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.

Inferior meatus augmentation procedure IMAP normalizes nasal airflow patterns in empty nose syndrome patients via computational fluid dynamics CFD modeling

 ### Summary of the Research Study on Empty Nose Syndrome and Inferior Meatus Augmentation Procedure

#### Background

Empty Nose Syndrome (ENS) is a controversial and often debilitating condition that arises from significant tissue loss in the nasal cavity, particularly affecting the inferior turbinates. Patients with ENS experience distressing symptoms such as nasal dryness, obstruction, burning, and crusting, which often occur after surgical procedures intended to widen the nasal passages by removing or reducing the inferior turbinates. Despite the apparent physical openness of the nasal passages post-surgery, patients with ENS report a paradoxical sense of nasal obstruction and discomfort.

The study in question investigates the efficacy of the Inferior Meatus Augmentation Procedure (IMAP) in alleviating ENS symptoms. IMAP involves the implantation of submucosal rib cartilage to restore the volume and contour of the nasal cavity, particularly in the inferior meatus. This study sought to understand the mechanisms behind the symptom relief provided by IMAP using advanced computational fluid dynamics (CFD) modeling.

#### Methods

The study involved five patients diagnosed with ENS who had undergone bilateral IMAP surgery. The procedure entailed the insertion of rib cartilage implants into the inferior meatus. Pre-operative and post-operative computed tomography (CT) scans were analyzed using CFD modeling to assess changes in nasal airflow patterns. The patients’ symptoms were evaluated using the Empty Nose Syndrome 6-Item Questionnaire (ENS6Q) both before and after surgery.

#### Results

1. **Symptom Improvement**: There was a significant reduction in ENS symptoms following IMAP surgery. The ENS6Q scores improved from a mean of 14.00 (indicating severe symptoms) to 4.80 (indicating mild symptoms), with a Cohen’s d value of 2.64 (p = 0.02), reflecting a substantial effect size.

2. **Airflow Dynamics**: CFD modeling revealed a notable shift in airflow patterns post-IMAP. Airflow distribution changed significantly, with a reduction in airflow through the middle meatus and an increase in airflow through the inferior meatus. This shift was observed across different slices of the nasal cavity:

   - **Anterior to the Implant**: Airflow through the middle meatus decreased from 67.13% to 46.18%, while airflow through the inferior meatus increased from 30.55% to 42.59% (p < 0.05).

   - **At the Implant**: A decrease in middle meatus airflow was noted (from 52.42% to 38.45%), although this was not statistically significant (p = 0.08).

   - **Posterior to the Implant**: No significant changes in airflow distribution were observed.

3. **Nasal Resistance**: There were no significant changes in nasal resistance pre- and post-IMAP, indicating that the improvement in symptoms was not due to changes in airflow resistance.

4. **Correlation with Symptom Relief**: A significant correlation was found between reduced airflow through the middle meatus and improved ENS6Q scores, suggesting that the shift in airflow patterns contributed to symptom relief.

#### Conclusions

The study supports the hypothesis that the symptoms of ENS are not solely related to nasal resistance but are significantly influenced by the abnormal distribution of nasal airflow. IMAP surgery effectively alters the airflow dynamics in the nasal cavity by redistributing airflow away from the middle meatus and enhancing airflow through the inferior meatus. This improvement in airflow patterns is associated with a reduction in ENS symptoms.

#### Key Findings and Implications

- **Mechanisms of Symptom Relief**: The symptom relief experienced by patients following IMAP surgery appears to be linked to the normalization of airflow patterns rather than changes in nasal resistance. The Coandă effect, where airflow adheres to the curvature of surfaces, may play a role in redistributing airflow towards the inferior meatus. 

- **Restoration of Nasal Function**: The augmentation of the inferior meatus via IMAP restores a more natural airflow pattern, providing patients with a more satisfying sensation of airflow and potentially addressing the root causes of ENS symptoms.

- **Future Directions**: While this study provides valuable insights into the benefits of IMAP, further research is needed to explore the exact mechanisms behind the observed airflow changes and to validate these findings in larger patient populations.

In summary, the research demonstrates that IMAP is a promising surgical intervention for ENS, providing significant symptomatic relief through the restoration of normal nasal airflow patterns.