11/15/2013

11/15/2013

Answers:

Which ossicle requires the longest period of development?
A) Incus 
B) Stapes 
C) Malleus 
D) They are all equal

The stapes requires the longest period of embryologic development. Additionally, it is derived from both branchial arch and otic capsule precursors which makes it's embryologic origins more complex. This is thought to be the reason why congenital anomalies of the stapes (40% of congenital ossicular lesions) are more common than that of either the incus or the malleus.

What does a "high riding" bulb refer to?

“High riding” bulb = jugular bulb (at junction of sigmoid sinus and inferior petrosal sinus) that rises above the inferior aspect of the bony annulus or the basal round of the cochlea.
-Present in 5% of people, may be related to poor pneumatization of mastoid.
-Can present with tinnitus, vestibular symptoms and CHL (due to compression of middle ear contents)
-Most commonly discovered incidentally on exam.
-Classically a blue mass is seen posteroinferior quadrant of TM.
-At risk of inadvertent laceration during myringotomy.

MC Questions:
All of the following are true with regards to congenital cholesteatomas except...
A) Often discovered incidentally 
B) Does not usually present with TM perf 
C) Patients w/ congenital cholesteatoma tend to have well aerated mastoids 
D) Can present in anterior or posterior quadrants 
E) All of the above are true

Free Response Question:
Where are congenital cholesteatomas "classically" found? What do they look like on otoscope exam?

Quick Facts:

Round Window Anomalies
-Aplasia/hypoplasia associated w/ endemic cretinism and mandibulofacial dysostosis.
-Nonsyndromic cases are rare (less than 10 cases reported)
-Management unclear.
-Often associated w/ stapes ankylosis and diagnoses in retrospect after stapedectomy unsuccessful.
-Better to manage w/ amplification as surgical fenestration has led to poor results and carries risk of SNHL.

11/14/2013

11/14/2013

Answers:

With regards to embryology, Meckel's cartilage leads to formation of the --- whereas Reichert cartilage leads to formation of the---.
A) Stapes Footplate; Sphenomandibular ligament 
B) Long Process of Incus; Stapes Suprastructure
C) Body of Incus; Mandible  
D) Head of Malleus; Manubrium of Malleus

-Meckel cartilage (from 1st pharyngeal arch) = head of malleus / body of incus  mandible / sphenomandibular ligament.
-Reichert cartilage (2nd pharyngeal arch) = manubrium of malleus, long process of incus, stapes suprastructure and tympanic part of stapes footplate. Also, facial nerve,muscles of facial expression, stapedius, upper hyoid and stylohyoid ligament.

All of the muscles of facial expression are innervated on their deep side except for what three exceptions?

Buccinator, Levator Anguli and Mentalis are the three muscles not innervated on their deep side. A good mnemonic to remember this is BLAM.

MC Questions:
Which ossicle requires the longest period of development?
A) Incus 
B) Stapes 
C) Malleus 
D) They are all equal

Free Response Question:
What does a "high riding" bulb refer to?

Quick Facts:

Congenital Cholesteatomas
-Congenital cholesteatomas = middle ear cholesteatoma in presence of intact TM w/o hx of perf, OM, otorrhea or oto surgery.
-Several features distinguish congential from aquired coleasteatomas:
-Acquired often present in setting of existing ear pathology.
-Acquired mass is often symptomatic (otorrhea, otalgia, hearing loss)
-Acquired is found to be expanding in direct continuity w/TM perf or retraction pocket.
-Congenital not associated w/ oto pathology, often clinically silent and discovered incidentally.
-Congenital tend to have well aerated mastoids, unlikely acquired.
-Pathogenesis unclear
-"classically” in anterosuperior quadrant of mesotympanum (27-67%)
-Small pearls next to long process of malleus (minimal ossicular involvement/hearing loss)
-Treat w/ surgical removal.
-Recur in 30-55% of cases after surgery.