Spaces of middle ear and their surgical importance

Speaker-DR SOUMYA

OVERVIEW

• EMBRYOLOGY• MIDDLE EAR FOLDS • MIDDLE EAR SPACES• SURGICAL IMPORTANCE

MIDDLE EAR FOLDS DEVELOPMENT

• 3rd and 7th fetal months -mesenchymal tissue of the middle ear cleft is gradually absorbed.

• At the same time, the primitive tympanic cavity develops by a growth of an endothelium-lined fluid pouch extending from the Eustachian tube into the cleft.

4

• The terminal end of the tubotympanic recess buds into four sacci: the saccus anticus, the saccus medius, the saccus superior, and the saccus posticus

• These sacci enlarge in the middle ear cleft n

replace the pre-existing mesenchyme.

• walls of the pouches- mucosal lining of middle ear cavity.

• At the plane of contact between two -pouches, mucosal folds are formed.

• Between the mucosal layers of the folds remnants of the mesenchyme -transform into ligaments and blood vessels supplying the “viscera” of the tympanic cavity.

MUCOSAL FOLDS

• Middle ear mucosal folds pass from the walls of the middle ear to its contents

• carry ligaments • blood vessels to the ossicles.• Forms compartment• Directs cholesteatoma spread• Not an effective barrier though

Embryology of MiddleEar Compartments

. • These sacci expand progressively to replace

middle ear mesenchyme and mastoid mesenchyme.

• 1ST arch cartilage-head of malleus Body of incus• 2nd arch cartilage-HOM,Long process of incus Stapes cruraeFootplate –otic capsule

S.A

S.MS.S

S.P

Saccus Anticus:

• anterior pouch of Von Troeltsch

• part of the anterior attic compartment

• Upward extension is limited upto semicanal for tensor tympani, wherein it comes in contact with the saccus medius’s anterior saccule part

• This point of contact forms the Tensor fold, and above this will be the anterior compartment of attic

AP OF VON T.

Saccus Medius:• Forms most part of the attic• Divides into 3 saccules• Anterior saccule: the anterior

compartment of attic• Medial saccule: Prussacks space • the superior incudal space by

growing over the incus body • Posterior saccule: extends

posteriorly to the anterior crus of stapes, medial to the long process of incus

• pneumatises that part of mastoid air cells in petrous bone

PRUSSPACE

SIS

Saccus superior:• posterior pouch of Von

Troeltsch • inferior incudal space• Extending posteriorly

crosses HOM and long crus of the incus then over saccus posticus and stapedial tendon and towards antrum

• pneumatises the squamous part of mastoid

PP OF VON T.

IIS

Saccus Posticus:• stapedial folds,• sinus tympani,• round window niche • lower half of oval

window niche• Extends along the

hypotympanum and under the stapedial tendon

• pneumatises the posterior tympanic sinus

ROUNDWIN.

SINUSTYMP.

KORNER’S SEPTUM

• The plane of fusion between the posterior saccule of the saccus medius, and the saccus superior.

• SM- which forms the medial part of mastoid air cells system

• SS-which forms the lateral part of mastoid air cells system,

• usually it breaks down. • If the breakdown fails, a bony septum persists

between the two parts, called the Korner’s septum

Ligaments & folds in the middle ear:

• Malleus • Superior malleolar fold• Anterior malleolar fold• Lateral malleolar fold• Posterior malleolar fold• Tensor tympani fold• Incus• Superior incudal fold• Medial incudal fold• Lateral incudal fold• Interossicular fold• Stapes• Obturator fold and other stapedial

folds

• Posterior incudal ligament

• Superior incudal ligament

• Superior malleolar ligament

• Anterior malleolar ligament

• Posterior malleolar ligament

The Posterior Malleal Fold

• inserts on the posterior portion of the neck of the malleus.

• It involves the upper portion of the handle of the malleus

• merges superiorly with the lateral incudomalleal fold.

• It inserts posteriorly on the posterior tympanic spine and represents the medial wall of the posterior pouch of von Tröltsch.

Anterior Tympano-Malleal Fold

• arises from the anterior portion of the neck of the malleus and inserts anteriorly on the anterior tympanic spine.

