RESULTS
Over the period between 2005 and 2015, 126 petrous bone DW-MRI were performed in our pediatric hospital. Distribution of the number of exams across the years is shown on Figure 1.
Forty-six MRI records, which were considered positive for cholesteatoma, were included. The average age of patients undergoing the MRI scan was 14.2±5.3 years old. The average delay between imaging and surgery was 111±78 days. Out of the 46 positives DW-MRI, a cholesteatoma was found surgically in 41 patients, which represents an 89% PPV. Regarding the histological reports, out of these 41 surgeries, keratin was found in all cases, and squamous epithelium in 29 cases. Therefore, DW-MRI sensitivities were 100.0% and 70.7% for respectively keratin and squamous epithelium.
True and false positives were compared (Table 1). There was no statistically significant difference between false positives and true positives, especially in terms of age, number of prior surgery, time between MRI and surgery, and ossicular prosthesis presence. However, two trends appear. First, 20.0% of the false positives had never had any previous ear surgery, versus 7.3% in true positives (p=0.341). Second, the average size of the diffusion hypersignal was smaller in false positives than in true positives: 6.68±4.29 mm versus 9.34±4.46 mm, although this difference was not significant (p=0.251).
The MR images of the 5 false positives DW-MRI were reviewed, with both surgical and pathological reports:
In conclusion, two patients didn’t have any ossicular lysis, three patients had T1 hypersignal, and two patients had a very small or thin DW-MRI hypersignal.