Middle Ear Disorders Flashcards
(20 cards)
What is a major function of the middle ear?
converting acoustic energy to mechnical by impedence matching mechanism (resistace of the flow of energy)
What are impedence matcing?
makes up for the for power loss of sound traveling from the pinnacle to EAC. This involves the TM and ossicular chain
What are the three primary ratios for impedence matching?
- Area ratio (17:1)
*TM is 17 times the area of the stapes footplate
(when the same force is applied to smaller area, there is a dramatic increase in pressure) - Ossicular level ratio (1.3: 1
*mallelus and incus are tigtly bonded at their articulation point, they move as a unit. - Buckling effect (2:1)
* annulus of the TM acts a lever allowing the TM to move back and forth causing pressure to reach the malleus
The three ratios create a force that is 46 times greater at the stapes footplate than at the TM…this translates into about ____ dB SPL of gain
33 dB SPL of gain
Without the middle ear mechanism there would be a loss of ____ dB SPL of the acoustic signal reaching of the oval window
33 dB SPL
The stapes footplate move _____ with moderate-intensity signals and _____ with high-intensity signals
rotate side-to-side (moderate intensity)
rock front to back (high intensity)
Describe the anatomy of
TM
attached to the temporal bone
has the epithelial layer, fibrous layer, and mucosal layer
pars flaccida (superior portion)
pars tensa (majority of TM)
Explain vascularization of ME
via internal cartoid artery
which can occassionally cause pulsatile tinnitus
The ME is innevated by CN 9 (glossapharyngeal) while CN ____ & travels via ME but has no sensory innervation
CN 7 facial nerve
*think about facial weakness
Cholesteatoma
benign skin growth in ME
can be caused by chronic inflammation and infection of ME
usually unilateral
Symptoms:
*chronic ME issues
*aural fullness
*otalgia
*smelly otorrhea
*numbness or muscle weakness of affected side
*hearing loss
*dizziness
dx:
*white mass behind TM, debris in EAC
*Type Ad or B
*CHL/MHL patterns with ARTs, audio (unilateral with normal speech), reduced or absent OAEs, VNG if dizzy
Disarticulation of the ossicular chain
disruption in chain, usually occurs at the incus and stapes join
possible congential, ear infections, or trauma
Symptoms:
*asymptomatic
*hearing loss (CHL/ MHL)
dx:
*Type Ad
*ARTs absent contralaterally
*OAEs absent due to Conductive
Eustachian tube dysfunction
ET fails to open or becomes chronically closed, which prevents ME from ventilating
creates NEGATIVE pressure which leads to other ME issues
Symptoms:
*otoscopy: WNL/ retraction
*Type C
*ART conductive patterns
ETF: no/ minimal change in peak pressure with Valsalva or Toynbee
*LF CHL with audio
*OAEs: absent or reduced
Glomus tumor
aka paragangliomas
slow-growing , bening vascular tumors that affect the ME space
Symptoms:
*pulsatile tinnitus
*aural fullness
*otaglia
*facial nerve weakness
*hoarse voice and dysphagia
*vertigo
Dx:
red mass behind TM; brown’s sign **
**Tymp: match heart beat ( can see with decay)
*Audio: unilateral CHL, MHL
*OAEs absent unilateral due to occupying ME space
VNG if dizzy
What are some classic signs of ME growth?
aural fullness
numbness or weakness
*dizziness/vertigo
otitis media
inflammation of the ME which creates effusion behind TM
primarly caused by ET dysfunction
Symptoms:
*otaglia
*ottorhea
*aural fullness
*possible recent respiratory infection
*possible facial nerve palsy (rare)
*pulling ears (child)
Dx:
*cloudy, bubbles, redness, inflammation; landmarks not visible
*Type B tymp
*ARTs show conductive pattern
*LF CHL
*OAEs: absent
Otosclerosis
Abnormal bone growth (metabolic alteration of temporal bone) occuring at the stapes footplate around oval window…leading to stapes fixation
Symptoms:
*Autophony
*Difficulty hearing when chewing
*possible tinnitus
*trouble hearing in background noisee
*hearing loss
*related to hormone changes; women in 30s/40s, after giving birth
Dx:
*Schwartze’s sign (TM appears reddish)
*Type As or A tymps
*ARTs with upward deflection
*Weber (CHL), Rinne (CHL louder on mastoid)
*Carhart’s notch (CHL with SNHL at 2kHz) can turn to flat MHL
OAEs consistent with audio
Perforation
hole in TM r/to trauma, infections, or surgery
type B with large ECV
ART with conductive patt4e4rn
audio: unilateral LF CHL
OAEs: absent unilateral
Temporal bone trauma
due to blunt force, penertrating compression, or barotrauma
otic capsule (cochlea and SCC remains intact)
Symptoms:
*otalgia
*bloody ottorhea
*LOC
*possible facial nerve issues
Dx:
*hematoma, debris or blood in EAC, CSF behind TM
*Tymps based on damage (Type Ad, As, B)
*unilateral CHL
*OAEs: absent unilateral
*VNG: possible BPPV
Tympanosclerosis
white calcified plaques on TM
Primarly asymptomatic
Dx:
*white areas on TMs
*Type A or As
*normal audio or CHL
*OAEs consistent with audio
What is the difference b/t blood supply for OE and ME?
OE receives blood supply from external cartoid artery
ME receives blood supply from internal cartoid artery
