What is the location of the modiolus of the cochlea?

Location of the Modiolus of the Cochlea

The modiolus is the central axis or core of the cochlea, containing the spiral ganglion cell bodies and serving as the bony structure around which the cochlear turns spiral.

Anatomical Position and Structure

• The modiolus forms the central bony pillar of the cochlea, around which the cochlear turns spiral 1
• It contains Rosenthal's canal, which houses the spiral ganglion cell bodies that transmit auditory signals from the cochlea to the brain 2
• The modiolus is located within the petrous portion of the temporal bone, forming part of the inner ear structure 1

Microanatomical Features

• Spiral ganglion cell bodies within the modiolus extend to an angular depth of 630-680° (near the end of the second turn of the cochlea) 2
• The apical modiolus can be accessed through a cochleostomy in the lateral second turn of the cochlea 3
• The modiolus demonstrates significant interindividual variability in size and shape, with variations similar to or greater than those observed in the lateral wall of the cochlea 4

Clinical Significance

• The modiolus is an important landmark in temporal bone CT imaging for evaluation of inner ear structures 1
• The distance between spiral ganglia in the modiolus and cochlear implant electrodes significantly affects the efficiency of electrical stimulation in cochlear implants 5
• Reduced cochlear modiolus area has been associated with certain cases of sudden deafness, potentially indicating insufficient maturation of the inner ear 6
• The modiolus is a target for potential stem cell-based and gene therapies for auditory nerve regeneration 3

Imaging Considerations

• High-resolution CT of the temporal bone provides excellent delineation of the bony modiolus 1
• MRI with dedicated internal auditory canal protocols, particularly high-resolution T2-weighted sequences, can visualize the fluid-filled spaces around the modiolus 1
• For optimal visualization of inner ear structures including the modiolus, thin-section imaging techniques are recommended 1

Surgical Considerations

• The variable anatomy of the modiolus is critical for cochlear implantation, particularly for perimodiolar electrode arrays that are designed to hug the modiolus 4, 5
• Optimal placement of perimodiolar cochlear implant arrays requires consideration of individual variations in modiolar dimensions (approximate range of 2-5mm) 4
• Surgical access to the apical modiolus can be achieved through a transcanal approach with a cochleostomy in the lateral second turn 3

The modiolus serves as a critical anatomical landmark in otologic imaging and surgery, with its precise anatomy being particularly important in cochlear implantation and potential future regenerative therapies for hearing loss.