Spaces of middle ear and their surgical importance

one of the imp topics in ENT that should be understood very thoroughly if u want to pursue as an otologist.I tried to simplify the topic with simple diagrams and models for better understanding .

1. Spaces of middle ear and their surgical importance Speaker-DR SOUMYA

2. OVERVIEW EMBRYOLOGY MIDDLE EAR FOLDS MIDDLE EAR SPACES SURGICAL IMPORTANCE

3. 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.

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5. 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 .

6. 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.

7. 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

8. Embryology of MiddleEar Compartments . These sacci expand progressively to replace middle ear mesenchyme and mastoid mesenchyme . 1 ST arch cartilage-head of malleus Body of incus 2 nd arch cartilage- HOM,Long process of incus Stapes crurae Footplate – otic capsule

9. S.A S.M S.S S.P

10. 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.

11. 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 PRUS SPACE SIS

12. 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

13. 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 ROUND WIN. SINUS TYMP.

14. 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

15. 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

16. 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 .

17. 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 .

18. 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

19. 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.

20. 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 .

21. 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 .

22. 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.

23. POSTERIOR INCUDAL FOLD The posterior incudal fold is the fold that runs between the fibres of the posterior incudal ligament

24. 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.

25. 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.

26. 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

27. 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.

28. 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 .

29. 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:

30. 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.

31. 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

32. 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.

33. 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)

34. POSTERIOR TYMPANIC ISTHMUS between the short process of the incus and the stapedial muscle. inconsistent.

35. 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)

36. 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

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

38. 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 .

39. 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:

40. 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:

41. 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 .

42. 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.

43. 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.

44. 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.

45. 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

46. MEDIAL SPACES OF RETROTYMPANUM depressions in the posterior wall of the middle ear between the facial nerve and pyramidal eminence laterally labyrinth medially….

47. 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.

48. 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.

49. 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.

50. 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.

51. Surgical importance During cholesteatoma surgery a good exposition 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

52. 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.

53. 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.

54. 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.

55. 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.

56. 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.

57. CLASSIFICATION ST’S DEPTH 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

58. 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 .

59. 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 .

60. 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

61. 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:

62. 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

63. 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.

64. 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

65. 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

66. 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 .

67. 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 .

68. 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 .

69. 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].

70. 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 can find a bulging of the carotid artery, in some cases could 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.

71. SURGICAL SIGNIFICANCE COMPARTMENTAL 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

72. 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

73. PATHWAYS OF SPREAD OF CHOLESTEATOMA

74. A.POSTERIOR EPITYMPANUM 1. prussacks space Superior incudal space aditus antrum 2.floor of prussacks space Post. Space of von troeltsch mesotympanum

75. . superior incudal space . aditus ad antrum . mastoid antrum ( chol lateral to ossicles ) . mastoid air cells 2. . post. Mesotympanum (thru floor of P space into post pouch of von troeltsch ) 1.Black arrow . superior incudal space . aditus ad antrum . mastoid antrum ( chol lateral to ossicles ) . mastoid air cells 2.dotted arrow post. Mesotympanum (thru floor of P S into post pouch of von troeltsch )

76. 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)

77. 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 7 th N dysfunction . Ant to head of malleus , supratubal recess . Geniculate ganglion of 7 th N involves, facial N dysfunction . Downward growth into anterior mesotympanum ( protympanum ) via Ant. Pouch of von troltsch

78. VENTILATORY ANATOMY

79. epitympanum

80. 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.

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