Objectives: To analyze communication routes between perilymph spaces and the modiolus in the human cochlea. Such pathways are of potential importance with regard to local inner ear drug delivery and pharmacokinetics.
Design: We analyzed the surface structure of the human cochlea, using high-resolution scanning electron microscopy (SEM) in macerated and freshly obtained specimens together with light microscopy of celloidin-embedded temporal bones.
Results: Combined SEM and light microscopy showed that perilymph and fluid spaces in the modiolar periphery form a common system. The modiolar wall of the scala vestibuli and tympani in the first and second turn is porous, forming a perilymphatic communication route to the perivascular and perineural spaces in the modiolus. A "perimodiolar lymph" or fluid space can be identified in the modiolar periphery. It communicates through a trabecular meshwork of porous membrane and web of connective tissue with the perilymph. The thin mesothelial cell sheets showed pores and displayed signs of vesicular activity.
Conclusions: This canalicular system may play a role in the circulation of perilymph in the human cochlea. We suggest that this system may represent an important fluid communication route between modiolus and perilymph and may represent a pathway for future drug and cell-based therapy to the inner ear.