mucosalfoldsofthemiddleear-180501021519.pptx

Mucosal folds in middle ear

1. Mucosal Folds of the Middle Ear Dr . Smruti Ranjan Samal First Year P.G. Department of E.N.T.,VIMSAR

2. Mucosal Fold Development Between 3 rd to 7 th month of fetal age , the mesenchymal tissue of middle ear cleft is absorbed. Simultaneously the primitive tympanic cavity develops by a growth of an endothelium-lined fluid pouch( Tubo Tympanic Recess) extending from the ET into the cleft. The terminal end of the TTR buds out to form 4 primary sacci - saccus anticus,saccus medius , saccus superior and saccus posticus The sacci or pouches start to enlarge in the middle ear cleft to replace the pre-existing mesenchyme.

3. Walls of the pouches  mucosal lining of middle ear Mucosal fold  Plane of contact between two neighbouring pouches.

4. 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- two types Composite fold : ligament+ lining mucosa ex : Ant.MLF , Lat.MLF and Post. Incudal fold Duplicate fold: fusion of two expanding air sac walls in absence of any interposing structure. ex: tensor tympani fold, lateral incudomalleal fold.

5. Important folds in middle ear: Anterior malleal fold Posterior malleal fold Anterior malleal ligamental fold Lateral malleal ligamental fold Superior malleal fold Superior incudal fold Posterior incudal fold Medial incudal fold Lateral incudomalleal fold Tensor tympani fold

6. Anterior Malleal Fold Origin : anterior portion neck of malleus Insertion : anteriorly on ant. tympanic spine Forms: medial wall of ant. Pouch of Von Troltsch Posterior Malleal Fold Origin : posterior portion neck of malleus Insertion : posteriorly on post. tympanic spine Forms: medial wall of post. Pouch of Von Troltsch

7. Anterior Malleal Ligamental Fold Originates from neck of malleus & extends to the anterior attic bony wall. Reflected from lateral wall of middle ear over - Ant. Process and ligament of malleus - Ant. Part of Chorda Tympani Low posterior part is broad and represents – ant. Limit of Prussak’s space.

8. 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

9. 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

10. 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

11. 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

12. 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

13. Tensor Tympanic 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

14. TTF results from fusion of saccus anticus & anterior saccule of the saccus medius Inclination angle of the TTF varies bet. 80 -100 depending on the variable growth of each saccule Determines the size of Supra Tubal Recess and Anterior Epitympanic Recess

15. TTF complete - total separation between ant. epitympanum and protympanum But in majority of population TTF is incomplete. Resulting in direct communication between ET to ant. Epitympanic recess and then to posterior attic. Hence prevents attic dysventilation.

16. Tympanic Diaphragm formed by Three malleal ligamental folds The posterior incudal fold The Tensor Tympani Fold The 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

17. Tympanic Isthmus Attic and mastoid are isolated from mesotympanum by Tympanic 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

18. Tympanic isthmus divided by the medial incudal fold into 2 portion 1. The Anterior Tympanic Isthmus Between TTM anteriorly & the stapes posteriorly 2. The Posterior tympanic Isthmus Between short process of incus & stapedial muscle

19. 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 Incomplete TTF 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 of TTF removal during surgical treatment of middle ear disease to ensure a good ventilation of the attic region

20. MIDDLE EAR SPACES anterior posterior

21. THE EPITYMPANUM (ATTIC) Situated above the imaginary line passing through the lateral process of malleus Lodges the - head and neck of malleus - body and short process of incus Boundaries Lateral wall – shrapnell’s membrane ( inf ) - scutum (sup) Posterior wall – almost entirely by aditus ad antrum

22. Medial wall- part of medial wall situated above the tympanic segment of the facial nerve & Tensor Tympani Muscle. - it contains lateral semicircular canal - this wall may pneumatized by supralabrynthine tract Posterior wall: by Aditus ad antrum Inferiorly: Tympanic Diaphragm divides attic into upper unit & lower unit ( Prussak”s space)

23. Upper Unit of Attic Above the tympanic diaphragm Medially – tympanic diaphragm separates upper unit from mesotympanum almost entirely except at tympanic isthmus Laterally – tympanic diaphragm separates the upper unit of attic from lower unit ( Prussak’s space) Posteriorly – communicates with mastoid cavity through aditus Superior Malleal fold in coronal orientation divide - posterior attic (larger) - anterior attic (smaller)

24. POSTERIOR ATTIC Contains mainly – post. part of the head of malleus, - body and short process of incus Distance from tip of incus to attic roof is 6 mm Superior Incudal fold – sagittal plane. Divides into - medial posterior (larger) -lateral posterior attic (smaller) Medial posterior attic Also called as Medial Incudal space Medially – lateral semicircular canal and fallopian canal Laterally – ossicles and superior Incudal fold Contains the tympanic isthmus

25. Lateral Posterior Attic Narrower Laterally – outer attic wall Medially – malleus head, incus body, superior Incudal fold Divided into 3 spaces 1.Upper lateral attic –Superior Incudal space,lateral Malleal space and 2.Lower lateral attic – inferior Incudal space Superior Incudal space Lies in a more superior position in relation to lateral Malleal space Inferiorly – incudomalleal fold (separates from inf. Incudal space)

