Mucosal folds and ventilation of middle ear

Middle ear mucosal folds and ventilation of middle ear with clinical and applied anatomy

1. - dr.alka kapil (PG student,vimsar ) Mucosal folds and ventilation of middle ear

2. MIDDLE EAR EMBRYOLOGY Between third and seventh fetal months an endothelium-lined fluid pouch ( tubotympanic recess) grows extending from ET into the cleft Mesenchymal tissue of the MEC is gradually absorbed primitive tympanic cavity terminal end of the Tubotympanic recess buds into 4 sacci Saccus anticus , medius , superior and posterior Remnants of the mesenchyme Ligaments and blood vessels supplying the viscera of TC plane of contact between two neighboring pouches Mucosal folds forming

3. EMBRYOLOGY OF MIDDLE EAR SPACES By 7 th week IUL,concomitant growth of 2 nd branchial arch constricts the midportion of Tubotympanic recess forming-primary TC n primordial ET APvT Lateral attic n antrum IIS n PPvT AER SIS n Prussak’s space

4. MUCOSAL FOLDS ANATOMY Middle ear mucosal folds walls of middle ear to its contents and carry ligaments and blood vessels to the ossicles These folds may orient the progress of middle ear pathologies but are not true barriers against their extension extend from

5. There are 2 different types of mucosal folds: COMPOSITE FOLDS ligament + lining mucosa expanding air sacs meet preexisting ligament and cover it with mucosal membrane Anterior Malleal Ligament Fold Lateral Malleal Ligament Fold Posterior Incudal fold DUPLICATE FOLDS fusion of two expanding air sac walls (No interposing structure inbetween ) their positions change (extent of the expansion of each air sac varies in different individuals) Tensor tympani fold Lateral Incudomalleal Fold

6. Middle ear mucosal folds

7. Anterior p ortion of the neck of malleus Anterior Tympanic Spine anteriorly medial wall of anterior Pouch of Von Troltsch Posterior tympano-malleal fold Ligamental fold Posterior portion of the neck of malleus Posterior Tympanic spine medial wall of the posterior Pouch of Von Troltsch medial edge envelops posterior portion of Chorda Tympani Anterior tympano-malleal fold

8. . Part of the tympanic diaphragm neck of malleus – anterior attic wall reflected from the lateral wall of middle ear over:- Anterior Process and ligament of malleus Anterior Part of Chorda Tympani Low posterior part represents – anterior limit of Prussak’s space Anterior malleal ligament fold

9. . Middle portion of neck of malleus outer attic wall Posteriorly confluent with anterior descending portion of LIMF Usually it is complete and represents - Roof of Prussak’s space - Floor of Lateral Malleal space Defects - usually in thin posterior membranous part (7%) - provide direct communication between upper and lower epitympanic units Thick and strong to prevents progression of pars flaccida retraction Lateral malleal ligament fold Develop a fanlike spread Lateral incudomalleal fold

10. Part of tympanic diaphragm Lies superiorly in relation to the LMF Level is about 1mm higher than the roof of Prussak’s space Defect in its anterior portion (20%) Lateral incudomalleal fold Separates the upper lateral attic space from the lower lateral attic space

11. . Posteriorly - horizontal extension medially onto the body of incus n incudomalleal joint Laterally medial surface of the bony wall of scutum Anterior portion bends inferiorly towards the neck of malleus LMF posterior limit of Lateral Malleal space merges wid post. portion of

12. Superior surface of malleal head tegman Contains Superior malleal ligament divides attic into anterior and posterior part Superior malleal fold

13. Superior incudal fold Extend like superior incudal ligament Superior surface of incudal body tegman Divides posterior attic in medial and lateral attic

14. . Posterior incudal fold Runs between the fibers of Posterior Incudal ligament Medial incudal fold long process of incus tendon of Stapedial muscle afa PE

15. . Part of tympanic diaphragm embryology-fusion of saccus anticus with anterior saccule of saccus medius Tensor tympani tendon Transverse crest bony canal of TTM AML (supratubal ridge) (medially) (laterally) Lateral part closely related to most anterior portion of Chorda Tympani Separates the Anterior epitympanic recess supratubal recess Tensor Tympani fold anterior attic wall (about 1.5 mm lower than the roof of Prussak’s space)

16. . Thick peripheral portion ,thin and transparent central portion Some ears, TTF is complete –l/t total separation between anterior epitympanum and protympanum Majority of ears, TTF is incomplete direct communication between ET and STR to AER and then to posterior attic prevents attic dysventilation

