Radiological Features of the Intraosseous Lipoma of the Sphenoid

Objective. Benign intraosseous lesions of the skull base are often identified in the course of routine radiological investigation. Imaging features associated with suspected intraosseous lipoma (IOL) can mimic more aggressive pathology. The features of this poorly described entity in the skull base were analyzed to aid the otolaryngologist in differentiation from other pathology. Study Design. Retrospective analysis of computed tomography (CT) and magnetic resonance imaging (MRI) images over the period from March 2007 to March 2009. Setting. Radiology service, tertiary hospital, Sydney, Australia. Methods. Images with diagnosis of incidental suspected IOL within the sphenoid were selected. Radiological features including trabecular pattern, secondary calcification, cortical bone thinning, and size and the presence of fat (defined as <-5 HU) were recorded. Results. Ten patients (5 male) were identified. Seventy percent had unilateral, single lesions occurring within the sphenoid bone. The mean size was 13.1 +/- 5.6 mm (range, 4-21 mm). Fat was demonstrated in all lesions. There were 3 cases of multiple lesions occurring within the sphenoid bone. In addition, 61.5% were associated with cortical bone thinning and 46.2% with secondary calcification within the lesion. Changes to normal trabecular bone occurred: 46.2% with a partial loss of and 53.8% with a complete absence of trabecular pattern. Histopathologic confirmation of IOL is presented. Conclusion. IOL is believed to be a more common benign intraosseous lesion within the skull base than previously reported. Cortical bone thinning and other features normally suggestive of aggressive pathology commonly occur. Otolaryngologists should be aware of these common lesions to avoid unnecessary further investigation.