Computational fluid dynamic analysis of aggressive turbinate reductions: is it a culprit of empty nose syndrome?

Empty nose syndrome (ENS) remains highly controversial, with aggressive inferior turbinate reduction (ITR) or mucociliary dysfunction frequently implicated. However, the appropriate degree of ITR is highly debatable. We applied individual computed tomography (CT)-based computational fluid dynamics (CFD) to 5 patients receiving relatively aggressive ITR but with no ENS symptoms, and compared them to 27 symptomatic ENS patients who all had histories of aggressive ITRs, and 42 healthy controls. Patients' surgical outcomes were confirmed with 22-item Sino-Nasal Outcome Test (SNOT-22) (ITR: 6.40 ± 4.56; ENS: 58.2 ± 15.9; healthy: 13.2 ± 14.9), Nasal Obstruction Symptom Evaluation (NOSE) scores (ITR: 4.00 ± 2.24; ENS: 69.4 ± 17.1; healthy: 11.9 ± 12.9), and Empty Nose Syndrome 6-Item Questionnaire (ENS6Q) (≥11 for ENS). Both aggressive ITR without ENS symptoms and symptomatic ENS patients had significantly lower nasal resistance (ITR: 0.059 ± 0.020 Pa·s/mL; ENS: 0.052 ± 0.015 Pa·s/mL; healthy: 0.070 ± 0.021 Pa·s/mL) and higher cross-sectional areas surrounding the inferior turbinate (ITR: 0.94 ± 0.21 cm2 ; ENS: 1.19 ± 1.05 cm2 ; healthy: 0.42 ± 0.22 cm2 ) than healthy controls. The lack of significant differences among patient groups indicated similar degrees of surgeries between ITR with and without ENS symptom cohorts. However, symptomatic ENS patients have paradoxical significantly less airflow in the inferior meatus (ITR: 47.7% ± 23.6%; ENS: 25.8% ± 17.6%; healthy: 36.5 ± 15.9%; both p < 0.01), but higher airflow around the middle meatus (ITR: 49.7% ± 22.6%; ENS: 66.5% ± 18.3%; healthy: 49.9% ± 15.1%, p < 0.0001) than aggressive ITR without symptoms and controls. Aggressive ITR patients have increased inferior meatus airflow as expected (p < 0.05). This imbalanced airflow produced less inferior wall-shear-stress distribution among symptomatic ENS patients only (ITR: 42.45% ± 11.4%; ENS: 32.2% ± 12.6%; healthy: 49.7% ± 9.9%). ENS patients (n = 12) also had impaired nasal trigeminal function, as measured by menthol lateralization detection thresholds (ITR: 15.2 ± 1.2; ENS: 10.3 ± 3.9; healthy: 13.8 ± 3.09, both p < 0.0001). Surprisingly, aggressive ITR patients without ENS symptoms have better menthol lateralization detection thresholds (LDTs) than healthy controls. Although turbinate tissue loss is linked with ENS, the degree of ITR that might distinguish postoperative patient satisfaction in their nasal breathing vs development of ENS symptoms is unclear. Our results suggest that a combination of distorted nasal aerodynamics and loss of mucosal sensory function may potentially lead to ENS symptomology.