• It forms the medial wall of the anterior pouch of von Tröltsch.

• ANTERIOR MALLEAL LIGAMENT• von Tröltsch in 1856• part of the tympanic diaphragm. • origin neck of the malleus and extends to the

anterior attic bony wall. • reflected from the lateral wall of the middle

ear over the anterior process and the anterior part of the chorda tympani.It represents the anterior limit of Prussak’s space

LATERAL MALLEAL FOLD

• Helmholtz in 1868.• Origin: middle portion ofneck of the malleus • fanlike spread before attaching to the outer attic

wall• posteriorly, it is confluent with the anterior

portion of the lateral incudomalleal fold• represents the roof of the Prussak’s space and

the floor of the lateral malleal space.

SUPERIOR MALLEAL FOLD

• Origin:superior surface of the malleus head insertion: the tegmen in a transversal plane.

• Contains superior malleal ligament • divides the attic into• 1. anterior mallelolar space • 2. anterior epitympanic recess

.

LATERAL INCUDOMALLEAL FOLD

• Part of the tympanic diaphragm. • Superior to:lateral malleal ligamental fold

separates the upper lateral attic space from the lower lateral attic space.

• 1 mm higher than the roof of the Prussak’s space.

• Anteroinferiorly insertion: neck of the malleus.

• MEDIAL INCUDAL FOLD• located between the long process of the incus

and the tendon of the stapedial muscle as far as the pyramidal eminence.

• SUPERIOR INCUDAL FOLD (SIF)• extends like the superior incudal ligament

from the superior surface of the incudal body to the tegmen.

• It divides the posterior attic into lateral and medial attic.

• POSTERIOR INCUDAL FOLD• The posterior incudal fold is the fold that runs

between the fibres of the posterior incudal ligament

TENSOR TYMPANI FOLD (TTF)

• part of the tympanic diaphragm. • It arises posteriorly from the tensor tympani

tendon, about 1.5 mm lower than the roof of Prussak’s space.

• It runs anteriorly towards the anterior wall of the attic inserting into a transverse crest: the supratubal ridge.

• Medially inserts on the bony canal of the TTM laterally inserts on the anterior malleal ligament.

• The lateral part of the tensor in close relationship with anterior portion of chorda tympani.

• It separates ANTERIOR EPITYMPANIC RECESS

superiorly from the SUPRATUBAL RECESS inferiorly.

In the majority of ears, the TTF is incomplete; this allows a direct communication from the Eustachian tube and supratubal recess to the anterior epitympanic recess and then to the posterior attic

Supratubal Recess (STR)

• superior extension of the protympanum • space lying between the superior border of

the tympanic orifice of the Eustachian tube and the tensor tympani fold.

• It lies below the anterior attic from which it is separated by the tensor tympani fold.

EPITYMPANIC DIAPHRAGM

• Chatellier and Lemoine introduced the concept of the “epitympanic diaphragm” in 1946, upon which the modern theories of tympanic ventilation have been developed.

• Palva et al. revised Chatellier’s concept.

• Comprises of 3 malleolar ligaments:– Anterior malleolar ligament– Lateral malleolar ligament– Posterior malleolar ligament

• The posterior incudal ligament and fold• Tensor tympani fold• Lateral incudal fold.

Epitympanic diaphragm:

• The tympanic diaphragm is not fully horizontal because its components are on different levels.

• It separates the upper unit of the attic superiorly from the mesotympanum and the lower unit of the attic, the Prussak’s space, inferiorly.

• Anterior pouch of von Tröltsch: between the anterior malleal fold

• the pars tensa• Posterior pouch of von Tröltsch: between the

posterior malleal fold and the pars tensa

• TYMPANIC ISTHMUS• The Eustachian tube opens in mesotympanum• , the attic and the mastoid are isolated from

the mesotympanum by the tympanic diaphragm.

• Attic aeration occurs through a 2.5 mm opening in the tympanic diaphragm called the TYMPANIC ISTHMUS.

ANTERIOR TYMPANIC ISTHMUS

• TTM anteriorly and the stapes posteroinferiorly.

