Question
Test used for function of the structure marked by an arrow shown in photograph below is ?
A. Caloric test.
B. Galvanic test.
C. Impedance audiometry.
D. BERA.
Show Answer
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Correct Answer » C Explanation |
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Ans:C. Impedance audiometry.
The part of ear marked by a red arrow in the picture above represents Eustachian Tube.
EUSTACHIAN TUBE/AUDITORY TUBE/PHARYNGOTYMPANIC TUBE
- 36mm long in adults(Range 32-38 mm)
- Two parts – Postero lateral bony part (12mm) and Antero medial fibro cartilaginous part (24mm)
- Tympanic end (bony) – anterior wall of middle ear.
- Pharyngeal end – lateral wall of nasopharynx, it raises an elevation called torus tubarius 1 cm behind the posterior end of inferior turbinate.
- Ostmann’s pad of fat- helps the tube closed at pharyngeal end Lined by pseudo stratified ciliated columnar, cilia beat in the direction of nasopharynx.
- Normally Eustachian tube (ET) is closed and opens intermittently during yawning, swallowing and sneezing through contraction of Tensor vili palatini and Levator veli palatini muscle.
FUNCTIONS OF EUSTACHIAN TUBE
- Ventilation & regulation of middle ear pressure
- Protection against nasopharyngeal sound pressure and reflux of nasopharyngeal secretions
- Clearance of middle ear secretions.
Impedance Audiometry
- It is a measurement of energy or air pressure flow, which involves the ear canal, eardrum, ossicular chain, tensor tympani, stapedius muscle, cochlea, CNs VII and VIII, and the brainstem. Mass, mobility, and resistance of the outer and middle ear systems affect this test.
The following tests are included:
- Tympanometry (most commonly used)
- Acoustic reflex thresholds
- Acoustic reflex decay
- Eustachian tube function testing
- Eustachian tube function testing can be implied by tympanograms.
- Type A – normal middle ear function. This situation only occurs if the eustachian tube is ventilating the middle ear.
- Type B – (No change in compliance with pressure changes) Middle ear fluid as inSecretory Otits Media due to eustachian tube blockage
- Type C – (Maximum compliance occurs with negative pressure in excess of 100 mm of H20) retracted tympanic membrane.indicates a malfunctioning eustachian tube
