it os main topic in ENT

1. MIDDLE EAR SPACES
AND BOUNDARIES
DR KHADEEJA ZEBA K
JUNIOR RESIDENT –ENT
MGM HEALTH CARE

2. EMBRYOLOGY
Third week- The tympanomastoid
system appears as an
outpouching of the first
pharyngeal pouch called the
tubotympanic recess.
Seventh week- second
pharyngeal arch constricts the
midportion of the tubotympanic
recess - the primary tympanic
cavity lateral to this constriction
primordial Eustachian tube
medial to this constriction

3. • The terminal end of the
tubotympanic recess buds into
four sacci: the saccus anticus,
the saccus medius, the saccus
superior, and the saccus post
• Expanding sacci envelop the
ossicular chain and line the
walls of middle ear cavity
• The interface between two
sacci gives rise to several
mesentery-like mucosal folds,
transmitting blood vessels and
ligaments to middle ear
contents.

4. SACCUS ANTICUS SACCUS MEDIUS
• Smallest saccus
• extends upward anterior to the
tensor tympani tendon to form
• Anterior epitympanic recess (AER)
• Anterior pouch of von Tröltsch.
• Divides into three saccules
1. ANTERIOR SACCULE
2. MEDIAL SACCULE
3. POST SACCULE
• Fuses with anterior saccule of the
saccus medius to form the TTF
• TTF separates the anterior
epitympanic recess superiorly from
the supratubal recess inferiorly

6. THE SACCUS SUPERIOR
Form the posterior pouch of von
tröltsch, the inferior incudal space, and
the lateral part of the antrum which
derives from the squamous part of the
temporal bone
The plane of fusion between the
posterior saccule of the saccus medius
and the saccus superior usually breaks
down
A BONY SEPTUM PERSISTS
BETWEEN THE TWO PARTS,
CALLED KOERNER’S SEPTUM
May cause difficulty in locating
the antrum and the deeper
cells and thus may lead to
incomplete removal of disease
at mastoidectomy

7. THE SACCUS
POSTICUS
 Extends along the
hypotympanum
 Form the round window
niche, the oval window
niche, the facial recess, and
the sinus tympani.

8. MIDDLE EAR
COMPARTMENTS
 The middle ear cavity divided
into five compartments:
 MESOTYMPANUM in the
centre
 EPITYMPANUM superiorly
 PROTYMPANUM anteriorly
 HYPOTYMPANUM inferiorly
 RETROTYMPANUM
posteriorly

9. PROTYMPANYM
 Lies anterior to a frontal plane drawn
through anterior margin of the
tympanic annulus
 widely open posteriorly into the
mesotympanum and leads anteriorly
into the Eustachian tube
 The protympanum starts superior to
a bony ridge called protiniculum

10. WALLS OF THE
PROTYMPANUM
Superior: the tegmen tympani and
entire tensor tympani canal,
Inferior: from the protiniculum (an
oblique bony ridge demarcating the
transition between protympanum and
hypotympanum)
Anterior: confluent with the
junctional and cartilaginous portion of
the ET
Posterior: confluent with the
mesotympanum
Medial: the cochlea posteriorly and
the lateral wall of the carotid canal
anteriorly,
Lateral: called the lateral lamina
separating this space from the
mandibularf fossa

11. THE SUPRATUBAL
RECESS (STR)
 superior extension of the
protympanum
 The size of the supratubal
recess depends on the anatomy
of the TTF.

12. THE HYPOTYMPANUM
 The hypotympanum is a crescent-shaped space
located at the bottom of the middle ear
 Extends from the funiculus posteriorly to the
protiniculum inferiorly and the Eustachian tube
orifice anteriorly.
 The anterior wall is formed by the carotid canal
medially
 The posterior wall is formed by the funiculus and
the inferior part of the styloid complex
 The posterior wall of the hypotympanum
corresponds to a vertical plane from the posterior
semicircular canal to the junction of the sigmoid
sinus with the jugular bulb
 The lateral wall is formed by the tympanic bone.

