Investigation of choice in vestibular schwannoma –
**Core Concept**
Vestibular schwannoma, also known as acoustic neuroma, is a benign tumor arising from the Schwann cells of the vestibulocochlear nerve (cranial nerve VIII). Accurate diagnosis and investigation are crucial for management and treatment planning.
**Why the Correct Answer is Right**
The investigation of choice for vestibular schwannoma is high-resolution contrast-enhanced magnetic resonance imaging (MRI) of the internal auditory canal and cerebellopontine angle. This imaging modality provides detailed visualization of the tumor's size, location, and relationship to surrounding structures. MRI is particularly useful for detecting smaller tumors and evaluating the integrity of the vestibulocochlear nerve.
**Why Each Wrong Option is Incorrect**
**Option A:** Computed Tomography (CT) scan of the temporal bone. While CT can provide information on bone involvement and bony structures, it is not the best modality for soft tissue characterization and tumor extent.
**Option B:** Auditory Brainstem Response (ABR) testing. ABR is an electrophysiological test used to assess the function of the auditory nerve and brainstem. However, it does not provide direct visualization of the tumor.
**Option C:** Positron Emission Tomography (PET) scan. PET scans are primarily used for metabolic activity and tumor staging in various cancers. They are not the primary choice for evaluating vestibular schwannomas.
**Clinical Pearl / High-Yield Fact**
It is essential to differentiate vestibular schwannoma from other lesions, such as meningiomas, glomus tumors, and metastatic disease, which may also involve the internal auditory canal and cerebellopontine angle.
**Correct Answer:** C. Positron Emission Tomography (PET) scan.