Tomographic Evaluation of Structural Variations of Nasal Cavity in Various Nasal Pathologies

Objective: The aim of the present study was to evaluate the structural variations of nasal cavity in reference to frequency and types at the key area i.e. the ostiomeatal complex. Materials and Methods: Computed tomography of Paranasal sinuses of 50 patients was studied for clinical suspicion of various sinonasal pathologies. Results: The most commonly encountered anatomical variations in this study were Deviated Nasal Septum in 78% (39 patients), followed by Concha Bullosa in 36% (18 patients), Agger Nasi cell in 18% (nine patients), Pneumatised septum in 12% (six patients), Paradoxical Middle Turbinate and Septated Maxillary Sinus in 10% (five patients each) and Pneumatised Uncinate Process 6% (three patients). In quite a few patients we witnessed more than one variation. Conclusion: The anatomical variations in the nose and ostiomeatal complex are not uncommon, with the most frequent ones involving the nasal septum and the middle turbinate.


Introduction
There are various sinonasal pathologies encountered in day to day clinical practice by otorhinolaryngologists.These pathologies sometimes do not respond to medical therapy.Computed tomography (CT) is the method of choice for evaluating these cases, particularly in patients, requiring surgical intervention [1].Endoscopic surgery demands a meticulous assessment and a detailed description of both nasal and paranasal cavities structures [2].In the last few years the anatomical CT variations and pathological findings were registered and supposed as a possible element which is favoring development of sinus pathology and shows symptoms usually connected with sinusitis [3].Considering that the main objective of this type of surgery is to reopen the natural ways of drainage of paranasal cavities, it is very relevant that the radiologist is aware of the ostiomeatal complex variants, by describing them in a comprehensible way for the otorhinolaryngologist [4,5].
The present study was aimed at evaluating the frequency and types of anatomical variants of the nasal cavity and ostiomeatal complex.

Materials and Methods
This prospective study spanning over a period of 2 years (August 2010 to August 2012), comprised of CT evaluation of 50 patients with clinical suspicion of sinonasal pathologies who were part of OPD or IPD care of department of ENT of AVBRH, Wardha.Patients with Rhinosinusitis, Septal Pathologies like deviated nasal septum (DNS), Nasal Polyp, Symptom of Nasal Obstruction with different causes, Headache due to Nasal Pathologies, Anosmia/Hyposmia due to structural pathologies etc were included in this study.Those patients included in the study where analysed using parameters like age, sex, signs, symptoms, nasal endoscopic and CT scan findings like DNS, Agger cells, pneumatised septum, paradoxical middle turbinate, septated maxillary sinus, Haller cell and conha bullosa.Patients with Septal Pathologies like haematoma, abscess, perforation, fracture nasal bone, nasal trauma, sinonasal malignancies and patients with previous nasal surgery were excluded from the analysis.
Patients were scanned on "Philips 16 slides CT machine".The protocol consisted of coronal and axial slices, respectively, perpendicular and parallel to the palate, with 2 -3 mm in thickness.Scanning parameters included 120 kV and 250 mA.For patients who could not tolerate the prone position (hyperextended neck) required for coronal images acquisition, helical acquisition was performed with 2 -3 mm collimation and computergenerated reconstructed coronal views.In all of the cases, soft tissue and bone algorithm were utilized for documentation.
A radiologist and an otorhinolaryngologist who were unaware of patients' symptoms analyzed CT scans independently.Only those patients in whom both specialists concurred on the anatomical and/or pathological changes were finally included in study.

Results
Out of 50 patients, 26 (52%) patients were male and 24 (48%) were female, ranging in the age of six to 70 years (mean age 31.66 years).
Maxillary sinusitis was the most common associated disease predominantly on the left side (11).Followed by right side (in seven patients) and bi-lateral (in four patients).
Antrochoanal polyp was the next common disease, which was seen in right side in six (54.5%) patients and in left side five (45.5%) patients.
Out of the total nine patients with sinusitis, most of them (eight) had bilateral disease.

Discussion
Instructive role of CT scan in guiding surgeons intraoperatively cannot be over-emphasized.It is like a road map, which is very handy for nasal endoscopic surgeons, not only for uneventful surgery but for avoiding possible complications.
In various studies since decades, subtle bony anatomical variations of nose, paranasal sinus and oeteomeatal complex are being detected.Data regarding "background" prevalence of these findings are needed to determine their clinical relevance.Current understanding of the localization and extent of the pathophysiology of sinus and skull base disease is based on detailed knowledge of anatomic structure [6].
The prevalence of anatomic variations of nose causing diseases has been variously described, ranging from pure anatomic descriptions to descriptions based on computed tomography examinations [7].Prevalence of structural variations of nasal cavity and paranasal sinuses around 67% has been reported previously [5].
In the present study of 50 patients, a in-depth analysis of CT scans of PNS, specially coronal plane, coupled with endoscopic instrumentation was done with special attention to bony anatomical variations.Anatomical variants were identified in all but one patient evaluated (98%).One patient with nasal polyp, did not have any noticeable structural bony variation.
Two anatomical variations were observed in almost half of these patients (50%), followed by single variation (32%), three variations in 14% and as many as four variations in 2% cases.Here is an account of individual variations.

