Middle ear ventilatory pathway and Mucosal folds

1. MIDDLE EAR MUCOSAL FOLDS
AND
VENTILATORY PATHWAY
- Dr. Saneesh Damodaran
- JR-1, Otorhinolaryngology

2. • Non-functional Middle Ear Ventilation creates
negative middle ear pressure, which is the basis for
the generation of a retraction pocket at the level of
the tympanic membrane (TM), mainly at the level
of the pars flaccida, which may extend to form
Primary Acquired Cholesteatoma.
• Factors that control the ventilation of the middle
ear:
• Eustachian Tube (ET) function
• Pressure buffer mechanism produced by the Middle
ear and Mastoid bone
• Transmucosal Gas Exchange in the tympanic cavity

3. • Isolated retraction
pocket of the pars
flaccida, endoscopic
views
(0° endoscope, Right ear)

4. Eustachian Tube
• If ET fails to equalize pressure, a negative pressure occurs, leading to
atelectasis of the TM and so to creation of a retraction pocket in the attic or
posterosuperior quadrant and consequently to adhesive otitis media that
can cause a cholesteatoma.
• Normally, the ET stays closed and opens when necessary to equalize
pressure.
• Other function: clearance of middle ear fluid while at the same time
preventing nasopharyngeal secretions refluxing into the middle ear space.
• Luminal dilatation of the ET is caused by muscle contraction causing
medial-superior rotation of the medial lamina, which in turn causes a
deformation of fatty tissue surrounding the ET (Ostmann’s fat pad)
• Although surgery generally has been successful in clearing cholesteatomas,
those patients with nonfunctioning or marginally functioning ET has less
success rates, and possible frequent recurrence.

5. Anatomy of the eustachian tube [Right ear]:
(a) The cartilaginous portion and related muscles
of the eustachian tube; posterior view
(b) The eustachian tube orifice: a view tangential
to the eustachian tube lumen at the level of the
rhinopharynx
(c) Bony and cartilaginous portions of the
eustachian tube, coronal view
tvpm- tensor veli palatini muscle
lvpm- levator veli palatine muscle
tuc- cartilaginous component of the eustachian
tube
psf- petrosphenoidal fissure
spcm- superior pharyngeal constrictor muscle
stl- suspensory tubal ligament

6. Total retraction of the eardrum in a patient with failure
of eustachian tube function: [Right ear]
(a) axial view at the epitympanic level
(b) coronal view
(c) sagittal view
In this case we observe a decrease of the pressure
throughout the middle ear and mastoid, with
subsequent retraction of the pars flaccida and pars
tensa.
in- incus; ma- malleus
s- stapes is- isthmus
tf- tensor fold fn- facial nerve
d- eardrum prs- Prussak space
imlf- lateral incudomalleal fold mlf- lateral malleal
fold
lsc- lateral semicircular canal cho- cochlea

7. • Another possible ET dysfunction is a continuous opening of the ET
(Patulous eustachian tube). Patients with this disorder complain about
autophony or hearing their own breathing or echolike vocalizations. Causes
can include hormonal changes (decreased estrogen levels), rapid weight
loss, or chronic middle ear dysfunction.

8. Transmucosal Gas Exchange
• The middle ear mucosa exchanges gas in a
similar fashion to alveoli in the lung. The direction
of gas exchange is predicated on the differences
in partial pressure of the component gases in the
middle ear cleft and mucosa. Inflammatory
processes that affect the thickness and blood
flow of the middle ear mucosa have a direct effect
on the rate of diffusion.
• Hypopneumatized mastoid (an indirect sign of a
poor gas exchange function due to a low amount
of mucosa in the ME) as well as ET dysfunction
may be closely related to these pathologies due
to a negative pressure level in the tympanum.
• Middle ear tended to shrink when the mucosa
was inflamed, probably due to disruption of the
diffusion and absorption of CO2.
• Studies based on gas exchanges in patients who
had mastoidectomy showed that, in ears after
surgery, recovery of both the gas exchange
function and aeration in the mastoid is to be
expected only when the mastoid mucosa can be
preserved even partially.

9. Mastoid Buffer
• Acc. to Boyle’s law, at a constant temperature, pressure multiplied by volume
equals a constant. Thus, pressure and volume are inversely
proportional. Applied to the mastoid bone, this means that small mastoid
volumes tend to cause greater changes in pressure.
• The mastoid air volume “dilutes” pressure changes in relation to its size;
volume change required to alter a given pressure in an average mastoid (6
mL) is six times that which is needed in a small mastoid (1 mL).
• ME with a small mastoid that is most vulnerable to pressure changes and
that may develop compensatory buffering mechanisms, such as additional
TM retraction (atelectasis) or ME volume reduction by fluid accumulation.

