one third portion of EAC
two thirds portion of EAC
fissures of Santorini courses:
anteriorly and inferiorly into parotid and neck
foramen of Huschke courses:
anteriorly into mandibular fossa (TMJ)
the ___ has a cylindrical configuration that curves anteriorly and superiorly as it courses from lateral to medial
external auditory canal
the number of natural constrictions that course the EAC
where are the two natural constrictions of the EAC located?
the first is at the junction between the cartilaginous and bony portion; the second is 5 mm from the tympanic membrane
what are the two protective functions of cerumen?
1) acidification of ear canal to a ph of 6.9
2) antimicrobial lysozymes
which two glands produce cerumen and where are the located?
sebaceous and apocrine; located in the lateral cartilaginous portion of EAC
what is the medial boundary of the external ear canal?
the tympanic membrane
embryonic remnants contained within the cartilaginous ear canal inferiorly and laterally
fissures of Santorini
fissures of Santorini can facilitate the spread of what?
tumors beyond the ear canal into the parotid gland and upper neck
embryonic remnants lateral to the ear drum along the bony EAC
foramen of Huschke
foramen of Huschke can facilitate the spread of what?
tumor or infection in an anterior inferior direction toward the tempro-mandibular joint
which nerve innervates the superior and anterior portions of the EAC?
which nerves innervate the posterior portion of the EAC?
vagus (arnold's nerve), facial (auricular branch), glossopharyngeal (jacobson's nerve)
which nerves innervate the inferior portion of the EAC?
greater auricular nerve and lesser occipital nerve
the EAC receives sensory innervation from which seven nerves?
trigeminal (5), facial (7), glossopharyngeal (11), vagus (10), nerves from C2 and C3
arnold's nerve is a branch off the vagus nerve within the ___ ___
arnold's nerve enters its own canaliculus termed what?
the mastoid canaliculus
prior to innervating the EAC, arnold's nerve receives branches off of what two nerves? and it exits at what suture?
facial nerve (VII) and glossopharyngeal (IX); tympanomastoid suture
which artery supplies blood to the anterior portion of the EAC?
superficial temporal artery (lateral)
which artery supplies blood to the posterior portion of the EAC?
postauricular artery (lateral)
which artery supplies blood to the inferior portion of the EAC?
deep auricular artery (medial)
the two branches that supply blood to the EAC laterally
postauricular and superficial temporal artery
an additional branch that supplies blood to the EAC medially
internal maxillary artery
the venous drainage is via the ___?
the superficial temporal drains into the ___?
external jugular system
the auricular drainage is primarily to which gland?
superficial parotid gland
list the four areas of auricular nodal drainage
1) superficial and deep parotid nodes
2) occipital nodes
3) postauricular nodes
4) occipital nodes
what are the three congenital malformations of the external ear canal?
aural atresia, branchial cleft, congenital ear canal stenosis
this disorder occurs when the EAC does not form properly
what is the prevalence of aural atresia?
uncommon; one in 10,000 for males and one in 20,000 for females
during development, the ___ ___ ___ must resorb to allow for formation over the ear canal. this does not occur in ___ ___, resulting in a ___ ___ ___ closing off the ear canal completely
bony atresia plate; aural atresia; bony atresia plate
with this disorder, the ossicular chain is typically involved as a malformed ossicular mass
T or F: in aural atresia, the facial nerve course is variable and often anomalous
what is the A grading scale Jahrsdoerfer?
a 10-point scale based on the CT imaging and the external appearance of the ear, with a higher score correlating to better surgical success
with the A grading scale Jahrsdoerfer, what score is considered a good candidate for surgical repair? what is not?
7 and above is good; 6 is marginal; 5 or below is poor
in aural atresia patients, individuals with a score of 7 or better have an 85% chance of achieving a ___ dB SRT or better after surgical repair
when is surgical correction performed for aural atresia? (age)
what are the potential complications of atresia repair surgery?
1) facial nerve injury
2) re-stenosis of the ear canal
3) sensorineural hearing loss
4) ossicular fixation
5) tympanic membrane lateralization
6) taste disturbances
what is a non-surgical rehabilitative option to aural atresia? what is the downside?
bone conduction hearing aids; can cause tissue necrosis from the compression of the aids against the skull (over time)
patients who have ______ can rarely have a normal tympanic membrane with normal middle ear structures
congenital ear canal stenosis
the malformations in congenital ear canal stenosis tend me to be more or less severe than aural atresia?
congenital ear canal stenosis can be defined as:
an ear canal that is present but has a diameter of 4 mm or less
if the stenosis is severe enough to trap desquamated skin medially, this can cause ___ to form
ear canals smaller than ___ in diameter carried a high chance of cholesteatoma formation with greater than ___% of patients 12 and older developing cholesteatoma
2 mm; 90%