Vestibular Evoked Myogenic Potentials — MCQs
What do motor evoked potentials primarily assess?
Recruitment phenomenon is seen in:
Cervical Vestibular Evoked Myogenic Potential (cVEMP) detects lesion of -
Which structure is supplied by the nerve causing this elevation?
Dix-Hallpike maneuver is used to assess-
The investigation of choice for vestibular schwannoma is
Vestibular evoked myogenic potential (VEMP) is a tool for evaluating which of the following?
In Fitzgerald-Hallpike caloric test, cold-water irrigation at 30 degrees centigrade in the left ear in a normal person will induce -
In a patient with right vestibular neuronitis, what will be the finding on the head impulse test?
A person presented to OPD with complaints of rotatory vertigo and nausea in the morning on change in position of the head. What is your diagnosis?
Vestibular Evoked Myogenic Potentials Indian Medical PG Practice Questions and MCQs
Question 1: What do motor evoked potentials primarily assess?
- A. Central motor pathways (Correct Answer)
- B. Both central and peripheral motor pathways
- C. Muscle regeneration
- D. Peripheral motor pathways
Explanation: ***Central motor pathways*** - **Motor evoked potentials (MEPs)** are generated by electrical or magnetic stimulation of the **motor cortex** and primarily assess the integrity of **central motor pathways**, specifically the **corticospinal tracts**. - MEPs are the **gold standard** for monitoring **upper motor neuron** function during neurosurgical and spinal procedures. - The technique is most sensitive to dysfunction in the **brain and spinal cord** (central nervous system), making this their primary clinical utility. *Peripheral motor pathways* - While MEPs do eventually activate peripheral motor neurons to produce muscle responses, they are **not the primary tool** for assessing peripheral pathways. - **Nerve conduction studies (NCS)** and **electromyography (EMG)** are direct and more specific measures for evaluating peripheral motor nerve function. *Both central and peripheral motor pathways* - Although MEPs provide information about the entire motor pathway from cortex to muscle, their **primary diagnostic strength and clinical application** is in detecting dysfunction within the **central nervous system**. - The latency and amplitude of MEPs are most sensitive to **conduction abnormalities along the corticospinal tract**, not peripheral nerves. *Muscle regeneration* - MEPs do **not assess muscle regeneration** or intrinsic muscle health. - **Electromyography (EMG)** with needle examination and **muscle biopsy** are the appropriate methods to evaluate muscle regeneration and myopathic processes.
Question 2: Recruitment phenomenon is seen in:
- A. Otitis media with effusion
- B. Otosclerosis
- C. Acoustic nerve schwannoma
- D. Meniere's disease (Correct Answer)
Explanation: ***Meniere's disease*** - The recruitment phenomenon, characterized by an abnormal increase in the perception of loudness for a given increase in sound intensity, is a classic finding in **cochlear hearing loss**, often seen in conditions like **Meniere's disease**. - This occurs due to damage to the **outer hair cells** in the cochlea, which normally compress the dynamic range of hearing. *Otitis media with effusion* - This condition involves **conductive hearing loss** due to fluid in the middle ear, and typically does not cause the recruitment phenomenon. - The problem lies in sound transmission, not in the processing of loudness within the cochlea. *Otosclerosis* - This condition causes **conductive hearing loss** due to abnormal bone growth around the stapes footplate, impeding sound transmission to the inner ear. - While it affects hearing, it does not directly lead to altered loudness perception or recruitment, as the cochlea itself is often intact. *Acoustic nerve schwannoma* - This tumor affects the **vestibulocochlear nerve (CN VIII)**, causing **sensorineural hearing loss** that is typically retrocochlear (beyond the cochlea). - While it causes hearing loss, recruitment is usually absent or minimal, as the pathology is neural, not cochlear.
Question 3: Cervical Vestibular Evoked Myogenic Potential (cVEMP) detects lesion of -
- A. Inferior Vestibular Nerve (Correct Answer)
- B. Cochlear Nerve
- C. Facial Nerve
- D. Superior Vestibular Nerve
Explanation: ***Inferior Vestibular Nerve*** - **cVEMP** primarily assesses the function of the **saccule** and its neural pathway via the **inferior vestibular nerve (IVN)**. - The saccule is sensitive to **vertical head movements and linear acceleration** and transmits signals through the IVN to the vestibulospinal pathway. - cVEMP is recorded from the **sternocleidomastoid muscle** and reflects the **vestibulocollic reflex**. *Cochlear Nerve* - The **cochlear nerve** is responsible for **auditory processing** and is assessed by tests like audiometry and ABR, not VEMPs. - While it's part of the vestibulocochlear nerve (CN VIII), its function is distinct from vestibular assessment. *Facial Nerve* - The **facial nerve (CN VII)** controls **facial muscles** and taste sensation, with no direct role in vestibular function. - Lesions are detected through facial movement assessment and electrophysiological tests like electroneuronography (ENoG). *Superior Vestibular Nerve* - The **superior vestibular nerve (SVN)** primarily innervates the **anterior and horizontal semicircular canals** and the **utricle**. - Its function is assessed by **oVEMP (ocular VEMP)**, **caloric reflex test**, or **head impulse test**, rather than cVEMP.
