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69 Cards in this Set
- Front
- Back
5 bony parts that make the Temporal Bone
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Squamous
Mastoid Petrous Tympanic Styloid |
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Mastoid Portion of temporal bone
(name three important anatomic landmarks) |
Mastoid Antrum
Adidis ad antrum Korner's Septum |
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Adidus ad antrum is latin for
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Entrance to the cavity
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What does the adidis ad antrum do?
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Connects the epitympanum of the middle ear cavity to the mastoid antrum
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What is Korner's Septum?
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Part of the petrosquamosal suture that runs posterolaterally through the mastoid air cells.
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What is function of Korner's Septum?
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- Services as barrier to the extension of infection from the lateral mastoid air cells to the medial mastoid air cells
- Also serves an an important surgical landmark within the mastoid air cells |
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Which portion of the temporal bone is the inner ear(otic capsule)?
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Petrous portion - often referred to as the petrous pyramid because it is shaped like a pyramid with anterior, posterior, and inferior structures
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Two important structures on the anterior surface of anterior surface of the petrous pyramid?
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Tegman tympani - roof or cover of the tympanic cavity
Arcuate eminence - the bone prominence over the superior semicircular canal(its a surgical landmark as the surgeon cuts along the floor of the middle cranial fossa) |
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Posterior surface of the petrous portion of the temporal bones contain _____?
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Porus acusticus
Vestibular aqueducts Cochlea aqueducts |
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What is the porus acusticus?
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Opening or mouth of the internal auditory canal
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What is the modiolus?
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The entrance to the cochlea through which the cochlear nerve passes
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What is the crista falciformis?
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The horizontal bony septum in the lateral 3 mm of the internal auditory canal fundus
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Vestibular Aqueduct transmit endolymphatic duct or perilymphatic duct?
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Endolymphatic duct and runs parallel to the petrous ridge
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Cochlear Aqueduct transmits endolympatic duct or perilympatic duct?
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Perilymphatic duct and is located vertically below the IAC running parallel to it.
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What is the petrous apx separated from the clivus by?
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Petrooccipital fissure and foramen lacerum.
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What forms the medial border of the EAC?
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Tympanic Membrane
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Where does the tympanic membrane attach superiorly and inferiorly?
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Superiorly - at the scutum
Inferiorly - at the tympanic annulus (see coronal figure 12-2 p 430 in Handbook of head and neck imaging) |
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The tympanic annulus serves as an important coronal CT landmark to determine if the lesion is _______?
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In the external or middle ear.
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Where does the external auditory canal and adjacent scalp drain and why is it important?
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Parotid lymp nodes, because when evaluating a parotid mass, it may represent nodal mets from an EAC squamous cell carcinoma or melanoma
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Three distinct regions of the middle ear are?
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Epitympanum
Mesotympanum(or tympanic cavity proper) Hypotympanum |
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The posterior wall of the mesotympanum has three important structures, what are they (Figure 17-1 p 429 Head and Neck)
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1. Pyramidal eminence
2. Sinus Tympani 3. Facial nerve Recess |
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What does the Pyramidal eminence contain?
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The belly and tendon of the Stapedius muscle.
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What is significant about the sinus tympani?
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It's a clinical blind spot during a standard mastoid surgical approach to the temporal bone.
Cholesteatoma can hide hear as a result. |
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What does the facial nerve recess contain?
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The descending facial nerve, either dehiscent or with a bony cover.
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The Superior wall of the middle ear cavity is also known as?
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Tegman tympani
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Clinical significance of tegman tympani?
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Loss of this bony separation can lead to leptomeningeal or brain parenchymal involvement with infection or tumor
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Inferior wall of the middle ear cavity is also known as ____?
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"jugular wall"
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Inferior wall(jugular wall), what is it and describe the normal variant a surgeon must know?
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- The bony plate that separates the middle ear cavity from the jugular bulb and be normally dehiscent(ie dehicent jugular bulb)
- Should be noted so that surgeon can ovoid a protuberent vein |
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The lateral wall of the middle ear cavity is also known as?
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"membranous wall"
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What forms the lateral wall of the middle ear cavity?
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The tympanic membrane, slopes inferomedially from the scutum attachment to the tympanic annulus
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Definittion of epitympanum?
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The tympanic cavity above the line drawn between the inferior tip of the scutum and the tympanic portion of the facial nerve
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Contents of the epitympanum?
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malleus head
body and short process of the incus Prussak's space |
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What is the most common site for the pars flaccida cholesteatoma?
