The answer is b) pituitary macroadenoma.

In the present case, the select axial CT scan image at the level of the suprasellar cistern reveals a 1.5 cm round enhancing (hyperdense) mass lesion in the cistern space, that should be all hypodense (black, due to the cerebrospinal fluid in that location). The differential diagnosis of such a lesion would include all of the options that were provided: intracranial aneurysm (the carotid arteries course just lateral to the pituitary sella, through the cavernous sinus regions), craniopharyngioma (a slow growing tumour of pituitary gland embryonic tissue origin, most common in children but can be seen in adults, which can grow quite large, up into the suprasellar cistern space region), meningioma (tumours of the meningeal lining, usually benign, typically strongly enhance, can occur anywhere in the head where the meninges exist) or thalamic glioma (which can become exophytic and extend inferiorly into the suprasellar CSF space). However, it’s the MR images that really help with the correct diagnosis. The coronal MR reveals that the mass lesion arises from the base of the sella turcica (ruling out glioma and meningioma), and is homogeneous and well-defined. A craniopharyngioma will also arise from the sella turcica but it’s typically very inhomogeneous, with extensive central cystic change and associated calcifications. The carotid arteries (the small black circles adjacent to the mass on either side on the MR image) were normal.

Pituitary gland adenomas are benign neoplasms arising from the anterior portion of the pituitary gland, which can be both “functioning” (secrete hormones leading to a variety of symptoms depending on the hormones released) and “non-functioning.” The hormones potentially secreted include prolactin (most commonly), growth hormone (GH), adrenal corticotrophic hormone (ACTH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). Both functioning and non-functioning tumours can also cause symptoms by secondary pressure effects on adjacent structures: compression of normal pituitary gland tissue (hypopituitarism), pituitary stalk (prolactin elevation), cranial nerves II, III, IV, V & VI in the adjacent lateral cavernous sinus regions, and the optic chiasm above, along the roof of the suprasellar cistern CSF space.

Pituitary gland adenomas are referred to as microadenomas when less than 10 mm in diameter, and macroadenomas when 10 mm or greater in diameter, by convention.

MRI is the imaging modality of choice when assessing the pituitary gland and the anatomy about the pituitary sella and suprasellar cistern. MR provides superior soft tissue delineation, direct multiplanar imaging (vital in this small select anatomical region), and doesn’t utilize ionizing radiation. Most cases performed for assessment of the pituitary gland can be performed without IV contrast administration, and even the application of 3D MR angiographic imaging of the adjacent Circle Of Willis arteries requires no contrast (instead utilizing the flow properties of arterial blood, and some really complicated physics stuff, to produce the resultant spectacular 3D mapping imagery).

In the case presented, the patient underwent surgical removal of the non-functioning macroadenoma and his vision gradually returned to normal.

References

1. Provenzale JM. Am J Roentgenol 2006;186:931-2.
2. Davis PC et al. Am J Roentgenol 1987;148:797-802.