Malignant external otitis: early scintigraphic detection.

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Abstract
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 [computed tomography] scans of head and neck. 99mTc methylene diphosphonate (MDP) and 67Ca citrate scintigraphy and single-photon emission computed tomography (SPECT) for detection of temporal bone osteomyelitis in 10 patients fulfilling the clinical diagnostic criteria of malignant external otitis. Skull radiographs were negative in all of the 8 patients studied. Thin-section tomography was positive in 1 of the 7 patients studied using this modality. CT scanning suggested osteomyelitis in 3 of 9 patients. Both 99mTc and 67Ga citrate scintigraphy were positive in 10 of 10 patients. Three patients who were considered to be in clinical remission had positive 99mTc scans and normal 67Ga scans. These results suggest that Tc and Ga scintigraphy are more sensitive than radiographs and CT scans for early detection of malignant external otitis. Ga scintigraphy appears to be more specific for follow-up evaluation of these patients.