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Prussak's space - in area beween the incus and lateral side wall of the epitympanum
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What are the remainder of the ossicles in the mesotympanum?
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manubrium of malleus
long process of the incus entire stapes |
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What two muscle s of middle ear are in the mesotympanum?
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Tensor tympani
Stapedius |
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Tensor tympani is innervated by?
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Cranial nerve V3
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Where is the tensor tympani located?
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in an anterior bony canal above the osseus eustachian tube
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Stapedius muscle is innervated by?
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Facial nerve
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Where is the stapedius muscle?
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It is contained within the pyramidal eminence, with its tendon reaching from the tip of the pyramidal eminence to the posterior surface of the head of the stapes
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What is the central bony axis that the entire cochlea encircles?
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Modiolus
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Subunits of the vestibule
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Utricle and saccule
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Utricle vs. saccule
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Utricle - more cephalad portion of the vestibule
Saccule - inferior part of the vestibule |
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The vestibule is separated laterally from the middle ear by ____?
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The oval window niche.
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What is the arcuate eminence?
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The upper bony margin of the superior semicircular canal that forms a convexity on the petrous pyramid roof
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The lateral semicircular canal is also known as ?
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Horizontal
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What is significant about the lateral semicircular canal and a typical epitympanic cholesteatoma?
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the canal just into the epitympanum and as a result a cholesteatoma has a propensity to fistulize the membranous labyrinth by eroding the lateral cortex of the lateral semicircular canal
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Where is the midtympanic portion of the facial nerve related to the lateral semicircular canal?
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Pass along the undersurface of the lateral semicircular canal.
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What does the cochlear aqueduct(perilymphatic) run parallel to?
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The IAC, it can be mistaken for that.
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Three segments of the facial nerve within the tympanic bone?
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Labyrinthine segment
Tympanic segment Mastoid segment |
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Where does the labyrinthine segment of the facial nerve terminate?
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in the anterior genu (ie geniculate ganglion)
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Describe the tympanic segment of the facial nerve?
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The facial nerve from the anterior genu(geniculate ganglion) to the posterior genu
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Describe the mastoid segment of the facial nerve?
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The facial nerve from the posteior genu to the stylomastoid foramen
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Function of the facial nerve in the parotid segment?
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The extracranial segment of the facial nerve that divides the parotid gland into superficial and deep lobes
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Four functions of the facial nerve that may be used to localize a lesion along its course?
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1. Lacrimation
2. Stapedius reflex 3. Taste, anterior 2/3 of tongue 4. Facial expression |
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What branch of facial nerve is responsible for lacrimation?
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The greater superficial petrosal nerve
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What does the stapedius reflex do?
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Sound dampening
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What branch of facial nerve provides taste?
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via chorda tympani nerve to lingual nerve to oral tongue
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If cranial nerve VI is also involved with VII, where is lesion?
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brainstem - VII circles the VI nerve nucles on its way out of the brainstem
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The external and middle ear are derived from embryologically?
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From the first and second branchial cleft apparatus(usually develop separate from inner ear)
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What is associated in EAC atresia that is critical to mention before surgery?
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Ectopic nerve VII, it is usually out of place and includes the posterior tympanic and mastoid semgents, need to know because surgical creation of a new EAC will result in facial nerve paralysis
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Conductive hearing loss in a child with no history of inflammatory ear disease suggests a ___________?
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Congenital cholesteatoma
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Where do congenital cholesteatomas arise from?
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aberrant epithelial rests
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An aberrant ICA may be mistaken by the surgery as a?
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paraganglioma, surgeon may want to biopsy this and it is disastrous!
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Describe the pathogenesis of an acquired cholesteatoma?
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- Occurs within the middle ear cavity and results from ingrowth of squamous epithelium through the eardrum
- the accumulation of squamous and keratin debris within the middle ear prduces a mass efect that erodes the bony walls and ossicles. |
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Two typical locations for cholesteatomas?
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1. Pars flaccida (prussak's space)
2. Pars tensa |
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All complications of cholesteatomas are related to ___________?
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Bony erosion
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Otoscopic examination reveals a "blue (vascular) tympanic membrane" in the absence of a pulsatile tinnitus when the lesion is in the middle ear>
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Cholesterol granuloma
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Mondini malformation?
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When the primary lesion on CT shows the lss of the normal two and one-half turns of the cochlea
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What part of the ossicles is most weakest and most susceptible to injury?
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Incudostapedial joint
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