17. . not fully horizontal – components are on different levels Made up of : 3 malleal ligaments ( anterior,posterior,lateral ) PIF TTF LIMF incus and malleus separates the upper unit of attic superiorly from lower unit of attic ( Prussak’s space) inferiorly Tympanic Diaphrarm This is why we call the prussack’s space the lower unit of attic

18. TYMPANIC DIAPHRAGM

19. Mesotympanum is connected with ET but the Attic and Mastoid are isolated from mesotympanum by Tympanic Diaphragm Attic aeration occurs through a 2.5mm opening in the TD called Tympanic Isthmus Extensions: Anteriorly - extends from tensor tympani muscle Posterosuperiorly - posterior incudal ligament Posteroinferiorly - pyramidal eminence Medially -limited by attic bone Laterally -limited by body and short process of incus and head of malleus Distance from TTM to anterior edge of PIL is 6mm TYMPANIC ISTHMUS Entire attic is ventilated through Tympanic Isthmus except the Prussak’s space - ventilated through post. pouch of Von Troltsch

20. . Tympanic isthmus is divided by medial incudal fold into 2 portions: a)Anterior tympanic isthmus - large open communication with the anterior epitympanum - Between TTM anteriorly and stapes posteroinferiorly - Diameter is 1-3 mm b) Posterior tympanic isthmus - less important - Between short process of incus and stapedius muscle

21. 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 ) 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 Therefore it is important to remove TTF during surgical treatment of middle ear disease to ensure a good ventilation of the attic region

22. MIDDLE EAR SPACES AND VENTILATION

23. Middle ear compartments

24. PROTYMPANUM Anterior to anterior 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 Superior extension of protympanum - supratubal recess Lies below the anterior attic Between superior border of tympanic orifice of ET and TTF ET TTF STR AER

25. HYPOTYMPANUM Crescent shaped space at the bottom of the middle ear inferior margin of fibrous annulus to inferior margin of cochlear promontory BOUNDARIES: 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 (may contain petrous apex cells ) Inferior wall – thin bony plate separating from jugular bulb Hypotympanic air cells – medial and inferior wall (may extend below the labyrinth to reach petrous apex cells – infralabyrinthine tract )

26. Surgical application Infracochlear approach through transcanal hypotympanotomy removal of bone n cells of medial wall drainage of petrous apex Retrofacial hypotympanotomy Dissection of retrofacial cells medial to the vertical segment of the facial nerve ( between the jugular bulb inferiorly and the posterior SCC superiorly ) without transposing facial nerve or taking down the posterior external auditory canal wall

27. RETROTYMPANUM Posterior aspect of the tympanic cavity medial and posterior to tympanic annulus Site of the highest incidence of middle ear pathologies especially retraction pockets and cholesteatoma Retrotympanum includes four spaces: 1. Lateral spaces( Facial recess) Medially – facial canal and pyramidal eminence Laterally – chorda tympani Superiorly – Incudal buttress (separates from aditus ad antrum) Inferiorly – chordo-facial angle (18 - 30 ) Chordal ridge – divides facial recess into : Facial sinus Lateral tympanic sinus

28. . 2. Medial spaces (Tympanic sinus) Depressions in posterior wall of middle ear Between CNVII n pyramidal eminence laterally and labyrinth medially Ponticulus divides tympanic sinus into: Posterior tympanic sinus Sinus Tympani

29. Endoscopic view of right middle ear showing sinuses and recesses of retrotympanum Posterior tympanic sinus Boundaries- superior to ponticulus Medial to pyramidal eminence and facial nerve 1 mm deep x 1.5 mm long posterior tympanic sinus is present in most middle ears confluent sinus During ME surgery,to reach PTS section of stapedial tendon n pyramidal process may be needed Sinus tympani largest sinus of the retrotympanum It lies medial to the mastoid portion of facial nerve lateral to the posterior SCC superiorly by ponticulus (1 ) n PE inferiorly by subiculum (2 ) n styloid eminence Variability shape size n depth-0.2 to 10mm ( avg 2mm) Type A - transcanal approach Type B- otoendoscope needed TypeC-transmastoid retrofacial approach Chordal ridge Pyramidal ridge PTS +ST

30. MESOTYMPANUM Central and biggest compartment but narrowest (depth – 2 mm) Boundaries: Medially – promontory Laterally – pars tensa Anteriorly – protympanum Posteriorly – retrotympanum Inferiorly – hypotympanum Superiorly – Tympanic diaphragm (separates from attic) Allows air from ET to Attic through tympanic isthmus

31. TYMPANIC MEMBRANE POUCHES Anterior pouch of Von Troltsch - Anterior Malleal fold pars tensa - Communicates with supratubal recess protympanum Posterior pouch of Von Troltsch -Posterior Malleal fold pars tensa -Develops posteroinferiorly to opens in the most cranial portion of mesotympanum -Main route of ventilation of Prussak’s space

