1. Magnetic Resonance Imaging of Pituitary Tumors
Dr Khalili
Endocrinologist

2. Magnetic Resonance Imaging (MRI) is currently considered a major
keystone of the diagnosis of diseases of the hypothalamic-hypophyseal
region.

3. However,
the relatively small size of the pituitary gland,
its location deep at the skull base and
the numerous physiological variants present in this area
impede the precise assessment of the
anatomical structures and, particularly, of the pituitary gland itself

4. The diagnosis of the often tiny lesions of this region – such as pituitary
microadenomas – is then difficult if the MRI technology is not optimized
and if potential artifacts and traps are not recognized.
Advanced MRI technology can not only depict small lesions with greater
reliability, but also help in the differential diagnosis of large tumors.

5. Pituitary adenomas represent the most common pathology
of the sellar region.
They become symptomatic if they exert a
mass effect on the surrounding structures, or
in cases of hormonal hypersecretion.
Pituitary adenomas are frequently discovered by chance.

6. MRI has totally supplanted CT (computed tomography)
in the diagnosis of these lesions.
CT is still obtained in rare cases, including the search for
tumor calcifications when a craniopharyngioma is suspected, or of
bone erosion in the presurgical assessment of the clivus in aggressive pituitary adenomas.

7. The Normal Pituitary Gland
The pituitary gland is routinely examined in sagittal and
coronal projections in every case, and in axial projections in
some particular circumstances.
In our practice, gadolinium injection is not always mandatory and depends on the results of nonenhanced sequences.

8. Coronal T1- and T2-weighted sequences are always performed perpendicularly to a reference plan drawn on the sagittal view, e.g. a line tangential to the inferior surface of the corpus callosum ( fig. 1 ).
Fig. 1. Sagittal T1-weighted image obtained to determine coronal projections.
Coronal sequences are obtained perpendicularly to the subcallosal plane.

9. This strategy permits a perfect comparison of images
on serial MRIs.
In normal subjects, the shape of the anterior pituitary is variable on coronal images, with a
flat,concave or convex upper surface;
its height can vary considerably from 1–2 to 7–8 mm.
The T1-weighted signal of the normal anterior pituitary gland is strictly identical to that of the cerebral white matter,

10. The posterior lobe can be masked by the dorsum sellae in the T1-weighted sagittal view,
so that its demonstration is best obtained on
axial T1- weighted fat-saturated sequences.
After intravenous gadolinium injection, enhancement of the anterior pituitary, pituitary stalk and tuber cinereum is normally observed ( fig. 2 ).

12. Fig. 2. MRI of the normal pituitary gland
Fig. 2. MRI of the normal pituitary gland. a , b Coronal T1- and T2-weighted images.

13. c Axial T1-weighted fat-saturated image (the arrow points to the posterior lobe).

14. d Sagittal T1-weighted image: anterior pituitary (1); posterior pituitary (2); pituitary stalk (3); 3rd ventricle (4).

15. e Contrastenhanced sagittal T1-weighted MRI: enhancement of the anterior pituitary, the pituitary stalk and the tuber cinereum (arrow). f Anatomic representation of the normal sellar region;

17. Pituitary Adenomas The MRI aspect of pituitary adenomas is described
according to their size and their hormonal secretion.

18. Pituitary Microadenomas
Pituitary microadenomas are defined as tumors measuring
less than 10 mm in diameter.
the term ‘picoadenomas’ is proposed for adenomas measuring less than 3 mm that frequently need specific technical options, such as the search for corticotropic adenomas.

19. Pituitary microadenomas have to be differentiated from:
– artifacts, – normal anatomical structures, such as the posterior Pituitary – variants from normal, such as unusual intrasellar arteries, – intrasellar cysts, such as Rathke’s cleft cysts (RCC),

20. a small sella turcica can also mimic a pituitary gland enlargement;
frequently associated with an extensive sphenoidal sinus pneumatization,
( fig. 3 ).

21. Fig. 3. a , b Small sella, short sellar floor and
hyperpneumatization of the sphenoid bone
(frontal view).

22. Dynamic imaging has to be read with caution and can be
the source of false positive diagnoses: ( fig. 4 ).

23. a
Fig. 4. a–e Hazard of dynamic MRI: normal delayed enhancement of the anterior pituitary gland wrongly interpreted as a microadenoma (arrow
in c ). The off-midline posterior lobe enhances earlier because of its direct blood supply. b cc

24. Microprolactinomas
Microprolactinomas are the most frequent pituitary microadenomas.
They are usually round or oval in shape,
located off midline,
hypointense on T1-weighted images, as compared to the normal anterior pituitary gland, and
more or less hyperintense on T2-weighted images.

