What are the indications for the use of computed tomography before septoplasty?

Abstract

Septoplasty is a common procedure performed for the primary indication of nasal airway obstruction. Physical examination with anterior rhinoscopy (AR) and nasal endoscopy (NE) is considered the gold standard for detecting and rating septal deviation. Computed tomography (CT) can also be used to evaluate the nasal septum. Otolaryngologists may use CT in selecting surgical candidates, especially because it is often ordered in the context of chronic rhinosinusitis, whereas insurance companies may request a CT scan for objective evidence to approve septal surgery. Moreover, preoperative CT can be used for further examination of the nasal anatomy and identification of ancillary sinonasal pathologies. However, this modality has additional costs, exposes patients to harmful radiation, and may provide a different assessment of septal deviation than a dynamic three-dimensional physical examination. It is therefore necessary to examine guidelines for its appropriate use before septoplasty. To investigate the indications for CT before septoplasty, a literature review was performed with the PubMed database. Using the search terms “computed tomography,” “septal deviation,” and “septoplasty,” five studies were identified and reviewed (Table 1). Several publications have evaluated the correlation between physical examination and CT in the quantitative assessment of septal deviation. In a prospective study (level 4) with 20 patients who presented with symptoms of chronic rhinosinusitis, Lebowitz et al.1 compared the findings of a radiologist who evaluated CT imaging and was blinded to the findings of physical examination, and an attending otolaryngologist who performed AR and NE and had not seen the CT scans. Both physicians graded the degree of deviation with an analog scale at three segments of the septum, including caudal, mid, and posterior locations. A poor relationship was found between physical examination and CT. While there was a tendency for CT to underestimate the degree of deviation at the caudal and midseptum, deviations of the posterior septum appeared less severe on NE. The authors promoted physical examination as the diagnostic gold standard and suggested that if CT is obtained, possible discrepancies between the two modalities should be considered. Sedaghat et al.2 also compared CT and physical examination for diagnosing septal deviation in a retrospective study (level 4) with 39 patients with a history of sinonasal symptoms. The authors compared the findings of a neuroradiologist and otolaryngologist who assessed four septal locations, including the nasal valve, cartilaginous, inferior/maxillary crest, and osseous septum with a sinus CT scan and physical examination, respectively. Both physicians were blinded to the findings of one another. The investigators found a statistically significant correlation between physical examination and CT only at the osseous septum. Moreover, there was a tendency for CT to underestimate the findings of physical examination for deviations of all four locations, especially those of the internal nasal valve. They concluded that CT is a poor substitute for physical examination, and argued that radiographic evidence should not be used to select surgical candidates or approve septoplasty. A limitation of the prior two studies is the use of a single otolaryngologist and radiologist. The relationship between subjective symptoms of nasal obstruction and anatomical parameters measured with CT has been investigated in the literature. In a retrospective study (level 3b) with 193 patients who underwent septoplasty, Lee et al.3 reviewed preoperative Nasal Obstruction Symptom Evaluation and Nasal Obstruction Visual Analog Scale scores and CT measurements of nasal cavity cross-sectional area at three nasal levels (interval nasal valve, ostiomeatal unit, and choana) and deviation angle at two nasal levels (internal nasal valve and ostiomeatal unit). The investigators found a correlation between subjective symptoms and CT measurements at the levels of the ostiomeatal unit and choana; no relationship was established at the level of the internal nasal valve. The authors concluded that otolaryngologists should use CT to select patients for septoplasty and pay attention to correction of middle and posterior deviations. They argued that NE can overlook the middle and posterior nasal cavity, and there is often a discrepancy between findings of physical examination and degree of subjective symptoms, because the angle of the endoscope may affect findings. In retrospect, this claim requires further validation and future research is needed to investigate the clinical significance of posterior deviations, which are considered less important than those of the anterior septum. CT imaging may be ordered before septoplasty for further evaluation of the nasal anatomy and identification of ancillary sinonasal pathologies to improve surgical outcomes. Karataş et al.4 demonstrated the contribution of preoperative CT in a retrospective study (level 3b) with 76 patients who planned to undergo septoplasty after clinical examination. Thirty-six patients were randomly assigned to undergo a preoperative CT scan. For these subjects, the investigators documented additional pathology identified by CT and procedures performed for these findings, including lateral resection of concha bullosa, out-fracture with submucosal cauterization of inferior concha bullosa, and endoscopic sinus surgery for chronic sinusitis. Both groups of patients reported changes in nasal obstruction after surgery; those who underwent preoperative CT and further surgical intervention reported a greater degree of improvement. The authors concluded that preoperative CT can identify pathology not visible on physical examination, assist with surgical planning, and help better relieve nasal obstruction. Günbey et al.5 substantiated the value of preoperative CT in a retrospective analysis (level 4) of 262 patients who presented with symptomatic nasal obstruction and underwent a CT scan after clinical examination. The authors found that CT changed the surgical plan in 8.3% of patients, most of which were additional resections of concha bullosa and endoscopic sinus surgeries. However, given the additional costs and harmful radiation exposure associated with CT, they investigated whether this modality is necessary for every patient undergoing septoplasty by determining the diagnostic value of AR and NE for obstructive sinonasal pathologies detected on CT. They found that NE was more sensitive for pathology in patients with mild septal deviation than in those with moderate to severe septal deviation. Moreover, NE had high sensitivity and specificity for uncinate hypertrophy, ostiomeatal complex pathology, paradox middle concha, and nasal polyps, and less sensitivity and specificity for concha bullosa, mucocele, and chronic sinusitis. Based on these findings, the authors recommended a preoperative CT scan for patients with obstructive middle turbinate hypertrophy or chronic sinusitis based on clinical history and findings of NE, or if a severe anterior deviation or nasal polyp impedes evaluation of the middle meatus and posterior nasal cavity. Based on the reviewed literature, reliance on CT for selection of septoplasty candidates or insurance approval of septal surgery is discouraged. CT was shown to underestimate the findings of NE for deviations of the internal nasal valve. Moreover, subjective symptoms of nasal obstruction did not correlate with anatomical parameters measured with CT at the internal nasal valve. This region of the nasal cavity significantly contributes to total nasal airflow resistance. Though one study recommended CT for evaluation of the posterior septum, the clinical significance of posterior deviations requires further investigation. On the other hand, preoperative CT can be helpful in identifying ancillary sinonasal pathologies contributing to nasal obstruction, especially concha bullosa and sinusitis. However, given the additional costs and exposure to radiation associated with CT, preoperative imaging should only be ordered for a subset of patients. Although it is advisable to order a preoperative CT when NE is limited by obstructive pathology or in the setting of chronic rhinosinusitis, future research is needed to establish a consensus on selection criteria. Two level 3b and three level 4 articles were evaluated in this review.