[Audiological characteristics of unilateral auditory neuropathy: 11 case study]

To investigate the audiological characteristics in unilateral auditory neuropathy (UAN).

By the retrospective studies, 11 patients which were diagnosed as UAN and bilateral auditory neuropathy (AN) group and control group were measured.

By the statistical studies of patients from otology clinic data from January 2001 to September 2006,11 patients (11 ear, 5 left ear and 6 right ear, 3.2%) in 340 AN patients diagnosed as UAN were summarized. Four patient were male and 7 were female in 11 patients (1: 1.75). The average age of 11 patients was 20 years old and the average period of diseases was 3.1 years. All patients complained of unilateral gradual hearing loss, and 6 patients in all UAN patients can't discriminate speech correctly. Four patients complained of tinnitus and none of UAN patients complained of dizziness. The pure tone audiograms of 5 patients in all UAN patients (45.4%) were descending curve and those of 4 patients (36.4%) were ascending curve. Eleven patients mostly showed severity degree or midrange degree (6 ear, 54.5%) sensorineural hearing loss. The average pure tone threshold of UAN was obviously higher than the AN group and the speech hearing of UAN is obviously worse, and ABR of all patients was absent, while uninjured side of UAN was normal. Bilateral ears of UAN patients were evoked distortion products otoacoustic emissions. The amplitude of DP-gram and SNR in UAN group was lower obviously (P < 0.05) than the normal control group at all frequencies (0.5-8.0 kHz) and was lower significantly (P < 0.01) at flat and high-frequency, but was lower obviously (P < 0.01) than the AN group at low-frequency. The contralateral suppression effect of DPOAE amplitude in 4 UAN patients of normal ears was suppressed, and that in injured ears was reduced or disappeared, even 0.5 kHz increased DPOAE amplitude. ENG and VEMP were observed in 5 UAN patients, and 1 patients shows semicircular canal failure and 1 patients shows paralysis unilateral. The VEMP of them showed no response in 1 (2 ear) of 5 and showed response in 4 of 5, but the amplitudes of VEMP were lower in 2 UAN patients.

The UAN patients mostly showed ascending curve and ponderosity degree sensorineural hearing loss. The diagnosis of UAN is different from other common sensorineural deafness. The detection of DPOAE and ABR has great significance in diagnosing the UAN.