9.1 Case Presentation

9.1.2 Imaging Findings and Impression

Axial (▶ Fig. 9.1a), sagittal (▶ Fig. 9.1b), and coronal (▶ Fig. 9.1c) CT scans of the head without contrast show symmetric thickening (white arrow) of the inner table of the frontal bone.

9.2 Differential Diagnosis

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  Hyperostosis frontalis interna:

  
  
  
  
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    Symmetrical thickening involving the inner table of the frontal bones with no enhancement. It is frequently seen in middle-aged women.

  
  
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  Acromegaly:

  
  
  
  
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    Diffuse calvarial thickening associated with enlargement of the sinuses, enlargement of the sella turcica, frontal bossing, and prominence of the mandible.

    
    
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    Other skeletal features are also present involving the spine and joints.

  
  
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  Fibrous dysplasia:

  
  
  
  
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    A non-neoplastic condition involving the bones and commonly occurring in children and young adults.

    
    
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    Normal bone is replaced with fibrous stroma and immature woven bone. The skull is involved in the polyostotic form.

    
    
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    It is characterized by focal or diffuse ground glass thickening of the skull.

    
    
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    The ethmoid bone is the most common involved area of the skull base.

    
    
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    The inner table is more frequently involved.

  
  
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  Paget’s disease of the bone:

  
  
  
  
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    A chronic bone disorder characterized by excessive bone remodeling with replacement of normal bone architecture with a coarsened trabecular pattern.

    
    
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    Commonly involved sites include the skull, spine, pelvis, and long bones.

    
    
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    It is more common in individuals older than 40 years with a slight male predilection.

    
    
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    Involvement of the skull is characterized by diffuse thickening of the inner and outer tables as opposed to fibrous dysplasia, which predominantly affects the inner table.

    
    
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    Other findings in the skull are widening of the diploic space, mixed lytic and sclerotic lesions (cotton wool appearance), or large well-defined lytic lesions (osteoporosis circumscripta).

    
    
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    Enhancement of the lesions is seen in active disease.

  
  
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  Meningioma:

  
  
  
  
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    An extra-axial tumor arising from the arachnoid cap cells of the meninges.

    
    
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    Classically, it presents as a homogeneously enhancing dural-based lesion with a characteristic dural tail sign.

    
    
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    It is often associated with hyperostosis of the overlying skull that has been shown to be due to either hypervascularity or direct infiltration of tumor cells.

  
  
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  Sclerotic metastasis:

  
  
  
  
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    It can arise from a variety of primary malignancies including prostate carcinoma, breast carcinoma, transitional cell carcinoma of urothelial origin, medulloblastoma, neuroblastoma, and lymphoma, among others.

    
    
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    It is characterized by single or multiple focal areas of increased density as compared to the normal skull.

    
    
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    It tends to enhance.