ABSTRACT
Background: Auditory neuropathy, auditory dys-synchrony, and auditory neuropathy spectrum disorder (ANSD) are variableterms used to describe an auditory disorder seen in patients ranging in age from infants to adults. The prevalence of ANSD indeaf schoolchildren is 2.46% within the age range of 6–12 years. In children, they are detected by the presence of otoacousticemissions (OAEs) in the absence of ABRs. In older age group, difficulty hearing in noise, fluctuating hearing, and speechperception performance not predict ed by the level of residual hearing have been reported. The multitude of etiologies forANSD results in heterogeneous group of patients – making the management strategies even more challenging. The commonetiologies put forward are – prematurity, neonatal insult, genetic abnormality, ototoxic drugs, and head injury.Aim of the Study: This study aims to study the audiological profile in ANSD in a tertiary care hospital and to study the etiologyof ANSD cases.Materials and Methods: A total of 42 patients attending the ENT Outpatient Department of Government Medical College,Kozhikode, with ANSD were included in the study. An ethical committee clearance was obtained before the commencement ofthe study. An ethical committee cleared consent form was used for the study. All ANSD patients were evaluated with a detailedhistory including perinatal and development history, ototoxic drug exposure, head trauma, neurodegenerative conditions, andfamily history. Following clinical evaluation which included general examinations, ENT examination, and central nervous systemexamination, an audiological evaluation, which included pure tone audiometry, speech audiometry, immittance evaluation, OAE,and auditory brainstem response, was done. Radiological investigation (magnetic resonance imaging brain with inner ear – focusingon any structural anomalies; cochlea, vestibulocochlear nerve, and internal auditory canal) was done. Patients were counseledregarding the rehabilitation options based on their audiological and radiological results and the need for follow-up was explained.Observation and Results: A total of 42 patients attending the ENT Outpatient Department (OPD) of Government MedicalCollege, Kozhikode, with ANSD were included in the study. Among the 42 patients, 21 (50%) were in the age group of 11–20 yearsfollowed by 13 patients who were between 0 and 10 years (30.95%). The remaining 8 were aged above 20 years (19.04%).The youngest patient was 10 months old and the oldest was aged 38 years with a mean age of 10.35 ± 2.10 years. Therewere 29 (69.04%) females and 13 (30.95%) males. 3/42 (7.14%) patients gave a history of exposure to ototoxic drugs suchas streptomycin, gentamicin, and kanamycin, but never had a history of loss of hearing before that. History of premature birthwas noted in 10 (23.80%) patients and the remaining patients did not show premature birth history. Among the 42 patients ofthis study group, 23 (54.76%) had low birth weight, of which 2/42 (4.76%) were <1.5 kg. 21/42 (50%) patients had birth weightabove 1.5 kg. 10/42 patients (23.80%) gave a history of neonatal intensive care unit (NICU) admissions at the time of their birth.Conclusions: The major risk factor identified in this study for ANSD was low birth weight with prematurity, NICU admissions,and viral infections having significant contributions. On audiological evaluation, hearing loss was of mild-to-moderate rangewith a low-frequency loss. There was no statistical correlation between pure audiometry values and speech audiometry whichwas a characteristic observation. OAEs were present in the majority of patients with absent cochlear microphonics (reversepolarity) and acoustic reflexes.