ASSESSMENT OF HEARING                                              MODERATOR:-DR N. JANARDHAN

                                                      BY:-RAMA RAJU

CONDUCTIVE HEARING LOSS:PATHOLOGY IN :

1. EXTERNAL EAR(OBST)

2.TYMPANIC MEMBRANE ( PERF )

3.MIDDLE EAR (EFFUSION)

4.OSSICLES (FIXATION)

5.E.T (OBST)

SNHL

1. COCHLEAR

2. VIII NERVE

3. CENTRAL CONNECTIONS.

2 AND 3 CONSTITUTE TO RETRO COCHLEAR REGION.

MIXED

IN OTOSCLEROSIS

CSOM

1. INCREASING A-B GAP :CONDUCTIVE DEAFNESS.

2. DECREASING BONE CONDUCTION INDICATES SNHL.

TUNING FORK TEST :

RINNE TESTPOSITIVE :(AC>BC)1. NORMAL 

2. SNHL

NEGATIVE : (BC>AC)3. CONDUCTIVE

DEAFNESS

4. SEVERE SNHL (FALSE -VE)

WEBERS TESTCENTRALISED : NORMAL

LATERALISED : 

TO AFFECTED EAR : CONDUCTIVE DEAFNESS

TO NORMAL EAR :SENSORINEURAL DEAFNESS 

ABSOLUTE BONE CONDUCTION TEST EAC OF BOTH SUBJECT AND EXAMINER OCLUDED.

PATIENT AND EXAMINER HEARS THE TUNING FORK FOR THE SAME TIME :-CONDUCTIVE DEAFNESS

1. SUBJECT HEARS THE TUNING FORK FOR SHORTER DURATION:-

             SNHL

SCHWABACH'S TEST

PATIENT HEARS THE FORK FOR SHORTER DURATION:-SNHL

DURATION IS LENGTHENED IN :-CONDUCTIVE DEAFNESS

BING TEST: BONE CONDUCTION TEST WHICH EXAMINES THE EFFECT OF OCCLUSION OF CANAL ON THE HEARING

BONE CONDUCTION LOUDER WHEN EAR CANAL IS OCCLUDED:-

1. NORMAL

2. SNHL

NO CHANGE :-CONDUCTIVE DEAFNESS

GELLE'S TEST:TO TEST THE FUNCTIONING OF OSSICULAR CHAIN

INCREASE IN PRESSURE OF MEATUS

1. DEECREASE IN LOUDNESS FROM BONE CONDUCTED STIMULUS:-NORMAL,SNHL

2. NO ALTERATION OF BONE CONDUCTION-FIXATION OF STAPES IN OTOSCLEROSIS

PURE TONE AUDIOMETRY

PURE TONE : SINGLE FREQUENCY SOUND WAVE.

AIMS OF PTA : TO KNOW IF SUBJECT HAVE DEFINITIVE

AUDITORY DISORDER.

TYPE OF HEARING LOSS - CONDUCTIVE/MIXED/SNHL.

SNHL: COEHLEAR OR RETROCOCHLEAR

DEGREE OF HEARING DYSFUNCTION

INTERPRETATION OF AUDIOGRAM

ONLY QUANTITATIVE TEST    NATURE OF PATHOLOGY AND SITE OF LESION NOT KNOWN .

AIR CONDUCTION THRESHOLD DEAFNESS GRADED INTO:

0-25 : NORMAL HEARING THRESHOLD

26-40 : MILD DEAFNESS

41-55:MODERATE DEAFNESS

56-70:SEVERE DEAFNESS

71-90:VERY SEVERE DEAFNESS

ABOVE 90:PROFOUND DEAFNESS

CONDUCTIVE DEAFNESS: 

BONE CONDUCTION - NORMAL (15-20 db HL)A-B GAP =>20 db 

 

•SENSORINEURAL DEAFNESS :BONE CONDUCTION=>20 db HL A-B GAP:<= 15 db

MIXED DEAFNESS:

