Morphometric comparison of endolymphatic and perilymphatic spaces in human temporal bones

Area of Science:

• Anatomy and Physiology of the Inner Ear
• Otology and Neurotology Research

Background:

• Accurate quantification of inner ear fluid spaces is crucial for understanding auditory and vestibular function.
• Previous studies have lacked precise measurements of endolymphatic and perilymphatic compartments in healthy human temporal bones.

Purpose of the Study:

• To precisely measure the volumes of the endolymphatic and perilymphatic spaces within the human inner ear.
• To determine the proportional distribution of fluid spaces in the cochlea and vestibule.

Main Methods:

• Utilized human temporal bones, selected for absence of pathology and structural integrity of the membranous labyrinth.
• Employed horizontal serial sections and a microcomputer digitizing tablet for precise area measurements.
• Measured scala tympani, scala vestibuli, scala media, and vestibular spaces, averaging three repeated measurements.

Main Results:

• The mean total labyrinthine fluid space was 204.5 mm³, with endolymphatic space at 38.1 mm³ and perilymphatic space at 166.4 mm³.
• The vestibular fluid space averaged 120.9 mm³ and the cochlear fluid space averaged 83.6 mm³.
• In the vestibule, perilymph occupied 74.8% and endolymph 25.2%; in the cochlea, perilymph occupied 90.8% of the fluid space.

Conclusions:

• The perilymphatic space constitutes the vast majority of the fluid volume in both the human cochlea and vestibule.
• These quantitative data provide a foundational reference for future research in inner ear physiology and pathology.