Faculty Bibliography

INTRODUCTION: Giant pituitary adenomas of excessive size, fibrous consistency or unfavorable geometric configuration may be unresectable through conventional operative approaches. We present our select case series for operative resection and long-term follow-up for these unusual tumors, employing both a staged procedure and a combined transsphenoidal-transcranial above and below approach. METHOD: A retrospective chart review was performed on patients operated via the staged, and combined approaches by the senior author (J.N.B.). Preoperative characteristics and postoperative outcomes were reviewed. A detailed description of the operative technique and perioperative management is provided. RESULTS: Between 1993 and 1996, two patients harboring giant pituitary adenomas underwent an intentionally staged resection, and between 1997 and 2006, nine patients harboring giant pituitary adenomas underwent surgery via a single-stage above and below approach. Nine patients (82%) presented with non-secreting adenomas and two patients (18%) presented with prolactinomas refractory to medical management. Gross total resection was achieved in six patients (55%), near total resection in 1 (9%), and subtotal removal in 4 (36%). Seven patients (64%) experienced visual improvement postoperatively and no major complications occurred. Long-term follow-up averaged 51.6 months. Panhypopituitarism was observed in four patients, partial hypopituitarism in four, persistent DI in two, and persistent SIADH in one. CONCLUSIONS: The addition of a transcranial component to the transsphenoidal approach offers additional visualization of critical neurovascular structures during giant pituitary adenoma resection. Complications rates are similar to other series in which complex pituitary adenomas are resected by other means. The above and below approach is both safe and effective and the immediate and long-term advantages of a single-stage approach justify its utility in this select group of patients.

OBJECTIVE:Up to 25% of patients experience subtle declines in post-operative neurocognitive function following, otherwise uncomplicated, carotid endarterectomy (CEA). We sought to determine if post-CEA neurocognitive deficits are associated with cerebral blood flow (CBF) abnormalities on post-operative MR perfusion brain scans. METHODS:We enrolled 22 CEA patients to undergo a battery of neuropsychometric tests pre-operatively and on post-operative day 1 (POD 1). Neurocognitive dysfunction was defined as a two standard deviation decline in performance in comparison to a similarly aged control group of lumbar laminectomy patients. All patients received MR perfusion brain scans on POD 1 that were analysed for asymmetries in CBF distribution. One patient experienced a transient ischemic attack within 24 hours before the procedure and was excluded from our analysis. RESULTS:Twenty-nine percent of CEA patients demonstrated neurocognitive dysfunction on POD 1. One hundred percent of those patients with cognitive deficits demonstrated CBF asymmetry, in contrast to only 27% of those patients without cognitive impairment. Post-CEA cognitive dysfunction was significantly associated with CBF abnormalities (RR=3.75, 95% CI: 1.62-8.67, p=0.004). CONCLUSION/CONCLUSIONS:Post-CEA neurocognitive dysfunction is significantly associated with post-operative CBF asymmetry. These results support the hypothesis that post-CEA cognitive impairment is caused by cerebral hemodynamic changes. Further work exploring the relationship between CBF and post-CEA cognitive dysfunction is needed.

OBJECTIVE:We sought to simulate the frontotemporal orbitozygomatic (FTOZ) craniotomy in a three-dimensional virtual environment on patient-specific data and to quantify the exposure afforded by the FTOZ while simulating controlled amounts of brain retraction. METHODS:Four computed tomographic angiograms were reconstructed with commercially available software (Amira 4.1.1; Mercury Computer Systems, Inc., Chelmsford, MA), and virtual FTOZ craniotomies were performed bilaterally (n = 8). Brain retraction was simulated at 1 and 2 cm. Surgical freedom and projection angle were measured and compared at each stage of the FTOZ. RESULTS:At 1 cm of retraction, surgical freedom increased by 27 +/- 14% for the removal of the orbital rim and by 31 +/- 18% for FTOZ (P < 0.01) when compared with frontotemporal (FT) craniotomy. At 2 cm of retraction, surgical freedom increased by 15 +/- 5% and 26 +/- 8% for the removal of the orbital rim and FTOZ, respectively (P < 0.01). With increased retraction, surgical freedom increased by 100 +/- 26%, 81 +/- 15%, and 82 +/- 27% for the FT, removal of the orbital rim, and FTOZ craniotomies, respectively (P < 0.001). Projection angle increased by 24.2% when orbital rim removal was added to the FT craniotomy (P < 0.01). CONCLUSION/CONCLUSIONS:Surgical freedom increases significantly at every step of the FTOZ craniotomy. This effect is less robust when brain retraction is increased. Brain retraction alone has a greater impact on surgical freedom than bone removal alone. Projection angle is significantly increased when orbital rim removal is added to the FT craniotomy. This model overcomes two major limitations of cadaver-based models: quantification of brain retraction and incorporation of patient-specific anatomy.

