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Magnetic resonance imaging characteristic of cholesteatoma of the skull base<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
江波 孟悛非 陈应明
JIANG Bo, MENG Quan－fei, CHEN Ying－ming1 Department of Radiology, The First Affiliated Hospital, Sun Yat－Sen University,Guangzhou 510080, China
Correspondence: JIANG Bo, Email: csujbo @1631com
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 reviewed1 The CSBs were categorized into type I and type II based on the difference of signal intensity on T1－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 T2－weighted image being similar to that of cerebrospinal fluid, and unenhanced tumor parenchyma on enhanced T1－weighted image were noted in the 15 cases of CSB1 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 T1－weighted image1 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 T1－weighted image coupled with unenhanced tumoral capsule and relatively normal skull base1 The tumor parenchyma of this type was consisted of homogeneous cholesterol crystal1 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 T1－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 T1－weighted image, marked increased signal intensity on T2－weighted image,unenhanced tumor parenchyma and type2related osseous encroachment of the skull base1
Key words：Cholesteatoma；Skull base；Tomography, X－ray computed；Magnetic resonance imaging | 
