Histopathology of Pseudomonas osteomyelitis of the temporal bone starting as malignant external otitis.

Although the natural history and treatment of "malignant external otitis" have been well described, available histopathologic data are limited to three case reports. The histopathology in two additional cases, in which the disease process was advanced and uncontrolled, is presented to illustrate the unique progression of temporal bone osteomyelitis due to the Pseudomonas organism. In both cases the bony labyrinthine capsule demonstrated remarkable resistance to the osteomyelitic process even though the infection seemed to pass around the inner ear from all sides. The most active area of osteomyelitis was at the skull base along the sigmoid sulcus, posterior fossa surface of the temporal bone, and petrous apex. Spread to the opposite petrous apex occurred anterior to the foramen magnum via the basisphenoid, cavernous sinus, and peritubal areas. The clinical and histopathologic data demonstrated that the disease process had a similar progression in both cases, starting in the external auditory canal with spread to the stylomastoid and jugular foramina. This resulted in septic thrombosis of the lateral venous sinus and subsequent extension to the petrous apex from both posterior and middle fossa surfaces of the petrous bone. The infection spread along vascular and fascial planes rather than through pneumatized tracts of the temporal bone. The treatment of this disease is discussed in the light of the histopathologic findings.