RATIONALE AND OBJECTIVES/OBJECTIVE:An automated method for identification and segmentation of acute/subacute ischemic stroke, using the inherent bi-fold symmetry in brain images, is presented. An accurate and automated method for localization of acute ischemic stroke could provide physicians with a mechanism for early detection and potentially faster delivery of effective stroke therapy. MATERIALS AND METHODS/METHODS:Segmentation of ischemic stroke was performed on magnetic resonance (MR) images of subacute rodent cerebral ischemia. Eight adult male Wistar rats weighing 225-300 g were anesthetized with halothane in a mix of 70% nitrous oxide/30% oxygen. Animal core temperature was maintained at 37 degrees C during the entire surgical procedure, including occlusion of the middle cerebral artery (MCA) and the 90-minute post-reperfusion period. To confirm cerebral ischemia, transcranial measurements of cerebral blood flow were performed with laser-Doppler flowmetry, using 15-mm flexible fiberoptic Doppler probes attached to the skull over the MCA territory. Animal MR scans were performed at 1.5 T using a knee coil. Three experts performed manual tracing of the stroke regions for each rat, using the histologic-stained slices to guide delineation of stroke regions. A strict tracing protocol was followed that included multiple (three) tracings of each stroke region. The volumetric MR image data were processed for each rat by computing the axis of symmetry and extracting statistical dissimilarities. A nonparametric Wilcoxon rank sum test operating on paired windows in opposing hemispheres identified seeds in the pixels exhibiting statistically significant bi-fold mirror asymmetry. Two brain reference maps were used for analysis: an absolute difference map (ADM) and a statistical difference map (SDM). Although an ADM simply displays the absolute difference by subtracting one brain hemisphere from its reflection, SDM highlights regions by labeling pixels exhibiting statistically significant asymmetry. RESULTS:To assess the accuracy of the proposed segmentation method, the surrogate ground truth (the stroke tracing data) was compared to the results of our proposed automated segmentation algorithm. Three accuracy segmentation metrics were utilized: true-positive volume fraction (TPVF), false-positive volume fraction (FPVF), and false-negative volume fraction (FNVF). The mean value of the TPVF for our segmentation method was 0.8877; 95% CI 0.7254 to 1.0500; the mean FPVF was 0.3370, 95% CI -0.0893 to 0.7633; the mean FNVF was 0.1122, 95% CI -0.0502 to 0.2747. CONCLUSIONS:Unlike most segmentation methods that require some degree of manual intervention, our segmentation algorithm is fully automated and highly accurate in identifying regions of brain asymmetry. This approach is attractive for numerous neurologic applications where the operator's intervention should be minimal or null.

OBJECT/OBJECTIVE:The aim of this study was to test the validity of the hypothesis that patients in whom brain metastasis is the first indication of an undiagnosed primary tumor have a better chance of survival than similar patients with a known primary lesion. METHODS:Between January 1983 and December 1998, 342 patients with computed tomography-diagnosed brain metastases were treated at a single institution. Information on potential prognostic factors, including primary diagnosis status, was collected retrospectively. Univariate and multivariate analyses were performed to identify prognostic factors related to survival. Survival was not statistically different between patients with an undiagnosed primary (UDP) lesion and those with a diagnosed primary (DP) tumor (6 and 4.5 months, respectively; p = 0.097). In the UDP group (122 patients [36%]), survival was not affected by the eventual identification of the primary disease (p = 0.905). The median survival for the entire population was 5.2 months, with 1-, 2-, and 3-year survival rates of 25, 11, and 4%, respectively. Prognostic factors for the overall population included treatment (p < 0.0001), an age less than 65 years (p = 0.004), discharge status (p < 0.001), absence of systemic metastasis (p = 0.036), and asymptomatic cerebral metastasis (p = 0.05). CONCLUSIONS:Treatment modality was the most significant independent variable affecting survival in patients with brain metastases. Eventual identification of a primary tumor does not affect overall survival; therefore, delaying therapeutic intervention in pursuit of a primary diagnosis may not be appropriate. Data in this study failed to demonstrate a statistically significant difference in survival between patients with UDP and those with DP lesions, on first presenting with brain metastases.

The focus of this project is to improve our understanding of the relationships between brain structure and function in patients presenting with anterior visual pathway compression using functional MRI (fMRI), visual field(VF) maps and diffusion tensor imaging (DTI). Significant visual loss can occur when large pituitary lesions compress the optic chiasm. Surgical resection of these lesions decompresses the chiasm and can lead to visual recovery. In this preliminary study, we selected patients presenting with slowly progressive visual loss secondary to a compressive pituitary region mass. Using preoperative DTI data, we reconstructed white matter projections of the optic radiations and demonstrated a structural correlation with functional vision as quantified by formal visual field mapping and fMRI. The structural data generated through a fiber tracking algorithm may represent a potentially powerful tool to better understand functional visual deficits in patients with anterior visual pathway compression. Furthermore, we believe that specific patterns in preoperative DTI data may predict the likelihood of postoperative visual recovery in a select group of patients.