BONE CONDUCTION=>20 db HL.A-B GAP: >= 15 db

CONDUCTIVE LESIONS:OTOSCLEROSIS:1.LEFT SLOPING AUDIOGRAM2.CARHART'S NOTCH IN BONE CONDUCTION HEARING LEVEL AT 2000HZ

SECRETORY OTITS MEDIA:RIGHT SLOPING AUDIOGRAM

OSSICULAR DISCONTINUITY:>60 db A-b GAP

SENSORINEURAL HEARING LOSS:FLAT AUDIOGRAM SUGGESTS ATROPY OF STRIA VASCULARIS(STRIAL PRESBYCUSIS)

SELECTIVE HIGH FREQUENCY LOSS WITH NORMAL HEARING IN MIDDLE AND LOW FREQUENCY SUGGESTS LESION OF CORTI DUE TO1.SOUND TRAUMA2.OTOTOXIC DRUGS 

ASCENDING CURVE (SLOPE TO LEFT) SUGGESTS EARLY ENDOLYMPHATIC HYDROPS

TROUGH SHAPED AUDIOGRAM SUGGESTS CONGENITAL SENSORINEURAL LESION 

FALLACIES OF PTA : 

1. IMPROPER TECHNIQUE : OVER MASKING/UNDERMASKING

FAULTY PLACEMENT OF HEADPHONES OR BONE CONDUCTION VIBRATOR

        2.IMPROPER TEST INSTRUMENT : IMPROPER CALIBRATION

LAX HEADBAND

         3.IMPROPER EXAMINER :

LIMITATIONS OF PTA :

1. PTA DOES NOT EVALUATE THE PROPERTIES OF SUPRA THRESHOLD HEARING i.e., FREQUENCY DISCRIMINATION AND TEMPORAL RESOLUTION.

2. IT DOES NOT IDENTIFY THE NATURE OF PATHOLOGY.

3. BONE CONDUCTION TEST DOES NOT ASSESS THE TRUE SENSORINEURAL RESERVE AS T.M AND OSSICLES ALSO CONTRIBUTE FOR BONE CONDUCTION.

IMPEDANCE AUDIOMETRY

1. USES:OBJECTIVE DIFFERENTIATION BETWEEN CONDUCTIVE AND S.N HEARING LOSS

2. D.D IN CASES OF CONDUCTIVE DEAFNESS

3. MEASUREMENT OF MIDDLE EAR PRESSURE AND E.T FUNCTION

4. D.D OF SNHL i.e COCHLEAR OR RETRO-COCHLEAR

5. IDENTIFICATION OF SITE OF FACIAL NERVE LESION AND CERTAIN BRAIN STEM PATHOLOGIES

TESTS OF IMPEDANCE AUDIOMETRY

1. TYMPANOMETRY

2. EUSTACHIAN TUBE FUNCTION TEST

3. ACOUSTIC REFLEX TEST

TYMPANOMETRY

TYMPANOMETRY IS DEFINED AS THE MEASUREMENT OF CHANGE OF IMPEDANCE OF THE  MIDDLE EAR AT THE PLANE OF T.M AS A RESULT OF CHANGE IN AIR PRESSURE OF E.A.C

PROCEDURE

1. PROBE WITH 3 CHANNELS FIT IN TO E.A.C,TO DELIVER A TONE OF 220 HZ

2. TO PICK UP A REFLECTED SOUND THROUGH A MICRO PHONE

3. TO BRING PRESSURE CHANGES IN E.A.C

PRESSURE CHANGED FROM +200 TO -600 WATER PRESSURE AND THE COMPLIANCE VALUES ARE RECORDED EVERY 50 mm change

PRESSURE AT WHICH COMPLIANCE IS MAXIMUM IS MIDDLE EAR PRESSURE

STATIC COMPLIANCECx=C2-C1range=.35to1.40

COMPLIANCE OF AUDITORY CONDUCTIVE SYSTEM AS MEASURED AT T.M

       COMPLIANCE 

1.OSSICULAR CHAIN DISCONTINUITY2.SCARRED T.M3.LARGE T.M4.POST STAPEDECTOMY EAR

       COMPLIANCE

1.OTOSCLEROSIS

2.SECRETORY O.M

3.OSSICULAR FIXATION

4.TYMPANOSCLEROSIS

NORMAL COMPLIANCE

1.SOME CASES OF OTOSCLEROSIS

2.EUSTACHIAN TUBE OBSTRUCTION EITH OUT SECRETORY CHANGES IN MIDDLE EAR

MIDDLE EAR PRESSURENORMAL MIDDLE EAR PRESSURE=+50 TO -50 OF WATER PRESSURE

NEGATIVE PRESSURE CONDT:

