NICU入院児のABRによる聴覚スクリーニングの有用性についての検討

Abstract

1988～1995年の8年間に奈良県立医科大学附属病院NICUに入院したハイリスク新生児437例にABRによる聴覚スクリーニング検査を行い,51例(11.7%)が少なくとも一側のV波閾値が60dBnHL以上でABR異常を認めた。ABR異常の重要な因子は①人工呼吸管理10日以上,②脳障害,③頭頸部奇形,④PPHN,⑤妊娠中の非細菌性感染の各因子であった。初回ABRが正常で,後に難聴と診断された例は4例あり,それらの危険因子は10日以上の人工呼吸管理(HFO使用)およびPPHNであった。NICUに入院した新生児の聴覚スクリーニング検査は,①から⑤の危険因子を認めるような例には早期にABRを行い,1歳前後に全例にCORを行うことが最も効率よく,かつ難聴の見逃しが少ない方法ではないかと考えた。

During 1988-1995, 437 iofants in the neonatal intensive care unit (NICU) of Nara Medical University were screened by auditory brainstem response (ABR). Wave Ⅰ and wave Ⅴ shortened with increasing infant age．Changes in wave Ⅴ were more drastic than those in wave Ⅰ, Ⅰ-Ⅴ interpeak latency shortened with increasing infant age, which supports a maturation process of the brainstem. Changes in ABR wave latencies continue beyond the 120th conceptional week. Neurological prognosis for the infants who showed no responsen to ABR was significant- ly bad (X²test). Wave Ⅴ latencies of mentally retarded infants were significantly longer than those of normal infants at the 56th conceptional week. Fifty-one infants out of 437 (11.7%) were judged to be abnormal because either or both ABR threshold was higher than 60 dBnHL. Significant predictors of ABR abnormality in high risk infants were (1) long-term respiratory care (longer than 10 days), (2) brain damage (due to hypoxia）(3) head and neck anomalies, (4) syndromes due to chromosome aberration or dysbolism, (5）persistent pulmonary hypertension of the newborn (PPHN), and (6) non - bacterial infection during the fetal stage. Four iofants developed bilateral profound hearing loss, although they had shown normal ABR at discharge from the NICU. Three of them had long-term respiratory care using high frequency oxygenation (HFO) and one of them also had PPHN. Another one had short- term respiratory care and PPHN. All of them seemed to have had severe hypoxia. We propose a new time-saving protocol for the delayed hearing disturbance, which consists of two tests as follows ; 1) ABR-test for the infants who have the above (1) to (6) neonatal predictors, with careful follow-ups, 2) （COR-test at the age of 12 months for all infants discharged from the NICU.