Magnetic resonance imaging characteristic of cholesteatoma of the skull base / 中华放射学杂志

ABSTRACT

Objective To evaluate the value of MRI categorization of cholesteatoma of the skull base (CSB) and its MRI diagnostic characteristic Methods The CT, MRI and pathological data of 15 patients with CSB were reviewed The CSBs were categorized into type I and type II based on the difference of signal intensity on T 1 weighted image, and the differences between the two types of CSB were compared in the aspects of CT and MRI findings and osseous encroachment of the skull base Results Extremely high signal intensity on T 2 weighted image being similar to that of cerebrospinal fluid, and unenhanced tumor parenchyma on enhanced T 1 weighted image were noted in the 15 cases of CSB Of the 15 CSBs, 6 were categorized as type I and the other 9 as type II on the basis of the difference of the signal intensity on T 1 weighted image The 6 CSBs of type I, located in the prepontine and cerebellopontine angle cisterns, appeared as homogeneous hypoattenuating on CT scan and homogeneously decreased signal intensity on T 1 weighted image coupled with unenhanced tumoral capsule and relatively normal skull base The tumor parenchyma of this type was consisted of homogeneous cholesterol crystal The 9 CSBs of type II, located in unilateral floor of middle or posterior cranial fossa, were demonstrated as mixed density on CT scan and mixed signal intensity on T 1 weighted image, of which 4 presented as decreased signal intensity scattered with increased signal intensity, 5 largely as increased signal intensity The 9 cases were noted with enhanced tumoral capsule and marked osseous encroachment of the skull base, and the parenchyma of which was mainly comprised of keratinized epithelia and proteins Conclusion The categorization of CSB into type I and type II is sensible, which reflects the distinction in both histopathology and biological behaviour between the two types of CSB and plays an important role in guiding MRI diagnosis of CSB The MRI diagnostic characteristic of CSB includes the versatile signal intensity on T 1 weighted image, marked increased signal intensity on T 2 weighted image, unenhanced tumor parenchyma and type related osseous encroachment of the skull base