• The diameter 1 to 3 mm. • It is a large open communication with the

anterior epitympanum, • always present.• Ventilates anterior epitymanum and upper

unit (superior attic)

POSTERIOR TYMPANIC ISTHMUS

• between the short process of the

incus and the stapedial muscle.• inconsistent.

STAPEDIAL FOLDS

• There are five folds around the stapes….OBTURATOR STAPEDIS (between the crura of the stapes)

• ANTERIOR STAPEDIAL FOLD (between promontory and ant crus)

• POSTERIOR STAPEDIAL FOLD (between promontory and post crus)

• PLICA STAPEDIUS (between the post crus and pyramidal eminence)

• SUPERIOR STAPEDIAL FOLD (between either of the crura and facial canal)

MIDDLE EAR SPACES

• MIDDLE EAR COMPARTMENTS. The middle ear cavity divided into five

compartments: • MESOTYMPANUM in the centre• EPITYMPANUM superiorly• PROTYMPANUM anteriorly• HYPOTYMPANUM inferiorly & • RETROTYMPANUM posteriorly

RETROTYMPANUM

• . The retrotympanum is the site of the highest incidence of middle ear pathologies especially retraction pockets and cholesteatoma

ANATOMY OF THE RETROTYMPANUM

• four spaces: • Two spaces medial to the vertical segment of the

FN and the pyramidal eminence two spaces lie lateral to them.

• These spaces are separated from each other by the bridges and the eminences of the posterior wall of the middle ear cavity.

• The pyramidal eminence -fulcrum of the retrotympanum.

• The pyramidal eminence– The pyramidal eminence is situated at the center of the

posterior wall immediately behind the oval window; it is about 2 mm height.

• The chordal eminence:– The chordal eminence is situated lateral to the pyramidal

eminence and 1 mm medial to the tympanic membrane. The chordal eminence shows a foramen: the iter chordæ posterius.

• The styloid eminence– The styloid eminence or Politzer eminence is a recognized

smoothed elevation at the inferior part of the posterior wall; it represents the base of the styloid process.

3 Retrotympanum eminences:

• The chordal ridge of Proctor– The chordal ridge runs laterally and transversally from the

pyramidal eminence to fuse with the chordal eminence.• The pyramidal ridge– The pyramidal ridge is very prominent. It runs inferiorly from

the base of the pyramidal eminence to the styloid eminence. It could be absent.

• The styloid ridge– The styloid ridge connects the styloid prominence to the

chordal eminence.• Subiculum: A ridge of bone running from the posterior lip of round

window niche to the styloid eminence.• Ponticulus: a ridge of bone extending from the pyramidal eminence

to the promonotary.

5 Retrotympanum ridges:

FACIAL RECESS

• medially facial canal and the pyramidal eminence• laterally by the chorda tympani.• Superiorly incudal buttress, bony boundary of

the incudal fossa, which lodges the short process of the incus.

• The incudal buttress separates the facial recess from the aditus ad antrum.

• Inferiorly, the facial recess is limited by the chordo-facial angle ranges from 18° to 30°;

• distance between the origin of the chorda tympani and the short process of the incus ranges from 5 to 10 mm.

• size is variable among individuals• it is near adult size at birth.• It measures about 2 mm at the level of the

round window and 3 mm at the level of the oval window.

• The chordal ridge, which runs between the pyramidal eminence and the chordal eminence, divides the facial recess into the FACIAL SINUS superiorly and the LATERAL TYMPANIC SINUS inferiorly.

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 transmastoid drilling of the posterior wall of the facial recess, between the chorda tympani laterally and the facial nerve medially.

• This surgical approach is called TRANSMASTOID POSTERIOR TYMPANOTOMY

MEDIAL SPACES OF RETROTYMPANUM

• depressions in the posterior wall of the middle ear between the

• facial nerve and pyramidal eminence laterally • labyrinth medially….

TYMPANIC SINUS

• The ponticulus, which runs from the promontory to the pyramidal eminence, divides the tympanic sinus in two spaces:

• POSTERIOR TYMPANIC SINUS

superiorly • SINUS TYMPANI inferiorly.

• 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.

