This is a retrospective analysis of a prospectively constructed database consisting of 59 patients who underwent transsphenoidal procedures at Memorial Sloan-Kettering Cancer Center by a single neurosurgeon (V.T.) in a 24-month period from February 2008 to February 2010. A complete endocrine profile was documented both pre- and postoperatively on all patients. An endocrinologist was involved in all cases where an endocrinopathy was identified. Preoperative visual field (VF) testing was performed on all patients who presented with visual complaints. Postoperative VF testing was performed when preoperative deficits were identified and /or if patients had sustained visual complaints. Three of the 52 adenoma patients had recurrent tumors with prior transsphenoidal resections. Fourteen of the 52 (27%) adenomas were hormone-secreting tumors. All resected specimens underwent routine histological and immunofluorescence staining as indicated by a neuropathologist. Patients had a mean length of follow-up of 7.2
0.5 months and a range of 12 days to 600 days.
High-Field iMRI Navigation System
Memorial Sloan-Kettering's BrainSuite consists of a 1.5-T iMRI scanner integrated with an image-guided neuronavigation system (BrainLab, Feldkirchen, Germany) that is installed within one of hospital's main operating room. The walls, floor, and ceiling contain radiofrequency shielding based on aluminum and copper mesh. The high-field-strength magnetic resonance scanner (Magnetom Espree; Siemens Healthcare, Erlangen, Germany) consists of a superconductive magnet with a length of 120 cm and an inner bore diameter of 70 cm. An elliptical line (8-m major and 5-m minor axis) is drawn around the scanner to mark the 5-G field limit for safety. The operating table is positioned parallel to the scanner during surgery so that the patient's head lies outside the 5-G line, allowing the use of standard operating equipment and instruments. The head holder has a bivalve shape, consisting of two separate parts, and containing an eight-channel receiver array. The upper part of the head holder contains 14 MRI-visible fiducial markers.
Calculations of preoperative tumor dimension and extent of resection were based on analysis of MRI sequences and independent evaluation by neuroradiologists at our institution. Preoperatively, thin-slice (3 mm, 0 interslice gap) coronal precontrast and dynamic postcontrast T1- and T2-weighted imaging of the sellar region was obtained in addition to axial thin section (3 mm, 0 interslice gap) T1-weighted and three-dimensional spoiled gradient postcontrast sequences of the entire brain. These sequences were performed as a part of BrainLab protocol in addition to the routine imaging of the brain, which includes axial and sagittal T1-weighted, axial T2-eighted, fluid-attenuated inversion recovery, and diffusion-weighted sequences. The dynamic imaging protocol consists of a precontrast and four successive rapidly obtained T1-weighted images acquired 15 to 20 seconds after intravenous bolus injection of contrast in the coronal plane. This preoperative scan is then integrated into the BrainSuite MR neuronavigation system. Intraoperative scans typically consist of T1-weighted sequences in the axial and coronal planes without and with contrast. T2-weighted images, dynamic sequences, and three-dimensional reconstructions are obtained at the discretion of the surgeon. The intraoperative scan is then used for repeat registration if additional resection or exploration is to be performed. Postoperative scans are typically obtained 3 months postoperatively if a definitive intraoperative scan showing the final operative result was not obtained. Gadolinium diethylenetriaminepentaacetic acid (Magnevist, Berlex Laboratories, Wayne, NJ) 0.1 mmol/kg was used as the contrast agent for all scans, and the intraoperative contrast administration was limited to a single dose.
All 59 patients underwent a preoperative thin-slice axial T1-weighted gadolinium-enhanced MRI for frameless stereotaxy. All procedures were performed under general endotracheal anesthesia. After intubation, two cottonoids soaked in 4% cocaine were placed in each nostril to promote vasoconstriction. Gauze was packed in the oropharynx to minimize drainage from the surgical site into the mouth and esophagus. The patients were placed on the MRI operating table in the supine position, and the head was rigidly fixed in an MRI-compatible frame suitable for frameless stereotaxy (BrainLab). We placed the head in a mildly extended configuration to facilitate access to the sphenoid sinus through the right nostril by the right-handed surgeon. Twenty-three patients (43.4%) had a lumbar drain placed at the beginning of the procedure to allow injection of saline solution, thus facilitating delivery of the suprasellar component of the tumor during resection. If an intraoperative leak was encountered, the lumbar drain was maintained for a minimum of 3 days postoperatively. Further vasoconstriction and nasal mucosa anesthesia were achieved by submucosal injection of 1% lidocaine with epinephrine solution. This was performed under the operating microscope (Leica, Wetzlar, Germany), which was used for the remainder of the procedure. The sphenoidal ostium was identified and the anterior wall of the sphenoid sinus rongeured using a variety of Kerrison instruments. The extent of resection of the anterior sphenoidal wall and vomer depended on tumor size and patient anatomy. The cartilaginous septum was displaced medially after incising the mucosa proximal to the vomer. The sellar anatomy and relative location of the cavernous sinuses and carotid arteries were confirmed with neuronavigation (BrainSUITE iMRI, BrainLab) and intracranial Doppler prior to opening the dura. In cases where the tumor invaded juxtasellar structures, such as the ethmoidal air cells, the clivus, or the lateral recesses of the sphenoid sinuses, the bony exposure was further extended as necessary. After incision of the dura, tumor resection was performed in a standard fashion. As mentioned above, a subset of patients had 10 to 50 mL normal saline injected through the lumbar drain to facilitate descent of suprasellar tumor into the sellar resection cavity. An equal volume of cerebrospinal fluid (CSF) was drained at the end of the resection, and the drain was removed unless an intraoperative CSF leak was identified.
When the surgeon felt that all resectable tumor had been evacuated, an iMRI was obtained. Preparation for imaging included a complete instrument and sponge/cottonoid counts and was often performed at the surgeon's indication while the surgical procedure was ongoing. A neuroradiologist was always available to analyze the iMRI images. Overall, there was minimal disruption of the usual workflow or violations of the sterile conditions. However, full instrument counts had to be performed prior to imaging each time an MRI had to be obtained, for safety purposes. Nursing staff received specific training for work within the iMRI suite. In the subset of patients who required more than one iMRI, no additional gadolinium was given after the first administration. Repeat registration for neuronavigation was performed using the intraoperative study.
After tumor resection was completed, the resection cavity was covered with Gelfoam (Pfizer, New York, NY) and Tisseal (Baxter, Deerfield, IL). CSF leaks were repaired with a fat graft or Duragen (Integra, Plainsboro, NJ) and Tisseal (Baxter), and a lumbar drain was placed. Nasal packing was used infrequently.
All population statistics are presented as mean
standard error of the mean.