Extremely low gestation infants are at high risk for auditory neuropathy

1. Extremely low gestation infants are at high risk for auditory neuropathy Lynn M. Iwamoto, MD; Konstantine Xoinis, MD; Yusnita Weirather, MA, CCC-A; Hareesh Mavoori, PhD; Steven Shaha, PhD Kapiolani Medical Center for Women & Children, Hawaii Pacific Health Center for Health Outcomes Honolulu, Hawaii

2. Faculty Disclosure Information • In the past 12 months, I have not had a significant financial interest or other relationship with the manufacturer(s) of the product(s) or provider(s) of the service(s) that will be discussed in my presentation. • This presentation will not include discussion of pharmaceuticals or devices that have not been approved by the FDA.

3. Auditory Neuropathy • Auditory dys-synchrony (AD) • Transmission of sound to the brain is abnormal • Abnormal brainstem evoked responses (ABR) • Normal acoustic emissions (OAE) • Preserved cochlear microphonics • Acoustic reflex absent • May be missed with OAE screening

4. Auditory Neuropathy • Pathophysiology • Cochlear inner hair cells • Neural pathways: CN VIII • Brainstem • Speech perception is impaired • Fluctuating losses • Difficulty in background noise • Prognosis is unpredictable • Optimum management is unclear

5. High risk neonates • Sensorineural hearing loss is 10 times more prevalent • Auditory neuropathy (AN) • Rance, et al 1999 • 1991-1996 • 5199 infants screened (at risk population) • 2.3/1000 AN • 11% of 109 SNHL • Berg, et al 2005 • Mar 2002-Dec 2003 • 24.1% of 432 NICU (regional perinatal center)

6. Risk Factors • Family history • Prematurity • Hyperbilirubinemia • Ototoxic medications • Hypoxia • Hydrocephalus • Meningitis

7. Objectives • Establish prevalence rate for auditory neuropathy in the high risk nursery • Differentiate infants with auditory neuropathy from those with cochlear hearing loss

8. Patient Population • Retrospective review • 1999-2003 • Kapiolani Medical Center for Women and Children Newborn Special Care Unit • Sensorineural hearing loss • Auditory neuropathy • Gestational age-matched controls

9. Data CollectedDemographics • Gestational age • Birthweight • Gender • Ethnicity • Apgar scores • Severity of illness • Length of hospitalization • Chronic lung disease • Intraventricular hemorrhage • Necrotizing enterocolitis

10. Data CollectedRisk Factors • Medications • Furosemide • Aminoglycosides • Vancomycin • Dexamethasone • Infections • CMV • Toxoplasmosis • Meningitis

11. Data CollectedRisk Factors • Mechanical ventilation • Conventional ventilation • High frequency ventilation • Hyperbilirubinemia • Pulmonary hypertension • Nitric oxide

12. AN vs SNHL vs Control *p<0.05 vs. Control †p<0.05 vs. SNHL

13. Gestational Age Distribution High Risk Nursery 1999-2003

14. PREVALENCE By Gestational Age Group

15. Exposure to Medications *p<0.05 vs control † p< 0.05 vs SNHL

16. Neonatal Morbidities *p<0.05 vs Control

17. Neonatal Morbidities * p<0.05 vs. control † p < 0.05 vs. SNHL

18. Summary • SNHL = 21/1000 in the NICU • AN/AD = 5.3/1000 • 26% of hearing loss • 2/3 were ≤ 28 wks gestation • 44% of hearing loss for those ≤ 28 wks

19. Summary • AN/AD vs. SNHL • Younger gestation • Lower birthweight • Greater exposure to potential ototoxic medications • Furosemide • Vancomycin • Higher incidence of BPD • Longer hospitalization

20. Conclusions • Auditory neuropathy is a significant problem in the high risk nursery population. • Extremely premature infants are at highest risk.

21. Perspective • Infants in the high risk nursery should be routinely screened by both ABR and OAE before hospital discharge. • Early identification of AN/AD will lead to a better understanding of the pathophysiology and the development of appropriate intervention strategies.