Deviated Nasal Septum
Nasal septal deviation has an important role in causing sinusitis.Asymmetric nasal septum can force nasal turbinates laterally and result in narrowing of the middle meatus and ultimately blocking drainage of the ipsilateral Maxillary, anterior ethmoid and frontal sinuses [8].We included any visually detectable nasal deviation from the midline in this group.
In current study, DNS was the most common anatomical variation with prevalence rate of 78%.Prevalence of this particular anatomical variation ranging from 13% -80% has been reported.Badia et al. (2005) [9], considered notable DNS, only when it was more than 4 mm deviation and found its prevalence to be only 13% -20%.On the other hand, Perez-Pinas et al. (2000) [5] considered DNS, when any visually detectable nasal deviation from the midline was seen and observed prevalence of it to be 80%.Different criteria applied to diagnose and consider septum to be deviated in different studies, accounted for variation in prevalence.
Majority of the studies showed DNS as the most common anatomical variations, as does the present study.[14] had prevalence rate of DNS as an anatomical variation 65%, 44%, 56.4%, 41.9%, 65% and 65.2% in their respective studies.

Concha Bullosa
The middle nasal concha is normally a flat bone.When it is pneumatised by extension of anterior ethmoid cells or less frequently, posterior ones, it is referred to as Concha Bullosa [15].The true concha bullosa is produced following pneumatisation of both portions (vertical lamina and inferior bulb) of the middle nasal concha [5].Lamellar pneumatisation and conchal Pneumatization, both were included in Concha Bullosa in our study and with this criteria, it's prevalence rate was 36%.

Agger Nasi Cell
The most anterior cells of the anterior ethmoid group, the prevalence of Agger Nasi cell ranges widely in different studies which can be attributed to loose anatomic definitions or due to technical miss-match.Herein the Agger Nasi cells are defined as those lying anterior to the upper end of the nasolacrimal duct [7].The frequency of Agger nasi cell (AN cell) in our study population was 18%.

Paradoxical Middle Turbinate
It is an anatomical variation of middle turbinate, where in it's convexity is reversed to face laterally.However it is not associated with any change in the normal middle turbinate attachments.This may lead to impingement of the middle meatus and thus sinusitis or other mucosal diseases of sinus, specially the large ones [7].

Haller Cell
The potential pathophysiologic importance of a Haller's cell is clear, but not the anatomic definition.As described by Albert von Haller in 1765, these cells grow into the bony orbital floor that constitutes the roof of the maxillary sinus [6].The definition of ethmoid cells given by Haller in eighteenth century is now controversial.Some authors (Kennedy and Zinreich, 1988) considered Haller cell as ethmoid cells which are the air cavities projecting below the ethmoid bulla within the orbital floor in the region of the opening of the maxillary sinus [5].However, Bolger et al. (1991) broadened the term to include any cell located between the ethmoidal bulla, the orbital lamina of the ethmoid bone and the orbital floor [15].

Sinonasal Pathologies
The diagnosis of nasal or inflammatory sinus diseases is often difficult clinically, as the nasal symptoms are neither sensitive nor specific in predicting the underlying pathology [17].Various investigations, like CT scan, helps to establish diagnosis.
Marcio M. Kinsui et al. (2002) in the study of 150 patients found that most affected paranasal sinus was Maxillary sinus (52.7%) in terms of mucosal abnormalities [20].
While agreeing with other studies, present study also points that Maxillary sinusitis is the commonest diagnosis.In other word, maxillary sinus is the most frequent involved sinus.
In the present study, Antrochoanal polyp on the Rt.[19] found Ethmoidal polyp out numbering AC polyp (18 of 27 patients with nasal polyp had Ethmoidal polyp).

Conclusions
Thus, with the pitfall of less sample size, this study has re-emphasized the concept that positions of the nasal septum and Osteomeatal complex are the key factors in the causation of various sinonasal pathologies like sinusitis or polyp.Different and frequent anatomical variants may be found in the anterior ostiomeatal complex, and a single individual may present with different variants.
In the present study, the most frequent variants involved the nasal septum (deviation or pneumatization), the middle turbinate, particularly their pneumatization and paradoxical curvature, pneumatized agger nasi cells, infraorbital ethmoid cells and uncinate process.Removal of disease from Osteomeatal complex region is the basic principle of FESS which is best appreciated on CT Scan.Before the suggestion of a casual relation between the anatomical variants and the sinusopathy in the tomographic analysis of a patient, these conditions should be considered in conjunction with the clinical picture.

Table 1 . Comparison of prevalence of anatomical variations (n = number of patients).
5% and on Lt. Side in 45.5% patients.No left or right bias with Antrochoanal polyp has been found in previous studies.It is also supported by P. Frosini et al.'s study (2009, in which, AC Polyp was in Rt. side for 48.5% and in Lt. side for 50% patients [21].4% of our patients has Ethmoidal polyp while 22% patients are diagnosed to have Antrochoanal polyp.In contrast to our study, Neena Chaudhary et al.'s (1999)