Near Dehiscence of the Endolymphatic Duct and SAC

This radiographic case report showcases bilateral near-dehiscence of the endolymphatic duct and sac on imaging of the temporal bone. The endolymphatic duct and sac are structures of the temporal bone and posterior cranial fossa that are normally well protected in bone. They are critical to inner ear function and can be at risk if exposed during skull lateral base surgery. In this case, the structures are near-zero--dehiscent and at greater risk during temporal bone drilling. Axial, sagittal, and coronal views on high definition computed tomography scans are available for display. The endolymphatic duct can clearly be seen in the hyperpneumatized temporal bone as a soft-tissue density linear structure communicating from the otic capsule to the posterior fossa. Bilateral images are included and show the entire course of the duct in single image. This patient underwent infralabyrinthine approach to a jugular foramen chondrosarcoma, and hearing preservation was achieved. Lateral skull base surgeons should be aware of the possibility of dehiscence or near-dehiscence of the endolymphatic sac and duct as injury with high speed drill could lead to complete hearing and vestibular loss.