XXI The Effects of Ionizing Radiation on the Ear

To determine how high-dose tumor radiotherapy affects the fine structure of the ear, 14 patients receiving 4000 to 6000 r Co/sup 60/ radiation at the region of the cochlea were studied. Radiation affected individuals selectively, causing a small shift in hearing threshold in some but not in others. The shift appeared to be primarily due to the development of a radiation otitis media. No changes were observed in some of the ears examined. The appearance of perceptive hearing loss and temporary recruitment is thought to be related to a transient vasculitis in the inner ear. The disturbed function of the cochlea is probably the result of an altered metabolism of the hair cells or an increased endo- or perilymphatic pressure due to the transient vasculitis. It is concluded that ionizing radiation in the dose used for head and neck tumors does not cause microscopically detectable changes during the course of treatment in the cochlea or labyrinth. The late effects of radiation result from changes in collagen, blood vessels, and bone and are a separate entity. Necrosis and breakdown of the skin of the external ear canal with or without secondary infection was seen less frequently during or following Co/sup 60/more » treatmert compared with conventional x- ray therapy.« less