Auditory / Vestibular System Flashcards
What is conductive deafness?
Deafness from obstruction or altered transformation of sound to the tympanic membrane or through the middle ear
What causes conductive deafness?
Occlusion of meatus, otitis media, otitis externa, otosclerosis, fracture of temporal bone (damage to ossicles or bleeding into middle ear)
What is sensorineural (nerve) deafness?
Deafness ( / tinnitus) from damage to nervous tissue
What are causes of sensorineural deafness?
Lesion of the cochlea, lesion of cochlear portion of CN VIII, prolonged loud noise exposure, treatment with certain antibiotics, infections, tumors
What is labrynthitis (or otitis interna)?
Deafness from infection or inflammation (sensorineural)
Central lesions rarely cause ________
complete deafness in one ear
What is otosclerosis?
Conductive hearing loss that occurs in 50% of cases where tissue overgrowth fixates the stapes in the oval window
Do hair cells regenerate?
HELL. NO.
How is the Rinne Test done?
1) Place vibrating tuning fork on mastoid process (tests BONE CONDUCTION) and hold until sound is not perceived any longer
2) Tuning fork is placed just outside the pinna for AIR CONDUCTION and hold until sound is no longer perceived
How do you interpret results of the Rinne Test?
- If sound heard via bone and NOT air: NEGATIVE Rinne Test (conductive deafness)
- If sound heard via air and NOT bone: POSITIVE Rinne Test (sensorineural deafness)
How is Weber’s Test done?
A vibrating tuning fork is placed in the midline of the skull (conduction should be done by both air and bone)
How is Weber’s Test interpreted?
- Normal: sound perceived equally in both ears
- Conductive loss: GREATER net vibration on AFFECTED side (louder in affected ear)
- Sensorineural loss: sound LOUDER in NORMAL ear
What is the stria vascularis?
Vascular supply within the spiral ligament (site of endolymph production)
What happens with damage to the stria vascularis?
Loss of endolymphatic potential –> failed mechanoelectrical transduction
How do cochlear implants work?
Electrodes tuned to broad frequency bands connected to an electrical receiver; input of electrodes must be at the correct tonotopic point along the spiral organ (for sensorineural hearing loss)
What is monaural deafness?
Deafness on one side (unilateral lesion of cochlear nerve or nucleus)
What does a lesion at or above the superior olive cause?
Not deafness! (due to binaural pathway, the trapezoid body)
Inattention to stimuli on CONTRALATERAL side or inability to follow convos in a crowded room (cocktail effect)
When higher centers impacted, the result is typically info disruption from BOTH ears.
What can occlusion of AICA cause? (labyrinthine a.)
- Monaural hearing loss
- Ipsilateral facial paralysis
- Inability to look TOWARD side of lesion (pontine gaze center)
- Also: vertigo, oscillopsia, nystagmus, ataxia
How is a lesion experimentally located in the auditory system?
Auditory Evoked Responses. Activity within structures correspond to specific waves on auditory brainstem response recording - shifts in latency indicate lesion/swelling
What is central deafness?
Results from damage to cochlear nuclei or central pathways relaying auditory information to auditory cortex
What do central lesions cause?
Deafness (infrequently though). More often altered perceptions of sound (brainstem/diencephalon/cortex).
What is pontine auditory hallucinosis?
Orchestra sound out of tune, buzzing insects, strands of music heard. Accompanied by other pontine lesions (CN deficits or long tract signs).
What is Wernicke Aphasia?
Damage to Area 22 on superior temporal gyrus (occlusion of branches of MCA) –> impaired comprehension of speech and difficulty in producing coherent speech
What is Broca Aphasia?
Damage to Area 44, 45 of pars opercularis and triangularis of inferior frontal gyrus (occlusion of branches of MCA) –> nonfluent, difficult speech (comprehension intact)
Broca’s area is connected to the primary visual cortex via _______
the arcuate fasciculus
What is the purpose of the middle ear reflex?
Activate the stapedius (VII) and tensor tympani (V) to affect conduction in middle ear by impeding ossicles and tympanic membrane, respectively. Protection against loud sounds with long duration and dampening background sounds (speaker’s voice).
How does the middle ear reflex work?
- Bipolar afferents first synapse in anterior cochlear nucleus
- Second neurons in chain synapse in superior olives (bilateral)
- Interneurons synapse in facial motor nucleus (stapedius) and trigeminal nucleus (tensor tympani)
- Efferents to mm.
A BILATERAL reflex
What is the acoustic startle reflex?
