Assessment of hearing
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ways to assess whether a person hears normally or not right from very basic upto advanced by Dr zeeshan ahmad presented in ENT NMCH patna on 10-02-11
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Assessment of hearing
- 2. ASSESSMENT OF HEARING by:- Dr ZEESHAN AHMAD NMCH PATNA INDIA
- 4. Pathways for air and bone conduction
- 6. A uditory cortex M GB I nferior collliculus L ateral lemniscus O livary nucleus(superior) C ochlear nucleus E ight cranial nerve E.COLI-MA PL Dhingra has simplified auditory pathway and made it easier to remember by a mnemonic
- 13. Various positions of tuning fork during tuning fork tests On mastoid At the opening of EAC Midline of skull
- 26. Pure Tone Audiometry -Audiometer is an electronic device which produces PURE TONES ,the intensity of which can be increased or decreased by 5dB steps -Air conduction thresholds are measured from 125 to 8000 Hz -Bone conduction thresholds from 250 to 4000 Hz -The intensity of sound to be raised above normal to make it hear is a measure of degree of hearing impairment -This is charted on a graph called AUDIOGRAM
- 29. Air conduction Bone conduction
- 32. It’s a Normal PTA Sensorineuronal/conductive abnormality ??
- 34. Hearing Loss Table Classification PTA Profound hearing loss >90 Severe HL 71-90 Moderately severe HL 61-70 Moderate HL 41-60 Mild hearing loss 21-40 Normal 0-20
- 36. Conductive Loss What’s this shows
- 38. Mixed Loss Now what does this one shows
- 44. Imepedence Audiometry (Tympanometry + stapedial reflex)
- 45. Tympanometry
- 48. Tympanometry Janet Stockard Sullivan 2003
- 49. Here’s how it works...
- 50. These 5 second motion video otomacroscopy (MVOM) samples resent a view of a 58 year male right tympanic membrane during tympanometry. The patulous pars flaccida was ejected at the outset of recording from a prior tympanometric trial. The Middle Ear Analyzer was set to run from +400 daPa though -600 daPa. MVOM and tympanograms were video-captured 15 f/s . The time lines between videos are only roughly coincident. The negative slope of the tympanogram corresponds to the period of rapid pars flaccida ejection.
- 51. videos Taken from--- http:// www.rcsullivan.com/www/tympavi.htm
- 64. OAE’s spontaneous evoked Transient (click) Distortion product (paired tones)
- 67. Distortion Product OTOACOUSTIC EMISSIONS
- 69. Brainstem Evoked Response Audiometry (BERA)
- 70. BERA Brainstem Evoked Response Audiometry
- 73. Cochlear nerves Cochlear nucleus Superior olivary complex Nulclei of lateral lemniscus Inferior colliculus
- 77. A COMPARISON Unsuitable for children Suitable for even young children Response begins after 50 - 300 milliseconds after stimulation Responses begin after 1 - 10 milliseconds after stimuli The patient must lie still through out the process Can be performed in awake and restless patients Responses are frequency specific Responses are not frequency specific Tone stimulus is used Click stimulus is used Recording is made from cortical potentials Recording is made from brain stem potentials CERA BERA
- 79. Electrocochleography setup The recording electrode is a thin needle passed through the tympanic membrane onto the promontory under L/A or G/A Non invasive Electrode placed on TM Invasive
- 81. Final Thought Tests are not infallible, they are only as good as those taking, administering and interpreting them…
Hinweis der Redaktion
- The decibel originates from methods used to quantify reductions in audio levels in telephone circuits. These losses were originally measured in units of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of power over a 1 mile (approximately 1.6 km) length of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and roughly matched the smallest attenuation detectable to an average listener. Standard telephone cable was defined as " a cable having uniformly distributed resistances of 88 ohms per loop mile and uniformly distributed shunt capacitance of .054 microfarad per mile " (approximately 19 gauge).[ citation needed ] The transmission unit (TU) was devised by engineers of the Bell Telephone Laboratories in the 1920s to replace the MSC. 1 TU was defined as ten times the base-10 logarithm of the ratio of measured power to a reference power level. [3] The definitions were conveniently chosen such that 1 TU approximately equaled 1 MSC (specifically, 1.056 TU = 1 MSC). [4] Eventually, international standards bodies adopted the base-10 logarithm of the power ratio as a standard unit, named the bel in honor of the Bell System 's founder and telecommunications pioneer Alexander Graham Bell . [5] The bel was larger by a factor of ten than the TU, such that 1 TU equaled 1 decibel. [6] For many measurements, the bel proved inconveniently large, giving way to the decibel becoming the common unit of choice.