eustachian tube anatomy DFTDTFYGUHDFCand physiology.pptx

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1. INTRODUCTION:- Auditory or Pharyngotympanic tube connecting nasopharynx with tympanic cavity

2. 36 mm long in adults running downwards, forwards and medially from its tympanic end forming 45 degree angle with the horizontal

3. PARTS OF EUSTACHIAN TUBE BONY:- Posterolateral 12mm 1/3 rd of total length Cartilaginous:- Anteromedial 24mm 2/3 rd of total length Isthmus:- Narrowest part of tube

4. Tympanic end:- Bony 5 by 2 mm size Attached to anterior wall of middle ear Pharyngeal end:- Slit like runs vertically Torus Tubarius - elevation of cartilage at pharyngeal end of eustachian tube on lateral wall of nasopharynx 1-1.25 cm behind posterior end of inferior turbinate Fossa of Rosenmuller - Posterior to torus tubaris is fossa of Rosenmuller , which is commonest site for malignancy of nasopharynx. *

5. MUSCLES ATTACHED TO EUSTACHIAN TUBE TENSOR VELI PALATINI:- Medial fibers attached to lateral lamina of tube Action-contract and open the tube LEVATOR VELI PALATINI:- Forms bulk under medial lamina Inferior and parallel to cartilaginous part of tube Action- by muscle contraction, Pushes tube upwards and medially and opens the tube ELASTIN HINGE:- Help to keep tube closed OSTMANN’S PAD OF FAT:- Laterally to membranous part of cartilaginous tube Helps to keep tube closed and protect it from reflux of nasopharyngeal secretions

6. LINING OF THE TUBE Mucosa:- Pseudo stratified ciliated columnar epithelium and mucous secreting goblet cells Submucosa:- Lines cartilaginous part of tube Ceruminous gland and cilia in direction of nasopharynx which drains secretions from middle ear to nasopharynx

7. NERVE SUPPLY Mandibular branch of trigeminal nerve:- Supplies Tensor Veli Palatini Glossopharyngeal nerve:- Cranial part- Motor nerve through pharyngeal plexus and Vagus nerve supplies Levator Veli Palatini , Salpingopharyngeus Tympanic part-Supplies mucosa of tube

8. INFANT ADULT LENGTH 13-18 mm 36 mm DIRECTION More horizontal At birth-10 degree At 7 years-45 degree 45 degree with horizontal ANGULATION AT ISTHUMS Not present Present BONY PART Longer and wider than cartilaginous part Cartilaginous part is longer and wider than bony part TUBAL CARTILAGE Flaccid- Retrograde nasopharyngeal secretions Rigid- remains closed and protects reflux DENSITY OF HINGE Less and not closed by recoil More and keep tube closed by recoil OSTMANN’S PAD OF FAT Less in volume Large and keeps tube closed

9. FUNCTIONS OF EUSTACHIAN TUBE Ventilation and regulation of middle ear pressure :- For normal hearing, it is essential that pressure on two sides of the tympanic membrane should be equal. Negative or positive pressure in the middle ear affects hearing. Thus, eustachian tube should open periodically to equilibrate the air pressure in the middle ear with the ambient pressure. Normally, the eustachian tube remains closed and opens intermittently during swallowing, yawning and sneezing. Tubal opening is less efficient in recumbent position and during sleep due to venous engorgement. *Tubal function is also poor in infants and young children and thus responsible for more ear problems in that age group. It usually normalizes by the age of 7–10 years.

10. Clearance of middle ear secretions:- Mucous membrane of the eustachian tube and anterior part of the middle ear is lined by ciliated columnar cells. The cilia beat in the direction of nasopharynx which helps to clear the secretions and debris in the middle ear towards the nasopharynx which is further augmented by active opening and closing of the tube.