1. BLOCKED E.T 

2. SECRETORY OTITIS MEDIA

POSITIVE MIDDLE EAR PRESSURE:

3. EARLY ACUTE OTITIS MEDIA

ABSENCE OF PRESSURE:

4. ADHESIVE OTITIS MEDIA

5. PERFORATION OF T.M

6. PATENT GROMMET IN T.M

7. CERUMEN BLOCKING EXTERNAL EAR

TYPES AND SHAPES OF TYMPANOGRAMS

TYPE A : SHARP MAXIMUM AT PEAK 0 mm OF H2O HgCONDT: 1.NORMAL EAR 

                         2.OTOSCLEROSIS (SOME CASES)

TYPE As: NORMAL MIDDLE EAR PRESSURE WITH LOW COMPLIANCE

CONDT: 1.OTOSCLEROSIS

                         2.THICKENED T.M

TYPE Ad: NORMAL MIDDLE EAR PRESSURE WITH HIGH COMPLIANCE

CONDT: 1.OSSICULAR DISCONTINUITY

                         2.SCARRING OF T.M

TYPE B : FLAT TYMPANOGRAM ( COMPLIANCE UNCHANGED OVER PRESSURE VARIATION)

CONDT : 1.OTITIS MEDIA WITH EFFUSION

                           2. ADHESIVE OTITIS MEDIA

                           3. PERFORATION OF T.M

TYPE C: NEGATIVE MIDDLE EAR PRESSURE WITH  NORMAL COMPLIANCE

CONDT:1.UNCOMPLICATED E.T OBSTRUCTION

                  

TYPE A:NORMAL TYMPANOGRAM WITH MAX COMPLIANCE AT AMBIENT ATMOSSPHERIC PRESSURE

TYPE Ad:NORMAL MIDDLE EAR PRESSURE ,HIGH COMPLIANCE TYMPANOGRAM1.OSSICULAR DISCONTINUITY2.SCARRED T.M

TYPE As:LOW COMPLIANCE ,NORMAL MIDDLE EAR PRESSURE1.STAPEDIAL OTOSCLEROSIS2.OSSICULAR FIXATION

TYPE B:FLAT TYMPANOGRAM WITHOUT MEASURABLE COMPLIANCE1.GROSS S.O.M2.GROSS ADHESIVE CHANGES3.PERFORATION

• NEGATIVE MIDDLE EAR PRESSURE,LOW COMPLIANCE TYMPANOGRAM 

-VE PRESSURE DUE TO E.T BLOCKADECOMPLIANCE IS DUE TO SOME AIR PRESENT

TYPE C : NEGATIVE MIDDLE EAR PRESSURE,NORMAL COMPLIANCE WITH SINGLE PEAK 

SUGGESTS BLOCKED E.T WITHOUT COLLECTION OF FLUID

•NORMAL MIDDLE EAR PRESSURE,LOW COMPLIANCE WITH SYSTEMIC WAVES IN THE TYMPANOGRAM CORRESPONDING WITH PULSE BEAT SUGGESTS GLOMUS JUGULARE IN MIDDLE EAR

EUSTACHIAN TUBE FUNCTION TESTS:

