Okay, let's tackle this question. The patient is a 50-year-old man with symptoms of vertigo when moving his head quickly. He feels the room spinning when he gets up or turns his head. The key points here are the positional nature of the vertigo and the elicitation of nystagmus upon head movement.

First, I need to recall the types of vertigo. There's peripheral and central vertigo. Peripheral is more common and related to the inner ear, while central is due to brain issues. The symptoms here suggest peripheral because he doesn't have neurological deficits like speech issues or ataxia.

The question mentions that the sensation can be reproduced by rapidly turning the head and nystagmus is present. That makes me think of Benign Paroxysmal Positional Vertigo (BPPV). BPPV is caused by otoliths (calcium carbonate crystals) dislodging from the utricle and entering the semicircular canals, usually the posterior one. When the head moves, these particles move and cause inappropriate stimulation of the cupula, leading to vertigo and nystagmus.

Other options might include Meniere's disease, which has vertigo, tinnitus, and hearing loss, but the patient's hearing is normal here. Vestibular neuritis could cause vertigo without hearing loss, but it's usually constant and not positional. Labyrinthitis has similar features but often with hearing loss. Central causes like stroke are less likely given the positional trigger and absence of other neurological signs.

So the correct answer is BPPV. The other options don't fit as well. The clinical pearl here is that BPPV is the most common cause of vertigo in the elderly and is positional, with nystagmus that's typically upbeating and torsional. The Dix-Hallpike maneuver is the diagnostic test.

**Core Concept**
This question tests the differential diagnosis of positional vertigo, focusing on **benign paroxysmal positional vertigo (BPPV)**. BPPV is caused by displaced otoconia in the semicircular canals, triggering transient vertigo and nystagmus with head position changes. Key features include **positional trigger**, **absence of tinnitus/hearing loss**, and **short duration (<1 minute)**. **Why the Correct Answer is Right** The patient’s symptoms align with BPPV: vertigo triggered by head movements (e.g., turning in bed), reproducible nystagmus, and no hearing loss. Pathophysiology involves **otoconial debris** in the posterior semicircular canal stimulating the **vestibular nerve** during head position changes. This causes **torsional/geysering nystagmus** during the Dix-Hallpike maneuver, resolving spontaneously as otoconia settle. **Why Each Wrong Option is Incorrect** **Option A: Meniere’s disease** – Incorrect. Characterized by vertigo, **fluctuating sensorineural hearing loss**, tinnitus, and aural fullness. Hearing is normal here. **Option B: Vestibular neuritis** – Incorrect. Presents with **spontaneous, persistent vertigo** without hearing loss, often with residual imbalance. No positional triggers. **Option C: Vestibular migraine** – Incorrect. Associated with **migraine history** and vert

✓ Correct Answer: A. Benign paroxysmal positional veigo