Chapter 46 - Pediatric ENT Anatomy, Embryology, Radiology Flashcards
Foramen of Huschke
Also called foramen tympanicum
Anatomic variation
Anteroinferior aspect of EAC, posteromedial to TMJ
Gradually closes by age 5, occasionally persists
May predispose to spread of infection to infratemporal fossa
Adults vs Kids EAC shape
Adult: Sigmoid, as cartilaginous posterior/superior, and bony angles anterior/inferior. Pull helix posterosuperiorly
Infant: EAC nearly straight, nearly adult size/shape by age 9
Dimeric TM
When perf heals without fibrous (rigid) layer
more easily retracted, affects sound conduction
How much energy is lost transmitting sound from air to fluid?
99.9%
How does our inner overcome the impedance mismatch?
TM that is 21x larger than stapes footplate
ossicles create lever force of 1.3x
Allow near full transmission of all sound energy to inner ear
By how much do tensor tympani and stapedius dampen sound?
15 dB
Function of stapedial artery
Normally only present in fetal development to connect ICA, ECA
Goes through stapes, creates obturator foramen, gives stapes stirrup shape
If persistent, you have pulsatile tinnitus, CHL, absent ipsilateral foramen spinosum
Two most common congenital anomalies of ossicles
congenitally fixed stapes
incudostapedial discontinuity
Isolated stapes anomalies usually unilateral
Other ossicle abnormalities usually bilateral
4 nerves travelling in middle ear
Jacobsen- br of IX, across promontory, innervates middle ear mucosa and eustachian tube, PNS to parotid
Arnold- br of vagus, sensory to EAC, causes cough with exam
Chorda- medial to malleus, exit via petrotympanic fissure
Facial- may be dehiscent sup to oval window, or positioned in middle ear if congenitally malformed
Does facial nerve run superior or inferior to cochlear nerve?
Superior
7up/Cokedown
Tympanic segment of VII
geniculate ganglion to second genu
in medial wall of tympanic cavivty over round window, below bulge of L SC
Cochleariform process
ridge of bone
houses tendon of tensor tympani
landmark to denote tympanic portion of VII
Borders of sinus tympani
S: ponticulus
I: subiculum
may be a difficult area to extract cholesteatoma
What is the promontory?
bulge on medial surface of middle ear
prominence of basal turn of cochlea
Cochleovvestibular aplasia/Michel deformity
3rd week arrest, complete absence of cochlea, vestibular strctures
Cochlear Aplasia
late 3rd week arrest
absent cochlea
normal, dilated or hypoplastic vestibule
Common cavivty
4th week arrest
Incomplete Partition Type I
arrest week 5 cystically enlarged cochlea No internal architecture dilated vestibule enlarged IAC
Cochlear hypoplasia
6th week arrest
Separation of cochlear and vestibular structures
small cochlear bud
Incomplete partition type II (Mondini)
7th week arrest
cochlea has 1.5 turns
cystically dilated middle and apical turn
slightly dilated vestibule
Most common CT finding profoundly deaf child
Radiographically NL middle ear
malformation limited to membranous labyrinth, cannot be sean by IMG
90% of children with profound hearing loss
Why children are more prone to nasoseptal hematoma
cartilage more pliable
less likely to fx
cartilage bends/buckles –> shearing force –> separation between perichondrium and cartilage –> bleeding within this space
Development of paranasal sinuses
Ethmoid: most developed at birth
Maxillary: present (mm) at birth, grow rapidly first three years then again between 7-12
Frontal: not present at birth, develop as extensions of ethmoid air cells anterosuperiorly, growth starts at age 2 vertically, near adult size by early teens
Sphenoid: begins around 3-4, adult size by 12-15
How many people do not develop any frontal sinuses? How many don’t develop one but do develop the other?