32. EPITYMPANUM (ATTIC) Situated above the imaginary line passing through the short process of malleus Occupies 1/3 rd of the entire tympanic cavity Lodges the - head and neck of malleus - body and short process of incus

33. Boundaries of epitympanum a)lateral wall - sharpnell’s membrane - scutum b)posterior wall - almost entirely by aditus ad antrum c)medial wall - wall above the tympanic segment of facial n.erve and tensor tympani muscle - contains the lateral semicircular canal d)inferiorly - tympanic diaphragm divides attic into - upper unit above the diaphragm - lower unit ( i.e. Prussak’s space) below the diaphragm

34. . Lies 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 it communicates with mastoid cavity through aditus UPPER UNIT OF THE ATTIC

35. Compartments of upper unit of attic Superior Malleal fold with a coronal orientation divides the upper unit of attic into -posterior attic (larger) - anterior attic (smaller)

36. . POSTERIOR ATTIC Contains mainly posterior 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 attic (larger) n lateral posterior attic (smaller) Medial posterior attic aka Medial Incudal space Medially – lateral semicircular canal and fallopian canal Laterally – ossicles and superior Incudal fold Contains the tympanic isthmus which is the main route of aeration of whole epitympanum

37. Compartments of posterior attic 1.7mm MIS

38. . Lateral posterior attic Narrower Laterally – outer attic wall Medially – malleus head, incus body, superior Incudal fold Divided into : Upper lateral attic – Lateral Malleal Space and Superior Incudal Space Lower lateral attic – Inferior Incudal Space LIMF

39. Compartments of lateral attic Lies in a more superior position in relation to lateral Malleal space Limited inferiorly by incudomalleal fold which separates it from inferior Incudal space Superior Incudal space Lateral Malleal space Inferiorly - lateral Malleal fold Medially – malleus head and neck Laterally – outer attic wall Anteriorly – anterior Malleal fold Posteriorly – downward turning end of incudomalleal fold Superiorly – open (free communication with superior Incudal space) In incomplete lateral Malleal fold –LMS communicates with Prussak’s space AMF

40. LOWER LATERAL ATTIC (INFERIOR INCUDAL SPACE) Lies below the LIMF inferior to tympanic diaphragm Medially – short process and body of incus Laterally – scutum Ventilation occurs through mesotympanum This region of ventilation is limited - medially by medial Incudal fold and - anteriorly by the inter ossicular fold

41. Anterior to the head of malleus and SMF Cog :bony crest that extends inferiorly from tegmen superior to cochleariform process anterosuperior to malleus head divides anterior attic into Anterior malleal space posteriorly (s) Situated between head of malleus posteriorly and cog anteriorly ANTERIOR ATTIC OR ANTERIOR EPITYMPANUM Anterior epitympanic recess anteriorly (l) AER AMS

42. Anterior epitympanic recess/sinus or sinus epitympani BOUNDARIES: Anteriorly – zygomatic root Posteriorly – cog Superiorly – anterior part of tegmen tympani Laterally – scutum Medially – anterior portion of the tympanic part of facial nerve and geniculate ganglion Floor _ cochleariform process and TTF AER

43. Clinical application 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 the TTF is complete – blocks aeration of anterior epitympanum from anterosuperior mesotympanum creating dysventilation syndrome Posterior tympanotomy + resection of the cog and TTF

44. . Formed from posterior pouch of Von Troltsch as a prolongation of either low/high portion of superior Saccus Boundaries - Roof : lateral Malleal fold - Floor : neck of malleus - Anterior : AMLF - Laterally : pars flaccida and scutum - Posteriorly : opened to posterior Pouch of Von Troeltsch Ventilation route is independent of the upper unit of attic through posterior pouch of Von Troeltsch rough and narrow when compared to tympanic isthmus Lower unit of attic ( Prussak’s space)

45. Clinical applications Prussak’s space dysventilation and attic cholesteatoma COM thick mucus secretions closure of post. Pouch of Von Troltsch SELECTIVE DYSVENTILATION OF PRUSSAK’S SPACE pars flaccida retraction pocket with adhesion to malleus neck

46. Attical cholesteatoma growth pattern From the Prussak’s space cholesteatoma can extend through one of the following three tracts: ( 1 ) through the posterior pouch of von Tröltsch to the lower lateral attic ( IIS ) ( 2 ) through a defect in the ( LMF ) to the LMS and then to the SIS or ( 3 ) from the lateral malleal space through the SMF to the anterior attic

47. Thank you !