1. FUNCTIONS OF E.T:MAINTAINANCE OF EQUALITY OF AIR PRESSURE b/w MIDDLE EAR AND AMBIENT ATMOSPHERIC PRESSURE

2. DRINAGE OF MUCOUS FROM MIDDLE EAR

I.A ASSES TUBAL FUNCTION OF MIDDLE EAR AND NOT JUST ANATOMICAL PATENCY

2TESTS

1.WILLIAMS TEST

2.TOYNBEE'S TEST

WILLIAM'S TEST

I.A MEASURES MIDDLE EAR PRESSURE IN 3 COND IN WILLIAMS TEST1.RESTING PRESSURE

2. SWALLOWING

3.VALSALVA MANOVEUR

NORMAL=NORMAL RESTING ATMOSPHERIC PRESSURE TURNS NEGATIVE  ON SWALLOWING AND POSITIVE ON VALSALVA MANOVEUR

PARTIALLY IMPAIRED=TURNS NEGATIVE ON SWALLOWING BUT RETAINS NORMAL ON VALSALVA AND VICE-VERSA

COMPLETELY IMPAIRED=NO CHANGE ON SWALLOWING AND VALSALVA

NORMAL : NORMAL ATMOSPHERIC PRESSURE TURNS NEGATIVE ON SWALLOWING AND POSITIVE ON VALSALVA MANOVEUR

PARTIALLY IMPAIRED :TURNS NEGATIVE ON SWALLOWING AND REMAINS NORMAL ON VALSALVA MANOVEUR AND VICE - VERSA

COMPLETELY IMPAIRED:NO CHANGE OF PRESSURE ON SWALLOWING AND VALSALVA

TOYNBEE'S TEST: (PERFORATED EARDRUM )

I.A IS PROGRAMMED TO ARTIFICIALLY INCREASE OR DECREASE THE AIR PRESSURE IN THE MIDDLE EAR AND THEN RECORD THE CHANGE IN THE PRESSURE OF MIDDLE EAR EACH TIME THE PATIENT SWALLOWS.

TEST IS CARRIED FOR 40 SEC.

PROCEDURE: PRESSURE IS INCREASED TO +250 OR -250 mm

WATER PRESSURE.

PATIENT IS ASKED TO SWALLOW REGULARLY.

LOOK IF PRESSURE IS BEING NEUTRALISED WITH EACH SWALLOW.

STEP LADDER TYPE OF GRAPH.

PARTIALLY IMPAIRED:IF RESIDUAL PRESSURE PERSISTS EVEN AFTER 5 SWALLOWS

GROSSLY IMPAIRED:IF THE PRESSURE CANNOT BE NEUTRALISED EVEN AFTER REPEATED SWALLOWS

ACOUSTIC REFLEX TEST:

1. HELPS INELIMINATION OF MIDDLE EAR PATHOLOGY

2. DIFFERENTIATION OF COCHLEAR FROM RETROCOCHLEAR LESION

3. DETECTION OF SOME BRAIN STEM PATHOLOGY

4. OBJECTIVE ESTIMATION OF AVERAGE HEARING THRESHOLD LEVEL

5. DETECTION OF NON ORGANIC HEARING LOSS

6. IDENTIFYING THE LEVEL OF LESION IN FACIAL NERVE PARALYSIS

INTERPRETATION OF ACOUSTIC REFLEX :

AR(+) :- 

1.  STRONGLY INDICATE ABSENCE OF PATHOLOGY IN                    THE REFLEX PATHWAY.

2. IN COCHLEAR LESIONS DUE TO LOUDNESS RECRUITMENT.

AR (-) :-1. EVIDENCE OF LESION IN REFLEX PATHWAY.

2. SOMETIMES EVEN IN NORMAL PEOPLE WHEN TEST IS DONE AT FREQUENCY OF 4000 Hz.

UNILATERAL MODERATE TO SEVERE CONDUCTIVE DEAFNESS 

STIMULUS IN DEAF EAR : I/L AR (-)

                                                        C/L AR (-)

AS STIMULUS FROM THE DEAF EAR DOES NOT REACH THE  REFLEX ARC .

STIMULUS IN NORMAL EAR : I/L AR (+)

                                                         C/L AR (-)

CONTRALATERAL AR (-) BECAUSE OF MIDDLE EAR PATHOLOGY.