SINUS TYMPANI

• largest sinus of the retrotympanum.• It lies medial to the mastoid portion of the

facial nerve,• lateral to the posterior semicircular canal. • superiorly :ponticulus and the pyramidal

eminence • inferiorly :subiculum and the styloid

eminence.

• great variability in size , shape and depth. • Its posterior extension varies between 0.2 and

10 mm with an average of 2 mm.• 10 % of the population, the sinus tympani and

posterior tympanic sinus form one confluent recess.

Surgical importance• During cholesteatoma surgery a good

exposition of the medial boundary of the sinus tympani is very important, because of two important risks.

1. potential persistence of disease inside the sinus due to incomplete removal.

2. The second is the increased risk for ossicular discontinuity and hearing loss due to cholesteatoma within the ST, which the surgeon cannot control

CLASSIFICATION OF ST BASED ON MORPHOLOGY

• 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.

• PARTITIONED SHAPE: when a ridge of bone extending from the third portion of the facial nerve to the promontory area is present, separating the sinus tympani into two portions (superior and inferior).

• RESTRICTED SHAPE: when a high jugular bulb is present thus reducing the inferior extension of the sinus tympani.

Based on its depth

• classified into three types with an equal frequency in the general population.

• Type A Small sinus tympani:-• it is small and does not reach the level of the

vertical portion of the facial nerve posteriorly. surgical transcanal access to the sinus tympani is possible.

• Type B deep Sinus Tympani• intermediate depth; it lies medial to the vertical portion

of the facial nerve but does not extend posteriorly deeper than the level of the facial nerve.

• A total and clear visualization of such sinus tympani could not be achieved without the use of an endoscope.

• Any blind dissection in the sinus tympani without endoscopic visualization carries a risk of residual disease or a possible injury to a dehiscent facial nerve or a high jugular bulb.

• Type C deep Sinus Tympani with post. Extension;• it extends posteriorly more deeply than the vertical

portion of the facial nerve.• This type is frequently seen in a well-pneumatized

mastoid.• Despite the use of an otoendoscope, the pathology of

such deep sinus could not be explored entirely from the middle ear; therefore, access should be obtained through a TRANSMASTOID RETROFACIAL APPROACH.

CLASSIFICATION ST’SDEPTH BASED ON AXIAL CT SCAN.

• A limited sinus tympani• B deep sinus tympani with medially• extension respect the facial nerve • C deep sinus tympani with posterior extension

respect the facial nerve

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.

• 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.

BOUNDARIES

• LATERAL WALL – inferiorly by Shrapnell’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 semicircular canal.

• POSTERIOR WALL - occupied almost entirely by the aditus ad antrum. It is 5–6 mm high

• INFERIOR - tympanic diaphragm divides the attic into an upper unit situated above the tympanic diaphragm and a lower unit of the attic (the Prussak’s space), which is below the diaphragm.

• Anteriorly by tympanosquamous suture

• Divided into 2 compartments:– Anterior epitympanum.– Posterior epitympanum.

• Posterior epitympanum divided into 2:– Medial portion– Lateral portion

• Lateral portion again divided to 2 parts:– Superior lateral attic– Inferior lateral attic

• Prussak space:• Anterior pouch of Von Tröltsch :• Posterior pouch of Von Tröltsch :

Epitypanic spaces:

• DIVISION OF UPPER ATTIC

• several folds and ligaments in the perpendicular planes lead to

further divisions and spaces of the upper

unit of the attic

• Medial Posterior Attic• It is bounded by the lateral semicircular canal

and the Fallopian canal medially and the ossicles and the superior incudal fold laterally.

• The distance between the lateral semicircular canal and the incus body is 1.7 mm.

• larger compartment of the posterior attic.

• Lateral Posterior Attic• Anterior Attic or Anterior Epitympanum• 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 cochleariform process and anterosuperior to the malleus head.

• It divides the anterior attic into a small posterior space, the anterior malleal space, and large anterior space: the anterior epitympanic recess

• Anterior Epitympanic Recess (AER)• ANTERIOR EPITYMPANIC SINUS / ANTERIOR

EPITYMPANIC 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

• Lower Unit of the Attic• Prussak’s space is formed from the posterior

pouch of von Tröltsch as a prolongation of the superior saccus, replacing the mesenchymal tissue between the neck of the malleus and Shrapnell’s membrane.

