How to differentiate sensorineural hearing loss from conductive hearing loss using latency versus intensity curves in Brainstem Auditory Evoked Potentials (BAEP)?

From the Guidelines

To differentiate sensorineural hearing loss from conductive hearing loss using latency vs intensity curves in Brainstem Auditory Evoked Potentials (BAEP), focus on the pattern of wave V latency changes across different stimulus intensities, as this approach is supported by the most recent clinical practice guidelines 1. When analyzing these curves, it's essential to understand that in conductive hearing loss, the latency-intensity curve shows a parallel shift to the right, indicating increased latencies at all intensities while maintaining a normal slope, as sound is simply attenuated by the conductive mechanism 1.

Key Differentiation Points

• In conductive hearing loss, the curve shifts in parallel, reflecting the need for higher intensities to achieve the same neural response, but neural transmission proceeds normally once the stimulus reaches the cochlea.
• In sensorineural hearing loss, the latency-intensity curve is abnormally steep, with disproportionately prolonged latencies at lower intensities, indicating cochlear pathology and potential neural transmission dysfunction.
• Absolute latencies of all waves are typically prolonged in conductive hearing loss but interwave intervals remain normal, whereas in sensorineural hearing loss, interwave intervals may be abnormal, particularly I-V.
• The amplitude ratio of wave V to wave I can also aid in differentiation, with sensorineural hearing loss often showing reduced wave I amplitude, while conductive hearing loss typically maintains normal amplitude ratios despite overall reduced amplitudes.

Clinical Implications

Given the importance of distinguishing between sensorineural and conductive hearing loss for proper diagnosis and management, as emphasized in recent guidelines 1, clinicians should prioritize this differentiation to improve patient outcomes, including hearing recovery and quality of life.

Evidence-Based Recommendation

The most recent and highest quality study 1 supports the use of latency vs intensity curves in BAEP as a critical tool for differentiating between sensorineural and conductive hearing loss, highlighting the need for prompt and accurate diagnosis to guide appropriate management and improve patient care.

From the Research

Differentiating Sensorineural Hearing Loss from Conductive Hearing Loss

To differentiate sensorineural hearing loss from conductive hearing loss using latency vs intensity curves in Brainstem Auditory Evoked Potentials (BAEP), several key points must be considered:

• BAEP is a useful tool for assessing the integrity of the auditory pathway from the ear to the brainstem 2, 3.
• Sensorineural hearing loss is associated with abnormalities in the BAEP, including prolonged latencies and reduced amplitudes 2, 3.
• Conductive hearing loss, on the other hand, typically does not affect the BAEP, as the problem lies in the middle ear rather than the auditory nerve or brainstem 4.

Latency vs Intensity Curves in BAEP

• The latency vs intensity curve in BAEP can help differentiate between sensorineural and conductive hearing loss 3.
• In sensorineural hearing loss, the latency vs intensity curve may show a prolonged latency at high intensities, indicating a problem with the auditory nerve or brainstem 3.
• In conductive hearing loss, the latency vs intensity curve is typically normal, as the middle ear problem does not affect the auditory nerve or brainstem 4.

Clinical Applications

• BAEP can be used to assess hearing loss in adults and children, including those with suspected sensorineural or conductive hearing loss 2, 3.
• The test can help identify the type and degree of hearing loss, and can be used to monitor changes in hearing over time 2, 3.
• Other tests, such as pure-tone audiometry and impedance audiometry, can also be used to assess hearing loss and differentiate between sensorineural and conductive hearing loss 4, 3.

Key Findings

• Sensorineural hearing loss is a common type of hearing loss in adults, and can be associated with abnormalities in the BAEP 2.
• Conductive hearing loss is typically associated with middle ear problems, and does not affect the BAEP 4.
• The latency vs intensity curve in BAEP can help differentiate between sensorineural and conductive hearing loss 3.