Autosomal recessive hereditary auditory neuropathy

Objectives: Auditory neuropathy (AN) is a sensorineural hearing disorder characterized by absent or abnormal auditory brainstem responses (ABRs) and normal cochlear outer hair cell function as measured by otoacoustic emissions (OAEs). Many risk factors are thought to be involved in its etiology and pathophysiology. Three Chinese pedigrees with familial AN are presented herein to demonstrate involvement of genetic factors in AN etiology. Methods: Probands of the above - mentioned pedigrees, who had been diagnosed with AN, were evaluated and followed up in the Department of Otolaryngology Head and Neck Surgery, China PLA General Hospital. Their family members were studied and the pedigree diagrams were established. History of illness, physical examination,pure tone audiometry, acoustic reflex, ABRs and transient evoked and distortion- product otoacoustic emissions (TEOAEs and DPOAEs) were obtained from members of these families. DPOAE changes under the influence of contralateral sound stimuli were observed by presenting a set of continuous white noise to the non - recording ear to exam the function of auditory efferent system. Some subjects received vestibular caloric test, computed tomography (CT)scan of the temporal bone and electrocardiography (ECG) to exclude other possible neuropathy disorders. Results: In most affected subjects, hearing loss of various degrees and speech discrimination difficulties started at 10 to16 years of age. Their audiological evaluation showed absence of acoustic reflex and ABRs. As expected in AN, these subjects exhibited near normal cochlear outer hair cell function as shown in TEOAE & DPOAE recordings. Pure- tone audiometry revealed hearing loss ranging from mild to severe in these patients. Autosomal recessive inheritance patterns were observed in the three families. In Pedigree Ⅰ and Ⅱ, two affected brothers were found respectively, while in pedigree Ⅲ, 2 sisters were affected. All the patients were otherwise normal without evidence of peripheral neuropathy at the time of this writing. Conclusions: In this study, patients with feature of non- syndromic hereditary auditory neuropathy were identified in three Chinese families.Pedigree analysis indicates autosomal recessive inheritances in the pedigrees. The observed inheritance and clinical audiologic findings are different from those previously described for non-syndromic low-frequency sensorineural hearing loss. This information should facilitate future molecular candidate genes screening for understanding the mechanism of AN.

Objectives: Auditory neuropathy (AN) is a sen-sorineural hearing disorder characterized by absent or abnormal auditory brainstem responses (ABRs) and normal cochlear outer hair cell function as measured by otoacoustic emissions (OAEs). Many risk factors are thought to be involved in its etiology and patho-physiology. Three Chinese pedigrees with familial AN are presented herein to demonstrate involvement of genetic factors in AN etiology. Methods: Probands of the above - mentioned pedigrees, who had been diagnosed with AN, were evaluated and followed up in the Department of Otolaryngology Head and Neck Surgery, China PLA General Hospital. Their family members were studied and the pedigree diagrams were established. History of illness, physical examination, pure tone audiometry, acoustic reflex, ABRs and transient evoked and distortion - product otoacoustic emissions (TEOAEs and DPOAEs) were obtained from members of these families. DPOAE changes under the influence of contralateral sound stimuli were observed by presenting a set of continuous white noise to the non - recording ear to exam the function of auditory efferent system. Some subjects received vestibular caloric test, computed tomography (CT) scan of the temporal bone and electrocardiography (EGG) to exclude other possible neuropathy disorders. Results: In most affected subjects, hearing loss of various degrees and speech discrimination difficulties started at 10 to 16 years of age. Their audio-logical evaluation showed absence of acoustic reflex and ABRs. As expected in AN, these subjects exhibited near normal cochlear outer hair cell function as shown in TEOAE & DPOAE recordings. Pure - tone audiometry revealed hearing loss ranging from mild to severe in these patients. Autosomal recessive inheritance patterns were observed in the three families. In Pedigree I and II, two affected brothers were found respectively, while in pedigree III, 2 sisters were affected. All the patients were otherwise normal without evidence of peripheral neuropathy at the time of this writing. Conclusions: In this study, patients with feature of non - syndromic hereditary auditory neuropathy were identified in three Chinese families. Pedigree analysis indicates autosomal recessive inheritances in the pedigrees. The observed inheritance and clinical audiologic findings are different from those previously described for non - syndromic low - frequency sensorineural hearing loss. This information should facilitate future molecular candidate genes screening for understanding the mechanism of AN.