Assessment of Olfaction Following Endoscopic Sinus Surgery

Abstract

To assess the olfactory outcomes following Endoscopic Sinus Surgery (ESS) in patients diagnosed with Chronic Rhinosinusitis (CRS) and Sinonasal polyposis (SNP). To assess and compare the pre-operative and post-operative olfactory scores of patients undergoing ESS/ ESS + polypectomy/ESS + Septoplasty by subjective and objective methods. This is a prospective, cohort study which included a total of 60 patients. Subjective assessment was done using a Questionnaire. Preoperative olfactory assessment was performed with Sniffing Sticks. Olfactory assessment was done at 1st,3rd, 6th and 12th week following surgery. The preoperative and postoperative scores were statistically analysed and compared. In patients who underwent ESS, there was a significant reduction in olfactory scores in the immediate few weeks after surgery which improved over time by the end of 3 months. In patients who underwent ESS with polypectomy, there was a significant improvement in olfactory scores from the third week following surgery which was sustained over 3rd month follow-up. In patients who underwent ESS with Septoplasy, there was a significant decrease in olfactory scores during the initial few weeks with a marginal improvement during 3 months follow-up. At the end of 12 weeks post ESS, no patient was found to be anosmic. Patients with pre-existing hyposmia did not show statistically significant change post surgery.However patients with anosmia showed statistically significant improvement in olfactory function, but did not become normosmic at 12th post-operative week. Majority of normosmics did not have alteration in their olfactory perception at 12th post-operative week.

Introduction

Olfaction is one of the important five special sense. It is a sensitive mechanism for detecting volatile odorants. Impaired Olfaction also affects taste[1].Factors that affect human olfaction include structural aspects of the nasal cavity that can modulate airflow and therefore odorant access to the olfactory cleft, and inflammatory disease, which can affect both airflow as well as olfactory nerve function.

The discovery of olfactory receptors by Axel and Buck sparked greater understanding of the molecular basis of olfaction[2]. It is estimated that more than 2.7 million adults in the United States (1.4% of the population) have chronic olfactory impairment[3]. Causes of these losses include head injury, ageing, paranasal sinus disease, neoplasm, medications, toxic exposure, upper respiratory tract infection, surgical trauma, and congenital defects[4, 5]. Despite the relatively high prevalence, there is a lack of public awareness regarding this problem. Impaired olfaction imposes health risks associated with inability to recognize danger signals from fire, gas. Among the various diseases causing impairment of olfaction, Chronic rhinosinusitis (with/without polyposis) is the commonest [6]. Any surgical procedure in the nose like Endoscopic Sinus Surgery (ESS), carry a potential risk of damage to the Olfactory sense[7]. However, the Olfactory sense is not routinely tested in the pre-operative & post-operative period.

Rhinosinusitis is defined as inflammation of the paranasal sinuses and nasal cavity [8, 9]. It is classified as acute (less than 4 weeks), subacute(4–12 weeks), or chronic (more than 12 weeks)[10]. Studies have shown that CRS is more common in female [11, 12]. It may be accompanied with nasal polyps in about 19% to 36% of patients[13, 14].

CRS has a varied presentation with nasal obstruction being the commonest (81–95%), followed by complaints of facial puffiness (70–85%), nasal discharge (51–83), and decreased perception of smell (61–69%) [15].

Though olfactory impairment is one of the important complications following ESS, only few prospective studies have assessed the olfaction following ESS[16]. This study was a prospective, cohort study conducted in the Department of Otorhinolarynogology and Head and Neck surgery in a tertiary care center over 2 years. The aim of our study was to assess the effect of ESS on olfaction. It was assessed in the preoperative period and during postoperative period at 1 week, 3 weeks, 6 weeks and 12 week follow-up.

Methodology

All patients who were diagnosed with CRS, based on the Rhinosinusitis Task Force criteria were evaluated for the study. The study was conducted in the Department of Otorhinolaryngology and Head and Neck surgery from Aug 2014 – Aug 2016. A total of 60 patients who underwent ESS were included in our study.

Patients between 18–60 years of age diagnosed with CRS (not responding to medical therapy) undergoing ESS/ ESS with polypectomy/ESS with septoplasty were included. The medical therapy given preoperatively for all patients included topical steroid sprays and antibiotics.

