Anatomy & Physiology of Eustachian Tube

Seema S

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History

• Bartolomeus Eustachius first described it

as pharyngo-tympanic tube in 1562.

• Antonio Valsalva named it Eustachian

tube.

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Embryology

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Embryology

• Develops from tubo-tympanic recess, derived from endoderm of 1st pharyngeal pouch.

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Anatomy

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Anatomy

• 36 mm long in adults.

• Directed anteriorly, inferiorly & medially from anterior

wall of M.E., forming angle of 450 with horizontal

• Enters naso-pharynx 1.25 cm behind posterior end of

inferior turbinate.

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Angulation

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Pharyngeal opening

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Parts

• Lateral 1/3 is bony

• Medial 2/3 is fibro-

cartilaginous.

• Junction b/w 2 parts is

isthmus, narrowest part

of Eustachian Tube.

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Anatomy of medial 2/3rd

Cartilage plate lies postero-

medially & consists of medial

+ lateral laminae separated

by elastin hinge. Fibrous

tissue + Ostmann’s fat pad lie

antero-laterally.

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Anatomy

• Lining epithelium: pseudo stratified ciliated columnar

• Arterial supply: ascending pharyngeal &

middle meningeal arteries

• Venous drainage: pharyngeal & pterygoid

venous plexus

• Lymphatic drainage: retropharyngeal node12

Anatomy

Muscle attachments:

1. tensor veli palatini or dilator tubae

2. levator veli palatini

3. salpingopharyngeus

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Nerve supply

• Tubal mucosa – tympanic branch of cranial

nerve IX

• Tensor veli palatini - Mandibular branch of

trigeminal

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• Levator veli palatiniPharyngeal plexus

• Salpingo pharygeus

Endoscopic Anatomy

• Medial end forms tubal

elevation / torus tubarius

• Lymphoid collection over

torus is called Gerlach’s tubal

tonsil.

• Postero-superior to torus is

fossa of Rosenmüller.15

Adult vs. Child (< 7 yr)

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Adult vs INFANT

ADULT INFANT

Length 36 mm 18 mm

Angle with horizontal 45 0 10 0

Lumen Narrower Wider

Angulation at isthmus Present Absent

Cartilage Rigid Flaccid

Elastic recoil Effective Ineffective

Ostmann’s fat More Less17

Infant E. tube

• wider shorter and more horizontal

So secretions even milk can regurgitate fromnasopharynx to middle ear if infant not fed in headup position

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Physiology

• Bony part is always open.

• Fibro-cartilaginous part is closed at rest.

• Opens on:

1. swallowing

2. yawning

3. sneezing

4. forceful inflation 19

Physiology

• Opens actively by contraction of tensor veli palatini &

passively by contraction of levator veli palatini (it

releases the tension on tubal cartilage).

• Closes by elastic recoil of elastin hinge + deforming

force of Ostmann’s fat pad.

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E.T. opening

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Functions

1. Ventilation & maintenance of atmospheric

pressure in middle ear for normal hearing

2. Drainage of middle ear secretions into

nasopharynx by muco-ciliary clearance,

pumping action of Eustachian tube &

presence of intra-luminal surface tension

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Functions

3. Protection of middle ear from:

– Ascending nasopharyngeal secretions due to

narrow isthmus & angulation between 2 parts of

E.T. at isthmus

– Pressure fluctuations

– Loud sound coming through pharynx

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Functions

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Conditions of Dysfunction

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Tests for E.T. function

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ET Function Tests

• VALSALVA TEST– Principle: positive pressure in the nasopharynx causes air

to enter the Eustachian tube

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– Tympanic membrane perforation- a hissing sound

– Discharge in the middle ear- cracking sound

– Only 65% of persons can do this test.

– Contraindications:

• Atrophic scar of tympanic membrane which can rupture

• Infection of nose & nasopharynx

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• Politzer test

– Done in children who are unable to perform valsalvatest.

– Olive shaped tip of the politzer’s bag is introduced into the patient’s nostril on the side of which the tubal function is desired to be tested

– Other nostril closed & the bag compressed while at the same time the patient swallows or says “ik,ik,ik”

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– By means of an auscultation tube a hissing sound is heard.

– Compressed air can also be used instead of politzer’s bag

– Test is also therapeutically used to ventilate the middle ear.

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• Catheterisation

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• Procedure for Catheterisation

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•Nose is anaesthetised

•E Tube catheter passed along the floor of nose till it reaches naso pharynx

•Rotated 90deg medially

•Pulled back till posterior border of nasal septum engaged

•Rotated 180 deg laterally – tip lies against tubular opening

• Politzer’s bag connected

• Air insufflated

• Entry of air to middle ear verified (lateral bulging of t.m)

6. E.T. catheterization

Air pushed into E.T. catheter by squeezing Politzer bag.

