**Question:** A patient is suspected to have vestibular schwannoma. The investigation of choice for its diagnosis is-

A. MRI (Magnetic Resonance Imaging)
B. CT (Computed Tomography) scan
C. Electrocochleography
D. Audiometry

**Correct Answer:** A. MRI (Magnetic Resonance Imaging)

**Core Concept:**
Vestibular schwannoma, also known as a vestibular neurinoma or acoustic neuroma, is a benign tumor that develops from the Schwann cells of the vestibular branch of the eighth cranial nerve. This tumor can cause a range of symptoms due to its effects on the inner ear and brainstem.

**Why the Correct Answer is Right:**
MRI (Magnetic Resonance Imaging) is the preferred imaging modality for diagnosing vestibular schwannoma due to its superior soft tissue contrast, multiplanar imaging capabilities, and the ability to visualize the tumor's size, location, and relation to surrounding structures. MRI is particularly useful for assessing the involvement of the brainstem and cerebellopontine angle.

**Why Each Wrong Option is Incorrect:**

A. CT (Computed Tomography) scan: While CT can detect calcifications in the tumor, it has limited soft tissue contrast and is not as effective as MRI in assessing the tumor's relation to the brainstem and cerebellopontine angle.

B. Electrocochleography: This test assesses the function of the cochlea and is used to diagnose disorders of the cochlea, not vestibular schwannomas.

C. Audiometry: Audiometry is a hearing test that evaluates hearing function but does not provide imaging information about the tumor.

**Clinical Pearl:**
Audiometry is a useful test for assessing hearing loss due to vestibular schwannoma, but it is not a diagnostic tool for the tumor itself. In contrast, MRI is the gold standard for detecting, assessing, and planning the management of vestibular schwannomas.

**Why the Correct Answer is Right:**
MRI is essential in diagnosing vestibular schwannoma due to its ability to visualize the tumor size, location, and relation to the brainstem and cerebellopontine angle. MRI can also assess the involvement of the facial nerve, which is critical in clinical decision-making for these patients.

**Why Each Wrong Option is Incorrect:**

A. CT scan: As mentioned earlier, CT is less effective in visualizing the tumor's soft tissue characteristics and assessing the brainstem and cerebellopontine angle involvement.

B. Electrocochleography: This test is used to investigate disorders of the cochlea and is not relevant in diagnosing vestibular schwannomas.

C. Audiometry: Audiometry is a hearing test and does not provide diagnostic imaging information about the tumor.