---
title: "Tos Classification - Pars Flaccida Retraction"
description: "Understand the Tos classification of pars flaccida retraction, with schematic representations and endoscopic correlations."
source: "The ENT Resident"
author: "Dr. Mausumi Das"
canonical_url: "https://www.theentresident.com/ent-notes-lectures/tos-classification"
categories: ["Otology", "Classifications and Gradings in ENT", "Drawings in ENT"]
video: "https://www.youtube.com/watch?v=DxdouHDcRz8"
image: "https://media.theentresident.com/og-images/tos-classification.png"
---

# Tos Classification - Pars Flaccida Retraction

Understand the Tos classification of pars flaccida retraction, with schematic representations and endoscopic correlations. Watch the full video lecture on YouTube: https://www.youtube.com/watch?v=DxdouHDcRz8

## 👂 Tos Classification of Pars Flaccida Retraction

![Tos Classification of Pars Flaccida Retraction](https://media.theentresident.com/post-images/tos-classification-pars-flaccida-retraction.png)

### ✅ **Stage 1**: Mild Retraction

- **Minimal dimpling** of pars flaccida.
- **Not in contact** with the neck of malleus.
- **Retraction is visible** but not adherent.

---

### ✅ **Stage 2**: Contact with Neck of Malleus

- Pars flaccida is **retracted and adherent** to the **neck of the malleus**.
- **Entire retraction pocket is visible** on otoendoscopy.

---

### ✅ **Stage 3**: Partial Erosion of Scutum

- **Part of the retraction pocket is out of view.**
- There is **partial erosion** of the **bony attic wall (scutum)**.
- The retraction is deeper and begins to hide in the attic.

---

### ✅ **Stage 4**: Severe Retraction and Erosion

- **Severe erosion** of the scutum.
- Retraction pocket is **deep, not fully visible**.
- **Complete adherence** to surrounding structures.

---

### 📝 Summary Table

| Stage | Key Features |
| --- | --- |
| 1 | Mild retraction, not touching malleus |
| 2 | Adherent to neck of malleus, fully visible pocket |
| 3 | Partial scutum erosion, pocket partly hidden |
| 4 | Severe erosion, deep non-visible pocket |

---

## About This Note

This free ENT note on Tos Classification - Pars Flaccida Retraction was written by Dr. Mausumi Das and is paired with a corresponding video lecture.

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- Otology: https://www.theentresident.com/ent-notes-lectures/category/otology.md
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- Drawings in ENT: https://www.theentresident.com/ent-notes-lectures/category/drawing-in-ent.md

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