Role of MDP SPECT/CT Bone Scintigraphy in Evaluation of Patients with Malignant Otitis Externa Compared to HRCT: A prospective Study.

Abstract

Background: Malignant otitis externa (MOE) is a potentially fatal disease; accurate assessment of the extent of this disease is warranted to plan the course of treatment and to predict the prognosis. The aim of the study was to compare the efficiency of high resolution computed tomography (HRCT) with that of 99mTechnetium methylene diphosphonate (99mTc-MDP) single photon emission computed tomography/computed tomography (SPECT/CT) in precise evaluation of the disease extent and to evaluate the prognostic value of SPECT/CT staging in terms of therapeutic response and survival in patients with MOE. Patients and Methods: This prospective study included twenty-five patients (17 males and 8 females) with clinically diagnosed MOE, all of themunderwent both HRCT and 99mTc-MDP SPECT/CT imaging of the skull. Based on 99mTc-MDP uptake in SPECT/CT scan, the findings were staged accordingly and compared with the findings of HRCT in all patients. In addition, clinical outcome and disease-free survival (DFS) were analyzed according to the SPECT/CT staging.Results: Out of 25 patients included in our study, HRCT showed osseous changes in only 4/25 (16%) patients, 99mTc-MDP SPECT/CT demonstrated more osseous involvement in 21/25 (84%) patients. No patients in stage I in this work, 8 patients had disease confined to the mastoid/temporal bone, not reaching midline (stage II), 6 of them were surviving with recovery and clinical improvement, and 2 patients died. Three patients had petrous involvement reaching midline (stage III), 2 of them were surviving with clinical improvement, and the 3rd patient died. Fourteen patients had sphenoid involvement/disease extended to the contralateral temporal bone (stage IV), 5 of them were surviving with recovery and clinical improvement, 5 were surviving, yet had disease progression, and 4 patients died within less than one year of diagnosis. At the end of follow up period; in total; 7 patients had died,of whom 3 in stage IV died due to MOE, while the remaining 4 cases (2 in stage II, 1 in stage III, and 1 in stage IV) died due to unrelated causes. Both of disease duration and SPECT/CT staging were statistically significant predictor factors for DFS (P=0.05 and 0.047 respectively).Conclusion: SPECT/CT has a higher sensitivity than HRCT in determining the exact extent of MOE and was much better correlated with disease prognosis.