Examiner hears by Toynbee auscultation tube put in

pt's ear.

Blowing sound = normal E.T. patency

Bubbling sound = middle ear fluid

Whistling sound = partial E.T. obstruction

No sound = complete obstruction of E.T. 33

– Complications:

• Injury to Eustachian tube opening

• Bleeding from nose

• Transmission of nasal & nasopharyngeal infection into middle ear

• Rupture of atrophic area of tympanic membrane

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• Toynbee’s test

– Uses negative pressure

– Ask the patient to swallow while nose is pinched

– Draws air from middle ear to nasopharynx – inward movement of t.m.

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• Tympanometry (inflation-deflation test)

– +Ve & -ve pressures are created in the external ear and the patient swallows repeatedly

– in patients with perforated or intact tympanic membrane

• Radiological Test

• Saccharine/ Methylene blue Test

– Saccharine solution

– Methylene blue dye

– Ear drops into ear with TM perforation

• Sonotubometry

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Disorders of ET

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Tubal Blockage

EROSION OF INCUDOSTAPEDIAL JOINT

RETRACTION POCKET/CHOLESTEATOMA

ATELECTATIC EAR/PERFORATION

OME(THIN WATERY OR MUCOID DISCHARGE)

TRANSUDATE IN ME/HAEMORRHAGE PROLONGED TUBAL BLOCKAGE/DYSFUNCTION

RETRACTION OF TM

-VE PRESSURE IN ME

ABSORPTION OF ME GASES

ACUTE TUBAL BLOCKAGE

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mechanical• intrinsic

• Extrinsic

functional •Collapse

both

Block

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• Symptoms of tubal occlusion

– Otalgia

– Hearing loss

– Popping sensation

– Tinnitus

– Disturbances of equilibrium

• Signs of tubal occlusion

– Retracted TM

– Congestion along the handle

of malleus and pars tensa

– Transudate behind TM

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• Clinical causes of ET obstruction

– Upper respiratory tract infection

– Allergy

– Sinusitis

– Nasal polypi

– DNS

– Hypertrophic adenoids

– Nasopharyngeal tumour/ mass

– Cleft palate

– Submucous cleft palate

– Down’s syndrome41

Adenoids

• Adenoids cause tubal dysfunction by:

– Mechanical obstruction of the tubal opening

– Acting as reservoir for pathogenic organisms

– Inflammatory mediators in allergy cause tubal blockage

• Adenoids can cause otitis media with effusion or recurrent acute otitis media

• Adenoidectomy

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large adenoid blocking left et

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Cleft palate

• Tubal dysfunction due to:

– Abnormalities of torus tubaris

– Tensor veli palatini doe not insert into the torus tubaris

• Otitis media with effusion is common in these patients

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Down’s syndrome

• Dysfunction due to:

– Poor tone of tensor veli palatini

– Abnormal shape of nasopharynx

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Barotrauma

• Non suppurative condition resulting from failure of E Tube to maintain M Ear pressure at ambient atmospheric level

• Cause:– Rapid descent during air flight– Under water diving– Compression in pressure chamber

• When atm pressure > M E pressure by critical pressure of 90mm Hg E T gets locked – Negative pressure in ME

• T M retraction - transudation/ h’ge

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Retraction Pockets & ET

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• Any obstruction in the ventilation pathway retraction pockets or atelectasis of tympanic membrane

– Obstruction of Eustachian tube total atelectasis of tm

– Obstruction at additus cholesterol granuloma & collection of mucoid discharge in mastoid air cells

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• Other changes

– Thin atrophic TM

– Cholesteatoma

– Ossicular necrosis

– Tympanosclerotic changes

• Management

– Repair of irreversible pathologic processes

– Establishment of ventilation

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Patulous Eustachian Tube

• ET is abnormally patent

• Causes:

– Idiopathic, rapid weight loss, pregnancy (esp 3rd

trim) & multiple sclerosis

• Chief complaints

– Autophony, hearing his own breath sounds

• Pressure changes in the nasopharynx are easily transmitted to the ME

• Movements of the TM can be seen with inspiration & expiration

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• Management

– Acute cases Usually self-limiting

– Weight gain & oral administration of KI

– Long standing cases = cauterisation/ insertion of grommet

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EXAMINATION OF EUSTACHIAN TUBE

Pharyngeal end of eustachian tube :posterior rhinoscopy, rigid nasal endoscope or flexible nasopharyngoscope

Tympanic end :microscope or endoscope

Simple examination of TM may reveal retraction pockets or fluid in the me

Movements of TM with respiration point to patulous eustachian tube

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• Aetiologic causes of eustachian tubedysfunction assessed through:

– Nasal examination

– Endoscopy

– Tests of allergy

– CT scan of temporal bones

– MRI to exclude multiple sclerosis

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