**Core Concept**
Glomus body tumors, also known as chemodectomas or paragangliomas, are rare, usually benign neoplasms originating from the glomus body cells in the jugular bulb or along the carotid body. These tumors arise from the paraganglion cells that are part of the autonomic nervous system.

**Why the Correct Answer is Right**
The correct answer, **D. Brain Metastasis is common**, is incorrect because glomus body tumors are known for their slow growth and low metastatic potential. Brain metastasis is not a characteristic feature of these tumors. Glomus body tumors typically cause symptoms due to their local growth and compression of surrounding structures, such as the jugular vein and cranial nerves.

**Why Each Wrong Option is Incorrect**
**Option A:** Glomus body tumors are indeed also known as chemodectomas, which is a correct statement. The term chemodectoma refers to the tumor's origin from the chemoreceptor cells of the carotid body.

**Option B:** Similarly, glomus body tumors are also known as paragangliomas, which is another correct statement. The term paraganglioma is used to describe the tumor's origin from the paraganglion cells of the autonomic nervous system.

**Option C:** Glomus body tumors are indeed more common in older age, which is a correct statement. These tumors typically present in the fifth to seventh decade of life.

**Clinical Pearl / High-Yield Fact**
A key characteristic of glomus body tumors is their slow growth, which can lead to delayed diagnosis and complications due to compression of surrounding structures.

**Correct Answer Line**
✓ Correct Answer: D. Brain Metastasis is common