Vestibular Lecture/BPPV Flashcards
(33 cards)
What are the key components of the vestibular system?
The key components are semicircular canals, otolith organs, ampulla, cupula, and vestibular nerve (CN VIII).
What do the semicircular canals detect?
They detect rotational (angular) head movements.
What are the otolith organs and their function?
The otolith organs include the utricle and saccule, which detect linear acceleration and gravity.
What is contained within the otolith organs?
They contain otoconia (calcium carbonate crystals) embedded in a gelatinous layer.
What is the ampulla?
The ampulla is a bulbed structure at the end of each semicircular canal that contains hair cells that detect movement.
What is the function of the cupula?
The cupula is a gelatinous structure that bends hair cells when fluid moves in the canal, sending signals to the brain.
What is the role of the vestibular nerve?
The vestibular nerve (CN VIII) transmits signals from the vestibular system to the brain.
What is the bony labyrinth?
The bony labyrinth is part of the temporal bone that contains the semicircular canals, cochlea, and vestibule, filled with perilymphatic fluid.
What is the membranous labyrinth?
The membranous labyrinth is suspended within the bony labyrinth, filled with endolymphatic fluid, and contains the utricle and saccule.
What do the semicircular canals (SCCs) work in?
SCCs work in functional pairs: Horizontal, LARP (Left Anterior-Right Posterior), and RALP (Right Anterior-Left Posterior).
What do the otolith organs detect?
They detect linear acceleration and head tilt relative to gravity.
What is the mechanism of how the vestibular system converts mechanical movement into electrical signals?
The cupula bends with fluid motion, causing hair cell deflection, which stimulates the vestibular nerve.
What happens when hair cells deflect towards kinocilium?
K+ ions flow into the cell, leading to depolarization and increased firing (excitation).
What happens when hair cells deflect away from kinocilium?
Hyperpolarisation occurs, closing ion channels and decreasing firing (inhibition).
What is the normal vestibulo-ocular reflex (VOR)?
The VOR maintains stable vision during head motion by moving eyes in the opposite direction of head movement.
What is the VOR gain?
VOR gain is the ratio of eye velocity to head velocity and should equal 1 (approximately 0.8-1.2).
What is vestibular nystagmus?
Vestibular nystagmus is an involuntary, rapid eye movement caused by asymmetry in vestibular input.
What are common symptoms of posterior circulation strokes?
Common symptoms include vertigo, ataxia, vomiting, headache, cranial nerve weakness, and muscle weakness.
What is Benign Paroxysmal Positional Vertigo (BPPV)?
BPPV is a condition characterized by brief episodes of vertigo triggered by changes in head position.
What triggers BPPV?
Common triggers include rolling over in bed, lying flat, bending over, and looking up.
What happens in BPPV?
Otoconia dislodge from the utricle and enter the semicircular canals, causing exaggerated stimulation of hair cells.
What are the types of BPPV?
Types include canalithiasis (common), horizontal canal BPPV, and anterior canal BPPV (rare).
What is the typical duration of nystagmus in canalithiasis?
Nystagmus lasts less than 60 seconds, typically 20-30 seconds.
What is Canalithiasis?
A type of BPPV where otoconia are free floating in the canal.
Treated with the Epley manoeuvre.