5% for both
Developmental frontal spaces where encephaloceles can form
Fonticulus frontalis - transient fontanelle between inferior frontal bone and nasal bone
Foramen cecum- passageway through skull base just posterior to where frontal sinus will eventually form
Prenasal space
These are possible paths for dermoid/enceph/glioma
Why CT scan is not preferred for nasofrontal imaging in children <1 yo
First 6-8mo nasal frontal process, nasal bones, ethmoid are unossified, similar on CT to brain/nasal cart
May look like bony dehiscence with nasal secretions
Frontal process, nasal bones, crista galli lack fat in first 8mo, so look like brain on T1
So, use MRI for nasofrontal region in young kids
Which muscles act on eustachian tube? Which is the main dilator
TVP - main dilator
TT
LVP
Salpingopharyngeus
Function of TVP
Medial pterygoid –> palatine aponeurosis
V3 (medial pterygoid)
Tense soft palate, assists in elevating palate to prevent nasal regurg, provides stability for pharynx to elevate during swallowing
Attaches to lateral cartilaginous lamina of ET, so assists in dilation with swallow/yawn
Function of tensor tympani
ET –> handle of malleus
medial pterygoid nerve (from V3)
pulls malleus medially to tense TM
Function of LVP
petrous apex T bone/medial lamina ET –> palatine aponeurosis
CN X
Elevate soft palate to prevent nasal regurg of food
Function of salpingopharyngeus
lower medial ET cart (makes posterior welt of torus tubarius)–> blend with palatopharyngeus to upper border thyroid cart
CN X
elevate pharynx/larynx with swallow, pull on torus tubarius
How does ET differ between infants and adults?
Smaller, horizontal or 10 deg from horiz.
Angle affects function of TVP
Adult: larger, 45 deg
Why are neonates obligate nasal breathers?
Larynx elevated with epiglottis in apposition to soft palate
Allows infant to drink and breathe simultaneously
Also means infants have difficulty breathing out of mouth
How is pediatric airway different than adult?
tongue larger in proportion to mouth larynx more anterosuperior pharynx smaller epiglottis larger and floppier trachea narrow, less rigid
5 arteries to palatine tonsils
dorsal lingual ascending palatine (facial) tonsillar br of facial ascending pharyngeal (ECA) lesser palatine (descending palatine)
Venous drainage of palatine tonsils
peritonsilar plexus
lingual and pharyngeal veins, then to IJ
Where is ICA in relation to tonsils?
2.5cm posterolateral
Immune function of tonsils
sample pathogens
synthesis of humoral immunoglobulins
produces lymphocytes
Effects of submucous cleft
abnormal palate motion
poor velopharynx closure
speech/swallow difficulty
Which pharyngeal arches lead to SLN and RLN?
SLN - 4
RLN - 6
Narrowest part of infant larynx
cricoid
Narrowest part of adult larynx
rima glottis / glottic opening
Significance of narrowest portion of infant airway being cricoid
Since narrowest portion is a rigid ring, ET tube too large may cause ischemic injury –> subglottic stenosis
Which does RLN wrap around structures it wraps around?
6th arch: develops aortic arch and subclavian, as well as RLN
Wraps around aortic arch on L, subclavian on R
What is associated with non-recurrent laryngeal nerve on R?
aberrant right subclavian artery
Difference between external and internal laryngeal nerves
Both br of SLN
external innervates cricothyroid, inferior constrictor
internal sensation from supraglottic larynx (CN X does sensation below glottis)
CHAOS
congenital high airway obstruction syndrome
failure of airway to recannulate during development of larynx (laryngeal atresia) or upper trachea
Very low survival if not ID’d prenatally
Unable to ventilate unless corresponding TEF
Why having C-shaped cartilage in trachea is advantageous
needed rigidity to maintain airway throughout respiration
allows for larger boluses of food to pass through esophagus
Blood supply to trachea
lateral pedicles from inferior thyroid, subclavian, supreme intercostal, internal thoracic, innominate, superior/middle bronchial
Killian’s triangle
weakned area of pharyngeal wall
between inferior constrictor and cricopharyngeus
Pressure in lower pharynx plus impaired relaxation of cricopharyngeus during swallowing can lead to zenker’s diverticulum here