BILATERAL CONDUCTIVE DEAFNESS

AR (-) IN BOTH EARS DUE TO THE PRESENCE OF MIDDLE EAR LESION WHICH CAUSES MECHANICAL OBSTRUCTION TO THE REFLEX.

UNILATERAL SEVERE SENSORINEURAL DEAFNESS

STIMULUS IN DEAF EAR :- I/L AR (-)

                                                          C/L AR (-)

STIMULUS DOES NOT REACH THE REFLEX PATHWAY

STIMULUS IN NORMAL EAR :-I/L AR (+)

                                                                  C/L AR(+)

AR(+) IN DEAF EAR AS THE MIDDLE EAR IS INTACT

IN BILATERAL SNHL:

SEVERE AND NEURAL:-AR(-) IN I/L AND C/L EARS

MODERATE AND COCHLEAR:AR(+) IN I/L AND C/L EARS

                       DUE TO LOUDNESS RECRUITMENT   

CENTRAL LESIONS:

AR(+):-BILATERALLY ON IPSILATERAL STIMULATION

AR(-):-ABSENT BILATERALLY ON C/L STIMULATION

LESIONS INVOLVE THE SITE OF CROSSINGS BETWEEN I/L AND C/L SIDES

RECRUITMENT:

ABNORMAL STEEP GROWTH OF LOUDNESS WITH INCREASING INTENSITY 

ASSOCIATED WITH SENSORINEURAL DEAFNESS DUE TO COCHLEAR PATHOLOGY

EXACT CAUSE OF MECHANISM OF RECRUITMENT NOT UNDERSTOOD

ABSENCE OF RECRUIMENT IS PATHOGNOMIC OF RETROCOCHLEAR LESION

ABSENCE OF RECRUITMENT DOES NOT RULE OUT COCHLEAR PATHOLOGY

TESTS 

1. ALTERNATE BINAURAL LOUDNESS BALANCE TEST :ITS A DIRECT TEST

2.SHORT INCREMENT SENSTIVITY INDEX :

ITS AN INDIRECT TEST

ABLB

PROCEDURE:

STEP 1: HEARING THRESHOLD BY AIR CONDUCTION FOR THE TESTING FREQUENCY IA ASCERTAINED

STEP2: ATTENUATOR DIAL FOR WORSE EAR IS 20 dB SL,FOR THE BETTER EAR IS 0 dB

STEP3: TONES ALTERNATE BETWEEN TWO EARS AND PATIENT IS ASKED TO INDICATE IN WHICH EAR SOUND APPEARS LOUDER

a)LOUDER IN WORSE EAR-FOLLOW STEP 4

b)LOUDER IN NORMAL EAR -FOLLOW STEP5

STEP 4: TONE IN BETTER EAR IS RAISED BY 5 dB 

STEP 5: TONE IN THE BETTER EAR DECREASED BY 5dB

INTERPRETATION OF ABLB RESULTS:

COMPLETE RECRUITMENT:THE DIFFERENCE IN THE HEARING LEVEL B/W WORSE AND BETTER EAR DIMINISHES RAPIDLY WITH INCREASE IN THE INTENSITY OF SOUND AND AT A POINT DIFFERENCE BECOME ZERO

ABSENCE OF RECRUITMENT:(NEURAL PATHOLOGY WITH NORMAL COCHLEAR FUNCTION)THE DIFFERENCE IN THE HEARING LEVEL REMAINS CONSTANT ,NO MATTER WHATEVER THE INTENSITYO OF SOUND IS

PARTIAL RECRUITMENT:THE DIFFERNCE IN THE HEARING LEVEL BETWEEN TWO EARS FOR EQUAL LOUDNESS SENSATION GRADUALLY DIMINISHES WITH INCREASING INTENSITY ,BUT DIFFERENCE NEVER BECOME ZERO

SISI  TEST

PROCEDURE :

1. DETERMINES THE CAPACITY OF PT TO DETECT A BRIEF 1 db INCREMENT 20 db  SUPRATHRESHOLD TONE IN VARIOUS FREQUENCY.

2. TWENTY SUCH 1 db INCREMENTS ARE PRESENTED TO EAR AND PATIENT ASKED TO COUNT HOW MANY OF THE 1 db INCREMENTS HE COULD CORRECTLY IDENTIFY.

