**Question:** In episodic positional vertigo which of the following tests is used?

A. Dix-Hallpike test
B. Epley manoeuvre
C. Frenzel's glasses
D. Caloric test

**Correct Answer:** .

**Core Concept:**
Episodic positional vertigo is a type of vertigo (dizziness) that occurs in response to changes in head position, typically when lying down or sitting up. It is characterized by a brief episode of severe vertigo and nystagmus (uncontrolled involuntary eye movements) that are triggered by specific head positions. The correct tests for diagnosing positional vertigo involve evaluating the affected individual's symptoms and conducting specific maneuvers to reproduce the vertigo and identify the affected semicircular canal.

**Why the Correct Answer is Right:**

1. **Dix-Hallpike test (Option A):** This test is used to diagnose Benign Paroxysmal Positional Vertigo (BPPV) caused by dislodged otoconia (calcium crystals) in the semicircular canals of the inner ear. The test involves lying on a table with the head positioned to simulate the affected head position during the vertigo attack, while observing for nystagmus.

2. **Epley manoeuvre (Option B):** Also known as the Epley repositioning maneuver, this is a series of four head movements performed to reposition the dislodged otoconia and restore the affected canal's function. The Epley manoeuvre is a more effective treatment option than the Dix-Hallpike test alone, as it directly relocates the otoconia and improves the patient's symptoms.

3. **Frenzel's glasses (Option C):** Frenzel's glasses are devices used to visually enhance the otoliths (calcium crystals) during the Dix-Hallpike test. They help to visualize the nystagmus more clearly, allowing a more accurate diagnosis of BPPV. However, they are not used as a diagnostic test, but rather as a tool to observe the nystagmus during the test.

4. **Caloric test (Option D):** The caloric test is a diagnostic test for vestibular function, evaluating the function of the vestibular system, not related to positional vertigo diagnosis. It measures the response of the vestibular nerve to warm and cold water stimulation and is helpful in diagnosing other vestibular disorders, but not positional vertigo.

**Why Each Wrong Answer is Incorrect:**

1. **Dix-Hallpike test (Option C):** Although the Dix-Hallpike test helps in diagnosing BPPV, it is not a test itself but a maneuver performed to induce vertigo during the Dix-Hallpike test.

2. **Frenzel's glasses (Option C):** Frenzel's glasses are used to enhance visualization of the nystagmus during the Dix-Hallp