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:
- Case 1: a 14 years old girl with Turner syndrome. On the CT, the
middle ear was filled with isodense content, showing neither convex
limits nor ossicular lysis. On the MRI, there was a T1 and T2
hypersignal with DW hypersignal. Cholesterol granuloma was found.
- Case 2: a 16 years old girl. On CT, there was an antral and attical
filling with a demineralization of the long process of the incus. On
the MRI, there was a 4 mm DW-MRI hypersignal, with restricted
diffusion and T1 hyposignal, consistent with an attical small
cholesteatoma.
- Case 3: a 16 years old girl. On CT, middle ear cavities were
opacified. An attical DW-MRI hypersignal, with restricted diffusion on
ADC map, 6.5 mm large, was found with a slight T1 hypersignal: a
cholesterol granuloma was confirmed surgically.
- Case 4: a 12 years old boy. Posterior attical cavity, antrum and
mastoid were filled by T1 hyperintense material consistent with
cholesterol granuloma. A thin, linear diffusion hypersignal was
present at the lateral part of the attic.
- Case 5: a 7 years old boy. The diffusion hypersignal was very small:
3.5 mm in its largest diameter. The corresponding hyperdensity on the
CT scan had an atypical bony margin. Regarding the pathological study,
bony and cartilaginous tissues were found, without keratin nor
squamous epithelium.
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.