26. Lateral Malleal space Lies above the lateral malleal fold Medially: malleus head & neck Laterally: outer attic wall Anterior : Anterior malleal fold Posteriorly: downward turning end of incudomalleal fold * Superiorly opened to superior incudal space

27. Lower Lateral Attic: Inferior Incudal Space Lies between short process and body of Incus medially & scutum laterally Anterior Attic or Anterior Epitympanum Anterior to the head of malleus and superior Malleal fold Cog – bony crest that extends inferiorly from the tegmen - superior to cochleariform process - anterosuperior to malleus head Divides anterior attic into 1. posterior (small) – Anterior Malleal Space 2. anterior (large) – Anterior Epitympanic Recess

28. Anterior Malleal Space Variable size Situated between head of malleus posteriorly and cog anteriorly

29. Anterior Epitympanic Recess Anterior epitympanic sinus/ Anterior epitympanic space/ sinus epitympani Superiorly – Anterior part of tegmen tympani Anteriorly – Root of zygoma Posteriorly – Cog Laterally – Scutum Medially – ant. portion of the tympanic portion of facial nerve and geniculate ganglion Floor - cochleariform process and tensor tympani fold

30. AER is highly important in cases of 1. recurrent otorrhea with central or anterior perforation not responding to medications 2. middle ear effusion that persists or recurs despite repetitive myringotomies with tube insertion 3. anterosuperiorly oriented retraction pocket In these cases if the TTF is complete – blocks aeration of anterior epitympanum from antero -superior mesotympanum creating dysventilation syndrome These patients will not respond to posterior atticotomy alone Resection of the cog and TTF is fundamental to create ant. Route of ventilation

31. Lower unit of attic ( Prussak’s space) Formed from posterior pouch of Von Troltsch as a prolongation of Superior Saccus Boundaries Roof – lateral Malleal fold Floor – neck of malleus Anterior – anterior Malleal fold Laterally – pars flaccida and lower edge of scutum Posteriorly – opened to post. Pouch of Von Troeltsch , posterior malleal fold Ventilation route is independent of the upper unit of attic Ventilation through posterior pouch of Von Troeltsch – rough and narrow when compared to tympanic isthmus

32. Prussak’s space dysventilation and attic cholesteatoma COM – thick mucus secretion – closure of post. Pouch of Von Troeltsch - selective dysventilation of Prussak’s space – pars flaccida retraction pocket with adhesion to malleus neck Initially sac of the retraction pocket remains small and superficial to ossicles Continued retraction and keratin accumulation – enlargement of sac and expansion via pathways of least resistance

33. PROTYMPANUM Lies ant. to a frontal line drawn through the ant. Margin of tympanic annulus Anteriorly – Eustachian tube Posteriorly – Mesotympanum Laterally – Lateral lamina ( separates PT from mandibular fossa) Medially – cochlea posteriorly and carotid canal anteriorly Roof – bony semicanal for Tensor tympani muscle and TTF SUPRATUBAL RECESS Superior extension of protympanum Lies between superior border of tympanic orifice of ET and TTF

34. Hypotympanum Lies below a horizontal plane from inf. margin of fibrous annulus to inferior margin of cochlear promontory Five walls Anterior wall – carotid canal medially and dense bone laterally Posterior wall – inferior part of styloid complex and vertical segment of facial nerve canal (may contain retrofacial cells) Outer wall – tympanic bone Medial wall – lower part of promontory and petrous bone Inferior wall – thin bony plate separating from jugular bulb

35. RETROTYMPANUM Posterior part of tympanic cavity medial & posterior to the tympanic annulus Vertical segment of Facial Nerve & the PE divides it- The Lateral Space( Facial Recess) Medially – facial canal and pyramidal eminence Laterally – chorda tympani Superiorly – Incudal buttress Inferiorly – chordo -facial angle (18 - 30 ) Chordal ridge – divides facial recess into - Facial sinus (superiorly) - Lateral tympanic sinus (inferiorly)

36. 2. The Medial Space Also called as the Tympanic sinus Ponticulus divides tympanic sinus to Posterior Tympanic Sinus(Superiorly ) Sinus tympani( Inferiorly)- Largest sinus of Retrotymp . In 10% population the sinus tympani and posterior tympanic sinus form one confluent recess Based on depth sinus tympani is of 3 type Type A(Shallow) Type B(intermediate) Type C(very deep)

37. Mesotympanum Narrowest & biggest compartment Boundaries Medially – promontory Laterally – pars tensa Anteriorly – protympanum Posteriorly – retrotympanum Inferiorly – hypotympanum Superiorly – Tympanic diaphragm Acts like a channel allowing air coming from ET to pass through the Tympanic Isthmus upward to provide aeration of whole attic

38. TYMPANIC MEMBRANE POUCHES 1. Anterior pouch of Von Troeltsch Situated between Anterior Malleal fold and pars tensa Communicates with supratubal recess and protympanum 2. Posterior pouch of Von Troeltsch Situated between posterior Malleal fold and pars tensa Develops posteroinferiorly and opens in the most cranial portion of mesotympanum Main route of ventilation of Prussak’s space