Patients with head trauma, acute sinusitis, neurodegenerative diseases, those undergoing revision Endoscopic Sinus Surgery, tumors of nose and paranasal sinuses were excluded from the study.

Selected cases underwent detailed history and examination. A diagnostic nasal endoscopy and CT of paranasal sinus was done preoperatively. The patients underwent surgery based on the extent of disease. All surgeries were performed by a single ENT surgeon. Postoperatively nasal packs were removed one day after surgery and patients were given antibiotics along with steroid nasal spray and saline nasal douches. It is important to note that, in all patients, topical steroid sprays were continued for a period of 2 months following surgery. However oral steroids were not prescribed for any patient in the preoperative or postoperative period.

Regular follow-up and olfactory assessment was done at 1st, 3rd, 6th and 12th post-operative week. Statistical analysis of pre-operative and post-operative olfactory scores was done.

Subjective Assessment

Patients were assessed pre-operatively and post-operatively with self scoring questionnaire consisting of 10 questions (each with a score of either 0 or 1). Hence the total maximum score given was 10 and the minimum was 0. (Table 1).

Table 1.

Questionnaire to assess the quality of life

Are you able to appreciate only strong odours?	(0—No, 1—Yes)
Can you appreciate all types of smell ?	(0—Yes, 1—No)
Do you have altered taste for food?	(0—No, 1—Yes)
Do you relish the taste of food with pleasant odour/flavour?	(0—Yes, 1—No)
Is your hunger reduced?	(0—No, 1—Yes)
Does it affect your occupation (fire fighters, chefs)?	(0—No,1—Yes)
Do you have any altered sense of smell (cacosmia)?	(0—No, 1—Yes)
Do you have fear that you are unable to smell smoke or fire?	(0—No, 1—Yes)
Are your visits to doctor increased due to your concern about lack of olfactory sense?	(0—No,1—Yes)
Do you feel depressed?	(0—No, 1—Yes)
Total olfactory score: 0–10
Lesser score correlates with better QOL

Objective Assessment

Measurement of Olfactory Function

Olfactory assessment was performed with Sniffing Sticks test (Burghart, Wedel, Germany). (Fig. 1) The test kits consist of 12 odour dispensing devices. The stick was placed in front of each nostril at a distance of 2 cm for 3 s. (Fig. 2) Each nostril was tested at a time. Four choices were given for each stick presented, and the patient was asked to identify what smell they perceive. (Fig. 3) A score between 0 to 12 was given for each nostril. The scores from both nostrils were added to get the final olfactory score.

Fig. 1.

Sniffing sticks test (Pen 1—Orange, Pen 2—leather, Pen 3—cinnamon, Pen 4—peppermint, Pen 5—banana, Pen 6—lemon, Pen 7—liquorice, Pen 8—coffee, Pen 9—clove, Pen 10—pineapple, Pen 11—rose, Pen 12—fish)

Fig. 2.

Measurement of olfactory function

Fig. 3.

Choices given to the patient

Interpretation

Patients were divided into 3 groups based on the final olfactory scores (Table 2).

Table 2.

Final olfactory scores

Olfactory scores	Category
0–8	Anosmic
9–16	Hyposmic
17–24	Normosmic

Surgical Technique

Based on the extent of disease, the patients underwent uncinectomy, middle meatal antrostomy, anterior ethmoidectomy, posterior ethmoidectomy and sphenoidotomy.

Patients with Sinonasal polyposis underwent polypectomy and patients who required a corrective surgery for septal deviation underwent Septoplasty along with ESS.

Of the 60 patients, 10 patients underwent ESS, 19 patients underwent ESS with Polypectomy and 31 patients underwent ESS with Septoplasty.

Results

Preoperative assessment of olfaction for the 60 patients using Sniffing sticks showed 35 patients (58.3%) were normosmic, 19 (31.6%) were hyposmic, 6 (10%) were anosmic. There was significant improvement in Olfactory scores of anosmic patients at 3 month postoperative follow up. In the normosmic group, 28 patients showed no change after surgery, whereas 7 patients showed worse olfaction Among the hyposmic patients only 4 (21%) improved after surgery and 15 (78.9%) did not show any change.

All patients were divided into 3 groups:

Group A Patients who underwent ESS

Group B Patients who underwent ESS with polypectomy

Group C Patients who underwent ESS with septoplasty

Statistical Analysis

Mean and standard deviation were calculated for each group. Statistical analysis was done using SPSS software. Various tests used were t test, Anova test and Post Hoc test.

