Intricacies of Middle Ear and Mastoid

8/8/2019 Intricacies of Middle Ear and Mastoid

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Dr N DDr N D ZingadeZingade


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The danger to the patient of an incompetent

operator, who does not know the manyanatomical details crowded together in the

narrow space of the temporal bone and their

extreme variability, is much greater here than

in any other region of the body

Textbook of Otology


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Middle ear cavity (tympanum)

B ox with four walls, a roof and a floor

Air filled space within the temporal bone

Three ossicles

Two muscles

NervesVessels


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E pitympanum

M edial wall : LSC and SSC ampullae

Tympanic portion of facial n

Structures : Head and neck of malleus

B ody of incus

Short pro and part of long pro of incus


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Mesotympanum

M edial wall : Tympanic portion of facial n

RWN

Structures : OW, RW, Stapes, Stapedius m,

canal for tensor tympani m


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H ypotympanum

Inferior to ETO and RWN

Structures : B ony trabeculae

B ony covering of J B


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Lateral wall

Tympanic membrane

Outer attic wall (Scutum of Leidy)

Three openings in the bone of the medial

surface of the lateral wall:

y Posterior canaliculus for chorda tympani n

y Petrotympanic (Glasserian) fissure

y Canal of Huguier


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R oof

Petrous portion of temporal bone

Squamous portion of the temporal bone

Petrosquamous suture: unossified in the

young and does not close until adult life


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F loor

Narrower than the roof

Jugular bulb

M ay be deficient

Junction of floor and the medial wall : inferior

tympanic canaliculus for Jacobsons n


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Anterior wall

Lower III

: Thin plate of bone covering CAPerforated by sup and inf

caroticotympanic n carrying symp

fibres to tymp plexus

M iddle III : Canal for tensor tymp m

ETO

Upper III : Pneumatized

ant epitympanic sinus


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Medial wall

Promontory

Oval window (fenestra vestibuli)

3.25mm x 1.75mmHorizontal portion of facial n : Pro coch

Round window (fenestra cochleae)

1.8 2.3mm

Ponticulus and subiculum


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P osterior Tympanum

Highest incidence of retractions &cholesteatomas : difficult to remove

F acial sinusPosterior tympanic sinus

Lateral tympanic sinusSinus tympani the largest


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P osterior wallP osterior wall

Wider above

aditusadantrum

Fossa incudis

Pyramid

F acial recess

chordo facial angle leads to M E C

( F acial recess approach )


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C ontents of M E C

Air

Ossicular assembly

I M Jt Saddle artI S Jt - B all & Socket art

M alleus : 7. 5 9 mm

Head, Neck, 3 processes

Ant & sup lig


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Incus : B ody, 2 processes

long pro precarious bl sup

lentiform pro ? IV ossicle

Stapes : Head, Neck, 2 crurae,

base(foot plate) : 3mm x1.4mm


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Muscles

Tensor tympani

N S med pte n (mand n)

Stapedius

N S facial n

Protection/Augmentation/Stabilization


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N erves

Chorda tympani

branch of V II n

post can- ant can( Glasserian fissure )

ant 2/3 tongue taste


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C ompartments

Sup mal fold - Ant mal space

Sup inc fold - Sup inc space

Med inc space

M esotymp - Inf inc space

Ant pouch of Von Troltsch

Post pouch of Von Troltsch

Prussacs space


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Mastoid antrum

14 mm :

9 mm :

7 mm :

Ant : a-a-aM ed : P S C, L S C

Lat : squ temp

Roof : teg antri

Post & F loor : mastoid portion


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C ont..

Variant III : S M S - cone shaped depression

EAC - ant wall(thick)bulge

SP - relatively long

Variant IV : S M S - absent

EAC - ant wall bulge/oval

SP - very long


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K orners S eptum

Petro squamous lamina

Embryological fusion: squ/pet of T B

Divides mast pro sup(squ)/deep(pet)

Consider if :

y Difficult to approach

y Small & constricted antrum

y Anomalous


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Air cells

Peri antral cells

Tegmental cells

Sinodural cells

Perisinusal cells

Central mastoid cells

M astoid tip cellsPerifacial cells

Zygomatic cells


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COR TICAL MAS TO IDEC TO MY


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SU MMAR Y

Temporal bone is uniquey Vol 1 Cubic inch / Olivey Concentration of vital structuresy Surrounded by pneumatic cellsM odern era of microear surgeryy Essential to understand the complex

anatomy of T B in all 3 dimentions.


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C ont

CT / M R / M RA imaging modalitiesy Proper imaging studyy Plan appropriate treatment

Otomicro surgeryy Taken tremendous strides with the pioneering work of

Zollner & Wullstein.y Clear & magnified view with microscope / endoscopey Precise removal of disease with drill enhancing

surgeons skill to eradicate disease & restore hearing


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Documents

Intricacies of Middle Ear and Mastoid