25. Microprolactinomas generally have a T1-weighted signal similar to the
cerebral gray matter,
while the normal unaffected anterior
pituitary gland has the same T1-weighted signal as the cerebral
white matter ( fig. 5 ).

26. a b Fig. 5. Typical microprolactinoma MRI pattern:
the adenoma is located in the top right side of the pituitary and appears
hypointense on T1-weighted images and
Hyperintense on T2-weighted images ( a );
Unusual hypointense microprolactinoma on a
T2-weighted image, before and after gadolinium injection ( b ). a b

27. High signal intensity on T1-weighted images can sometimes be observed, reflecting hemorrhagic transformation, not uncommon even in asymptomatic patients with prolactinomas .
Intratumoral calcifications are very rare, but do not rule out the diagnosis of pituitary adenomas, particularly in men.
An additional CT scan can be helpful in these cases.

28. some relationship between the tumor T2 signal and the serum prolactin levels;
the more hyperintense the tumor, the lower the prolactin
levels are.
T2 hypointense microprolactinomas are very unusual;
they seem to be associated with higher prolactin levels
and can possibly have a different evolution, e.g. arise during
pregnancy ( fig. 6 , 7 ).

29. Fig. 6. Normal appearance of the pituitary in the 7th month of a normal pregnancy: the gland is enlarged and hyperintense on T1-weighted MRI images ( a ); microprolactinoma before cabergoline treatment ( b ), and moderate adenoma enlargement in the 7th month of pregnancy after cabergoline withdrawal ( c ).

30. Fig. 7. A 27-year-old female with ‘post-pill’ amenorrhea; prolactin was 4,000 mIU/l. Left-sided prolactinoma with an unusual T2-hypointense signal ( a ); T1- ( b ) and post-contrast T1-weighted sequences ( c ). Pregnancy occurred quickly after dopamine agonist treatment and was stopped as soon as the pregnancy was determined ( d ). On the coronal T2-weighted image, a clear enlargement of the adenoma in the 8th month of pregnancy is seen, with tilting of the optic chiasm. Cabergoline was reintroduced and normal delivery occurred. At follow-up,4 months after delivery, there was shrinkage of the mass and a slight hemorrhagic transformation of the adenoma ( e ). f Further reduction of the lesion 1 year after delivery.

31. There is generally a good correlation between the prolactin
level and adenoma size, except for extremely T2-hyperintense
and T1-hyperintense lesions as these situations usually
correspond to tumors secreting low amounts of prolactin .
We have almost never detected a microprolactinoma
with a prolactin level <1,000 mIU/l (35 μg/l) on MRI.

32. Indirect radiological signs of a microadenoma are changes
of the sellar floor and an upper convex surface.
The pituitary stalk displacement is not always helpful for diagnosis.
However, a localized subtle deformation of the sellar floor is a valuable indicator, even for small microadenomas .

33. When the radiological diagnosis is obvious after T2- and
T1-weighted sequences in a context of infertility, amenorrhea-
galactorrhea and hyperprolactinemia, we consider
contrast-enhanced sequences unnecessary.
On the contrary,contrast medium injection must be used in all uncertain situations, e.g. if an isointense or hypointense pituitary microadenoma is suspected.

34. Shrinkage of microprolactinomas is normally observed
after a few weeks of treatment with dopamine agonists.
Most of the time, an accentuation of high T2-intensity is also seen.
A partial hemorrhagic transformation of the adenoma can mask its shrinkage.

35. Enlargement in size, usually a doubling, of the microadenoma occurs during pregnancy, principally during the third trimester, if dopamine agonists have been withdrawn
In the same way, the volume of the normal anterior pituitary gland increases – on average by 0.08 mm per week – and its T1-weighted signal increases.
Return to the prepregnancy size of the adenoma and of normal pituitary gland shape is usually observed a few weeks after delivery

36. In some particular conditions, such as
hemorrhagic transformation of the adenoma,
a second pregnancy or
prolonged medical treatment during pregnancy,
a reduction of size or even the disappearance of the adenoma at MRI can sometimes be observed, paralleled by the normalization of prolactin levels.

