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Auditory Dys-Synchrony in Very Low Birth Weight Infants: Preliminary Data

Explore the incidence, screening results, and risk factors for auditory neuropathy/dys-synchrony in very low birth weight infants. Learn about physiological and behavioral findings, study objectives, and screening protocols.

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Auditory Dys-Synchrony in Very Low Birth Weight Infants: Preliminary Data

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  1. Auditory Dys-Synchrony Among Very Low Birth Weight InfantsPreliminary Data Courtney A. O’Neil, MS, CCC-A Winnie Chung, AuD Betty Vohr, MD Supported in part by Natus Medical, Inc

  2. Women & Infant’s Hospital and RIHAP(Rhode Island Hearing Assessment Program) • ~13,000 infants born in RI annually • ~ 9,000 infants born at W&I • ~1,500 admitted to NICU

  3. Literature Review • Absent ABR with present OAEs and/or CM with or without measurable hearing has been reported since 1979 – Davis H, Hirsh S. (1979). Audiology 18: 445-461. • 10% of all hearing loss– Starr et al (1996). Brain 119: 741-53. • 1/433 or 2.3 in 1000 children with risk factors • Rance et al (1999). Ear & Hearing June: 238-251. • At least 10 % of children who fail AABR have normal OAEsNorton et al.(2000). Ear & Hearing 21: 508-528. • Occurs in as many as 40% of NICU infants secondary to hypoxiaRea et al.(2003). Laryngoscope 113: 257-263. • 24% of NICU graduates pass OAE, but fail AABR Berg et al. Pediatrics 116: 933-938

  4. Risk Factors for AN/AD By order of frequency of occurrence in AN/AD: • High levels of bilirubin • Hypoxia • Low birth weight • Hydrocephalus • Syndromic disorder such as Charcot-Marie-Tooth • Cerebral Palsy • Cranio-facial anomaly • Neonatal meningitis Rance G, Beer DE, Cone-Wesson B, Shepherd RK, Dowell RC, King AM, Rickards FW, & Clark GN (1999). Clinical finding for a group of infants and young children with auditory neuropathy. Ear & Hearing June: 238-251. Starr A, Picton TW, Sininger Y, Hood LJ, & Berlin CI (1996). Auditory neuropathy. Brain 119: 741-53.)

  5. Auditory Neuropathy/Dys-synchrony Screening Results • Pass oto-acoustic emissions – normal outer hair cell function • Fail automated ABR (AABR) – poor conduction along auditory (VIII) nerve

  6. Auditory Neuropathy/Dys-synchrony Physiological Definition • Absence of wave V in ABR test • Presence of Cochlear Microphonic with/out wave I • Presence of Oto-acoustic Emissions • Absence of contralateral suppression of OAE emissions • Absent Acoustic Reflexes with Normal Tympanometry

  7. Auditory Neuropathy/Dys-synchrony Behavioral Findings • Behavioral testing in older children often reveals variable thresholds which can range from normal hearing sensitivity to severe/profound hearing loss • Word recognition scores do not correlate well with behavioral thresholds • Speech perception difficulties, especially in noise

  8. ABR Waveforms of an Infant with Normal Auditory Function

  9. ABR Waveforms of an Infant with a Profound Sensorineural Hearing Loss

  10. ABR Waveforms of Infant with Auditory Neuropathy / Dys-synchrony Note “ringing microphonic”

  11. Study Objective • To determine the incidence of auditory neuropathy / dys-synchrony in a cohort of very low birth weight infants (<1500 grams) • ~10-12% of NICU admits have birth weight <1500g

  12. Current Hearing Screen Protocol at W&I Hospital • 2 stages • TEOAE performed first • AABR only if infants fail TEOAE • Are we missing infants with AN?

  13. Study Protocol • Study period: March 1st-Dec. 31st, 2006 • Infants <1500g at birth received OAE & AABR • For OAE : OtoDynamics ILO-V6 TEOAE • For AABR: Natus algo 3i (handheld)

  14. Subjects: 03/01-12/31/06 • 180 eligible: • 149 screened with study protocol • 5 (2.8%) screened without protocol @ W&I • 13 (7.2%) transferred – screened without protocol - results available • 13 (7.2%) transferred – no screen results available

  15. Study Sample 03/01-12/31/06

  16. 149 Infants Completed Protocol 83 56% 34 20 23% 12 13% 8%

  17. 20 Infants Failed Both OAE & AABR • 15 had normal dx ABR • 1 transferred from W& I – no dx avail • 3 suspected HL, awaiting confirmation • 1 diagnosed with Auditory Neuropathy

  18. 12 Infants Passed OAE, but Failed ABR • 10/12 (83%) Normal ABR • 2 Awaiting final ABR results

  19. 18 Infants Screened Without Protocol • 5 @ Women & Infant’s Hospital • 2 pass OAE only - infant transferred before AABR • 3 pass AABR only • 1 O2 too high for OAE to run • 2 transferred before OAE could be administered • 13 Screened @ other hospitals • 3 OAE only: all pass • 10 AABR only: • 9 pass • 1 fail – no diagnostic information available

  20. Incidence of Confirmed AN/AD in infants with BW <1500 grams • Recall: babies with AN/AD will pass OAE, but fail AABR • 149 infants - screened with OAE/AABR protocol • 129 infants - passed AABR • 33 infants – AN/AD ruled-out with diagnostic ABR testing • 1 infant diagnosed with AN/AD Rate: 1 in 163 Incidence: 6.1 in 1000

  21. Conclusions: For infants <1500g • The Pass OAE / Fail AABR rate was (12/149) or 8.05% • AN rate: (1/163) 0.61% or 6.1 per 1000 • Lower than some prior reports, higher than others • Total HL rate: (5/163): 3.07% or 30.7 per 1000 • VLBW infants remain at risk of HL

  22. Strengths of This Study • 83% of all infants in a tertiary care center who weighed under 1500 grams were screened with the study protocol • Follow-up diagnostic testing was completed to confirm or rule-out AN/AD in those who failed the screen

  23. Speculation: • Early screening with both OAE and AABR of unstable VLBW infants may result in high false positive screen rates for Auditory Neuropathy / Dys-Synchrony. This contributes to false conclusions about rates of both AN/AD and SNHL.

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