endolymphaticus

Endolymphaticus is a term sometimes used in anatomical literature to describe the endolymphatic duct and its associated endolymphatic sac, parts of the inner ear’s endolymphatic apparatus. The endolymphatic duct and sac play a role in regulating the volume and composition of endolymph within the membranous labyrinth, which is essential for the function of the auditory and vestibular systems.

Anatomy and location: The endolymphatic duct originates from the vestibule of the inner ear and travels within the vestibular aqueduct to reach the endolymphatic sac. The sac lies within the dura of the temporal bone near the posterior labyrinth. The vestibular aqueduct houses the duct and sac as the endolymphatic compartment communicates with the rest of the labyrinth.

Development and histology: These structures arise from the otic placode during embryogenesis and are lined by epithelium continuous with the membranous labyrinth. They form part of the system that maintains endolymph homeostasis in the inner ear.

Function: The endolymphatic sac is thought to resorb endolymph and contribute to maintaining proper endolymphatic volume and ionic balance, which supports hair cell function in both hearing and balance.

Clinical significance: Abnormalities of the vestibular aqueduct or endolymphatic sac, such as enlargement (large vestibular aqueduct syndrome), can be associated with sensorineural hearing loss. Endolymphatic hydrops, reflecting excessive endolymph, is linked to Menière’s disease. Imaging assessment includes CT for bony anatomy and MRI for soft-tissue and hydrops evaluation; surgical approaches sometimes target the endolymphatic sac to alleviate symptoms.