Fibrous dysplasia - skull base
Teenager attends ENT with left retro-auricular pain, mild fever and a facial palsy on examination.
Loading Stack -
0 images remaining
Extensive sclerotic bony expansion with a groundglass appearance involving the left zygoma, sphenoid and petrous temporal bone.
The bony expansion is centred on the medullary bone and has abrupt transition zones.
Almost complete bony stenosis of the left external auditory meatus down to 1-2mm with consequential fluid in the external auditory canal and middle ears. Ossicular chain intact.
The left mastoid air cells are under-pneumatised, and completely occupied by fluid.
The left internal auditory canal is normal, however, the bony expansion involves both the tympanic and mastoid segments of the facial canal which are obliterated/stenosed.
Fibrous dysplasia (FD) is a non-neoplastic tumour-like congenital process, manifested as a localised defect in osteoblastic differentiation and maturation, with replacement of normal bone with large fibrous stroma and islands of immature woven bone.
Fibrous dysplasia is found predominantly in children and young adults, with ~75% of patients presenting before the age of 30 years. Upto 25% occurs in the face and skull.
Typical CT features ( as shown in this case ) are:
- ground-glass appearance to bone
- homogeneously sclerotic bone
- well-defined borders ( abrupt transition )
- expansion of the bone, with overlying cortical bone intact
It may be a mono-ostotic or poly-ostotic disease and in some cases is part of a syndrome such as McCune-Albright.