Characteristics of Congenital Hearing Loss

Barbara S. Herrmann, Ph.D. CCC-AAudiology Department

Massachusetts Eye and Ear InfirmaryHarvard Medical School

Examine outcomes of UNHS

For one metropolitan nursery:

What types/degrees of hearing loss are being identified in newborns referred by UNHS

What happens to those hearing losses over the first few months/years

My UNHS Background:

Data presented: From UNHS program at Massachusetts

General Hospital Initiated NICU screening in 1981, UNHS

in 1997 Follow-up evaluation at Massachusetts

Eye and Ear Infirmary Audiology Department scheduled within 1 to 3 weeks of hospital discharge

If hearing loss, usually next evaluation at 4 months of age

UNHS Flow in Massachusetts

Hearing ScreenAudiologist Supervise

EBC

Notify ParentPediatrician

Notify ParentPediatrician

Make F/UAppt

Pass

Refer

Discharge

DPHPass

ReferDPH Parent

Liason

Keep F/UAppt

Phone Call to Parent

Critical Elements for Critical Elements for SuccessSuccess

Hearing ScreenAudiologist Supervise

EBC

Notify ParentPediatrician

Notify ParentPediatrician

Make F/UAppt

Pass

Refer

Discharge

DPHPass

ReferDPH Parent

Liason

Keep F/UAppt

Phone Call to Parent

1

3

2

4

5

Screening Protocol at MGH

ALGO Infant Hearing Screeners (ALGO I to ALGO 3i)

Audiologists or Technicians 35 dB HL shaped-click at 37/sec over 25

msec analysis time. Custom ear couplers. Electrode montage; Vertex (+), Nape (-),

Forehead (ground). Single Screen

All MGH Nursery: 2000 to 2005N=21,613 babies

Bilateral Pass97.9%

UnilateralRefer1.5%

Bilateral Refer0.6%

Bilateral Pass

Unilateral Refer

Bilateral Refer

Bilateral Pass98.1%

UnilateralRefer1.5%

Bilateral Refer0.4%

Bilateral Pass95.2%

Bilateral Refer3.1% Unilateral

Refer1.7%

MGH Level 1N=19,252

MGH Level 3N=1,371

MGH Statistics by Nursery Level

Follow-up between 1 and 4 weeks after discharge

Bone-Conduction

Right Ear Threshold

Left Ear Threshold

AER Estimated Audiogram

First follow-up test

Normal Hearing65%

Hearing Loss35%

N=393 of 455 refers(12% transferred or lost to follow-up)

Normal hearing = AER thresholds of 20 dB HL or better

First follow-up by refer type

Bilateral Refers Unilateral Refers

Type of Neonatal Hearing Loss

19%

4%

24%

13%

4%1%

11%

24% Bilateral Sensorineural

Bilateral Mixed

Bilateral Conductive

Bilateral Unknown

Unilateral Sensorineural

Unilateral Mixed

Unilateral Conductive

Unilateral Unknown

Percent of Babies with Hearing Loss ( N=135)

Incidence of Hearing Loss overall - 0.6%Incidence of sensorineural loss – 0.15%

60% bilateral loss; 40% unilateral loss

Degree of Hearing loss: Classified by threshold at 2000 Hz toneburst

Classification rules: Normal: 20 dB HL or better at 2000 and

4000 Hz Borderline: 25 db HL Mild: 30 to 40 dB HL Moderate: 45 dB to 65 dB HL Severe: 75 to 85 dB HL Profound: 90 dB HL or greater

No response at 102 dB HL

Borderline Mild

Moderate Severe Profound

Range of thresholds for each degree

Degree of Hearing Loss: all loss ears

N=215 ears

0

10

20

30

40

50

60

70

Borderline Mild Moderate Severe Profound

23% 28% 32% 5% 12%

51% of refers have 2000 Hz thresholds between 25 and 40 dB HL

0

10

20

30

40

50

60

70

Borderline Mild Moderate Severe Profound

Sensorineural/Mixed Conductive/Unknown

Degree of Hearing Loss: by type

N=215 ears

3%

21%

20%

3%10%

20%

7% 12% 2%

2%

65% conductive/unknown type35% known sensorineural component

Further details:

