Vestibular System Flashcards
What vestibular fluid has similar composition to CSF?
Perilymph
What movements are monitored by the semicircular canals?
Rotational head movements/Angular acceleration
What movements are monitored by the utricle and saccule?
Translational head movements/linear acceleration
What are the primary arteries supplying the vestibular system?
Labyrinthine A. (primary source) from AICA
Stylomastoid A.
Where are the sensory receptors for the semicircular canals located?
Base of the ampulla
What is the orientation of the receptors within the utricle and saccule?
Utricle - Longitudinal orientation
Saccule - vertical orientation
What structure connects the saccule to the cochlea?
Ductus reuniens
What disease is characterized by abnormal distention of membranous labyrinth?
Meniere’s disease
What type of cells have a single, long kinocilium projecting from the apical surface? What is its function?
Hair cells with stereocilia
Vestibular sensory receptor
What is the difference between a Type I and Type II hair cell?
Type 1: chalice shaped, surrounded by nerve calyx
Type II: Cyllindrical, innervated by nerve boutons
In the ampulla, which hair cells are located more centrally and more peripherally in the crista?
Type I - centrally
Type II - peripherally
What structure within the ampulla surrounds the hair cells and displaces them in the same direction as head movements?
Cupula (Displaced by endolymph)
What structure displaces the hair cells in the macula?
Otolith membrane
What movements displace the otoconia?
Changes in head position relative to gravity/linear acceleration
Which vestibular nuclei are located in the superolateral pons?
Superior vestibular nucleus
Medial vestibular nucleus
Lateral Vestibular nucleus
Which vestibular nuclei are found in the part of the medulla that makes up the floor of the 4th ventricle?
Medial vestibular nucleus
Lateral vestibular nucleus
Which vestibular nuclei are found in the upper and lower medulla?
Medial vestibular nucleus
Inferior vestibular nucleus
What side do the vestibular afferents project to?
Contralateral
What structure do the primary vestibulocerebellar fibers travel through in the cerebellum and where do they terminate?
Inferior cerebellar peduncle
Terminate in Dentate Nucleus as mossy fibers
Where do the secondary vestibulocerebellar projectsions come from? Where do they go?
Vestibular nuclei => fastigial and dentate nuclei
What nuclei do the vestibulovestibular fibers arise from? What side do they connect with?
Superior and medial nuclei
The analogous contralateral nucleus
What nuclei do the spinovestibular fibers provide input to?
Medial and lateral vestibular nuclei
What is the reflex that achieves compensatory eye stabilization, allowing you to focus keep a fixed gaze on an object while the head is moving?
Vestibuloocular reflex
What reflex is being suppressed so that you can focus your eyes on a moving target?
Vestibuloocular
What vestibular structures are associated with vertical eye movements?
Vertical semicircular canals
Saccule
What vestibular structures are associated with horizontal eye movements?
Horizontal canals and utricle
What vestibular structures are associated with torsional eye movements?
Vertical semicircular canals
Utricle
If you are focusing on an object and turn your head to the left? Which CN nuclei are activated? What is inhibited?
Activated: Ipsilateral CN III (oculomotor), contralateral abducens
Inhibited: Ipsilateral abducens N.
What is the linear vestibuloocular reflex?
Linear head movements result in linear eye movements in a direction equal to and opposite of the head movement
Stabilizes gaze
Describe the two phases of nystagmus.
Slow phase - vestibuloocular reflex directs eyes slowly in direction opposite to head motion
Fast phase - Eyes rapidly spring back to central position to the same direction as the head
(Named for direction of fast phase)
How is the caloric test performed? What is a normal result?
Warm water - nystagmus beats toward ear which warm water was poured
Cold water - nystagmus beats away from cold water
Should be equal bilaterally
What is an abnormal result of a caloric test?
Reduced/absent nystagmus ipsilaterally
An unresponsive patient arrives in the ED. In order to evaluate the condition of the brainstem, you perform a Doll’s Eyes maneuver. What result would indicate that the patient’s brainstem was intact? What part of the brainstem?
Pt’s eyes move in opposite direction of the head turn
Reticular formation intact
What laminae do the fibers of the vestibulospinal tracts terminate in?
Lamina VII to IX
What vestibular tract terminates on the alpha and gamma motor neurons?
Laateral vestibulospinal tract
Which vestibular tract monitors neck flexor and extensor motor neurons?
Medial vestibulospinal tract
Where do the fibers of vestibular nuclei project and terminate? On what side?
Contralateral thalamic nuclei
What are the areas of the vestibular cortex associated with primary somatosensory cortex?
Area 2v - sensations of whole body motion
Area 3a - motor control of head and body
What part of the vestibular cortex is the parietal cortex associated with?
Area 7
What is the function of area 7 of the vestibular cortex?
Houses neurons involved in spatial coding, visual (optic flow), and vestibular motions signals
Integrates cues of body motion in space (spatial awareness)
What is the function of the insular area of lateral sulcus and Parietoinsular vestibular cortex (PIVC)?
Monitor body motion, somatosensory, proprioceptive, and visual motion stimuli
PIVC lesions would result in what symptoms?
Episodes of vertigo, unsteadiness, loss of perception for “visual vertical”
What is the function of the vestibular cortex portion of prefrontal cortex and superior frontal gyrus?
Receive vestibular signals
Related to frontal eye field
Controls saccades and smooth pursuit eye movements
If a patient feels like he is spinning, but the environment around him is not, what is the most likely disorder?
Subjective vertigo
If a patient feels like he is not spinning but that the room is spinning around him, what is his disorder?
Objective vertigo
What type of vertigo would you see nystagmus? In what direction?
Objective vertigo
Nystagmus beating in opposite direction to rotation
What disorder results from cupulolithiasis? What happened?
Benign Paroxysmal Positional Vertigo
Probably otoconia separated from the otolith membrane and became lodged in the cupula => abnormal cubula deflections when head changes position
What does a Vestibular Schwannoma typically impinge upon?
CN VII, CN VIII, Labyrinthine A.
Where is a Vestibular Schwannoma typically located?
Cerebellopontine angle/Internal acoustic meatus
What can a Vestibular Schwannoma present with?
Hearing loss
Gait difficulties
Tinnitus
Irritation of the vestibular ganglion from a virus can cause what disorder? What symptoms will a patient present with?
Vestibular neuritis
Severe vertigo, nausea/vomiting (NO hearing loss)
