The acoustic reflex latency test: clinical application

Area of Science:

• Audiology
• Neurotology
• Diagnostic audiology

Background:

• Acoustic reflex latency measures the delay between auditory stimulus and middle-ear muscle contraction.
• Retrocochlear lesions affecting the VIIIth nerve may prolong this latency.

Purpose of the Study:

• To develop and clinically validate the Acoustic Reflex Latency Test (ARLT) for detecting retrocochlear pathologies.
• To test the hypothesis that retrocochlear lesions prolong acoustic reflex latency.

Main Methods:

• Developed the Acoustic Reflex Latency Test (ARLT) protocol, including equipment and procedures.
• Measured absolute latency and interaural latency differences (ILD) in normal subjects and patients with cochlear or retrocochlear lesions.
• Utilized ipsilateral and contralateral measurements with 100 Hz and 2000 Hz stimulus frequencies.

Main Results:

• Acoustic Reflex Latency Test (ARLT) demonstrated significant latency prolongation in patients with retrocochlear lesions, including acoustic tumors.
• Optimal test effectiveness was achieved using both ipsilateral and contralateral measures, specific frequencies, and considering both absolute latency and ILD.
• The ARLT proved to be a valid, cost-effective, and simple clinical procedure.

Conclusions:

• The ARLT is a valuable tool for diagnosing retrocochlear pathologies, particularly acoustic tumors.
• The ARLT offers comparable diagnostic information to Brainstem Evoked Response Audiometry (BERA) with greater efficiency and reduced cost.
• Minor modifications to standard impedance equipment are sufficient for ARLT implementation.