Rj. Bohinski et al., Intraoperative magnetic resonance imaging to determine the extent of resection of pituitary macroadenomas during transsphenoidal microsurgery, NEUROSURGER, 49(5), 2001, pp. 1133-1143
OBJECTIVE: Well-established surgical goals for pituitary macroadenomas incl
ude gross total resection for noninvasive tumors and debulking with optic c
hiasm decompression for invasive tumors. In this report, we examine the saf
ety, reliability, and outcome of intraoperative magnetic resonance imaging
(iMRI) used to assess the extent of resection, and thus the achievement of
preoperative surgical goals, during transsphenoidal microneurosurgery.
METHODS: Our magnetic resonance operating room contains a Hitachi AIRIS II
0.3-T, vertical-field open magnet (Hitachi Medical Systems America, Inc., T
winsburg, OH). A motorized scanner tabletop moves the patient between the i
maging and operative positions. For transsphenoidal surgery, the patient is
positioned directly on the scanner tabletop so that the surgical field is
located between 1.2 and 1.6 m from the magnet isocenter. At this location,
the magnetic field strength is low (< 20 G), thus permitting the use of man
y conventional surgical instruments. Thirty consecutive patients with pitui
tary macroadenomas underwent tumor resection in our magnetic resonance oper
ating room by use of a standard transsphenoidal approach. After initial res
ection, the patient was advanced into the scanner for imaging. If residual
tumor was demonstrated and deemed surgically accessible, the patient underw
ent immediate re-exploration.
RESULTS: iMRI was performed successfully in all 30 patients. In one patient
, iMRI was used to clarify the significance of hemorrhage from the sellar r
egion and resulted in immediate conversion of the procedure to a craniotomy
. In the remaining 29 patients, initial iMRI demonstrated that the endpoint
for extent of resection had been achieved in only 10 patients (34%) after
an initial resection attempt, whereas 19 patients (66%) still had unaccepta
ble residual tumor. All 19 of these latter patients underwent re-exploratio
n. Ultimately, re-exploration resulted in the achievement of the planned en
dpoint for extent of resection in all of the 29 completed transsphenoidal e
xplorations. Operative time was extended in all cases by at least 20 minute
s.
CONCLUSION: iMRI can be used to safely, reliably, and objectively assess th
e extent of resection of pituitary macroadenomas during the transsphenoidal
approach. The surgeon is frequently surprised by the extent of residual tu
mor after an initial resection attempt and finds the intraoperative images
useful for guiding further resection.