**Core Concept**
The Positive Romberg test with eyes closed indicates a defect in the proprioceptive pathways, specifically the vestibular system. The semicircular canals of the inner ear play a crucial role in maintaining balance and equilibrium.

**Why the Correct Answer is Right**
When the eyes are closed, the individual relies solely on the vestibular system to maintain balance. The semicircular canals, filled with fluid called endolymph, contain sensory hair cells that detect changes in head movement, allowing the brain to calculate the position and movement of the head. A defect in the semicircular canals would lead to difficulty maintaining balance, resulting in a positive Romberg test. The affected canal would be the posterior semicircular canal, as it is primarily responsible for detecting rotational movements.

**Why Each Wrong Option is Incorrect**
**Option A:** The utricle and saccule are involved in detecting linear acceleration and changes in head position, not rotational movements.
**Option B:** The cochlea is responsible for sound processing and hearing, not balance.
**Option C:** The otolith organs (utricle and saccule) are involved in detecting linear acceleration, not rotational movements.

**Clinical Pearl / High-Yield Fact**
The Romberg test is a useful clinical tool for assessing the integrity of the proprioceptive pathways, particularly in cases of peripheral neuropathy or vestibular dysfunction.

**Correct Answer: C. The posterior semicircular canal.**