13. THE HYPOTYMPANUM
 The medial wall is formed by the lower part of the
promontory and a part of the petrous bone which extends
under the promontory
 The inferior wall or the floor is dome shaped and
corresponds to a thin bony plate separating the
hypotympanum from the jugular bulb

14. SURGICAL IMPORTANCE
 Hypotympanum is occupied by
trabeculae
 When the trabeculae are absent, the
jugular wall raises up to the cochlear
capsule
 Opening the hypotympanum, surgery is
safe when the trabeculae are present,
 Jugular dome is 6 mm deeper and the
sigmoid sinus is posterior.
 16% of cases bony jugular wall is
dehiscent
 The surgeon should be very careful
during cholesteatoma surgery
 high jugular bulb may be associated
with an anteriorly placed sigmoid sinus

15. AIR CELLS IN THE HYPOTYMPANUM
Hypotympanic Air Cells Retrofacial Cells
present in the medial and inferior
wall of the hypotympanum, may
extend below the labyrinth to
reach the petrous apex cells
extend from the mastoid tract
posterior and medial to the facial
nerve and drain into the
hypotympanic cells.
Surgical Applications-Through a
transcanal hypotympanotomy-
approach for the drainage of the
petrous apex
Surgical Application- Dissecting
the retrofacial cells medial to the
vertical segment of the facial
nerve-provides a good access to
the hypotympanum and the
related structures without
transposing the facial nerve or

16. RETROTYMPANUM
Site of the highest
incidence of middle
ear pathologies
especially retraction
pockets and
cholesteatoma

17. THE ANATOMY OF
RETROTYMPANUM
 Four spaces:
 Two spaces medial to the
vertical segment of the facial
nerve and the pyramidal
eminence
 two spaces lie lateral to them.

19. THE ANATOMY OF RETROTYMPANUM

20. LATERAL SPACES
 Forms the facial recess
 Medially –facial nerve canal and pyramidal eminence
 Laterally by chorda tympani
 Superiorly – incudal buttress
 The incudal buttress separates the facial recess from the aditus ad
antrum
 Chordal ridge divide the lateral space into
 Facial sinus superiorly -
 Lateral tympanic sinus inferiorly –lies between 3 eminence :
pyramidal eminence, styloid eminence, and chordal eminence

21. SURGICAL
APPLICATION
 The facial recess serves as a
posterior window to reach the
middle ear from the mastoid
cavity,
 Enables visualization of the OW
and ponticulus superiorly and
the RW and subiculum
inferiorly.
 It is done by a trans mastoid
drilling of the posterior wall of
the facial recess, between the
chorda tympani laterally and
the facial nerve medially.
 This surgical approach is called
TRANSMASTOIDPOSTERIOR
TYMPANOTOMY

22. MEDIAL SPACES OF RETROTYMPANUM
Superior retrotympanum/ Tympanic
sinus
 Depressions in the posterior wall of the
middle ear
 Lies between the facial nerve and
pyramidal eminence laterally and the
labyrinth medially
 ponticulus, which runs from the
promontory to the pyramidal eminence,
divides the tympanic sinus in two spaces
Inferior Retrotympanum

23. Tympanic sinus
(Superior
Retrotympanum)
Posterior Tympanic
sinus
Sinus Tympani

24.  POSTERIOR TYMPANIC SINUS Surgical Application
 Present in most middle ears,
 It lies superior to the ponticulus, medial to the pyramidal
eminence and facial nerve
 It is about 1 mm deep and about 1,5 mm long
 During middle ear surgery, in order to reach the posterior
tympanic sinus, section of the stapedial tendon and drilling
of the pyramidal process may be required,

25. SINUS TYMPANI
 Largest sinus of the retro tympanum
 It lies medial to the mastoid portion of the facial
nerve,
 Lateral to the posterior semi circular canal.
 Superiorly :ponticulus and the pyramidal
eminence
 Inferiorly :subiculum and the styloid eminence
 Great variability in size, shape and depth
 10 % of the population, the sinus tympani and
posterior tympanic sinus form one confluent
recess.

