Temporal bone findings suggest mechanical obstruction of arachnoid villi by focal hemorrhage within the cochlear aqueduct midportion. Increased perilymphatic fluid pressure was evidenced by fluid "backing up" through soft tissue about the cochlear aqueduct, and reaching the internal auditory canal. Backing up of perilymphatic fluid, rather than its mixing with fresh blood in a widely patent cochlear aqueduct, provides evidence that arachnoid villi have a resorptive function within the cochlear aqueduct, and that the cochlear aqueduct is not a free, open passageway between cerebrospinal fluid and perilymph.
A previously reported case showed a similar tract between cochlear aqueduct and internal auditory canal. The aqueduct and tract contained fibrotic arachnoid, possibly representing true obstruction, rather than dural scarring that filled the cranial aperture of the aqueduct. The scarring of both dura and arachnoid suggest previous infection.
Gussen R. Arachnoid Villi Obstruction in the Cochlear Aqueduct. Arch Otolaryngol. 1972;96(6):565–569. doi:https://doi.org/10.1001/archotol.1972.00770090843013
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