10. Blockage of Middle Ear Ventilation
Routes
• All epitympanic compartments receive their aeration via the large tympanic isthmus
between the medial part of the posterior incudal ligament and the tensor tendon.
• Obstruction of the tympanic isthmus is common in various types of middle ear disease
and causes significant disturbance to air diffusion within the temporal bone pneumatic
system, leading to complete or incomplete separation of the tubotympanic cavity from
attico-mastoid airspace.
• Morpho-functional partition(by epitympanic diaphragm) separates the middle ear into:
• Anteroinferior compartment corresponds to the middle ear cleft (mesotympanum,
protympanum, retrotympanum, and protympanum) and could be compared to the nose;
Pseudostratified and ciliated epithelium with mucus cells; connective tissue is relatively thick and
dense; function of this compartment is mainly mucociliary clearance.
• Posterosuperior compartment corresponds to the epitympanum, antrum, and mastoid cells and
could be compared to the lung; epithelial layer is monocellular and contains flat cells; function of
this compartment is gas exchange.
• Factors that cause obstruction of the tympanic isthmus were mucosal fold variations,
inflammatory webs and exudate, retracted tympanic membrane, diseased attic mucosa,
and cholesteatoma.

11. Epitympanic diaphragm in a patient with a Complete tensor
fold: [Right ear]
Epitympanic diaphragm in a patient with an Incomplete
tensor fold: [Right ear]
s-stapes; fn-facial nerve; cp- cochleariform process; ma-
malleus;
in-incus; aes-anterior epitympanic compartment;
amf-anterior malleolar fold; pes-posterior epitympanic
compartment; pil-posterior incudal ligaments; tf-tensor fold; mlf-
lateral malleal fold; imlf-lateral incudomalleal fold; is-isthmus;
pe-pyramidal eminence.

12. Middle ear aeration pathway in a patient with
normal function of the eustachian tube: [Right
ear]
(a) axial view at the epitympanic level
(b) coronal view
(c) sagittal view
in, incus; ma, malleus; s, stapes; is, isthmus; tf,
tensor fold; fn, facial nerve; dr, eardrum; prs,
Prussak space; imlf, lateral incudomalleal fold;
mlf, lateral malleal fold; cho, cochlea; lsc, lateral
semicircular canal.

13. Mucosal Fold Development
 3rd to 7th month fetal age - mesenchymal tissue of middle ear
cleft is absorbed.
 Simultaneously, primitive tympanic cavity develops by growth of an
endothelium-lined fluid pouch(TuboTympanic Recess) extending
from the ET into the cleft.
 The terminal end of TTR buds out to form 4 primary sacci-
 Saccus Anticus, Saccus Medius, Saccus Superior, Saccus Posticus.
 The sacci or pouches start to enlarge in the middle ear cleft to
replace the pre-existing mesenchyme.

14.  Walls of the pouches Mucosal lining of middle ear
 Mucosal fold  Plane of contact between two neighboring pouches.

16.  Mucosal folds extend from the wall of middle ear to its content & carry ligaments
and blood vessels to the ossicles.
 These folds orient the progress of middle ear pathologies but are not true
barrier against their extension.
 Mucosal folds [2 types]
 Composite fold: Ligament+ Lining mucosa
[Ant.MLF, Lat.MLF, Post. Incudal fold]
 Duplicate fold: fusion of two expanding air sac walls in absence of any
interposing structure.
[Tensor tympani fold, Lateral incudomalleal fold]

17. Important folds in middle ear
1. Anterior malleal fold
2. Posterior malleal fold
3. Anterior malleal ligamental fold
4. Lateral malleal ligamental fold
5. Superior malleal fold
6. Superior incudal fold
7. Posterior incudal fold
8. Medial incudal fold
9. Lateral incudomalleal fold
10. Tensor tympani fold

18. Anterior Malleal Fold:
• Origin : anterior portion neck of malleus
• Insertion : anteriorly on ant. tympanic spine
• Forms: medial wall of ant. Pouch ofVonTroltsch
Posterior Malleal Fold:
• Origin : posterior portion neck of malleus
• Insertion : posteriorly on post. tympanic spine
• Forms: medial wall of post. Pouch of VonTroltsch

19. • Anterior Malleal Ligamental Fold
 Originates from neck of malleus & extends
to the anterior attic bony wall.
 Reflected from lateral wall of middle ear
overAnt. Process andligament of malleus.
 Ant. Part ofChordaTympani
 Low posterior part is broad and represents
ant. Limit of Prussak’s space.

