SEMIQUANTITATIVE SKULL PLANAR AND SPECT BONE-SCINTIGRAPHY IN DIABETIC-PATIENTS - DIFFERENTIATION OF NECROTIZING (MALIGNANT) EXTERNAL OTITISFROM SEVERE EXTERNAL OTITIS

Early diagnosis of necrotizing external otitis (NEO) includes the use of bone scintigraphy since clinical assessment alone cannot differenti ate the necrotizing type of otitis from the severe type of external ot itis in which there is no extension to the adjacent bone. Four-hour pl anar bone scintigraphy may reflect soft-tissue infection, and therefor e may not be useful in distinguishing NEO from severe external otitis (SEO). Twenty-four-hour bone scintigraphy using planar or SPECT imagin g may better reflect bone uptake and increase the accuracy of the test . Methods: Twenty-six diabetic patients (12 diagnosed NEO; 14 SEO) and 10 nondiabetic (ND) patients were studied. Lesion-to-nonlesion (UN) c ount ratios obtained from planar and SPECT imaging at 4 hr, 24 hr and 24 hr/4 hr (24/4) were assessed. Results: Count ratios obtained from t he 4- and 24-hr planar and SPECT images were significantly higher in t he NEO patients compared to SEO patients for both planar and SPECT stu dies (p < 0.001, 0.005). The 24/4 count ratio was also significantly h igher in the NEO patients on the planar (p < 0.01) and the SPECT studi es (p < 0.001). The ND patients were not different from SEO patients o n 4-hr planar, 4- and 24-hr SPECT as well as 24/4-hr planar and SPECT studies. The UN count ratio threshold yielding the best sensitivity fo r detecting NEO was 1.05 for the 24/4 SPECT study. Conclusion: In diab etic patients, an early distinction between NEO and SEO patients can b e reliably made by using UN count ratios on 24/4 or 24-hr SPECT bone s cintigraphy.