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

 ### Summary of the Study: Computational Fluid Dynamics of Aggressive Turbinate Reductions and Empty Nose Syndrome

#### **Background**

Empty Nose Syndrome (ENS) is a controversial condition associated with nasal surgeries, particularly aggressive inferior turbinate reductions (ITR). Despite common knowledge that ITR aims to alleviate nasal obstruction, some patients report paradoxical symptoms like nasal dryness, pain, and obstruction post-surgery. 

#### **Objective**

This study aimed to explore the relationship between aggressive ITR and ENS by analyzing nasal airflow dynamics and mucosal sensory function in patients who had undergone ITR. The goal was to identify specific factors that might contribute to the development of ENS.

#### **Methods**

- **Study Design**: The research involved a comparative analysis using computational fluid dynamics (CFD) based on CT scans of the nasal cavity.

- **Participants**: 

  - **Aggressive ITR without ENS Symptoms**: 5 patients who had undergone aggressive ITR but showed no ENS symptoms.

  - **Symptomatic ENS**: 27 patients with documented ENS symptoms post-ITR.

  - **Healthy Controls**: 42 individuals with no nasal issues.

- **Evaluations**:

  - **CFD Analysis**: Compared airflow dynamics, cross-sectional areas, and nasal resistance among the groups.

  - **Questionnaires**: Utilized SNOT-22, NOSE, and ENS6Q to assess nasal symptoms and quality of life.

  - **Trigeminal Function**: Measured through menthol lateralization detection thresholds (LDTs) to assess sensory function.

#### **Results**

1. **Nasal Airflow and Resistance**:

   - Both aggressive ITR patients without ENS and symptomatic ENS patients had lower nasal resistance and larger cross-sectional areas around the inferior turbinate compared to healthy controls. 

   - However, ENS patients exhibited significantly less airflow in the inferior meatus but more airflow in the middle meatus compared to both healthy controls and aggressive ITR patients without symptoms.

   - This imbalance in airflow distribution suggests altered nasal aerodynamics in ENS patients.

2. **Wall Shear Stress**:

   - ENS patients had significantly lower wall shear stress in the inferior meatus, indicating reduced interaction between airflow and the nasal mucosa in this region.

   - This contrasts with both aggressive ITR patients without ENS and healthy controls, who had more evenly distributed shear stress.

3. **Mucosal Sensory Function**:

   - ENS patients showed significantly impaired trigeminal sensory function, as indicated by lower menthol LDTs, compared to both aggressive ITR patients without symptoms and healthy controls.

   - Interestingly, aggressive ITR patients without ENS had slightly better sensory function compared to healthy controls, a surprising finding that may warrant further investigation.

#### **Conclusions**

- **Link Between Turbinate Reduction and ENS**: The study supports that aggressive ITR can alter nasal airflow patterns and mucosal function, which may contribute to ENS development. However, ENS symptoms are not solely attributable to the degree of turbinate reduction as similar degrees of turbinate reduction were observed in both ENS patients and those without symptoms.

- **Nasal Aerodynamics and Sensory Function**: The combination of distorted nasal aerodynamics and impaired mucosal sensory function appears to play a significant role in the development of ENS symptoms. ENS patients showed an abnormal distribution of airflow and reduced sensory feedback, which may contribute to their symptoms.

- **Implications for Surgery**: The findings suggest that while aggressive ITR can alter nasal airflow, careful consideration of how these changes impact mucosal function is crucial in preventing ENS. Balancing airflow distribution and preserving sensory function could be key in improving surgical outcomes and avoiding ENS.

#### **Key Learnings**

- **Airflow Dynamics**: Disrupted airflow patterns in ENS patients indicate that the condition may arise from more complex interactions between nasal anatomy and airflow, rather than just the extent of turbinate reduction.

- **Sensory Function**: Sensory impairment in ENS patients highlights the importance of maintaining nasal mucosal function during surgery.

- **Further Research**: More research is needed to refine surgical techniques and preventive strategies to mitigate ENS risk, potentially involving a more nuanced approach to turbinate reduction and sensory preservation.

This study provides valuable insights into the mechanisms underlying ENS and emphasizes the need for a balanced approach to turbinate reduction in nasal surgeries.