**Question:** Vestibular function is assessed by -

A. Caloric test
B. Rotary chair test
C. Dix-Hallpike test
D. Electrocochleography

**Correct Answer:** C. Dix-Hallpike test

**Core Concept:** Vestibular function refers to the assessment of the function of the vestibular system, which is responsible for maintaining balance and spatial orientation in the human body. The vestibular system consists of the inner ear and the neural pathways that transmit sensory information to the brain.

**Why the Correct Answer is Right:** The Dix-Hallpike test is a specific vestibular function test that evaluates the function of the semicircular canals, which are the primary sensory organs for balance and spatial orientation. The semicircular canals contain fluid that moves when the head is rotated, generating an electrical signal in the vestibular nerve. This signal is then transmitted to the brainstem and cerebellum, where it is integrated with other sensory inputs to maintain balance.

**Why Each Wrong Option is Incorrect:**

A. Caloric test: This test evaluates the function of the vestibular hair cells in the utricle and saccule, which are responsible for detecting linear acceleration and gravity, respectively. Although the Caloric test is used to evaluate the function of the vestibular system, it is not specific to the semicircular canals, making it less relevant for evaluating balance and spatial orientation disorders.

B. Rotary chair test: This test is used to evaluate the vestibulo-ocular reflex (VOR), which is responsible for stabilizing the visual input during head movements. The Rotary chair test primarily evaluates the oculomotor system, not the vestibular system.

D. Electrocochleography: This test evaluates the function of the cochlea, which is responsible for hearing, not balance and spatial orientation. Electrocochleography assesses the electrical activity in the auditory nerve, while the Dix-Hallpike test assesses the function of the semicircular canals in the vestibular system.

**Core Concept:** The Dix-Hallpike test is a clinical maneuver used to provoke the Benign Paroxysmal Positional Vertigo (BPPV), a condition characterized by episodes of vertigo (dizziness) induced by specific head positions.

**Why the Correct Answer is Right:** The Dix-Hallpike test is a simple and widely used clinical maneuver that can provoke BPPV in patients with vestibular hypofunction or dysfunction. During the test, the patient lies on the examination table with their head on a 45-degree angle. The examiner then rapidly rotates the patient's head from the supine position to the lateral decubitus position (lying on the side) and back to the supine position. This provides a specific stimulus to the affected semicircular canal, causing the release of otoconia (calcium carbonate particles) from the utricle into the affected semicircular canal, triggering the onset of