Reflex "delay" in sensorineural hearing-loss

Area of Science:

• Audiology
• Neuroscience
• Otolaryngology

Background:

• The acoustic reflex, a crucial auditory response, is characterized by latency and rise-time.
• Instrumentation and stimulus characteristics influence these parameters, necessitating standardized measurement protocols.
• Normative data reveal age, recording method, and waveform variations affect acoustic reflex latency.

Purpose of the Study:

• To investigate the diagnostic utility of acoustic reflex latency and rise-time in various auditory pathologies.
• To establish normative values for acoustic reflex parameters and identify deviations in different patient groups.
• To correlate acoustic reflex abnormalities with specific types of hearing loss, including cochlear and retrocochlear lesions.

Main Methods:

• Measurement of acoustic reflex latency and rise-time using commercial audiometric equipment.
• Comparison of acoustic reflex parameters in healthy individuals across different age groups.
• Analysis of acoustic reflex latency and rise-time in patients with cochlear (Ménière's disease, ototoxic lesions) and retrocochlear lesions.
• Evaluation of interaural latency difference (ILD) for enhanced diagnostic accuracy.

Main Results:

• Normal acoustic reflex latency ranges from 150 ms (ipsilateral) to 200 ms (contralateral), with ILD not exceeding 40 ms.
• In cochlear deafness, latency and rise-time were slightly shorter in 25% of cases, particularly when ILD was assessed against the normal ear.
• Retrocochlear lesions, without cochlear involvement, showed lengthened latency and rise-time, with significant ILD values.
• Acoustic reflex delay was also noted in cases of brain-stem involvement.

Conclusions:

• Acoustic reflex latency and rise-time are valuable indicators of auditory pathway integrity.
• Deviations in acoustic reflex parameters can help differentiate between cochlear, retrocochlear, and brain-stem pathologies.
• Interaural latency difference is a critical parameter for diagnosing retrocochlear and brain-stem auditory impairments.