Unknown or type not determined

Conductive hearing losses

Sensorineural / mixed hearing loss

Insight into current issues

Unknown/ Type not determined

Degree of loss for Unknown/ Type not determined

0

5

10

15

20

25

30

35

40

Borderline Mild Moderate Severe Profound

56% 20% 18%3% 3%

N=66 ears

Primarily symmetric

0

2

4

6

8

10

12

Left ear

Right ear

0

5

10

15

20

25

30

35

40

Borderline Mild Moderate Severe Profound

Conductive hearing loss

Right masked bone

Conductive hearing lossConductive hearing loss

0

5

10

15

20

25

30

35

Borderline Mild Moderate Severe Profound

10% 46% 41% 3%

N=71 ears

Again, primarily symmetric

0

1

2

3

4

5

6

7

8

9

Left ear

Right ear

0

5

10

15

20

25

30

35

Borderline Mild Moderate Severe Profound

0

10

20

30

40

50

60

70

Borderline Mild Moderate Severe Profound

Sensorineural/Mixed Conductive/Unknown

Conductive and Unknown ears similar, so have grouped them

3%

21%

20%

3%10%

20%

7% 12% 2%

2%

65% of all loss are conductive or unknown origin: 41% of those are mild or better

What have we learned About 60% of ears with conductive or

type not determined hearing loss identified within 1 month of newborn screen have mild or borderline degree of loss.

Most of the babies have similar degrees of loss in each ear

Sensorineural / Mixed Losses

Sensorineural / Mixed Loss Ears

0

5

10

15

20

25

30

Borderline Mild Moderate Severe Profound

8% 20% 36% 9% 28%

N=76 ears

Again, mostly symmetric

0

5

10

15

20

25

30

Borderline Mild Moderate Severe Profound

0

1

2

3

4

5

6

7

8

What have we learned

66% of ears with sensorineural hearing loss identified within 1 month of newborn screen have moderate hearing losses or better.

30% of sensorineural hearing loss identified by UNHS have hearing thresholds better than 40 dB HL

What happens over time…. Infants scheduled for another AER

evaluation three months after initial test After that usually seen at 3 month

intervals using behavioral audiometry Many with borderline hearing do not

keep appointment Have re-evaluation data for 65 of 135

infants

0

5

10

15

20

25

Normal Better No Change Poorer

Conductive/Unknow n Sensorineural/Mixed

Sensorineural / Mixed Losses

N=65 babies

46%

26%

22%

7%9%

82%

9%

Most conductive losses resolve to normal within 3 monthsMost sensorineural loss do not change

Questions that have arisen in UNHS Are we identifying mild losses with ABR?

What about unilateral refers with bilateral loss?

Will any screening technique catch all losses?

Should we follow unilateral refers?

Are we identifying mild losses with ABR?

0

5

10

15

20

25

30

Borderline Mild Moderate Severe Profound

8% 20% 36% 9% 28%

N=76 ears

Yes

First follow-up at 2 days, now 18 monthshearing stable

First follow-up at 3 days, now 7 years hearing stable

Bilateral ReferBilateral Refer

What about unilateral refers with bilateral loss?

0

5

10

15

20

25

30

35

BilateralCond_Unkn

BilateralSens_M ixed

UnilateralCond_Unkn

UnilateralSens_M ixed

Bilateral Refer Unilateral Refer

3 cases of sensorineural/mixed loss on first follow-up in this cohort

Case 1 and Case 2

No response left ear at 85 dB HL

Identified at 3 weeks, now 3 years oldHearing stable

Identified at 6 weeks, now 12 monthsHearing stable

Case 3

First AER Follow-up AER

Which was correct – the screen or first follow-up bone?

Will any screening technique catch all losses?

ABR bilateral refers; present OAEs

First follow-up by refer type

Bilateral Refers Unilateral Refers

Should we follow unilateral refers?

Yes

Unilateral ReferAge 6 months

First BehavioralAge 1 year

YES

Age 2.6 years Age 3.5 years

Things to keep in mind….

Fluctuating conductive always an issue in follow-up studies

3 weeks of age 5 months of age

Fluctuating conductive always an issue in follow-up studies

5 months of age 8 months of age

Fluctuating conductive always an issue in follow-up studies

Lots of confusion over earphones…..

ALGO ear coupler has the least variation from baby to baby than any earphone

Voss andHerrmann2005

What we have learned: 66% of bilateral refers have hearing loss at about one month

80% of unilateral refers have normal hearing at about 1 month.

About 60 to 65% of ears with hearing loss are conductive.

About 60% of ears with conductive or type not determined hearing loss identified within 1 month of newborn screen have mild or borderline degree of loss.

66% of ears with sensorineural hearing loss identified within 1 month of newborn screen have moderate hearing losses or better.

30% of sensorineural hearing loss identified by UNHS are borderline of mild (hearing thresholds better than 40 dB HL)

Most of the babies have similar degrees of loss in each ear

What else...

Almost half of the conductive hearing losses are normal by 3 months of age.

Most sensorineural hearing losses do not change over first few years.

We are identifying mild losses with ABR.

Unilateral refers with bilateral loss tend to be borderline cases

No current screening technique catch all losses; one must chose which to miss.

We should follow unilateral refers