Vestibular Evoked Myogenic Potentials (VEMPs) and Vestibular Lesions Quiz

Vestibular Evoked Myogenic Potentials (VEMPs)

• Evoked by short-duration auditory tones or clicks via headphones
• Stimulates primarily the utricle and saccule
• Influences both vestibulo-spinal and vestibulo-ocular pathways
• Auditory clicks/tone bursts evoke a muscular response in tonically active muscles
• Elevates the function of otolithic organs in the inner ear, which maintains balance and spatial orientation

Vestibular Lesions

Peripheral Vestibular Lesions

• Damage to labyrinths or vestibulo-cochlear nerve (VIII)
• Causes a lag in patients' eyes returning to fixation on the examiner
• Nystagmus on eccentric gaze that changes directions is indicative of a central lesion

Central Vestibular Lesions

• Damage to vestibular nuclei or pathways projecting to brainstem, thalamus, or cerebellum

Unilateral Vestibular Lesions

• Vertigo: due to spontaneous nystagmus even at rest
• Can be caused by lesions anywhere in the vestibular pathway
• Most cases are caused by peripheral disorders involving the inner ear
• Nausea: due to sensory mismatch or conflict
• Vestibular autonomic connections (flight or fight, gut response)
• Postural instability
• Rhomberg test, Fukuda test, Dynamic posturography
• Fall or turn to side of lesion

Abnormal VOR

• Eyes are dragged off the target when the head turns (in one direction)
• Followed by eye movements back to the target

Other Conditions

Meniere's Disease

• Patient has recurrent episodes of vertigo, accompanied by fluctuating and stepwise, progressive hearing loss and tinnitus
• Episodic (minutes – hours): First: fullness in ear, hearing loss, tinnitus; Next: vertigo, nausea, imbalance, drop attacks (vestibular attacks)
• Mechanism: Increased endolymph volume and pressure
• Small ruptures of membranous labyrinth
• Causes: unknown – viral / autoimmune/ genetic
• Lifestyle factors can increase attack such as salt, caffeine, alcohol, and stress are triggers
• Treatment: Lifestyle change, surgery (vestibular nerve section, labyrinthectomy, endolymphatic saculotomy, transtympanic gentamicin)

Periplymph Fistula

• Increase in pressure suddenly, see a tar in ear
• The pressure increases firing rate to hair cells
• Traumatic Injury or severe pressure damage (SCUBA diving, ascent/descent on a plane)
• Round/oval window ruptures allowing pressure changes to affect inner ear
• Treated with rest or surgery
• Abnormal nystagmus triggered with additional pressure (Fistula Test)
• Tracks eye movements while pressure is applied to ear canal

Benign Paroxysmal Positional Vertigo (BPPV)

• Due to trauma or age
• Otoconia dislodged and free in canals (usually posterior canal)
• Identified with Dix-Hallpike Maneuver
• Treated with Physical Therapy (Epley Maneuver - series of head movement)
• Symptoms triggered by sudden position change of the head
• Occitana membranes come off and free flows in endolymph fluid

Bilateral Vestibular Loss (BVL)

• Common symptoms: Postural Instability (without vision), Blurry vision (when moving and fixating)
• Because no RVEM response, eyes bounce around in the head and can't fixate on an object
• Causes: Ototoxic medication – gentamicin (up to 50% of BVL), Meningitis in children less than one year of age, Meniere's disease (bilateral)

Central Vestibular Lesions

• Opto-kinetic reflex involves medial vestibular nucleus
• Adjusts eye position to reduce retinal slip
• Can use combinations of tests to indicate whether lesion is peripheral or central
• Use combo of OKR and VOR which relies on both central and peripheral
• If damage central vestibular nucleus, both pathways are damaged
• Abnormal VOR but normal OKR means there is an injury only in peripheral system