11. Protection against Nasopharyngeal sound pressure:– Abnormally, high sound pressures from the nasopharynx can be transmitted to the middle ear if the tube is open thus interfering with normal hearing. Normally, the eustachian tube remains closed and protects the middle ear against these sounds. A normal eustachian tube also protects the middle ear from reflux of nasopharyngeal secretions into the middle ear. This reflux occurs more readily if the tube is wide in diameter (patulous tube), short in length (as in babies) or the tympanic membrane is perforated (cause for persistence of middle ear infections in cases of tympanic mem- brane perforations). High pressures in the nasopharynx can also force nasopharyngeal secretions into the middle ear, e.g. forceful nose blowing, closed-nose swallowing as in the presence of adenoids or bilateral nasal obstruction.

12. EUSTACHIAN TUBE FUNCTION TESTS MANEUVERS BUILDING POSITIVE PRESSURE IN NASOPHARYNX VALSAVA TEST POLITZER TEST CATHETERIZATION MANEUVERS BUILDING NEGATIVE PRESSURE IN NASOPHARYNX TOYNBEE’S TEST TYMPANOMETRY(INFLATION-DEFLATION TEST) MUCOCILLIARY DRAINAGE/CLEARANCE SACCHARINE (METHYLENE BLUE TEST) ANTIBIOTIC/ STEROID EAR DROPS RADIOLOGICAL TEST SONOTUBOMETRY

13. VALSAVA TEST Principle:- Build positive pressure in nasopharynx so that air enters eustachian tube If perforation, hissing sound If discharge, crackling sound Contraindications:- Atrophic scar in tympanic membrane causes rupture of tympanic membrane Infections of nose and nasopharynx causes otitis media *Method-Patient pinches his nose. Patient takes a deep breath through mouth and then closes his mouth. Patient tries to blow his cheeks and pushes air into the ears.

14. POLITZER TEST For children unable to perform Valsalva Patent, hissing sound Therapeutic use, to ventilate middle ear *Method-Olive shaped tip of Politzer bag is inserted patient’s nostril on one side where tubal function is desired to test, while other nostril is closed and Compress bag while patient swallow

15. CATHETERIZATION COMPLICATIONS:- Injury to eustachian tube opening causes scarring Bleeding from nose Transmission of nasal and nasopharyngeal secretions, otitis media If too much pressure, rupture of tympanic membrane atrophic area * Method-Nose is anesthetized by topical spray of lignocaine. Eustachian catheter is passed along the floor of nose till it reaches the nasopharynx. The catheter is than rotated 90° medially and then gradually pulled outward so that it touches the posterior border of nasal septum. The catheter is then again rotated 180° laterally so that tip lies in the pharyngeal opening of the ET. A Politzer bag is connected to the catheter and air is insufflated . Entry of air into the middle ear is verified by an auscultation tube.

16. TOYNBEE’S TEST:- Uses negative pressure *Method- The patient is asked to swallow while he/she keeps the nose pinched. The maneuver draws air from the middle ear into the nasopharynx and causes inward movement of tympanic membrane, which can be seen through an otoscope/ microscope. TYMPANOMETRY(INFLATION-DEFLATION):- *Method- In this test, positive and negative pressures are created in the external ear canal and the patient swallows repeatedly. The ability of the tube to equilibrate positive and negative pressures to the ambient pressure indicates normal tubal function. The test can be done both in patients with perforated or intact tympanic membranes. Can be performed in both intact and perforated tympanic membrane Radiological test:- Radiological dye used- Hypauqe or lipoidal Time taken for dye to reach nasopharynx is noted and indicates its clearance function No longer popular now

17. SACCHARINE OR METHYLENE BLUE TEST:- Solution is injected in middle ear through perforation and time taken by it to stain pharyngeal secretions are noted. SONOTUBOMETRY:- Tone is presented to the nose and its recording is taken from external canal. Patent, Tone is heard louder Gives information about active tubal opening Accessory sound produced in nasopharynx while swallowing interfere with test results *This test is under development.

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