A&P
The inferior vestibular nerve branch innervates these structures.
Saccule & posterior semicircular canal
The mneumonic COWS stands for what and is used to predict fast phase direction during this test
Cold Opposite, Warm Same; Caloric testing
Alexander's law describes this relationship between gaze direction and nystagmus intensity.
Nystagmus is strongest when gazing in the direction of the fast phase (and weakest/reversed in the opposite direction).
You may see this type of nystagmus with a central lesion
Vertical or direction changing nystagmus
This otolith organ is sensitive to vertical linear acceleration.
Saccule
This bedside test delivers brief, high acceleration head impulses to assess VOR gain for each semicircular canal.
A corrective saccade during a head impulse test suggests this.
A significant asymmetry ratio on calorics is typically considered abnormal above this percentage
Around 25%
Hair cells in this structure are embedded in a gelatinous cupula.
Crista ampullaris
This tests the utriculoocular pathway via the superior vestibular nerve and contralateral inferior oblique muscle.
Unilateral weakness on caloric testing suggests dysfunction in this structure/system.
This term describes the inability to maintain stable vision during head movement.
Oscillopsia.
This central structure integrates vestibular, visual, and proprioceptive input to coordinate balance and eye movements.
The cerebellum.
What structures are assessed by the cVEMP (cervical vestibular evoked myogenic potential)?
The Saccule and the inferior branch of the Vestibular nerve.
In a patient with absent oVEMP but normal cVEMP, which anatomical structures are most likely affected?
The Utricle and the superior branch of the Vestibular nerve.
This neurotransmitter is released by vestibular hair cells onto afferent neurons.
Glutamate.
In the horizontal VOR, a rightward head turn produces leftward eye movement using the left lateral rectus and right medial rectus. These cranial nerves innervate those yoked muscles.
Abducens nerve and Oculomotor nerve
This VNG subtest evaluates the ability to suppress vestibular nystagmus with visual fixation, and if fixation is not obtained, it is indicative of the this type of lesion.
Fixation suppression; Cental lesion
Direction fixed horizontal nystagmus that follows Alexander's Law suggests this type of lesion.
Peripheral lesion
Deflection of hair cells toward this structure increases firing rate.