• The aeration pathway remains the same as the route of origin which is the posterior pouch of von Tröltsch.

• PRUSSAK’S SPACE• The Prussak’s space is situated inferior to the

tympanic diaphragm and represents the lower unit of the attic.

» ROOF is the lateral malleal fold » 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 von

Tröltsch and then to the mesotympanum.

protympanum

The protympanic space is a pneumatic portion of the middle ear that lies anteriorly to the mesotympanum and inferiorly to the AES

• . The cochleariform process and the tensor fold with the tensor tympani canal represent the upper limit of protympanic space

• posteriorly promontorium.

• less important in middle ear surgery because chronic disease seldom involve this recess.

• but some important structures are in there. Tympanic portion of Eustachian tube starts from the protympanum and is usually 11–12 mm in diameter. It can present different shapes:

rectangular(35%), triangular (20%) irregular shape (45%) [31].

• Above and medially to the Eustachian tube opening runs the internal carotid artery.

• Bone over this structure couldbe thick or pneumatized with some cells in there (protympanic cells).

This variant is important because we canfind a bulging of the carotid artery, in some casescould be uncovered.we find protympanic cells in patients with

cholesteatoma involving the protympanic space, we have to pay more attention because these cells might hide the presence of cholesteatoma persistence.

SURGICAL SIGNIFICANCECOMPARTMENTAL SPREAD OF DISEASE

• By compartmentalisation of the middle ear, these folds may limit the disease process for a SOME time in one or more compartments, before spreading to other regions

• If cholesteatoma is contained in its sac and compartment, it may be possible to remove the sac entirely and preserve the underlying mucosal folds and the Viscera

• Surgery can thus be aimed at establishing proper communication between attic and the mesotympanum, rather than any radical procedures, like

1.Removal of the tensor fold often along with tensor tympani tendon

2.Removal of incus body and leaving incus long process attached to stapes and medialising the tympanic membrane over the long process of incus

If communication is thus reestablished there will not be the need to remove the mastoid cells in non suppurating ears

PATHWAYS OF SPREAD OF CHOLESTEATOMA

A.POSTERIOR EPITYMPANUM

• 1. prussacks space

Superior incudal space

aditus

antrum

• 2.floor of prussacks space

Post. Space of von troeltsch

mesotympanum

. super ior incu dal sp ace

. aditus ad ant rum

. mast oid ant rum ( chol la t er al t o oss ic les )

. mast oid air c ells2.. post. Meso tym panum ( t hr u floor of P spa ce int o post

pouc h of vo n t r oe lt sch)

1.Black arrow. superior incudal space. aditus ad antrum. mastoid antrum (chol lateral to ossicles). mastoid air cells2.dotted arrow post. Mesotympanum (thru floor of P S into post pouch of von troeltsch)

POSTERIOR MESOTYMPANUM• SINUS TYMPANI and

FACIAL RECESS

Through posterior tympanic isthmus

• Inf incudal space

• Aditus and then antrum

• Extension to mastoid (sac remains medial to ossicles)

• FACIAL RECESS

Through posterior tympanic isthmus

• Inf incudal space

• Aditus and then antrum• Extension to mastoid (sac

remains medial to ossicles heads)

ANTERIOR EPITYMPANUM• Anterior space of von

troelstch

• Mesotympanum• invagination of

epitympanum ant to malleus head & neck creates cholesteatoma that threatens horizontal F. N. and geniculate ganglion leading to 7th N dysfunction

. Ant to head of malleus, supratubal recess. Geniculate ganglion of 7th N

involves, facial N dysfunction. Downward growth into anterior

mesotympanum (protympanum) via Ant. Pouch of

von troltsch

VENTILATORY ANATOMY

epitympanum

Prussak’s Space Dysventilation & Attic Cholesteatoma

• The possibility of closure of the posterior pouch of von Tröltsch following thick mucus secretion formation during chronic inflammatory otitis is high.

• This event may cause a selective dysventilation of Prussak’s space and development of pars flaccida retraction pocket with adhesion to the malleus neck.

• THANK YOU FOR YOUR PATIENCE