Arrested pneumatisation of the sphenoid

Case contributed by Dr Erik Ranschaert


This 24 year-old woman was complaining of headaches and photophobia with intermittent nausea and vomiting for several years. Physical, neurological and laboratory investigations were unremarkable.

Patient Data

Age: 24
Gender: Female

Check the individual description for each sequence. 

Check the individual description for each sequence. 

Case Discussion

The normal process of pneumatisation of the skull base and paranasal sinuses starts at the age of 4 months and develops through young adulthood. Red bone marrow is being replaced by fatty marrow prior to pneumatisation of the paranasal sinuses, including the sphenoid bone. The precise mechanisms that remain largely unclear. This bone marrow conversion precedes the invasion of epithelial cells to form the respiratory mucosa. When one of the steps described above is halted, no or reduced pneumatisation of the sinus will occur.

Imaging consists of CT and MR studies involving the skull base. 

CT findings: characteristic features on CT is the presence of 

  • a non-expansile lesion with
  • internal curvilinear calcifications and 
  • sclerotic margins 

MRI findings: hallmark of MR imaging is 

  • presence of internal fat and microcystic components
  • absence of any mass effect 

The non-expansile nature of the lesion is best evaluated at the inferior orbital fissure and vidian cannal, which are not displaced nor disrupted.

Differential Diagnosis: 

  • fibrous dysplasia
  • ossifying fibroma
  • chondrosarcoma
  • osteomyelitis
  • chordoma 
  • bone metastasis

In contrast with arrested pneumatisation, all of these conditions lack the presence of internal fat, or usually show signs of mass effect on the surrounding structures.

With courtesy of drs. M. de Jong and drs. Th. Fassaert 

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Case information

rID: 10700
Published: 7th Sep 2010
Last edited: 7th Oct 2015
Inclusion in quiz mode: Included

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