**Question:** Thornwaldt's abscess is seen in -

**Core Concept:** Thornwaldt's abscess is a type of deep neck space infection that involves the retropharyngeal space, which is a potential space located between the prevertebral fascia of the neck. This space is a reservoir for lymphatic and hematogenous spread, and infections in this space can lead to serious complications such as mediastinitis, sepsis, and airway compromise.

**Why the Correct Answer is Right:** Thornwaldt's abscess is a condition caused by infections in the retropharyngeal space, which is a potential space in the neck. The correct answer (C) refers to the retropharyngeal space, which is the correct location for Thornwaldt's abscess. The infection can spread through this space, leading to complications such as mediastinitis and sepsis.

**Why Each Wrong Option is Inaccurate:**

A. (D) Submandibular space - This is a different deep neck space, located inferior to the hyoid bone and contains the submandibular salivary gland. Thornwaldt's abscess involves the retropharyngeal space, not the submandibular space.

B. (A) Parapharyngeal space - This space is located superior to the hyoid bone and contains the retropharyngeal lymph nodes. Although both Thornwaldt's abscess and parapharyngeal space infections can lead to complications, the correct answer (C) specifically refers to the retropharyngeal space, which is the correct location for Thornwaldt's abscess.

D. (D) Submandibular space - This space is mentioned earlier, and it is different from Thornwaldt's abscess, which involves the retropharyngeal space.

**Clinical Pearl:** Deep neck space infections like Thornwaldt's abscess highlight the importance of distinguishing between different deep neck spaces and their potential complications. Rapid diagnosis and management are crucial to prevent severe complications like airway compromise and mediastinitis.

**Correct Answer:** C - Submandibular space

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Thornwaldt's abscess refers to an infection within the retropharyngeal space, a region of the body that plays a role in the spread of infections and lymphatic drainage in the neck. Understanding the anatomy of deep neck spaces is essential in making an accurate diagnosis and managing these infections effectively. Infections in the submandibular space are different from Thornwaldt's abscess and may lead to different complications, highlighting the importance of recognizing the specific deep neck space involved.