characterised by the inflammation of paranasal sinus and nasal mucosa, which is now most common, affecting 16.3% of the adult population.[1] The diagnosis of CRS is mainly based on clinical features, confirmed by diagnostic nasal endoscopy and computed tomography (CT).

As the human acquired the present erect position by evolution, the maxillary sinuses become susceptible to infections leading to maxillary sinusitis. The maxillary sinus secretions have to be transported by the mucociliary clearance against the gravity. Therefore, the normal functioning of a sinus depends on normal quality and quantity of secretions, normal mucociliary clearance and patency of the ostium.

Accessory ostium (AO), also known as Giralde’s orifice, are the openings in the lateral wall of the nose, in the fontanelles, which leads to the maxillary sinus, in addition to the natural ostium. They are thought to develop as sinus infections damage the fontanelles.[2] These, in turn, cause recurrent maxillary sinus infection due to mucous recirculation. Most of the AOs occur in single. There are few cases with multiple ostia. They are rarely congenital and mostly acquired. However, the aetiology of accessory ostia is still a controversial one.

Mucous clearance in maxillary sinus is exclusively by mucociliary action. It occurs against gravity. The cilia in the sinus beat only towards the primary maxillary ostium. Although an accessory maxillary ostium is located in a more advantageous position with respect to gravity, the secretions are not transported out through it as one might assume.

In AOs of up to 4 mm, the secretions with a normal viscosity bypass around, rather than pass through it. If a larger AO is present, the part of the mucous carpet moving through the centre of the AO alone gets transported out into the middle meatus. The portion of the mucous in the periphery passes along its margins is taken into the natural ostium. On the other hand, the secretion that has already been transported out through the natural ostium can re-enter through the AO, and this time, when it enters, the mucous carries with it all the pathogens that have got adhered to its outer viscous layer. Thus, the pathogens in the nasal cavity gain free access into the antrum via this “extra hole.” This recirculation can go on and on, thus perpetuating the infection and working as a vicious cycle.

A similar scenario can occur following endoscopic sinus surgery for chronic sinusitis. While doing a middle meatal antrostomy, if the surgically created opening is not connected to the natural ostium, it is equivalent to an iatrogenic AO. This is called the “missed ostium sequence.” Here, due to the same recirculation phenomenon, a persistent sinusitis results despite the surgery. Joining the surgically created ostium with the natural ostium solves the problem.

Our study is an attempt to find the prevalence of the maxillary AO in patients of CRS and in those without CRS. Here, we have investigated the presence of AOs by diagnostic nasal endoscopy. We have deliberately avoided CT paranasal sinus (PNS) as a diagnostic method as this study had included normal subjects as well.


Our study was conducted at ear nose throat (ENT) diseases outpatient department, Government Medical College and Hospital, for a period of 1 year from October 2020 to October 2021. The study design was cross-sectional observational study.

Kennedy’s endoscopic study[3] showed a prevalence of AOs to be 5% in the general population. The prevalence of AOs in patients with CRS was 22%, in an another study[4] conducted in the Rajiv Gandhi University of Health Sciences, Karnataka. To get an Indian standard, the value of 22% was used for calculation. The sample size was calculated using OpenEpi Version 3, an open-source calculator (Available at URL:

Eighty-three patients in the age group of 15–45 years with chronic maxillary sinusitis (exposed population), diagnosed as per Rhinosinusitis Task Force Criteria, who consulted the our ENT outpatient department and 83 subjects who attended the ENT outpatient department for reasons other than chronic sinusitis and normal volunteers (unexposed population in our study), during the period October 2020 to October 2021, were enrolled for the study, after getting institutional ethical committee approval and informed written consent from the participants. They were examined with diagnostic nasal endoscopy for the presence of AO.

The 1997 Rhinosinusitis Task Force Diagnostic Criteria for Chronic Rhinosinusitis[5] (>12 weeks). Major factors included facial pressure/pain, nasal obstruction, anosmia/hyposmia, nasal discharge/postnasal drip and purulence on examination. Minor factors included headache, fever (all non-acute), dental pain, halitosis, cough, fatigue and ear pain/fullness/pressure. Diagnosis of CRS was made if two major factors or one major and two minor factors were present. In the absence of another major symptoms or signs, facial pain/pressure alone does not constitute a suggestive history for diagnosis.

As our study also had normal subjects as well, we did not use the radiological findings as a diagnostic criterion to avoid unnecessary exposure to radiation. Hence, in our study, we only adhered to the Task Force Criteria and Nasal Endoscopic findings for diagnosing chronic sinusitis. The diagnostic nasal endoscopy was done using Stryker HD camera (24 mm), high-definition light emitting diode (LED) monitor, 4 mm –30° and 0° Karl Storz (Karl Storze Se &Co. KG, Germany) endoscopes.

Normal maxillary sinus ostium is actually not visible during diagnostic nasal endoscopy. If it is present, it comes into view during diagnostic nasal endoscopy. AO is present more posteriorly. While the natural ostium of the maxillary sinus is oriented transversely and oval in shape, AO is oriented anteroposteriorly and spherical in shape.

Statistical analysis

Descriptive statistics for continuous variables are reported as mean and standard deviation. Categorical variables are presented as numbers and percentages. A P < 0.05 was considered statistically significant.


Among the 83 CRS patients enrolled for the study, 24 (29%) had an AO, and in the 83 unexposed persons, it was 9 (11%) (P < 0.001) (Table 1). Table 2 shows the side on which the AO was present in patients with and without CRS. AO was more commonly seen on the posterior nasal fontanelle than the anterior nasal fontanelle (ANF). Two patients with CRS had multiple AO. Double ostia were not seen in the unexposed group in our study (Figures 1-5).

