THE MIDDLE EAR CLEFT

Presenter -Dr.Razal M SherifModerator -Dr.Jyothi Swarup R

THE MIDDLE EAR CLEFT

• Eustachian Tube anteriorly

• Middle ear Cavity/Tympanic Cavity

• Aditus • Mastoid Antrum• Mastoid Air Cells

posteriorly

Middle Ear Cavity• The tympanic cavity

o irregular, air-filled space within the temporal bone o between the tympanic membrane laterally and the

osseous labyrinth of inner ear medially. • Six sided Cavity

o Roofo Floor o Anterior Wallo Posterior Wallo Medial Wall o Lateral Wall

• Contains auditory ossicles ,Intratympanic Muscles

ROOF Is a thin bony plate

separates the middle ear from the middle cranial fossa called as Tegmen tympani formed by both the petrous and squamous portions of

the temporal bone . Petrosquamous suture line,

does not close until adult life, can provide a route of access for infection into the

middle cranial fossa from middle ear in children.

FLOOR• Thin bone separates the cavity from the dome of

the Jugular bulb. • In some cases the floor may be deficient and the

jugular bulb is then covered only by fibrous tissue and a mucous membrane.

LATERAL WALL• Main part is formed By the Tympanic membrane.• Superiorly an area of Bone called SCUTUM (outer

attic wall.)

ANTERIOR WALL• The lower-third of the anterior wall

o consists of a thin plate of bone covering the internal carotid artery

• The middle-third comprises o the tympanic orifice of the Eustachian tube, which is

oval and 5 x 2mm in size.

MEDIAL WALLseparates the Middle ear from the Inner ear.

• Promontory-o bulging part of on the medial wall which overlies the

basal turn of the cochleao has small grooves on its surface containing the nerves

which form the tympanic plexus. • Tympanic plexus

• Oval Windowo Behind and above the promontory is the oval windowo that connects the tympanic cavity with the vestibule,

closed by the footplate of the stapeso it is 3.25 mm long and 1.75 mm wide.

• Round windowo RW membrane is usually out of sight, obscured by the

overhanging edge of the promontory

Ponticulus & Subiculum

• Two small bony projections are present on the medial wall, posterior to promontory.

• Ponticuluso Is the upper projection

posterosuperior to promontory.o Above the ponticulus is the

Oval Window• Subiculum

o Lower projection posteroinferior to promontory

o Below the subiculum is the round window

• Facial Nerve canal (or Fallopian canal) o runs above the promontory and oval window in an

anteroposterior direction. • Processus cochelariformis

o a curved projection of bone on which the tendon of the tensor tympani muscle takes a hook and turns laterally to get attached to neck of malleus.

o This forms the landmark for 1st genu of facial nerve – Posterosuperior to processus cochelariformis

POSTERIOR WALL • The posterior wall is wider above than below.• Aditus - A large irregular opening in its upper

part• Fossa incudis – A small depression below the

aditus, it houses the short process of the incus and its suspensory ligament.

• Pyramid - a small hollow conical projection with its apex pointing anteriorly. o This houses the stapedius muscle and tendon, which

inserts into the posterior aspect of the neck of stapes. o Nerve to stapedius runs through the hollow canal with in

the pyramid.

Facial Recess & Sinus tymapni

Facial recess - A 3D space situated between the • tympanic annulus and chorda tymapni laterally• Pyramid and vertical portion of facial nerve mediallySinus tympani – A 3D space situated between• Pyramid and vertical portion of facial nerve laterally• Ponticulus medially• Also extends deep to promontory• the most inaccessible site in the middle ear• Cholesteatoma which has extended to the sinus tympani is

extremely difficult to eradicate

Division Of Middle Ear Cavity• EPITYMPANUM/

ATTIC• MESOTYPANUM• HYPOTYMPANUM

EPITYMPANUM/ATTIC• Middle ear cavity above the level of anterior and

posterior Malleolar folds • Contains

o Head of Malleus, Body of incus, ossicular ligaments and Mucosal folds.

Prussack Space • Space between Pars flacida laterally and Neck of

Malleus medially. • It is the primary site of acquired Cholesteatoma

MESOTYPANUM• Part lying Medial to pars Tensa

o and its air filled spaceo Conatins

• handle of MALEUS• long process of Incus,• Stapes

HYPOTYMPANUM• Part lying below the lower margin of Tympanic

membrane• Contains

o Bulge produced by the jugular Bulb

• If the floor is deficient thus jugular bulb may project into tympanic cavity.

