Temporal bone histopathological features of a worker who received high doses of radiation in a criticality accident: a case report.

In 1999, three workers received high doses of radiation in a small Japanese plant while they were preparing fuel for an experimental reactor. This criticality accident at melting point was caused by the addition of too much uranium enriched to a relatively high level, causing a 'criticality' (a limited uncontrolled nuclear chain reaction), which continued intermittently for 20 h. The three workers concerned were hospitalized, two in a critical condition. The first worker died 12 weeks later, and the second worker 7 months later. The third worker is in a healthy condition. We report on the temporal bone histopathological features of the second worker. Our temporal bone study revealed: 1) the large loss of bone marrow tissue with a small number of myelocytes remaining in the mastoid bone and the abundance of fatty tissue in the mastoid bone, 2) inflammation of the mucosal layer of the middle ear and the mastoid air cells, 3) mild degeneration of the spiral ganglions and the sensory hair cells of the cochlea, 4) mild degenerative changes of sensory hair cells of the semicircular canals and otolith organs, and 5) vestibular ganglions and geniculate ganglions were well preserved.