Table 1:
No. of subjects with accessory ostium
Table 2:
Side distribution of accessory ostium
Figure 1:
Diagnostic nasal endoscopy showing accessory ostium on the right lateral nasal wall of a patient with chronic rhinosinusitis
Figure 2:
Diagnostic nasal endoscopy showing left-sided posterior nasal fontanelle accessory ostium in a 24-year-old female without chronic rhinosinusitis
Figure 3:
Diagnostic nasal endoscopy showing accessory ostium in posterior nasal fontanelle on the right side in a 16-year-old male patient with chronic rhinosinusitis
Figure 4:
Diagnostic nasal endoscopy showing another accessory ostium in posterior nasal fontanelle on the left side of the same 16-year-old male patient with chronic rhinosinusitis – bilateral accessory ostia
Figure 5:
Diagnostic nasal endoscopy showing double accessory ostia on the same side of a 35-year-old male patient

Table 3 shows the variation in proportion of symptoms and signs such as discoloured postnasal drip, halitosis, purulence on examination. Furthermore, recirculation phenomenon was found only in two patients of CRS.

Table 3:
Distribution of signs and symptoms among chronic rhinosinusitis patients with and without accessory ostia


Our study shows that 24 out of 83 (29%) CRS patients had an AO and that 9 out of 83, subjects without CRS had an AO. All of them were round in shape.

In a prospective cohort study[6] conducted in rhinology clinic patients and general ENT clinical controls, they found that 7% of rhinology patients and 2% of the controls had AO. Out of the rhinology patients with rhinitis and sinusitis, 8% showed AO.[6] Prevalence rates reported in cadaver studies have ranged from 13.8%-26%.[7–9]

In our study, of the CRS patients with AO, 11 were on the left, 8 were on the right and 5 were present bilaterally. Moreover, in the unexposed group, 5 were on the left, 3 on the right and 1 was found bilaterally. In a study,[10] 68.3% of AOs were bilateral in patients with CRS as opposed to none the normal subjects. In another study[11] done on patients with and without post-nasal discharge, 57.5% were present bilaterally in those with post-nasal discharge as against none in the group of healthy subjects. There is no mention about the right/left side distribution in either of these studies.[10,11] In another study[9] authors have reported on a 2.7% laterality. In a cadaver study[12] the findings were as follows: right 66.7%; left 33.3%; there were no bilateral cases. In another cadaver study[8] reported that AO occurred on the right side in 60% of cases and on the left in 40%.

Out of 24 AOs in the CRS group, 23 (95.8%) were single ostia and only 2 cases had double ostia. In the unexposed group, no one had double ostia. AOs are usually single and rarely multiple. One to three AOs may be present, mostly in the anteroinferior fontanelle.[13] In a cadaver study[12] a 44.4% incidence of double AO.[12] Another study[8] reported a 35% incidence of double AO, and all of the AOs were in the ANF. In a cadaver study[14] reported 18% double, 9% multiple and 72% single ostia.

Cadaver studies[8,12,14] have given a larger incidence of AOs than the studies on live subjects. In particular, the incidence of multiple/double ostia is also larger in these cadaveric studies.[8,12,14] This reason may be the fact that moist nasal mucosa undergo shrinkage after death, and following drying and fixing, the fontanelles undergo damage resulting in the formation of AOs.[7]

Majority (95%) of CRS patients complained of headache and 42% had facial pain. 79 out of 83 (95.1%) patients complained of post-nasal discharge. Hence, there was no significant difference in its presence between those with and without AO. Halitosis was a complaint only for 40% of patients. However, it was higher in those with AO (66.7%) than those without AO (40.7%). Purulence on examination was higher in the presence of an AO (79.1%) in contrast to those without (71.2%) (P = NS).

In the present scenario, where CT and nasal endoscopy play a major role in the diagnosis and treatment of CRS, it is suggested to be aware of all the anatomical and pathological variants of the nasal cavity and PNS, one such being, our AO. The presence of an AO in an individual with nasal symptoms can be an indicator that the person is suffering from chronic sinusitis or say chronic maxillary sinusitis. Often, we can even witness the re-entry of the mucus during a diagnostic nasal endoscopic examination. Thus, it can help in our decision-making regarding the plan for the surgery.

The radiologist should be aware of this anatomical variant, as in a CT of the paranasal sinuses, it will be seen as an additional communication between the maxillary sinus and the nasal cavity. Sometimes, when stacked one above the other, it may be seen as two openings in a coronal CT.

When a patient is planned up for endoscopic sinus surgery, a middle meatal antrostomy is not always needed, if the natural ostium is seen patent after the uncinectomy procedure. If, however, an accessory ostium is seen, it has to be joined to the natural maxillary sinus ostium. It can be performed by introducing a back-biting forceps into the AO and extending it anteriorly into the natural ostium. Failure to identify the natural ostium, and therefore connecting it to the accessory ostium, will result in recirculation of mucous between nasal cavity and maxillary sinus, leading to persistence of infection. In other words, a pseudo middle meatal antrostomy is created with a resultant failure of functional endoscopic sinus surgery.

Patients who come with episodes of recurrent sinusitis following endoscopic sinus surgery should undergo an endoscopic nasal examination. After a course of medical treatment, a CT of the paranasal sinuses should be taken and carefully examined for the presence of a separate natural ostium and an AO or a posterior fontanelle ostium. If it is found, the patient should be taken up for a second surgery where the two ostia should be connected. As mentioned above, a back-biter should be inserted into the AO and cut forwards to the natural ostium. A microdebrider can be used to trim away the excess tissue after creating this tissue edge.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


The authors would like to thank Dr Vrinda B. Nair, Kerala, for her constant support by encouraging and her help in conducting the study.


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Accessory ostium; maxillary sinus; maxillary sinusitis

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