Depending on authors, intra-cavernous invasion by a pituitary adenoma
is found in 9% to 40% of cases. In the light of our own experience, we
think that such an invasion is probably much less frequent than usual
ly evoked on CT-scan and MRI. In our study, it was confirmed in only o
ne case over 125 (0.80%), though radiological data suspected an intra-
cavernous invasion 17 times. An anatomical study on 20 cadavers showed
that 30% of normal pituitary glands present with a lateral expansion
into one or both cavernous sinsuses (CS). These natural invaginations
were already evoked by Harris and Rhoton in 1976. They can resemble an
intra-cavernous extension or invasion on MRI views, moreover when an
adenoma increases the volume of this expansion, and in the abscence of
any rupture of the medial wall of the CS. The medial wall of the CS i
s, in fact, constituted by a dural pouch which close-fits the pituitar
y gland and its expansions; its invaginates more or less in the CS, de
pending on the importance of the pituitary lateral expansion. In case
of a large adenoma, the finger-glove lateral distension of the pouch d
isappears progressively during the tumoral removal. Finally the dura r
eturns to its normal place back, at the end of the procedure. This con
cept of invagination of the CS medial wall, as opposed to that of inva
sion and therefore of rupture of the dural plane, explains the wide ra
nge of figures concerning the frequency of intra-cavernous invasion by
pituitary adenomas, in the literature. These figures are all the more
variable as there is not absolute criteria of intra-cavernous invasio
n on CT-scan nor MRI views. In the same way, no clinical criteria can
be retained to assume the existence of such an invasion. So, an ophtha
lmoplegia seems to be usually linked to a compression of oculomotors n
erves; it recovers in a large majority of cases, after the adenoma is
removed. In conclusion, we emphasize the necessity of interpreting wit
h great care radiological imaging when it evokes a possible intra-cave
rnous invasion of a pituitary adenoma. The indication of an eventual r
adiotherapy should be retained with as much care as possible, since co
mplete removal of an adenoma and its lateral expansion(s) is almost al
ways feasible through a trans-sphenoidal route.