3. THIS WHEN MULTIPLIED WITH 5 GIVES THE % OF SISI SCORE.

4. INITIALLY HIGHER INCREMENTS (6 db,5 db,3 db etc) given to familiarise the patient with of identifying the smaller lessions. 

INTERPRETATIONS OF SISI SCORE

SISI SCORE IS USED TO DIFFERENTIATE BETWEEN COCHLEAR AND RETROCOCHLEAR LESSIONS.

SESI % :

70-100% - (>1000 Hz) 80-100% -(2000-4000 Hz) 0-20%    - RETROCOCHLEAR PATHOLOGY                    NORMAL HEARING                    CONDUCTIVE DEAFNESS

SISI : NOT ENTIRELY FOOLPROOF HAS ITS OWN LIMITATIONS

LIMITATIONS OF SISI 

REQUIRES PATIENT CO-OPERATION.PT WITH SEVERE DEAFNESS (>85 db) CANNOT BE TESTED AS MOST CLINICAL AUDIOMETER USUALLY HAVE MAX SOUND OUTPUT OF UPTO 100 db.

MILD (30 db) SNHL - DOES NOT SHOW HIGH SCOREEVEN IF DEAFNESS IS DUE TO COCHLEAR LESSIONS.

TONE DECAY TEST

IT MEASURES THE RAPIDITY OF DETERIORATION IN THE THRESHOLD OF HEARING WHEN A CONTINUOUS TONE IS PRESENTED TO EAR.

1. OF ALL TEST,TONE DECAY TEST IS COMMONLY USED TO DETECT THE SITE OF PATHOLOGY IN THE SENSORINEURAL PATHWAY.

2. TEST IS MANDATORY TO BE CARRIED OUT IN EVERY CASE OF SENSORINEURAL DEAFNESS.

3. EXACT PATHOPHYSIOLOGY OF TONE DECAY IS NOT KNOWN.

PROCEDURE

TYPES :1. CARHART'S METHOD

2. GREEN'S MODIFIED METHOD

3. OLSEN AND NOFFSINGER TEST

4. ROSENBERG'S METHOD

5. SUPRATHRESHOLD ADAPTION TEST (STAT)

CARHART'S METHOD

MOST POPULAR METHOD

STEP 1 :- PURE TONE STIMULUS IS PRESENTED 10 db BELOW THRESHOLD AND RAISED IN 5 db STEPS TILL THE PATIENT RESPONDS.

STEP 2 :- AFTER THE PATIENT RESPONDS A STOP WATCH IS STARTED AND TONE IS CONSTANTLY MAINTAINED.

STEP 3 :- AS SOON AS HE FAILS TO HEAR THE TONE  TIME ON THE STOP-WATCH IS NOTED.IF THE TONE IS HEARD FOR ONE FULL MIN. THEN TEST IS TERMINATED,IF PATIENT STOPS HEARING < 1 min,THEN TIME IS RECORDED AND STEP IV IS STARTED.

STEP 4 :- TONE RAISED BY 5 db WITHOUT ANY GAP RAISING OF THE INTENSITY OF THE TONS BY 5 db STEPS IS CONTINUED TILL 30db ABOVE THRESHOLD.

INTERPRETATION OF TONE DECAY RESULTS

1. 0-5 db = normal

2. 10-15  = mild

3. 20-25 = moderate

4. 30 and above = severe

SEVERE DECAY IS CONSIDERED TO BE SUGGESTIVE OF RETROCOCHLEAR LESSION (>30 db )

IT IS NOT FOOLPROOF EVIDENCE OF RETROCOCHLEAR PATHOLOGY.

AFTER TONE DECAY TEST, IF SEVERE THEN THE PATIENT SHOULD BE SUBJECTED TO DETAILED NEURO-OTOLOGICAL EXAMINATION.

THE END