Baseline Patient Characteristics and Demographics

Gender distribution in this study was 24 male (41.7%) and 36 female (58.3%).

The age range was between 18 and 60 years. The mean age group was 34.15 ± 11.22. Maximum number of patients fell in the age group 21–30 years.

Postoperative Results

t TEST

At the end of 12 weeks out of the 60 patients, 43 patients showed no change in olfaction. 10 patients had improvement in olfaction and 7 patients had a decrease in olfaction.

The mean olfactory score preoperatively, at the end of 1st week, 3rd week, 6th week and 12th week was 15.70 ± 4.51, 13.70 ± 3.711, 14.22 ± 3.395, 15.12 ± 3.026 and 16.20 ± 2.785 respectively. There was a decrease in mean olfactory scores during the first few weeks of postoperative period. By the end of 3 months following surgery, there was an improvement in scores compared to the preoperative period (Table 3).

Table 3.

Mean olfactory scores

Paired samples statistics
		Mean	N	Std. deviation	Std.error mean
Pair 1	Olfaction score—Preop	15.70	60	4.515	0.583
	Olfaction score—1 week postop	13.70	60	3.711	479
Pair 2	Olfaction score—preop	15.70	60	4.515	0.583
	Olfaction score—3 weeks postop	14.22	60	3.395	438
Pair 3	Olfaction score—Preop	15.70	60	4.515	0.583
	Olfaction score—6 weeks postop	15.12	60	3.026	0.391
Pair 4	Olfaction score—Preop	15.70	60	4.515	0.583
	Olfaction score—12 weeks postop	16.20	60	2.785	0.360

t Test for Patients who Underwent ESS (GROUP A)

At the end of 12 weeks, out of 10 patients, 9 patients showed no change in olfaction and 1 patient had a decrease in olfaction.

The mean olfactory score pre-operatively, at the end of 1st week, 3rd week, 6th week and 12th week was 18.30 ± 2.452, 16.40 ± 1.838, 16.60 ± 1.776, 16.60 ± 1.853 and 17.50 ± 2.273 respectively. The mean olfactory scores for patients in group A, had a statistically significant reduction in the immediate few weeks, however it improved over time by the end of 3 months following surgery (Table 4).

Table 4.

Mean olfactory scores for group A

Paired samples statistics
		Mean	N	Std. deviation	Std. error mean
Pair 1	Olfaction score—Preop	18.30	10	2.452	0.775
	Olfaction score—1 week postop	16.40	10	1.838	0.581
Pair 2	Olfaction score—Preop	18.30	10	2.452	0.775
	Olfaction score—3 weeks postop	16.60	10	1.776	0.562
Pair 3	Olfact on score—Preop	18.30	10	2.452	0.775
	Olfaction score—6 weeks postop	16.90	10	1.853	0.586
Pair 4	Olfaction score—Preop	18.30	10	2.452	0.775
	Olfaction score—12 weeks postop	17.50	10	2.273	0.719

t Test for Patients who Underwent ESS with Polypectomy (GROUP B)

At the end of 12 weeks, out of 19 patients, 10 patients had an increase in olfaction and 9 patients showed no change in olfaction.

The mean olfactory score preoperatively, at the end of 1st week, 3rd week, 6th week and 12th week was 11.63 ± 5.510, 10.84 ± 4.438, 11.89 ± 4.026, 13.11 ± 3.680 and 14.95 ± 3.535 respectively. Hence the mean olfactory scores for patients in group B, showed an improvement from the third week following surgery which was sustained over 3 month follow up. There was a statistically significant improvement in the scores compared to pre-operative score at the end of 3 months following surgery (Table 5).

Table 5.

Mean olfactory scores for group B

Paired samples statistics
		Mean	N	Std. deviation	Std. error mean
Pair 1	Olfaction score—Preop	11.63	19	5.510	1.264
	Olfaction score—1 week postop	10.84	19	4.438	1.018
Pair 2	Olfaction score—Preop	11.63	19	5.510	1.264
	Olfaction score—3 weeks postop	11.89	19	4.026	0.924
Pair 3	Olfaction score—Preop	11.63	19	5.510	1.264
	Olfaction score—6 weeks postop	13.11	19	3.680	0.844
Pair 4	Olfaction score—Preop	11.63	19	5.510	1.264
	Olfaction score—12 weeks postof	14.95	19	3.535	0.811

t Test for Patients who Underwent ESS with Septoplasty (GROUP C)

At the end of 12 weeks, out of 31 patients, 25 patients had no change in olfaction. 6 patients had a decrease in olfaction.

