Posture systematically alters ear-canal reflectance and DPOAE properties.

Area of Science:

• Auditory Neuroscience
• Otoacoustic Emissions
• Intracranial Pressure Monitoring

Background:

• The auditory system's sensitivity to posture is linked to intracranial pressure (ICP) fluctuations.
• Current ICP monitoring is invasive, necessitating the development of noninvasive methods.
• Distortion product otoacoustic emissions (DPOAE) and power reflectance are potential indicators of ICP changes.

Purpose of the Study:

• To investigate the impact of postural changes on DPOAE magnitude, DPOAE angle, and power reflectance.
• To assess the feasibility of using ear-canal based measures for noninvasive ICP monitoring.
• To evaluate the reliability and variability of these auditory measures under different postural conditions.

Main Methods:

• Measurements of DPOAE magnitude, DPOAE angle, and power reflectance were conducted on 12 normal-hearing subjects.
• Subjects were tested in two postural positions: upright (90 degrees) and tilted (-45 degrees).
• Each measurement was repeated five times across five separate sessions to ensure reliability.

Main Results:

• Significant changes (p<0.001) in DPOAE magnitude, DPOAE angle, and power reflectance were observed between upright and tilted positions for frequencies between 500 and 2000 Hz.
• DPOAE angle changes were significant across all measured frequencies (500-4000 Hz).
• Intra-subject variability was generally lower in the upright position compared to the tilted position.

Conclusions:

• Postural changes significantly alter auditory measures, including DPOAEs and power reflectance.
• These findings support the potential for ear-canal based auditory measurements as a noninvasive method for monitoring ICP.
• Further research is warranted to validate these auditory measures for clinical ICP assessment.