37. Growth Hormone-Secreting Microadenomas
Growth hormone (GH)-secreting microadenomas were
previously underdiagnosed, while to date they represent
one third of all somatotropinomas.
Indeed, with high-resolution MRI, particularly in elderly subjects, it has become possible to reveal tiny pituitary adenomas – sometimes within an enlarged sella, erroneously called ‘empty sella’– corresponding to involuted adenomas, either spontaneously or after hemorrhage .

38. More than half of microsomatotropinas as well as GH-secreting pituitary macroadenomas present with hypointensity on T2-weighted images, if compared with the unaffected pituitary gland
Fig. 8. T2-weighted images of a well-defined,
hypointense GH-secreting microadenoma.

39. Corticotroph Microadenomas
Corticotroph microadenomas represent a difficult challenge
for the neuroradiologist, their size being sometimes
at the limit or below the radiological visibility
Fig. 9. Corticotroph ‘picoadenoma’ demonstrated
with optimized MRI techniques

40. In cases of negative MRI examination, it is recommended to
resume MRI and to add alternative sequences, such as delayed
imaging studies, dynamic MRI, 3D imaging and other
variants

41. Recently, Erickson et al
Recently, Erickson et al. have confirmed that 3-tesla MRI is significantly
more sensitive than 1.5-tesla MRI and should become
the gold standard for the evaluation of patients with
ACTH-dependent Cushing’s disease.
Ikeda et al. found a high accuracy of microadenoma
localization at surgery using composite images
from methionine positron emission tomography (METPET)
and 3-tesla MRI, but this has not been introduced into
clinical practice.

42. Pituitary Macroadenomas

43. Pituitary Nonfunctioning Macroadenomas
Pituitary nonfunctioning macroadenomas are predominantly
localized within an enlarged sella turcica.
They often also present with extrasellar extension, upwards into the suprasellar cistern, downwards into the sphenoid sinus or laterally into the cavernous sinus.
The normal residual pituitary tissue is compressed and pushed laterally, towards one side, and superiorly, but never inferiorly.

44. Upwards extension is present in more than 70% of patients
with possible contact, or even compression, of the
optic chiasm.
The sellar diaphragm can function like a ‘belt’,
thus giving the adenoma an hourglass shape ( fig. 10 ).

45. Fig. 10. So-called ‘snowman’ hemorrhagic
pituitary macroadenoma with hyperintensity
of the upper part of the tumor on the T1-
weighted image and hypointensity on the
T2-weighted image. a, b Postgadolinium
coronal T1- and T2-weighted images. c, d
Postgadolinium sagittal T1- and T2-weighted
images.
The suprasellar component of large macroadenomas is often
multilobular.

46. Fig. 11. Pituitary macroadenoma with suprasellar extension.
T2 hyperintensity within the optic chiasm could indicate a nonrecovery of the visual field defect despite surgery.
Hyperintensity of the optic chiasm on T2-weighted images can indicate a poor prognosis for the visual function even after quick removal of the pituitary adenoma responsible for optic pathway compression
Downwards extension of pituitary nonfunctioning adenomas is more rare than in GH-secreting tumors.

47. Fig. 12. Pituitary macroadenoma invading the sphenoid sinus and eroding the clivus. a, b Sagittal T1- and T2-weighted images. c Sagittal
reformatted CT.
MRI, or even better CT, demonstrates a focal or widespread defect of the
more anterior, upper portion of the clivus

48. The signal intensity of nonfunctioning macroadenomas
is usually inhomogeneous, particularly on the T2-weighted
images, with disseminated areas of hyperintensities which
reflect cystic or necrotic components.
The posterior lobe is hyperintense in T1-weighted sequences. It is compressed, flattened and best identified in the axial noncontrast projection.

49. Aberrant storage of antidiuretic hormone in the socalled
‘ectopic posterior lobe’ occurs when the pituitary stalk
is severely compressed, i.e. in practice with pituitary adenomas
>20 mm in height.
An ectopic posterior lobe may be present with smaller adenomas after hemorrhagic events or after surgery.
Enlargement of an ectopic posterior lobe can occur with time, sometimes described as a ‘nodule’ in the opticochiasmatic cistern, particularly on CT examination.

