**Core Concept**
The **glomus tumor**, also known as a paraganglioma, is a rare, usually benign neoplasm arising from the **glomus body**, a specialized arteriovenous structure involved in thermoregulation. These tumors can occur in various locations, including the middle ear, where they are known as **glomus jugulare** or **glomus tympanicum** tumors.

**Why the Correct Answer is Right**
The earliest symptom of a glomus tumor, particularly those located in the middle ear, is often related to its location and the structures it affects. Given the proximity to the auditory apparatus, symptoms related to hearing are common. The correct answer is related to the impact of the tumor on the ear's function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be related to a different symptom or condition altogether, not specifically associated with the early presentation of glomus tumors.
**Option B:** Similarly, this option does not accurately reflect the most common initial symptom of glomus tumors.
**Option C:** This option might be a symptom of advanced disease or a different condition, not the earliest manifestation.
**Option D:** This is not typically the first symptom that patients with glomus tumors present with.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **hearing loss** or **tinnitus** can be early signs of a glomus tumor due to its potential to affect the middle ear structures. Recognizing these symptoms early can lead to timely diagnosis and treatment.

**Correct Answer:** D. Pulsatile tinnitus.