27.  During cholesteatoma surgery a good exposure of the medial
boundary of the sinus tympani is very important, because of two
important risks,
 Potential persistence of disease inside the sinus due to incomplete
removal,
 The second is the increased risk for ossicular discontinuity and
hearing loss due to cholesteatoma within the ST, which the surgeon
cannot control
SURGICAL IMPORTANCE

28.  CLASSICAL SHAPE: when the sinus is located between the ponticulus
and subiculum lying medial to the facial nerve and to the pyramidal
process.
 CONFLUENT SHAPE: when an incomplete ponticulus is present and the
ST is confluent to the posterior sinus.
CLASSIFICATION OF ST BASED ON MORPHOLOGY

29. SINUS TYMPANI TYPES
Type A is a shallow sinus tympani
Type B sinus tympani is of intermediate depth
Type C sinus tympani is very deep

30. THE INFERIOR RETROTYMPANUM
Superiorly- Subiculam
Inferiorly- Finiculus

31.  The Sinus Sub-tympanicus
 The “Subcochlear
Canaliculus” Confound
with the “Proctor’s
The Inferior
Retrotympanum

32. SINUS SUB-
TYMPANICUS
The subiculum superiorly and
posteriorly
– The finiculus inferiorly and
anteriorly
– The styloid prominence posteriorly
and inferiorly

33. SUBCOCHLEAR
CANALICULUS
 Smooth bony structure,
 Forms the floor of the
round window chamber
 links the styloid
Proeminence with the
basal turn of the cochlea
 Connects the inferior
retrotympanum with the
petrous apex via a series
of pneumatized cells.

34. The subcochlear tunnel presents a pathway for the extension of
cholesteatoma inferior to the otic capsule through this tunnel

35. THE EPITYMPANUM
OR THE ATTIC
Anatomy of the Attic(The
Epitympanum)
 The attic is the part of the
tympanum situated above an
imaginary plane passing through
the short process of the malleus
 The attic occupies approximately
one-third of the vertical dimension
of the entire tympanic cavity and
lodges the head and neck of the
malleus, the body, and the short
process of the incus,

36.  Upper Unit of the Attic lies above the
tympanic diaphragm.
 A communication between both
spaces for ventilation purposes is
only possible through an opening of
the tympanic diaphragm, called the
tympanic isthmus
 The tympanic isthmus is situated
between the tensor tympani muscle
anteriorly and the posterior incudal
ligament posteriorly.

38. BOUNDARIES
 LATERAL WALL : Inferiorly by Shrapnel's membrane and superiorly by a bony
wall, called the outer attic wall.
 MEDIAL WALL : Part of the medial wall situated above the tympanic segment of
the facial nerve and tensor tympani muscle. It contains the lateral semi circular
canal.
 POSTERIOR WALL : Occupied almost entirely by the aditus ad antrum. It is 5-6
mm high
 INFERIOR - : Tympanic diaphragm divides the attic in to an upper unit situated
above the tympanic diaphragm and a lower unit of the attic (the Prussak'sspace),
which is below the diaphragm. Anteriorly by tympanosquamous suture

39. ORGANIZATION
OF THE
DIFFERENT
COMPARTMENTS
OF THE ATTIC

40.  Medially : It is bounded by the
lateral semi circular canal and the
Fallopian canal
 Laterally : Ossicles and the
superior incudal fold.
 The distance between the lateral
semi circular canal and the incus
body is 1.7 mm.
 Larger compartment of the
posterior attic.
MEDIAL POSTERIOR ATTIC

41. THE LATERAL POSTERIOR ATTIC
DIVIDED INTO THREE SPACES
Lateral posterior attic is narrower, located between
the outer attic wall laterally and the malleus head,
incus body, and superior incudal fold medially
superior incudal space
The lateral malleal space forming
together the upper lateral attic
Inferior incudal space, called the
lower lateral attic