The mean olfactory score preoperatively, 1st week, 3rd week, 6th week and 12th week was17.35 ± 2.122, 14.58 ± 2.419, 14.87 ± 2.50, 15.77 ± 2.186 and 16.55 ± 2.127 respectively. There was a statistically significant decrease in the mean olfactory scores during the initial few weeks with a marginal improvement during 3 months follow-up (Table 6).

Table 6.

Mean olfactory scores in group C

Paired samples statistics
		Mean	N	Std. deviation	Std. error mean
Pair 1	Olfaction score—Preop	17.35	31	2.122	0.381
	Olfaction score—1 week postop	14.58	31	2.419	0.434
Pair 2	Olfaction score—Preop	17.35	31	2.122	0.381
	Olfaction score—3 weeks postop	14.87	31	2.500	0.449
Pair 3	Olfaction score—Preop	17.35	31	2.122	0.381
	Olfaction score—6 weeks postop	15.77	31	2.186	0.393
Pair 4	Olfaction score—Preop	17.35	31	2.122	0.381
	Olfaction score—12 weeks postop	16.55	31	2.127	0.382

At the end of 12 weeks post ESS/ESS with Poypectomy/ESS with Septoplasty, no patient was found to be anosmic.

During 3 months follow-up, patients in group A (ESS) and patients in group C (ESS with Septoplasty) showed a slight decrease in the olfactory scores compared to the preoperative scores of their respective groups. Whereas patients in group B (ESS with polypectomy) showed an improvement in the scores compared to the preoperative period.

Discussion

Functional endoscopic sinus surgery was introduced by Messerklinger in late 1970s. This technique was popularized and standardized in the beginning of the 1980s by Kennedy in United States and Stammberger, Wigand and Houseman in Europe. In the 1980s and 1990s many series were published on the treatment outcome after ESS, with varying success rates.

Among the many complications of ESS reported, Olfactory impairment is one aspect which has been given very less importance. It has a negative impact on patient’s quality of life and one that requires continued research. In this study we found that there was an improvement in olfaction following ESS in patients with anosmia compared to patients with hyposmia.

It is believed that patients with nasal polyposis had only temporary resolution of olfactory impairment [17]. However our study showed significant improvement in olfactory scores in anosmic patients with nasal polyposis which was sustained till 3 months follow-up. The improvement of post-operative olfactory functions in patients with nasal polyposis can be attributed to the increase in intranasal volume following removal of mechanical obstruction from the olfactory cleft. However a larger study group and longer followup is required, since polyposis has a higher prediction to recur.

A prospective study done by Pade and Hummel [18] showed nasal polyposis as the most important factor in determining olfactory improvement after ESS. This study reported that following ESS, about 23% of patients had an improvement in sense of smell, 9% had a decrease in olfaction and 68% showed no change. Minovi et al.[19] reported higher success rate of olfactory improvement in women, in patients operated for high degree of nasal polyposis compared to other patients. They did not find any correlation between age, number of preoperative surgical interventions, history of asthma to the outcome of surgery.

In contrast to our results, a few studies believed that patients with anosmia would have underlying multifactorial olfactory impairment due to direct inflammation of the neuroepithelium and physical obstruction of the olfactory cleft. Hence they would not benefit from surgery[20]. As per our study, all anosmic patients improved and only few hyposmic patients improved. Incidentally in our study it was found that all the anosmic patients had nasal polposis. These patients were likely to have complete obstruction of the olfactory cleft, hence surgical resection would have improved olfaction.

Our study reported that 20% of normosmic patients became hyposmic after surgery, however none of them became anosmic. A 1 percent risk of anosmia from nasal surgery has been reported. However the patient in the study had undergone a septoplasty under local anaesthesia and not ESS. All patients undergoing ESS should be counselled preoperatively regarding a risk of iatrogenic anosmia (less than 1%) after ESS.

