History of imaging the pituitary region
The history of imaging the pituitary region encompasses many different modalities and has greatly evolved over the years, including plain radiographs, pneumoencephalography, angiography, CT and MRI. The pituitary gland is situated in the central skull base, closely related to the sphenoid sinus, cavernous sinuses and optic chiasm and is subject to a wide array pathologies which can involve these important adjacent structures.
Plain radiographs and tomography
Plain radiographs of the skull are able to demonstrate remodelling of the pituitary fossa, erosion of the tuberculum sella as well as outlining tumoral calcification (e.g. craniopharyngioma) or hyperostosis (e.g. meningioma). It is, however, incapable of visualising suprasellar extension of disease.
Tomography was also used extensively and was able to better delineate changes in pituitary fossa morphology.
Pneumoencephalography, performed by injecting air into the subarachnoid space and manoeuvring it into the basal cisterns. Extension of a pituitary mass into the suprasellar cistern would, therefore, become apparent.
Catheter angiography was also extensively used. Not only is it able to demonstrate displacement of regional vessels (e.g. elevation of the anterior cerebral arteries) thereby inferring the presence of a large mass, it is also useful in directly visualising tumours which have altered vascularity.
Inferior petrosal sinus sampling has also been used to try and confirm the presence of a microadenoma which is occult on imaging.
Computed tomography (CT) was revolutionary in imaging all parts of the body, but especially the central nervous system. Routine CT of the brain is able to demonstrate changes in the pituitary fossa, however, it was the development of true coronal technique and dynamic scanning which, for the first time, was able to directly visualise microadenomas.
The patient would be placed prone on the CT gantry and their next hyperextended. Axial imaging would then pass in a near-coronal plane through the pituitary fossa.
Imaging the pituitary repeatedly as IV contrast was injected allowed microadenomas to be seen as areas of delayed enhancement.
Magnetic resonance imaging (MRI) has essentially replaced all other modalities for routine imaging of the pituitary region, with CT reserved to help assess bony changes as well as on occasion perform CT angiography.
A typical MRI protocol of the pituitary region comprises sagittal and coronal imaging including dynamic post contrast acquisition.
- 1. Shlomo Melmed. The Pituitary. ISBN: 9780123809278