- Tumorous pathology of the pituitary region is rich and diverse.
- It mainly consists of macro and microadenomas,
which represent :
o 15% of all the intracranial tumors.
o 90% of the pituitary tumors.
- It mainly affects adults ++,
and is exceptional in children.
- The aspect od pituitary adenomas varies in relation with their volume and their secretory type.
- Pituitary adenomas are classified according to :
Anatomy,
in :
- Pituitary picoadenomas : when the diameter is <3mm.
- Microadenomas : between 3-10mm.
- Macroadenomas : >10mm with supra,
latero or infrasellar extension.
Hormones,
in :
- Secreting adenomas,
which are detected because of biological disorders :
o Prolactin-secreting adenomas : young female subject with galactorrhea,
amenorrhea,
hyperprolactinemia.
o Growth hormone-secreting adenomas : acromegaly (adults) or gigantism (children)
o ACTH-secreting adenomas : Cushing’s disease (exceptional).
o Thyroid stimulating and gonadotrophic adenomas (FSH-LH secreting ones) : generally dignosed at the invasive macroadenoma stage.
- Non-secreting adenomas,
which are detected at the macroadenoma stage,
with neurological or ophtalmological symptoms.
- MRI is now the preferred examination for a morphological study of the hypothalamo-hypophyseal axis.
- CT scan is still a second-line examination,
which allows us to analyze bone structures and aerial cavities of the basal skull.
- Thanks to the multiple plane examination and its very good contrast resolution,
MRI allowx a better appreciation of : the tumor’s size,
morphological characteristics,
and,
most importantly,
its extrasellar extension :
v Suprasellar :
o Elevation of the diaphragme sellae.
o Breach of the diaphragma sellae : « brioche aspect ».
o Invasion of the opto-chasmatic cisterns : optic nerves compression.
o Elevation of the 3rd ventricle : hydrocephalus.
v Infrasellar :
o Distorsion of the sellar floor.
o Invasion of the sphenoidal sinus
v Posterior :
o Filling of the pre-pontic cisterns.
v Lateral :
o Invasion of the cavernous loggia (internal carotid artery,
veinous plexus and cranial nerves : III,
IV,
V,
VI) : Knosp Grade.
Knosp et al offered a grading system for showing invasion of
cavernous sinus by a
pituitary macroadenoma.
Briefly,
the more laterally the adenoma grows and surrounds the
internal carotid artery (ICA),
the higher the grade is.
The grading is defined by the relation of the carotid lines with the limits of invasion of the adenoma.
These lines pass through the supra- and intracavernous parts of ICA in a coronal view.
There are medial,
median and lateral carotid lines.
Grade 0 - adenoma does not extend the medial carotid line.
Grade 1 - adenoma extends the medial line,
but doesn't reach the median line,
so-called “intercarotid” line.
Grade 2 - tumor extends beyond the median line,
but doesn't extend beyond or is tangent to the lateral line.
Grade 3 - tumor extends beyond the lateral line.
Grade 4 - tumor totally wraps around the intracavernous carotid artery.
Other signs of invasion of the cavernous sinus :
o Repelling of the intra-cavernous carotid artery
o Asymmetry of the cavernous sinuses’ sizes
o Bulging of the lateral wall
o No visualization of the median and medial intercarotid lines.
- Hence,
the objective of this study was to illustrate the contribution of MRI in exploring the sellar and suprasellar pathology by showing :
o The exact origin of the tumor,
its extent,
its relation with its surroundings,
especially the optic chiasm.
- Describe the imaging semiology of the different types of pituitary tumors.