A recent study done on 97 danish patients in 2015 stated that ESS improved quality of life and olfactory function (measured by sniffing sticks test) for both the (CRS with polyposis and CRS without polyposis) groups, with a 50% reduction in SNOT-22 score during 1 month follow-up and it sustained during 6 months follow-up. However, the same study also reported a deterioration in olfactory function in minor proportion of patients after ESS[21].

Another prospective study was conducted in London in 2016 by Andrews et al. on a total of 113 patients, divided into 2 groups (CRS with nasal polyposis and CRS without nasal polyposis). Olfactory sensation was measured using University of Pennsylvania Smell Investigation Test (UPSIT) and the ‘sense of smell’ visual analogue scale (VAS). The Nasal Obstruction and Symptom Evaluation (NOSE) scale, the Sinonasal outcome test (SNOT 22) and the Lund–Kennedy (LK) were also measured preoperatively and postoperatively at 6 months. This study reported a mismatch between the UPSIT and VAS olfactory scores which implies that patients had improvement in subjective olfactory perception but worsening objective olfactory function. The UPSIT measurement significantly improved following ESS in the patients with CRS with nasal polyposis subgroup and so was the VAS score. But in CRS without nasal polyposis subgroup, there was no significant improvement in VAS and UPSIT measurements. The NOSE, SNOT 22 and LK scores all improved significantly. It was found that Endoscopic sinus surgery significantly improved the sense of smell in patients with CRS with nasal polyposis subgroup which is likely to improve the patient's quality of life [22].

A study by Bugten et al. stated that patients with CRS with nasal polyposis had complaints of nasal blockage and decreased olfactory perception whereas patients with CRS without nasal polyposis complained more of headache and facial pain, but they found that both groups responded similarly and they did not find a significant difference in subjective symptoms between the groups following ESS[23].

Shriever et al. in 2013 used Sniffing sticks test to assess the effects of nasal surgery (both ESS and septal surgery) on olfaction. There was a significant improvement in olfactory outcomes in the sinus surgery group compared to a non-significant improvement in the septal surgery group at the end of 3.5 months following surgery. They both became non-significant at 12 months. They also stated that polyps and eosinophilia were good prognostic factors for olfactory outcome improvement[24]. In our study, the temporary decrease in olfactory sensation in patients who underwent Septoplasty along with ESS, could be attributed to more oedema in the olfactory region. However a longer followup period is required to assess the long term effects of ESS with Septoplasty on olfaction.

Rudmik and Smith performed a literature review on efficacy of ESS in CRS-related olfactory dysfunction and concluded that the efficacy is equivocal and not significant[25]. Lund et al. demonstrated a significant improvement in olfactory function following ESS[26].

Dealank et al. stated an improvement in olfactory perception in 70% of patients following ESS and worsening of olfaction in 8% of patients [27].

In our Indian population, there was a marked difference in identification of different odours of the Sniffing sticks test. Common odours were identified by most of the patients, however there were few odours like liquorice and leather which could be identified by only few patients since they were uncommon. This warrants the need for development of kits to assess olfaction specific to the study population.

Long-term follow-up is important because patients assessed within the first few weeks after surgery may still be healing from surgery. The presence of granulation tissue and edema may also affect the results. Complications like synechiae formation or recurrence of disease (polyposis have high prediction to recur), and new polyp formation, may reduce olfactory perception even though there may have been an initial improvement. These are the potential limitations of our study. Hence a longer study period and a larger study group is required.

Our study did not compare the effects of allergy associated CRS with non-allergy associated CRS. Future studies maybe required for the same.

Conclusion

Olfaction is an important function which can be altered by Sinonasal disease and sinonasal surgeries. Olfactory impairment is a common complaint in patients with Chronic rhinosinusitis and the role of ESS on Olfaction has not been researched. In this Prospective cohort study, a decrease in olfactory perception was observed in all patients in the immediate post-operative period, which improved over a period of time and normalised at 12th week postop. Patients with pre-existing hyposmia did not show statistically significant change or improvement post surgery. However patients with anosmia showed statistically significant improvement in olfactory function, but did not become normosmic at 12th week postop. Majority of normosmic patients did not have alteration in their perception of smell at 12th week post-op. As evidenced by this study it is important to counsel the patients about the loss of perception of smell in the immediate post-operative period which is highly likely to recover by 12 weeks postop. Olfactory impairment is an important patient safety and quality-of-life issue for patients with CRS and one that requires continued research.