Contents Of Middle Ear

• Ossicles o Malleuso Incuso Stapes

• Muscles of Tympanic Cavityo Tensor Tympanio Stapedius Muscle

The Malleus• Largest of the three ossicles - 9mm length • It Has Head, Neck, Anterior and Lateral Process,

Handleo Suspended by the superior ligament between head and

the tegmen tympani.• Head has saddle - shaped facet on its

posteromedial surfaceo to articulate with the body of the incus.

• An anterior ligament arises from the anterior process to insert into the petrotympanic fissure.

Head

NeckAnterior Process

Handle

LateralProcess

The Incus• It has a Body, Short Process and a long process

and a lenticular process• body of the incus

o is suspended by the superior incudal ligament that is attached to the tegmen tympani.

• Long process o extends downwards behind the handle of malleuso articulates with the head of the stapes by its lenticular

process.

• Short processo Lodges in the fossa incudis

• Lenticular processo Sometimes been called the fourth ossicle because of its

incomplete fusion with the tip of the long process

BodyShort Process

Facet

LenticularProcess

Long Process

The Stapes • Shaped like a stirrup • Consists of a head, neck, the anterior and

posterior crura and a footplate. • The Head points laterally and has a small

cartilage-covered depression for a synovial articulation with the lenticular process of the incus

• The foot plate directs medially and closes the Oval window.

• Stapedius tendon inserts into the posterior part of the neck and upper portion of the posterior crus.

Anterior Crus

Foot Plate

Head

Neck

Posterior Crus

Tympanic Plexus • It lies over the promontory

o Tympanic Branch of Glossopharygeal Nerve (Jacobsons Nerve)

o Sympathetic fibers from plexus round internal carotid artery.

• It supplies o Tympanic membrane(mucosal Surface)o Tympanic Cavityo Mastoid air cellso Bony estuation tube.o Carries secrtomotor fibers for parotid gland.

Chorda Tympani Nerve

• Branch of Facial Nerve• Arises from the vertical segment of facial nerve

below the pyramid• Crosses the posterior tympanic annulus • Runs over the posteror malleloar fold and in between

the handle of the malleus and long process ,above the attachment of the tensor tympani

• Leaves the middle ear through the canal of HUGAIER in the anterior wall

• It carries the taste sensation from ant 2/3 of tongue and secretomotor fibers to sub maxillary and sub lingual salivary glands.

Muscles In the Tympanic Cavity

• Tensor Tympanio Origin –

• cartilaginous part of Eustachian tube • Bony canal over ET• greater wing of sphenoid.

o Lies above the Eustachian tube • enters the middle ear via the canal for tensor tympani in the

anterior wall above the Eustachian tube opening.o Hooks around the processes cochelariformis on the posterior wall and

then changes the direction laterally and get inserted into neck of malleus.

o Action• It tenses the tympanic membrane, by pulling the malleus medially

and protects from barotrauma.

• Stapedius MuscleoOrgin - From the Pyramid in the

posterior wallo Insertion - Neck Of Stapeso Supplied by Facial Nerve (Nerve to

Stapideus)oAction - Pulls the Stapes Laterally

(Prevents Barotrauma)

Mastoid Process And Air Cells

• Mastoid Process o Part of temporal bone and situated behind the ear.o Development by 1 year.o Based on the degree of pneumatisations

• Celluar – 80% - Fully pneumatised• Sclerotic – Cells are replaced by dense bones.• Diploeic – Cells are less and small.

o Mastoid antrum• Biggest and most consistent air cell• Connected anteriorly to tympanic cavity via the

aditus and posteriorly to other air cells.• Relations

o Roof – Tegment antri – seperates from middle cranial fossa.

o Floor – Mastoid portion of temporal boneo Medial wall – Petrous portion of temporal boneo Lateral wall –Squamous portion of temporal bone

• Mac Ewans triangleo Landmark for mastoid antrumo Suprameatal crest aboveo Tangential to posterior meatal wall cutting the supra

meatal cresto Posterior margin of EAC

• Antrum lies postero superior spine of henle.

EUSTACHIAN TUBE• Connects middle ear cavity to nasopharynx.• From the anterior wall of middle ear it passes

downwards, forwards and medially.• Length 36mm

o Lateral 1/3rd Bonyo Medial 2/3rd is cartilaginous.

• The pharyngeal end situates 1cm behind and a little below the end of inferior turbinate.

• Functions of ETo In resting stage collapsed.

On chewing and yawning it opens up.Helps to equalize air pressure between middle ear and nasopharynx.

o Controls ventilation of middle ear cleft.o Helps drainage from middle ear.

• Muscles attached to ETo Tensor tympanio Tensor palatio Levator palatio Salpingopharynx.

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