**Core Concept**
Körner's septum is a bony partition or septum in the temporal bone, specifically located at the petrosquamous suture. This suture is a fibrous joint between the petrous and squamous parts of the temporal bone. The presence of Körner's septum is clinically relevant as it can be a site for the formation of a cholesterol granuloma, a benign but potentially symptomatic lesion.

**Why the Correct Answer is Right**
The petrosquamous suture is a weak point in the temporal bone where the petrous and squamous parts meet. This suture is prone to dehiscence, and the resulting bone defect can be a site for the formation of Körner's septum. The septum is thought to be a bony outgrowth or partition that forms in response to the dehiscence, creating a small cavity or sinus. The presence of a Körner's septum can be identified on CT scans or MRI, and it may be associated with symptoms such as hearing loss, tinnitus, or aural fullness.

**Why Each Wrong Option is Incorrect**
**Option B:** The temporosquamous suture is a separate suture line between the temporal bone and the squamous part of the occipital bone, and it is not associated with Körner's septum.
**Option C:** The petromastoid suture is a suture line between the petrous part of the temporal bone and the mastoid part of the temporal bone, and it is not related to Körner's septum.
**Option D:** The frontozygomatic suture is a suture line between the frontal bone and the zygomatic bone, and it is not associated with Körner's septum.

**Clinical Pearl / High-Yield Fact**
When evaluating patients with temporal bone pathology, it is essential to be aware of the presence of Körner's septum, as it can be a site for the formation of cholesterol granulomas. These lesions can cause symptoms such as hearing loss, tinnitus, or aural fullness, and they may require surgical intervention.

**✓ Correct Answer: A. Petrosquamous suture**