Question 4: Which structure is supplied by the nerve causing this elevation?
- A. Risorius
- B. Masseter
- C. Lateral rectus
- D. Superior oblique (Correct Answer)
Explanation: ***Superior oblique*** - The **trochlear nerve (CN IV)** causes the elevation visible in the image at the **dorsal midbrain** level, supplying the **superior oblique muscle**. - This nerve is unique as it **decussates completely** and has the longest intracranial course, making it prone to injury. *Risorius* - The **risorius muscle** is innervated by the **facial nerve (CN VII)**, which exits at the **pontomedullary junction**. - This nerve does not cause elevations at the **dorsal midbrain** level where the arrow is pointing. *Masseter* - The **masseter muscle** is one of the muscles of mastication innervated by the **mandibular division of the trigeminal nerve (CN V)**. - The trigeminal nerve has its motor nucleus in the **pons**, not at the dorsal midbrain level where the elevation is visible in the image. *Lateral rectus* - The **lateral rectus muscle** is supplied by the **abducens nerve (CN VI)**, which exits at the **pontomedullary sulcus**. - The abducens nerve pathway does not create the elevation seen at the **dorsal midbrain** in this image.
Question 5: Dix-Hallpike maneuver is used to assess-
- A. Ear Ossicle continuity
- B. Cochlear function
- C. Brainstem function
- D. Vestibular function (Correct Answer)
Explanation: ***Vestibular function*** - The Dix-Hallpike maneuver is a diagnostic test performed to identify **benign paroxysmal positional vertigo (BPPV)**. - It assesses the integrity of the **posterior semicircular canal** within the vestibular system by provoking nystagmus and vertigo. *Ear Ossicle continuity* - This is typically assessed through **tympanometry** and **audiometric testing**, not through a positional maneuver. - Problems with ossicular continuity lead to conductive hearing loss, not usually positional vertigo. *Cochlear function* - **Cochlear function** relates to hearing and is assessed using tests like **audiometry** and **otoacoustic emissions**. - The Dix-Hallpike maneuver does not evaluate the auditory function of the inner ear. *Brainstem function* - **Brainstem function** is evaluated by assessing cranial nerve reflexes, motor and sensory pathways, and level of consciousness. - While vestibular pathways involve the brainstem, the Dix-Hallpike specifically targets the **peripheral vestibular system** in the inner ear.
Question 6: The investigation of choice for vestibular schwannoma is
- A. Gadolinium enhanced MRI (Correct Answer)
- B. PET scan
- C. SPECT
- D. Contrast enhanced CT scan
Explanation: ***Gadolinium enhanced MRI*** - **Gadolinium-enhanced MRI** is the gold standard due to its superior spatial resolution for soft tissues, allowing for clear visualization of the tumor within the **internal auditory canal** and **cerebellopontine angle**. - It effectively detects even small **vestibular schwannomas**, which are typically missed by other imaging modalities. *PET scan* - **PET scans** are primarily used for assessing metabolic activity in tumors and are more relevant for distinguishing between benign and malignant lesions, or for staging cancer, rather than purely anatomical localization of a **vestibular schwannoma**. - Its resolution is often insufficient to precisely delineate small lesions in the **internal auditory canal**. *SPECT* - **SPECT** uses gamma-ray emitting radiotracers and is more commonly employed in nuclear medicine for functional imaging of organs or to assess blood flow, particularly in cardiac or neurological conditions like epilepsy, rather than for detailed anatomical imaging of tumors such as **vestibular schwannomas**. - Its spatial resolution is generally lower than MRI, making it less suitable for detecting small lesions in complex anatomical regions. *Contrast enhanced CT scan* - While a **contrast-enhanced CT scan** can show larger tumors and bony erosion, its soft tissue contrast is inferior to MRI, which means it may miss smaller **vestibular schwannomas**. - It also exposes the patient to **ionizing radiation**, and its primary role in vestibular schwannoma detection is often limited to cases where MRI is contraindicated.
Question 7: Vestibular evoked myogenic potential (VEMP) is a tool for evaluating which of the following?
- A. Superior vestibular nerve disorders
- B. Cochlear nerve lesions
- C. Auditory nerve function
- D. Inferior vestibular nerve disorders (Correct Answer)
Explanation: ***Inferior vestibular nerve disorders*** - **VEMP** uses **loud acoustic stimuli** or **bone vibration** to activate the **saccule**, with the response pathway: saccule → inferior vestibular nerve → vestibular nucleus → vestibulospinal tract → muscle response. - **Cervical VEMP (cVEMP)** is recorded from the **sternocleidomastoid muscle**, while **ocular VEMP (oVEMP)** is recorded from **extraocular muscles**; absent or delayed responses indicate **saccular or inferior vestibular nerve dysfunction**. *Superior vestibular nerve disorders* - The **superior vestibular nerve** innervates the **utricle** and **semicircular canals**, which are assessed by **head impulse test** and **caloric testing**, not VEMP. - **VEMP** is the only clinical test specifically assessing **otolith (saccule) function** and does not evaluate semicircular canal pathways. *Cochlear nerve lesions* - **Cochlear nerve** assessment requires **pure tone audiometry**, **auditory brainstem response (ABR)**, and **otoacoustic emissions**. - **VEMP** evaluates vestibular pathways through **muscle reflexes**, not auditory nerve conduction or cochlear function. *Auditory nerve function* - **VEMP** is a vestibular test that evaluates **otolith organs** and their neural pathways, not auditory function. - While VEMP uses **acoustic stimuli** to trigger the response, it measures **vestibulospinal or vestibulo-ocular reflexes**, not hearing or auditory nerve conduction.