20. Lateral Malleal Ligamental Fold
• Originates from middle portion of the neck of
malleus & attaches to attic outer wall
• Posteriorly confluent with ant.
• Descending portion of Lat. IMF
• Mostly complete, thick fold and strong , so
prevents progression of pars flaccida
retraction
• Represents roof of Prussak’s space and the
floor of the lateral malleal space

21. Superior Malleal Fold:
• Extends between superior surface of Malleal head and tegmen.
• Contains Superior Malleal ligament.
• Divides upper unit of attic into anterior and posterior parts.
Superior Incudal Fold:
• Extends between superior surface incudal body to tegmen
• Divides posterior attic to lateral and medial part

22. Posterior Incudal Fold:
• Lies between the fibres of the post. incudal ligament
Medial Incudal Fold:
• Lies between the long process of the incus and the tendon of the stapedial
muscle upto pyramidal eminance

23. Lateral Incudomalleal Fold
• Present superiorly in relation to lateral malleal ligamental fold
• Divides upper lateral attic space from the lower lateral attic space
• It has 2 extensions:
• Posteriorly it horizontally extends to insert medially onto body of the incus & incudomalleal joint.
• Laterally , it insert onto the medial surface of the bony wall of scutum
• Ant. Portion of the this fold bends inferiorly towards the neck of malleus & merges with post.
portion of lat. MLF representing the post. limit of Lat. Malleal space
• Level is about 1mm higher than the roof of Prussak’s space

24. TensorTympanic Fold:
• Part of tympanic diaphragm
• Arises posteriorly from the tensor tympani tendon
• Anteriorly inserts into a transverse crest(supratubal ridge) of anterior wall of the attic
• Medially insert on the bony canal of the TTM
• Laterally insert on anterior malleal ligament
• Separates the anterior epitympanic recess superiorly from the supratubal recess inferiorly

25. • TTF results from fusion of saccus anticus & anterior saccule of the saccus medius
• Inclination angle of theTTF varies bet. 800 -1000 depending on the variable
growth of each saccule
• Determines the size of SupraTubal Recess andAnterior Epitympanic Recess
• TTF complete -total separation between ant. epitympanum and protympanum
• But in majority of populationTTF is incomplete. Resulting in direct
communication between ET to ant. Epitympanic recess and then to posterior
attic. Hence prevents attic dysventilation.

26. Tympanic Diaphragm formed by
• 3 malleal ligamental folds
• Posterior incudal fold
• TensorTympani Fold
• Lateral incudomalleal fold
• Incus and Malleus
• As theses components are on different level
Tympanic Diaphragm is not fully Horizontal
• Separates the upper unit of attic superiorly and
lower unit of attic, the Prussak’s space
inferiorly from mesotympanum

27. Tympanic Isthmus
• Attic and mastoid are isolated from mesotympanum byTympanic
Diaphragm
• Attic aeration occurs through a 2.5 mm opening in the tympanic
diaphragm -Tympanic Isthmus
• Anteriorly - extends from tensor tympani muscle
• PosteroSuperiorly – post. Incudal ligament
• PosteroInferiorly – pyramidal eminence
• Medially – limited by attic bone
• Laterally – limited by body and short process of incus and head of malleus

28. • Tympanic isthmus is divided by the medial incudal fold into 2 portions:
• The AnteriorTympanic Isthmus
• BetweenTTM anteriorly & the stapes posteriorly
• The Posterior tympanic Isthmus
• Between short process of incus & stapedial muscle

29. Clinical Correlation:
• In long standing COM, granulation tissue and webs - block the tympanic
isthmus – failure of attic ventilation even in presence of normal ET and well
aerated mesotympanum
• This is called Selective Attic Dysventilation
• Results in chronic attic inflammation, attic retraction pockets and attic
cholesteatoma
• IncompleteTTF allows good ventilation from the protympanic space to
anterior attic and prevents attic dysventilation even in case of tympanic
isthmus blockage
• This signifies the importance ofTTF removal during surgical treatment of
middle ear disease to ensure a good ventilation of the attic region

31. THANKYOU