MRI appearances of the sphenoid sinus at the late follow-up of trans-sphenoidal surgery for pituitary macroadenoma.

We aimed to demonstrate the appearances of the sphenoid sinus on MRI performed later than 2 years post- transsphenoidal surgery (TSS). We retrospectively reviewed 47 patients in whom follow-up MRI scans had been performed at least 2 years post-TSS. We specifically reviewed the clinical and imaging of those patients in whom the sphenoid sinus was filled with signal abnormality or masses were present arising from the sinus roof and classified them as tumour or indeterminate abnormalities on imaging criteria. We documented other clinicoradiological details. Twelve of 47 patients demonstrated sphenoid sinus filling or sinus roof masses and in six of 12 patients it was possible to classify them as tumourous using imaging and clinical criteria. The indeterminate and non-tumourous sphenoid sinus abnormalities most frequently had a T1-weighted signal similar to subsellar tumour and displayed rim enhancement and thus could not be reliably distinguished from tumourous abnormality on the basis of signal or enhancement characteristics. The presence of a well-defined surgical defect in the sella floor was associated with resolution of abnormality on MRI follow-up. We concluded MRI findings of sphenoid sinus filling or sinus roof masses are present in approximately 26% of scans performed longer than 2 years post-TSS. Half of these are of indeterminate origin and follow-up is required to discriminate tumour from non- tumour with certainty. A well-defined surgical defect in the sella floor is, however, suggestive of a non-tumourous abnormality.