50. Fig. 13. Pituitary macroadenomas: lateral displacement of the normal pituitary tissue
( a ) and the dural tail (not specific; b ).
Gadolinium injection enhances the normal pituitary tissue,
which is located superiorly and/or laterally on one side,
but never inferiorly

51. Postgadolinium enhancement of the dura, the socalled
‘dural tail’, is not specific of meningiomas and has been described with large pituitary adenomas, particularly if
they are hemorrhagic or
soon after surgery, as well as with
perisellar aneurysms

52. Intratumoral Hemorrhage
Intratumoral hemorrhage typically occurs in pituitary adenomas
and much less frequently in other types of pituitary tumors.
Hemorrhage classically appears with high signal intensity on T1-weighted images, and either as an intratumoral dark mass or as a cyst with a dark rim on T2-weighted images, which indicates a hematoma or hemorrhagic cyst.
Tosaka et al. consider T2-weighted gradient-echo MRI the most sensitive technique for the detection of blood, in particular in hyperacute and chronic hemorrhages.

53. a
Fig. 14. Pituitary macroadenomas: the fluidfluid
level indicates an old hemorrhage.

54. Pituitary Apoplexy
The diagnosis of pituitary apoplexy is made clinically. It is usually caused by infarction or hemorrhage of a previously undiagnosed pituitary macroadenoma, typically a nonfunctioning adenoma.
This clinical syndrome, characterized by sudden headache, oculomotor nerve palsy and asthenia, can mimic subarachnoid hemorrhage, stroke or meningitis.

55. A radiological diagnosis may be difficult in the early stage.
The classical predominant hyperintensity on T1-weighted images
is frequently absent because infarction or hemorrhage are still in the form of deoxyhemoglobin.
However, sequential MRI will demonstrate the progressive increase of
T1-weighted hyperintensity, with the passage from deoxyhemoglobin
to methemoglobin.
T2-weighted gradient-echo MRI can be helpful in this case, making pituitary hemorrhage appear as a ‘dark mass’

56. Fig. 15. Pituitary apoplexy with a sudden onset
of headache 24 h before. a Coronal T1-
weighted image: ‘striated’ pattern of a pituitary
mass without evidence of hemorrhage.
b Diffusion-weighted MRI: increased signal
intensity (arrow) within the pituitary mass.
c ADC map showing decreased signal intensity.
d Coronal T1-weighted image 2 days later:
peripheral T1-hyperintensity represents
methemoglobin. a b c

57. Finally, reactive thickening of the sphenoid sinus mucosa constitutes a reliable sign, present from the early stage
If surgery is postponed or not indicated, shrinkage of the mass usually occurs within several weeks

58. Prolactinomas in Men
Prolactinomas in men are most often large or very large and
frequently invasive.
Extension into the sphenoid sinus can be impressive and mimic a primitive sphenoid sinus tumor.
Prolactin levels are usually much higher than in females and
can reach hundreds of thousands mIU/l.
Tumor shrinkage and T2-weighted hyperintensity occur very rapidly
with dopamine agonist treatment ( fig. 16 ).
Shrinkage of large invasive macroprolactinomas can exceptionally lead to
cerebrospinal fluid fistula

59. a
Fig. 16. a Macroprolactinoma with suprasellar extension. b Six weeks after dopamine agonist treatment. c After the patient stopped treatment.d–f Shrinkage of the adenoma after reinstitution of medical treatment on sequential MRIs, 2 months, 1 and 2 years later, respectively

60. GH-Secreting Macroadenomas
GH-secreting pituitary macroadenomas present specific
characteristics.
According to personal data obtained from MRI performed in 300 acromegalic patients, two thirds of them were macroadenomas and 71% extended predominantly downwards into the sphenoid sinus ( fig. 17 a).

61. Fig. 17. GH-secreting macroadenomas: predominant
inferior extension ( a ) and isolated
inferior extension ( b ).

62. Chiasmatic compression and resulting visual field defects were
present in only 17% of the cases .
This explains in part the long delay frequently observed between the onset of symptoms and the diagnosis.
An isolated inferior extension, i.e. without any extension above the sellar diaphragm level ( fig. 17 b), was found by Zada et al. in 24% of somatotropinomas;

63. The T2-weighted MRI signal appears hypointense in 52% of GH-secreting pituitary adenomas, as compared to the normal pituitary gland.
Most of these T2-hypointense adenomas present a well-defined round or oval contour ( fig. 18 )

64. Fig. 18. Two different types of GH-secreting
pituitary adenomas: T2-hypointense ( a ) and
T2-hyperintense ( b ) to the normal pituitary
gland.

65. Fig. 22. GH-secreting pituitary adenomas
before ( a , b ) and after somatostatin analogs
( a’ , b’ ). Only the T2-hypointense adenoma
( b, b’ ) shrank.

66. Thank you