Malignant external otitis: Early scintigraphic detection
Pseudomonas otitis externa in elderly diabetics may extend aggressively to adjacent bone, cranial nerves, meninges, and vessels, leading to a clinical diagnosis of "malignant" external otitis. Early diagnosis is necessary for successful treatment. This study compares the findings of initial radiographs, thin-section tomography of temporal bone, CT scans of head and neck, technetium-99m methylene diphosphonate (MDP) and gallium-67 citrate scintigraphy, and single-photon emission computed tomography (SPECT) for detection of temporal bone osteomyelitis in ten patients fulfilling the clinical diagnostic criteria of malignant external otitis. Skull radiographs were negative in all of the eight patients studied. Thin-section tomography was positive in one of the seven patients studied using this modality. CT scanning suggested osteomyelitis in three of nine patients. Both Tc-99m and Ga-67 citrate scintigraphy were positive in 10 of 10 patients. Three patients who were considered to be in clinical remission had positive Tc-99m scans and normal Ga-67 scans. These results suggest that technetium and gallium scintigraphy are more sensitive than radiographs and CT scans for early detection of malignant external otitis. Gallium scintigraphy appears to be more specific for follow-up evaluation of these patients.