It is sensory-motor integration to turn head TOWARDS sound.
What does the acoustic startle reflex work? (generally)
Two ways.
1) Reticulospinal neurons sample the lateral lemniscus and lead to a very rapid response
2) Superior colliculus integrates info from the inferior colliculus and auditory cortex and projects via tectobulbospinal fibers.
Acute vestibular disorders can disrupt vestibular autonomic response, leading to…
Orthostatic hypertension, postural tachycardia, frequent falls, motion sickness, and emesis (vomiting)
This is from damage to the medial and inferior vestibular nuclei connecting to the solitary tract and ventrolateral medullary reticular area.
What is BPPV? (Benign Paroxysmal Positional Vertigo - and no, that’s not the answer)
Tilting of the head in a certain way lead to vertigo, commonly a result of cupulolithiasis or canalithiasis.
Speaking of which…what is cupulolithiasis?
Otolith breaks off of utricle and lodges in cupula. This is longer-lasting and resistant to maneuvers (fixing is 50% success rate).
And what is canalithiasis?
Otolith stuck in the semicircular canal. Latency of several seconds, duration of 10-20 seconds, and 80% are in the posterior canal.
What are some other causes of BPPV?
Cerebellar infarct, cerebellar disorders, intracranial tumors, vascular compression of CN VIII, migraine, MS, Chiari malformation, drug effects
What is the Dix-Hallpike Test?
Manipulation of head attempting to generate nystagmus via rolling the otoliths into the semicircular canal (if some are loose).
What is the Epley Maneuver?
Rotation of the head in a specific manner to encourage the removal of the otoliths from the semicircular canals (come on, little guys!)
Who is the greatest basketball player currently playing the game?
Steph Curry
What is nystagmus?
Slow phase movement of eyes opposite to rotation, then RAPID in direction of rotation. This is normal when the environment is changing more rapidly than the eyes can adapt.
An acute temporal bone fracture than damages the semicircular canals can cause ______
nystagmus that persists for several hours or days
A central lesion ______ vertical nystagmus, _____ change in direction, and nystagmus ______ vertigo.
can cause vertical nystagmus, can change in direction, and nystagmus can occur in absence of vertigo
A peripheral lesion ______ vertical nystagmus, _____ change in direction, and nystagmus ______ vertigo.
cannot cause vertical nystagmus, cannot change in direction, and nystagmus only occurs with vertigo
What is vestibular labyrinthitis?
Inflammation of the inner ear affecting the vestibular system leading to balance issues, hearing loss, tinnitus, and attacks of vertigo
What is vestibular neuritis?
Edema of the vestibular nerve (of ganglion) as a result of viral infection (herpes simplex), leading to severe vertigo, nausea, and vomiting
How could one treat vestibular neuritis?
Antiemetics, vestibular suppressants, corticosteroids, antivirals
….what is an acoustic neuroma? (Yes, I know - this is test #3 featuring the acoustic neuroma)
Vestibular schwannoma, tumor of CN VIII –> swelling and impingement of CN VII (and others, as well) –> vertigo, nystagmus, Bell’s palsy, decreased taste, corneal reflex efferent (VII) lost, etc.
In an acoustic neuroma, the impulses traveling through CN VIII on the affected side are decreased, so _______
Contralateral vestibular nuclei receive high impulse frequency –> head turn AWAY from side of lesion
What is ototoxicity?
Commonly unilateral damage to the vestibular apparatus.
- Gentamicin: 8.6% vestibulotoxicity and minor hearing toxicity, 2 wk toxic level
- Vancomycin: synergistic with gentamicin (maybe moderate hearing loss)
What is the Arnold-Chiari malformation?
Part of cerebellum herniates through foramen magnum –> pressure on brainstem (medulla) –> vertigo, nystagmus, other deficits
What is migraine-associated dizziness?
Most common cause of vertigo. 60-80% of those with recurrent vertigo w/o hearing loss have migraines
What is vestibular function testing, and name a few ways to do it.
Induce sensation of spinning the patient to stimulate the sense of environment change (induce nystagmus or neck turning, depending on test). Done via video (optokinetic), rotary chair (actually spinning them), or VEMP (most common).
What is VEMP?
Vestibular Evoked Myogenic Potential. Administration of sound (headphone) to stimulate the saccule to stimulate the vestibular nuclei and generate impulse within tectospinal tract (medial vestibulospinal reflex) –> neck turning
What is Vertigo?
A 1958 classic Hitchcock thriller starring the man himself, Jimmy Stewart.
