Asymmetric pneumatization of the anterior clinoid process

Case contributed by Dr Katia Kaplan-List


30-year-old male with headaches and visual disturbances.

Patient Data

Age: 30-year-old
Gender: Male

ASNR 2016: This case was submitted as part of the American Society of Neuroradiology (ASNR 2016) Case Of The Day competition, in collaboration with 

There is a high T1 iso-T2 nonenhancing structure located in the expected region of the right anterior clinoid process, laterally to the intracranial portion of the right optic nerve that represents normal marrow and surrounding cortical bone. The contralateral anterior clinoid process is pneumatized and appears extremely hypointense on all pulse sequences.

Illustrative case showing a similar finding on CT (another patient)


A different patient for comparison purposes. There is asymmetric pneumatization of the anterior clinoid processes with the left side pneumatized. 

Case Discussion

Asymmetrically pneumatized anterior clinoid process may present a diagnostic challenge when seen on MRI and may be misinterpreted as a thrombosed aneurysm or a mass.

It is easy to characterize on CT.

Asymmetrically underpneumatized anterior clinoid process contains normal marrow and surrounding cortical bone, and appears as high T1 iso-T2, non-enhancing structure. Completely pneumatized anterior clinoid process appears hypointense on all pulse sequences and may mimic the flow void of an aneurysm. 


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