42. Lateral malleal space (LMS)
 The lateral malleal space is a distinct anatomic
area, part of the lateral attic; it lies above the
lateral malleal fold. It is limited,
 Medially by the malleus head and neck
 Laterally by the outer attic wall
 Anteriorly by the anterior malleal fold
 Posteriorly by the downward turning end
of the incudomalleal fold

43. ANTERIOR ATTIC OR
ANTERIOR EPITYMPANUM
 situated anterior to the head of malleus and
the superior malleal fold
 Anterior Attic or The anterior epitympanum
is divided into two spaces by the cog.
 The cog is a bony crest that extends
inferiorly from the tegmen; it is superior to
the cochlear form process and
anterosuperior to the malleus head,

44. ANTERIOR
EPITYMPANIC
RECESS (AER)
 ANTERIOR EPITYMPANIC SINUS /
ANTERIOREPITYMPANIC SPACE /
SINUS EPITYMPANI
 Superiorly: anterior part of
the tegmen tympani
 Anteriorly: zygomatic root
 Posteriorly: cog
 Laterally: scutum
 Medially geniculate ganglion•
 Floor: cochleariform process
and the TTF

45.  TTF seperates supratubal recess (STR)
and the anterior epitympanic recess
(AER) as two distinct spaces
 congenital defect in the TTF results in
direct communication with the
supratubal recess serving as an
accessory route of aeration to the attic
called the anterior route of ventilation

46. CLINICAL APPLICATION
 In recurrent otorrhea with central or anterior perforation not responding to
conventional medical therapy or in front of a mucoid middle ear effusion that
persists or recurs despite repetitive myringotomies with tube insertion
 AER is highly important to consider
 In these cases cases, the TTF is complete and blocks the aeration of the anterior
epitympanum from the anterosuperior mesotympanum creating a dysventilation
syndrome.

47. THE LOWER UNIT OF THE ATTIC (PRUSSAK’S SPACE)
 Prussak’s space is situated inferior to
the tympanic diaphragm and
represents the lower unit of the attic.
 Laterally, Prussak’s space extends
superior to the roof of the external
auditory canal

48.  FLOOR is formed by the neck of
the malleus
 ANTERIOR LIMIT is the anterior
malleal fold
 LATERAL WALL is formed by the
pars flaccida and the lower edge
of the outer attic wall
 POSTERIOR WALL is opened to the
posterior pouch of vonTröltsch and
then to the mesotympanum.
PRUSSAK'S SPACE

49. PRUSSAK'S SPACE
 The ventilation route of Prussak’s space is independent of the upper unit
of the attic. Prussak’s space is ventilated through the posterior pouch
 The posterior pouch of von Tröltsch is bounded laterally by the pars tensa
of the tympanic membrane and medially by the posterior malleolar
ligament fold (PMF)
 closing of the posterior pouch by viscous secretions is a plausible
cause of a chronic selective dysventilation associated with a
retraction of Shrapnell’s membrane and its adhesion to the malleus
neck

50. PATHWAY 1
Posterior pouch
of von Tröltsch
inferior incudal
space
Medial attic

51. PATHWAY 2
Thin part of the lateral
malleal fold
upper unit of the attic
posterior attic, aditus,
and then to the antrum

52. PATHWAY 3
From the lateral
malleal space
Through the superior
malleal fold defect
The anterior attic

53. MESOTYMPANUM
 Central and the largest compartment of the middle ear cavity
 Medially by the promontory and laterally by the pars tensa of the
tympanic membrane
 Widely open anteriorly, inferiorly, and posteriorly to the
protympanum, hypotympanum, and retrotympanum,
 Acts like a tunnel, allowing air coming from the Eustachian tube

54. • Anterior Pouch of von
Tröltsch
Between the anterior malleal
fold and the pars tensa of the
eardrum
communicates with the
supratubal recess and the
protympanum

55. POSTERIOR POUCH
OF VON TRÖLTSCH
 Between the posterior
malleal fold and the pars
tensa of the eardrum
main route of ventilation of
Prussak’s space