Vastibular and Auditory pathway Flashcards
Where is the vestibule?
- central portion of inner ear
the system is found within the TEMPORAL bone
What is the vestibular system responsible for?
- balance, posture and equilibrium
- coordinates head and eye movement
What makes up the Vestibular system?
- 3 Semicircular canals —-that lie on diff. planes
(X,Y,Z)
—-filled with endolymph
What do the ampulla of the semicircular canals contain?
- – hair cells that BEND with rotation
- —-these hair cells RELEASE NT > AP prodn
- —-signals produced is based on MOTION
Which organs of the vestibule contain otolith?
-UTRICLE and SACCULE
otolith= ear stones= Calcium carbonate crystals
What is the otolith responsible for?
- —sits on TOP of hair cells
- drags hair cells in response to LINEAR MOTION (up, down, forward and backward)
- —-generating VESTIBULAR neural activity
Where does the Vestibular nerve send signals to ?
- the BRAINSTEM (vestibular nuclei)
- the CEREBELLUM
Where is the vestibular nuclei found?
- beneath the FLOOR of the 4th ventricle (in PONS/ MEDULLA)
3 typical symptoms a.w dysfxn of the Vestibular system?
- VERTIGO: spinning room (when head is still)
- nystagmus
- N.V
Describe how nystagmus presents as?
- rhythmic beating of the eyes
- –slow drift of eye to one direction
- —correction to the other directions
What form of nystagmus does a pt have, if their RIght eye quickly corrects to the left side?
- Left-ward nystagmus
- –named for direction of the fast correction
Name the diff. types of nystagmus, which indicate a PERIPHERAL vestibular dysfxn.
- left, right and torsional
- –issues with the vestibular apparatus in the INNER ear
Name the types of nystagmus a.w CENTRAL vestibular dysfxn.
UPBEAT and DOWNBEAT
—in brainstem lesions (strokes/ tumors)
Which form of nystagmus is bad, central or peripheral?
CENTRAL
- –indicative of potential:
- brainstem/cerebellar lesion
- TIA/ vertebrobasilar stroke
- tumor (posterior fossa)
- cerebellar infarction and hemorrhage
Name benign causes of nystagmus.
- peripheral lesions/ conditions > Inner Ear problem > BPV (benign positional vertigo) > vestibular neuritis > Meniere's disease
What are the signs of Central vertigo?
- pure VERTICAL nystagmus
- —nystagmus changes direction with gaze (look r; upbeat/ L= downbeat)
- DIPLOPIA
- DYSMETRIA (nose-finger test)
- —skew deviation (vertical misalignment of the eyes)
- POSITIONAL testing= IMMEDIATE nysatgmus
—-other CNS symptoms
What is seen with peripheral nystagmus?
- mixed horizontal and torsional nystagmus
- —DELAYED nystagmus (on positional testing)
- —nystagmus FATIGUES over time
- —-stable ROMBERG
How to perform postional testing?
- DIX-HALLPIKE MANEUVER
- –done to reproduce vertigo and cause NYSTAGMUS
- –seated pt, turn head to side; rapidly lie pt on table; heading hanging over end
What helps DX BPV?
- Dix Hallpike Maneuver
What is seen in a typical DHM?
- BPV
- —no symptoms for 5-10s
- —-room spins (vertigo) and TORSIONAL nystagmus occurs
- —resolved with SITTING up
- FEWER symptoms with repeated maneuvers
Why does BPV develop?
- Nystagmus that develops due to HEAD turning and positioning
- due to calcium debris in the semicircular canals; weighs down on hair cells (CANALITHIASIS) —-
What helps BPV to go away?
- Epley Maneuver (repositions otoconia)
What causes vestibular neuronitis?
- VIRAL or POST-inflammatory neuropathy of the VESTIBULAR portion of CN VIII
- –benign/ self limited
What occurs in Meniere’s disease?
- endolymph fluid accumulation
(HYDROPS)
—swelling of the labyrinthine system
What are the signs and symptoms of Meniere’s disease?
