A 57-year-old banker complains of 2 days of severe dizziness. When she sits up or rolls over in bed, she has a spinning sensation that lasts for a few seconds and is followed by nausea. These episodes have occurred many times a day and prevent her from working. She denies fever or upper respiratory symptoms and takes no medications. When moved quickly from a sitting to a lying position with her head turned and hanging below the horizontal plane, she complains of dizziness, and horizontal nystagmus is noted. The most likely diagnosis is

**Question:** A 57-year-old banker complains of 2 days of severe dizziness. When she sits up or rolls over in bed, she has a spinning sensation that lasts for a few seconds and is followed by nausea. These episodes have occurred many times a day and prevent her from working. She denies fever or upper respiratory symptoms and takes no medications. When moved quickly from a sitting to a lying position with her head turned and hanging below the horizontal plane, she complains of dizziness, and horizontal nystagmus is noted. The most likely diagnosis is

A. Benign Paroxysmal Positional Vertigo (BPPV)
B. Ménière's disease
C. Dehydration
D. Migraine

**Correct Answer:** A. Benign Paroxysmal Positional Vertigo (BPPV)

**Core Concept:** BPPV is a condition characterized by dizziness, vertigo, and positional nystagmus due to disturbed calcium carbonate crystals in the inner ear. It is a common cause of vertigo in older adults.

**Why the Correct Answer is Right:** The patient presents with a history of severe dizziness, especially triggered by sudden head movements like sitting up or rolling over in bed, which is characteristic of BPPV. The episodes are relieved when the patient is made to lie down, and the nystagmus is noted when the patient is moved from a sitting to a lying position with her head turned and hanging below the horizontal plane.

**Why Other Options Are Incorrect:**

**Option B (Ménière's disease):**
- Ménière's disease is a chronic disorder characterized by recurrent episodes of vertigo, tinnitus, hearing loss, and aural fullness. It is not triggered by positional changes and is less responsive to lying down.

**Option C (Dehydration):**
- Dehydration is unlikely in this case as the patient denies any fever or upper respiratory symptoms, which are common in fluid-related disorders like dehydration. Dehydration is more likely to present with generalized weakness, fatigue, and sometimes confusion, rather than specific positional vertigo and nystagmus.

**Option D (Migraine):**
- Migraine is unlikely due to the patient's age, as migraine typically affects younger individuals. Positional vertigo and nystagmus are not typical features of migraine.

The correct answer (A) is Benign Paroxysmal Positional Vertigo (BPPV), which is more likely in older adults and presents with positional vertigo and nystagmus on lying down.

✓ Correct Answer: D. Benign paroxysmal positional vertigo (BPPV)