**Core Concept**
Prolonged blockade of the Eustachian tube can disrupt normal middle ear pressure regulation, leading to a condition characterized by impaired hearing, discomfort, and potential complications.

**Why the Correct Answer is Right**
The Eustachian tube connects the middle ear to the nasopharynx and plays a crucial role in equalizing atmospheric pressure in the middle ear. When the Eustachian tube is blocked, air cannot enter the middle ear, causing a negative pressure that leads to retraction of the tympanic membrane and subsequent damage to the middle ear structures. This condition is known as **serous otitis media** or **middle ear effusion**. The prolonged blockade can also lead to **ossicular damage**, **tympanic membrane perforation**, and **sensorineural hearing loss**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the consequences of prolonged Eustachian tube blockade. While hearing loss can occur, it is not the primary or most direct consequence.
**Option B:** This option is incorrect because it is a symptom of the condition rather than a direct consequence of prolonged Eustachian tube blockade.
**Option C:** This option is incorrect because it is not a direct consequence of prolonged Eustachian tube blockade.

**Clinical Pearl / High-Yield Fact**
It is essential to note that prolonged Eustachian tube blockade can be caused by various factors, including allergies, upper respiratory tract infections, and anatomical abnormalities. Prompt recognition and treatment of the underlying cause can prevent long-term complications.

**Correct Answer: C. Serous otitis media**