Vestibular tract Flashcards
Vestibular schwannoma
benign tumor (from schwann cells of vestibular root) in cerebellopontine angle, where it impinges on structures in internal acoustic meatus (CN 7, 8 and labyrinthine A)
pts present with hearing loss, gait difficulties and tinnitus
Vestibular neuritis
edema from vestibular nerve causese severe vertigo, nausea and vomiting (NO hearing loss). Caused by viral infection like herpes or syphilis
Objective vertigo
feels like walls are spinning (object), while pt is not. Eye exam shows nystagmus that beats in OPPOSITE direction to rotation of head movement
Meniere’s Disease
disruption of normal endolymph volume, resulting in swelling (endolymphatic hydrops). Sx include fluctuating hearing loss, vertigo, positional nystagmus and nausea. Can have unpredictable attacks of auditory and vestibular symptoms including vomiting tinnitus and inability to make head movements or even stand passively.
Tx: diuretics and salt-restricted diet, can implant shunt into swollen endolymphatic sac
Caloric test
Cold water -> head moves away from side of water (so nystagmus beats away as well)
Warm water -> head moves towards (nystagmus beats towards same side)
What does horizontal head movement do to ampulla movement?
Head movement to the right, ampulla displaced left
Where are otoconia found?
calcium carbonate crystals in the macula (saccule/utricle) that are more dense than endolymph, so gravity needed to move them (vertical/horizontal motion)
What is the otolith membrane?
gelatinous coating over hair cell stereocilia in the macula
What are the 4 vestibular nuclei?
superior, medial, lateral, inferior
Describe the vestibulo-ocular reflex
- Head rotating left: left vestibular system activates left vestibular nuclei (right inactivates)
- Left vestibular nuclei cross contralat thru medial longitudinal fasciculus (MLF) to stimulate contralat abducens nerve -> LR
- Abducens interneurons cross back over to activate ipsilateral oculomotor neurons -> MR
