Date post: | 03-Jul-2015 |
Category: |
Health & Medicine |
Upload: | ajusarma |
View: | 1,572 times |
Download: | 8 times |
Anatomy & Physiology of Eustachian Tube
Seema S
1
History
• Bartolomeus Eustachius first described it
as pharyngo-tympanic tube in 1562.
• Antonio Valsalva named it Eustachian
tube.
2
Embryology
3
Embryology
• Develops from tubo-tympanic recess, derived from endoderm of 1st pharyngeal pouch.
4
5
Anatomy
6
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.
7
Angulation
8
Pharyngeal opening
9
Parts
• Lateral 1/3 is bony
• Medial 2/3 is fibro-
cartilaginous.
• Junction b/w 2 parts is
isthmus, narrowest part
of Eustachian Tube.
10
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.
11
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
13
Nerve supply
• Tubal mucosa – tympanic branch of cranial
nerve IX
• Tensor veli palatini - Mandibular branch of
trigeminal
14
• 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)
16
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
18
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.
20
E.T. opening
21
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
22
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
23
Functions
24
Conditions of Dysfunction
25
Tests for E.T. function
26
ET Function Tests
• VALSALVA TEST– Principle: positive pressure in the nasopharynx causes air
to enter the Eustachian tube
27
– 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
28
• 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”
29
– 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.
30
• Catheterisation
31
• Procedure for Catheterisation
32
•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
34
• 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.
35
• 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
36
Disorders of ET
37
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
38
mechanical• intrinsic
• Extrinsic
functional •Collapse
both
Block
39
• 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
40
• 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
42
43
large adenoid blocking left et
44
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
45
Down’s syndrome
• Dysfunction due to:
– Poor tone of tensor veli palatini
– Abnormal shape of nasopharynx
46
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
47
Retraction Pockets & ET
48
• 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
49
• Other changes
– Thin atrophic TM
– Cholesteatoma
– Ossicular necrosis
– Tympanosclerotic changes
• Management
– Repair of irreversible pathologic processes
– Establishment of ventilation
50
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
51
• Management
– Acute cases Usually self-limiting
– Weight gain & oral administration of KI
– Long standing cases = cauterisation/ insertion of grommet
52
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
53
• Aetiologic causes of eustachian tubedysfunction assessed through:
– Nasal examination
– Endoscopy
– Tests of allergy
– CT scan of temporal bones
– MRI to exclude multiple sclerosis
54
55