Alternatively: tinnitus, hearing loss, aural fullness, nausea/vomiting, phonophobia/photophobia, headache, syncope, weakness, numbness
What are some triggers for vertigo?
Head position, movement, visual stimuli, pressure changes, noise, foods (?), and weather
What is the vestibuloocular reflex?
Reflexive conjugated eye movements in response to head rotation, linear movement, or a combination - facilitates continued focus on object in the visual field. It is compensatory. Eye movement OPPOSITE to head movement.
What is the pathway for the vestibuloocular reflex (horizontal)?
- CN VIII input to lateral and medial vestibular nuclei
- Lateral vestibular nucleus sends signal to oculomotor nucleus for ipsilateral medial rectus
- Medial vestibular nucleus sends signal to abducens nucleus for contralateral lateral rectus
- Contralateral abducens nucleus send excitatory signal to opposite oculomotor as well
What is caloric testing of vestibular function?
Irrigation of ear with warm (40 C) or cold (30 C) water to generate convection currents within semicircular canals; resemble movement of endolymph caused by turning the head (elicit change in vestibular nerve firing)
What happens with cold water in caloric testing?
Cold water irrigation –> endolymph falls –> decreased firing –> SLOW eye movement TOWARD that side and FAST eye movement to OPPOSITE side
What happens with warm water in caloric testing?
Warm water irrigation –> endolymph rising –> increased firing –> SLOW eye movement OPPOSITE that side and FAST eye movement to TOWARD that side
How can we remember the results of caloric testing?
COWS!
Cold Opposite, Warm Same (in reference to fast eye movements)
What is semicircular canal dehiscence?
Exposure of the normally closed bony labyrinth to the extradural space
Leads to vertigo, oscillopsia as a result of loud sound (Tullio phenomenon) or maneuvers that change intracranial of middle ear pressure.
Nystagmus aligns _____ of dehiscent superior canal
with the plane
What is oscillopsia?
Objects oscillating in visual field
What is the vestibulocolic reflex?
Series of responses that stabilize the head in space.
Person falls forward –> medial vestibulospinal tract (MVST) receives input from saccule, utricle, vertical semicircular canal –> EXCITATORY signals to dorsal neck flexors and INHIBITORY signals to anterior neck extensors (protects head).
A VPL lesion will cause:
Misperceptions of visual vertical and postural instability
A parietal cortical area lesion will cause:
Confusion in spatial awareness
A parieto-insular vestibular cortex lesion will cause:
Vertigo, unsteadiness, loss of perception for visual vertical
What is dizziness?
Spatial disorientation may or may not involve feelings of movement; nausea, postural instability.
Different from vertigo in that vertigo perceives movement when none is occurring.
What is subjective vertigo?
Patient experiences sensation of spinning
What is objective vertigo?
Patient experience sensation of objects spinning
Damage to vestibular system, hippocampus, and dorsal thalamus causes:
Difficulty in orientation in familiar environments, hard to navigate, hard to find way home
What is an auricular hematoma?
Bleeding within auricle resulting from trauma, localized between perichondrium and auricular cartilage –> fibrosis and deformed ear (cauliflower ear)
What does a normal otoscopic examination look like?
Membrane translucent/pearly gray
- Pull ear posterosuperiorly for adult
- Pull ear inferoposteriorly for infants
What is the light reflex?
Bright cone of light reflected at inferior end of handle, radiates anteroinferiorly in healthy ear
What is otitis media?
Earache, bulging red tympanic membrane (pus in middle ear), ear popping. Can block pharyngotympanic tube, could damage ossicles.
What is a myringotomy?
Incision to release pus form middle ear
What is tympanostomy or pressure equalization tubes?
Enable drainage of effusion and ventilation of pressure in middle ear
What is mastoiditis?
Infection of mastoid antrum and air cells from middle ear that causes inflammation of mastoid process
What is osteomyelitis of tegmen tympani?
Infection. Spreads superiorly into middle cranial fossa via petrosquamos fissure
Paralysis of the stapedius causes:
hyperacusis, hyperacusia
What is Meniere Disease?
Increase in endolymphatic pressure (hydrops), characterized by recurrent attacks of tinnitus, positional nystagmus, hearing loss, and vertigo; sense of pressure in ear, distortion of sounds, sensitivity to noises.
May be from blockage of cochlear aqueduct, but largely unknown. If really bad, can’t make head movements or stand passively.
What are treatments for Meniere Disease?
- Diuretic, low-salt diet
- If that doesn’t work, shunt or gentamicin