Question 8: In Fitzgerald-Hallpike caloric test, cold-water irrigation at 30 degrees centigrade in the left ear in a normal person will induce -
- A. Nystagmus to the left side
- B. Positional nystagmus
- C. Direction changing nystagmus
- D. Nystagmus to the right side (Correct Answer)
Explanation: ***Nystagmus to the right side*** - According to **COWS** (Cold Opposite, Warm Same) mnemonic, **cold-water irrigation** in the left ear inhibits the left horizontal semicircular canal. - This inhibition mimics a head turn to the right, causing nystagmus with the **fast phase to the opposite (right)** side. *Nystagmus to the left side* - This would occur with **warm-water irrigation** in the left ear, which excites the left horizontal semicircular canal. - Excitation would mimic a head turn to the left, causing nystagmus with the fast phase to the **same (left)** side. *Positional nystagmus* - This type of nystagmus is typically observed when the **head is moved into specific positions** and is indicative of benign paroxysmal positional vertigo (BPPV) or central lesions. - It is not the expected or primary response to a **caloric stimulus** in a normal individual. *Direction changing nystagmus* - This implies that the **direction of the nystagmus** changes depending on the gaze direction or with different stimuli, which can be a sign of a central vestibular lesion. - In a normal caloric test, the nystagmus direction following a specific stimulus (cold water in one ear) is **consistent**.
Question 9: In a patient with right vestibular neuronitis, what will be the finding on the head impulse test?
- A. Head turned to right, corrective saccade to the left (Correct Answer)
- B. Head turned to left, corrective saccade to the right
- C. Head turned to right, no corrective saccade
- D. Head turned to left, no corrective saccade
Explanation: ***Head turned to right, corrective saccade to the left*** - In **right vestibular neuronitis**, the right vestibular apparatus is impaired, affecting the **vestibulo-ocular reflex (VOR)** on that side. - During the head impulse test, when the head is rapidly turned **to the right** (toward the affected side), the impaired VOR cannot maintain eye fixation on the target. - The eyes initially move **with the head** (to the right), then a visible **corrective saccade** (catch-up saccade) brings them **back to the left** to refixate on the target. - This corrective saccade is the **hallmark positive finding** in head impulse test for right vestibular dysfunction. *Head turned to left, corrective saccade to the right* - This would indicate a **left vestibular lesion**, not right vestibular neuronitis. - When turning the head to the left with left vestibular dysfunction, a corrective saccade to the right would be observed. *Head turned to right, no corrective saccade* - This would indicate **normal VOR function** on the right side. - A normal response shows no corrective saccade because the eyes maintain fixation throughout the head turn. - This is the **opposite** of what is expected in right vestibular neuronitis. *Head turned to left, no corrective saccade* - This indicates normal VOR function on the left side. - In right vestibular neuronitis, turning the head to the left (away from the affected side) typically shows **normal VOR** with no corrective saccade needed.
Question 10: A person presented to OPD with complaints of rotatory vertigo and nausea in the morning on change in position of the head. What is your diagnosis?
- A. BPPV (Correct Answer)
- B. Meniere's disease
- C. Vestibular neuronitis
- D. Labyrinthitis
Explanation: ***BPPV (Benign Paroxysmal Positional Vertigo)*** - The symptoms of **rotatory vertigo** and **nausea** that occur specifically with **changes in head position** (e.g., getting out of bed in the morning) are classic for BPPV. - BPPV is caused by the displacement of **otoconia** (calcium carbonate crystals) into one of the semicircular canals, typically the posterior canal. *Meniere's disease* - Characterized by a **triad of symptoms**: episodic vertigo, tinnitus (ringing in the ears), and fluctuating sensorineural hearing loss. - The vertigo in Meniere's disease is spontaneous and not typically triggered solely by specific head movements. *Vestibular neuronitis* - Presents as a **sudden onset, severe, persistent vertigo** often accompanied by nausea and vomiting, but without hearing loss. - Unlike BPPV, the vertigo is continuous for days and not solely precipitated by head position changes. *Labyrinthitis* - Similar to vestibular neuronitis but also involves **hearing loss** and/or tinnitus due to inflammation of the entire labyrinth. - The vertigo is continuous and severe, not intermittent or position-dependent like in BPPV.
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