OBJECTIVETo explore the clinic characteristics, audiological characteristics and location of lesions in children with retrocochlear auditory nerve impairment which, including auditory neuropathy characterized by severely abnormal results of ABR and normal results of DPOAE.

METHODSBetween 2002 and 2006, eighty-six cases (165 ears) with severely abnormal ABR but normal results of DPOAE were enrolled in the study group. The mean patient age was one year and one-month-old, with a range of 8 days to 7 years. The cases with abnormal conductive function were excluded. The cases with severely abnormal ABR and normal cochlear functions as measured by DPOAE and without abnormal conductive function were selected as the cochlear lesion group. Some same age healthy children without hearing loss were subjected as normal control group. The latency and amplitude of waves I, III and V, the inter peak latency I-III was compared among the three group.

RESULTS(1) Fifty-one cases (59.3%) had a history of hypercholesterolemia during neonatal period, but 40 cases (46.51%) had a severe hypercholesterolemia and 11 cases (12.79%) had mild or moderate hypercholesterolemia. Clinical features common among the population included a history of dyskinesia [n = 40 (46.51%)], hearing and language disorder [n = 10 (11. 63%)]. Thirty-two cases (37.2%) were accompanied by cerebral palsy . (2) Among the 165 ears, absent ABRs to click stimuli presented at 103 dB was in 103 ears, only wave I was developed in 27 ears and only wave V was developed in 19 ears,wave I and III in 13 ears and differentiated wave I and V in 3 ears. (3) When compared to control group, the latency of wave I was prolonged and amplitude of wave I was lower in cases with only wave I developed (t = -6.75 and 2.58, P < 0.05). For for cases with only wave I and III differentiated, the latency and amplitude of wave I was the same but the latency of wave III was prolonged and amplitude of wave III was lower while interpeak latency I-III was prolonged.

CONCLUSIONSAuditory neuropathy which was characterized by severely abnormal ABR was the most common type of retrocochlear auditory nerve impairment. It was mainly due to a disorder of VIII nerve. The pathologies that affect higher levels of the auditory pathway, from the brainstem to the auditory cortex, might be the main sites of lesion in cases with only wave I developed. Superior olivary nucleus where wave III was generated and higher levels of the auditory pathway might be the main sites of lesion in cases with wave I and III differentiated. The low-amplitude wave V was not characteristics of auditory neuropathy. Cerebral cortex, brain stem auditory nucleus and VIII nerve might be damaged successively in cases with retrocochlear auditory nerve impairment induced by hypercholesterolemia.