- TINNITUS
- Sensorineural hearing loss (WEBER is LOUDER in NORMAL ear) —Rinne: AC> BC
- Vertigo
How to treat meniere’s disease?
- avoid high salt (REDUCES swelling)
- avoid caffeine, nicotine (vasoconstrictors, reduce flow from inner ear)
- diuretics
What are the 3 bones of the inner ear? What do these bone do?
Malleus, INcus and Stapes
- amplify the tympanic membrane motion
What does the stapes do?
- PUSHES the fluid-filled cochlea
- —-> tiny hair cells get stimulated; depending on freq. of sound ===> electrical signal is generated
Once sound is picked up by the cochlear nerve, where to next?
- cerebellopontine angle
- —LATERAL pons
—–at this angle most brainstem lesions with hearing loss is here
What is conductive hearing loss? Why may it come about?
- Sound waves CAN’T convert to NERVE signals
- —d.t obstruction (WAX), INFECTION (otitis media) or otosclerosis (bony OVERGROWTH of stapes)
What causes sensorineural hearing loss?
- issue with the nerve
- d.t Cochlea disease/ cochlear nerve failure (acoustic neuroma)
or CN damage
What is presbycusis?
- age-related hearing loss
- –degen. of ORGAN of CORTI > sensorineural hearing loss (slow developm)
What is a NORMAL Weber’s Test?
- should be heard EQUALLY in both ears; when tuning fork is placed on the forehead
Does the Weber test indicate what type of hearing loss the pt has?
NO
—just makes you aware of A POTENTIAL hearing defect
In Weber test, if the pt has conducitve hearing loss in the right ear. What is the expected results in this test?
- LOUDER in the BAD ear in CONDUCTIVE hearing loss
- —no background noise
- –louder in R ear
IF the pt has sensorineural hearing loss in the L ear, what is expected in the Weber test?
- LOUDER in the GOOD ear
- —no nerve to sense condxn
- –LOUDER in R ear
What is a normal Rinne Test?
- AC >BC
should be easy for sound waves to move through AIR and not bone
What is expected in conductive hearing loss in Rinne Test ?
—pt CANNOT hear NEXT to the ear
AC
What is expected in Sensorineural hearing loss in Rinne test?
- AC >BC
- —but BOTH are reduced
- –in bad ear just 5s of AC and BC (as opposed to 10s in good ear)
What are the results for RINNE and WEBER in CONDUCTIVE HEARING LOSS?
WEBER: LOUDER in BAD ear
RINNE: AC
What results for sensorineural hearing loss?
WEBER: louder in GOOD wear
RINNE: reduced AC>BC (like normal)
How to truly diagnose hearing loss?
with AUDIOMETRY
When may one experience SUDDEN hearing loss?
- after LOUD noise
- —d/t TYMPANIC membrane rupture
What occurs with LONG -term exposure to noise?
- damage tociliated cells of Organ of Corti
- —-high freq. is LOST
Where do fibres carrying info with LOW freq. sound end?
- in the ANTEROLATERAL part of the auditory cortex
——posteromedial part for HIGH freq. sound)
What happens with damage to Broca’s area?
- diff. to PRODUCE language
- -aka MOTOR aphasia
- no problem comprehending
What occurs with damage to Wernicke’s Area?
- can’t comprehend language
- —-puts words out of order and make up meaning less word
What does the vestibular nuclei relay info to ?
- thalamus
- Cerebellum
- Nuclei of CNs III, IV, VI
- Cerebellum
- Spinal cord
Where does the LOWER visual field projected to ?
- to the gyrus SUPERIOR to the calcarine sulcus
—upper is projected to gyrus inferior to the calcarine sulcus
Where does the macula project to?
- to the POSTERIOR pole of VISUAL cortex
- —occupies GREATER proportion of the cortex
How does the upper visual field end up projecting to the gyrus INFERIOR to the calcarine sulcus?
—-upper visual field fibres from the geniculocalcarine tract will first LOOP anteriorly AROUND the TEMPORAL part of lateral ventricle in Meyer’s loop
