Anatomy & Physiology of Eustachian Tube Dr. Vishal Sharma

History & Embryology Bartolomeus Eustachius first described it as pharyngo-tympanic tube in 1562. Antonio Valsalva named it Eustachian tube. Develops from tubo-tympanic recess, derived from endoderm of 1st pharyngeal pouch.

Bartolomeus Eustachius

Antonio Maria Valsalva

Embryology

Anatomy

Anatomy 36 mm long in adults. Directed anteriorly, inferiorly & medially from anterior wall of M.E., forming angle of 450 with horizontal & sagittal planes. Enters naso-pharynx 1.25 cm behind posterior end of inferior turbinate.

Angulation

Pharyngeal opening

Parts Lateral 1/3 is bony Medial 2/3 is fibro-cartilaginous. Junction b/w 2 parts is isthmus, narrowest part of Eustachian Tube.

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.

Anatomy Muscle attachments: 1. tensor veli palatini or dilator tubae 2. levator veli palatini 3. salpingopharyngeus 4. tensor tympani Nerve supply: 1. Sphenopalatine ganglion 2. Mandibular nv 3. Tympanic plexus

Anatomy Lining epithelium: respiratory epithelium Arterial supply: ascending pharyngeal & middle meningeal arteries Venous drainage: pharyngeal & pterygoid venous plexus Lymphatic drainage: retropharyngeal node

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.

Adult vs. Child (< 7 yr)

Adult vs. Child (< 7 yr) 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 Less

Physiology Bony part is always open. Fibro-cartilaginous part is closed at rest. Opens on: 1. swallowing 2. yawning 3. sneezing 4. forceful inflation

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.

E.T. opening

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

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

Functions

Conditions of Dysfunction

Bluestone’s Flask Model

Adult vs. Pediatric

TM perforation & nose blowing

O.M.E. & Barotrauma

Grommet insertion in O.M.E.

Tests for E.T. function

1. Valsalva Maneuver Forced expiration with mouth & nose closed. Otoscopy shows lateral bulging of Tympanic membrane

2. Frenzel Maneuver Hands free Valsalva for pilots Compression of nasopharyngeal air by muscles of tongue Otoscopy shows lateral bulging of tympanic membrane

2. Frenzel Maneuver

3. Toynbee Maneuver More physiological Swallowing with mouth & nose closed Otoscopy shows retraction of tympanic membrane

4. Pneumatic otoscopy & Siegelization Air pressure is alternately increased & decreased within external auditory canal Mobility of tympanic membrane is observed Normal mobility indicates good patency of Eustachian tube

Siegelization

Pneumatic Otoscope

Normal Tympanic Membrane

Eustachian Tube dysfunction

Early otitis media with effusion

Late otitis media with effusion

Acute suppurative otitis media

Ear drum perforation

5. Politzerization

Politzer Bag

5. Politzerization Rubber tube attached to a Politzer bag put into one nostril & both nostrils pinched Patient asked to swallow or repeat “k” Politzer bag is squeezed simultaneously Otoscopy shows lateral bulging of ear drum in patent Eustachian tube

6. E.T. catheterization

Eustachian tube catheter

6. E.T. catheterization E.T. catheter passed along nasal floor till it touches posterior wall of naso-pharynx. Catheter rotated 90° medially & pulled forward till it impinges on posterior nasal septum. Catheter rotated 180° laterally, & its tip inserted into opening of E.T. Politzer bag attached to outer end of catheter

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.

7. Tymapanometry

7. Tymapanometry Type C = E.T. dysfunction Type B = fluid in middle ear

8. William’s pressure equalization test 200 mm H2O pressure is created in patient’s external auditory canal Patient asked to swallow 10 times Residual pressure in patient’s external auditory canal after 10th swallow is noted Test repeated with -ve 200 mm H2O pressure created in patient’s external auditory canal

William’s Test Residual Pressure Result Up to + 50 mm H2O normal E.T. function + 51 to + 100 mm H2O mild dysfunction + 101 to + 199 mm H2O moderate dysfunction + 200 mm H2O severe dysfunction

9. Sono-tubometry Sound made in pt’s nasal cavity & detected with stethoscope in patient’s external auditory canal Loud sound = patent Eustachian tube 10. Eustachian tube Salpingogram Dye instilled through E.T. catheter & X-ray taken 11. C.T. scan & M.R.I. of skull

12. Trans-nasal E.T. video-endoscopy 13. Test for E.T. patency in T.M. perforation Saccharine crystal / antibiotic ear drop / methylene blue placed in middle ear via ear drum perforation. Sweet taste / bitter taste / blue staining of secretions indicates patent Eustachian tube

Patulous Eustachian Tube

Clinical Features Aural fullness, humming tinnitus, hearing their own voice (autophony), hearing their own breath sounds (tympanophonia). Symptoms resolve in supine position, in forward bending with head between knees, in U.R.T.I. Aggravated by mastication.

Otoscopy: T.M. moves during breathing. Associated conditions: radiation therapy, hormonal therapy, nasal decongestants, 3rd trimester pregnancy, stress, sudden weight loss, multiple sclerosis. Treatment: Reassurance, weight gain, oral potassium iodide.

Surgical interventions Electro-cauterization of E.T. orifice Peri-tubal injection with Teflon paste Transposition of tensor veli palatini muscle medial to pterygoid hamulus Plugging of E.T. orifice in Middle ear + myringotomy & grommet insertion

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