Endoscopic ear surgery (EES) is a minimally invasive approach similar to standard microscopic techniques. Initially endoscope was used to assist traditional operations to visualize middle ear hidden areas. Therefore, instrumentals, optics, light and camera systems improvements allowed endoscope to be a main tool in middle ear surgery.

Middle ear is an irregular cavity filled with air in the center of the temporal bone in tympanic portion (Figure 25-1).

Limits

• 
  

  Superior: called tegmen, a plate of bone below middle cranial fossa dura and temporal lobe.

  
  
• 
  

  Inferior: narrow and thin plate of bone above jugular bulb. Careful approach to middle ear is necessary if patient has a high or dehiscent jugular bulb.

  
  
• 
  

  Medial: cochlear promontory (cochlea basal turn), tympanic plexus (Jacobson nerve), oval and round windows, tympanic segment of facial nerve, and lateral semicircular canal.

  
  
• 
  

  Lateral: tympanic membrane, annulus fibrosus, and scutum.

  
  
• 
  

  Anterior: formed by petrous bone. From superior to inferior:

  
  
  
  
  1. 
     

     Tensor tympani muscle canal

     
     
  2. 
     

     Eustachian tube

     
     
  3. 
     

     Internal carotid artery (vertical segment)

  
  
• 
  

  Posterior: formed by the petrous bone and aditus ad antrum that communicates attic and mastoid antrum.

Epitympanum (Attic)

• 
  

  It is the upper portion of middle ear cavity above tympanic membrane level and an imaginary plane through malleus short process (Figures 25-2, 25-3, and 25-4).

  
  
• 
  

  Communicates with mastoid antrum.

  
  
• 
  

  Plays a fundamental role in ventilation routes.

  
  
• 
  

  Limits:

  
  
  
  
  1. 
     

     Superior: tegmen tympani

     
     
  2. 
     

     Inferior: tympanic diaphragm and isthmus

     
     
  3. 
     

     Medial: facial nerve canal and lateral semicircular canal

     
     
  4. 
     

     Lateral: pars flaccida of tympanic membrane and scutum (Chaussé spur)

     
     
  5. 
     

     Anterior: zygomatic root

     
     
  6. 
     

     Posterior: incudal fossa and aditus ad antrum

  
  
• 
  

  Posterior epitympanum compartment is posterior to superior malleal fold:

  
  
  
  
  1. 
     

     Posterior part of malleus head

     
     
  2. 
     

     Incus body and short process

     
     
  3. 
     

     Posterior route ventilation: most important pathway to attic

  
  
• 
  

  Anterior epitympanum compartment is anterior to superior malleal fold:

  
  
  
  
  1. 
     

     Anterior portion of malleus head

     
     
  2. 
     

     Anterior route of ventilation: accessory pathway to attic

  
  
• 
  

  Tympanic diaphragm is made of various folds and ligaments:

  
  
  
  
  1. 
     

     Posterior incudal ligament

     
     
  2. 
     

     Lateral incudomalleal fold

     
     
  3. 
     

     Lateral malleal fold

     
     
  4. 
     

     Lateral malleal ligament

     
     
  5. 
     

     Anterior malleal fold

     
     
  6. 
     

     Anterior malleal ligament

     
     
  7. 
     

     Tensor tympani fold (or posterior malleal fold)

     
     
  8. 
     

     Tensor tympani muscle tendon

  
  
• 
  

  Tympanic isthmus is a 2.5-mm opening in the tympanic diaphragm that ventilates entire attic.

  
  
  
  
  1. 
     

     Anterior tympanic isthmus: between incudostapedial joint and tensor tympanic muscle tendon. It is the largest and most important ventilation route to attic. Granulation tissues and web blockages at this region lead to attic selective dysventilation, chronic edema, exudate, inflammation, infections, retraction pockets, and cholesteatoma.

     
     
  2. 
     

     Posterior tympanic isthmus: posterior to incudostapedial joint, between stapedial muscle tendon, pyramidal eminence, and incus short process.

  
  
• 
  

  Prussak space:

  
  
  
  
  1. 
     

     Superior: lateral malleal fold (tympanic diaphragm)

     
     
  2. 
     

     Inferior: malleus neck

     
     
  3. 
     

     Medial: malleus head

     
     
  4. 
     

     Lateral: pars flaccida of tympanic membrane (Sharpnell membrane)

     
     
  5. 
     

     Anterior: anterior malleal fold

     
     
  6. 
     

     Posterior: posterior malleal fold

     
     
  7. 
     

     Ventilation route: independent, rough, narrow, through posterior pocket of von Troltsch. Thick and viscous secretions may close posterior pocket and lead to sectorial dysventilation of Prussak space, pars flaccida membrane retraction, and adhesion to malleus neck. This could happen without any involvement of anterior and posterior epitympanum, aditus, and mastoid cells.

Mesotympanum

• 
  

  It is the central, the biggest, and the narrowest compartment of middle ear (Figure 25-5).

  
  
• 
  

  Limits:

  
  
  
  
  1. 
     

     Superior: tympanic diaphragm, open to epitympanum (attic)

     
     
  2. 
     

     Inferior: open to hypotympanum (Figures 25-6 and 25-7)

     
     
  3. 
     

     Medial: promontory

     
     
  4. 
     

     Lateral: pars tensa of tympanic membrane

     
     
  5. 
     

     Anterior: open to protympanum

     
     
  6. 
     

     Posterior: open to retrotympanum

  
  
• 
  

  Structures:

  
  
  
  
  1. 
     

     Malleus: handle (manubrium)

     
     
  2. 
     

     Incus: long process and lenticular process

     
     
  3. 
     

     Stapes: capitulum, anterior and posterior crus, footplate, stapedial tendon

     
     
  4. 
     

     Cochlear promontory (cochlea basal turn)

     
     
  5. 
     

     Tympanic plexus (Jacobson nerve) and inferior tympanic artery (branch of the ascending pharyngeal artery)

     
     
  6. 
     

     Caroticotympanic arteries (branches of the internal carotid artery)