The ability of diffusion tensor MRI to detect the preferential diffusion of water in cerebral white matter tracts enables neurosurgeons to noninvasively visualize the relationship of lesions to functional neural pathways. Although viewed as a research tool in its infancy, diffusion tractography has evolved into a neurosurgical tool with applications in glioma surgery that are enhanced by evolutions in crossing fiber visualization, edema correction, and automated tract identification. In this paper the current literature supporting the use of tractography in brain tumor surgery is summarized, highlighting important clinical studies on the application of diffusion tensor imaging (DTI) for preoperative planning of glioma resection, and risk assessment to analyze postoperative outcomes. The key methods of tractography in current practice and crucial white matter fiber bundles are summarized. After a review of the physical basis of DTI and post-DTI tractography, the authors discuss the methodologies with which to adapt DT image processing for surgical planning, as well as the potential of connectomic imaging to facilitate a network approach to oncofunctional optimization in glioma surgery.
Fraser Henderson Jr., Kalil G. Abdullah, Ragini Verma, and Steven Brem
Kalil G. Abdullah, Daniel Lubelski, Paolo G. P. Nucifora, and Steven Brem
Diffusion tensor imaging (DTI) is increasingly used in the resection of both high- and low-grade gliomas. Whereas conventional MRI techniques provide only anatomical information, DTI offers data on CNS connectivity by enabling visualization of important white matter tracts in the brain. Importantly, DTI allows neurosurgeons to better guide their surgical approach and resection. Here, the authors review basic scientific principles of DTI, include a primer on the technology and image acquisition, and outline the modality's evolution as a frequently used tool for glioma resection. Current literature supporting its use is summarized, highlighting important clinical studies on the application of DTI in preoperative planning for glioma resection, preoperative diagnosis, and postoperative outcomes. The authors conclude with a review of future directions for this technology.
Andrew M. Garfinkle, Irena R. Danys, David A. Nicolle, Austin R. T. Colohan, and Steven Brem
✓ Terson's syndrome refers to the occurrence of vitreous hemorrhage with subarachnoid hemorrhage (SAH), usually due to a ruptured cerebral aneurysm. Although it is a well-described entity in the ophthalmological literature, it has been only rarely commented upon in the neurosurgical discussion of SAH.
Fundus findings are reported in a prospective study of 22 consecutive patients with a computerized tomography- or lumbar puncture-proven diagnosis of SAH. Six of these patients had intraocular hemorrhage on initial examination. In four patients vitreous hemorrhage was evident on presentation (six of eight eyes). In the subsequent 12 days, vitreous hemorrhage developed in the additional two patients (three of four eyes) due to breakthrough bleeding from the original subhyaloid hemorrhages.
The initial amount of intraocular hemorrhage did not correlate with the severity of SAH. Two of the six patients with intraocular hemorrhage died, whereas five of the 16 remaining SAH patients without intraocular hemorrhage died. Of the four survivors with intraocular hemorrhage, three showed gradual but significant improvement in their visual acuity by 6 months. The fourth underwent vitrectomy at 8 months after presentation and had a good visual result. With modern and aggressive medical and microsurgical management, Terson's syndrome should be recognized as an important reversible cause of blindness in patients surviving SAH.
Faith G. Davis, Sally Freels, James Grutsch, Suna Barlas, and Steven Brem
Object. The authors present population-based survival rate estimates for patients with malignant primary brain tumors based on an analysis of 18 years of data obtained from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute.
Methods. Estimates of survival rates at 2 and 5 years after diagnosis for patients with specific histological tumor types were categorized by patient's age at diagnosis (≤ 20 years, 21–64 years, and 65 years or older) and by the time period in which the patients were diagnosed (1973–1980, 1981–1985, 1986–1991). Where appropriate, survival estimates were adjusted for changing patterns in the mean age at diagnosis.
Conclusions. The authors observed a pattern of declining survival rates in patients with increasing age of the patient at diagnosis for most histological groups and overall improvements in survival rates of patients across these time periods adjusting for age at diagnosis. There were improvements in 2- and 5-year survival rates over the three time periods for children and adults with medulloblastoma and for adults with astrocytoma and oligodendroglioma. Improvements in survival rates for pediatric patients with medulloblastoma have leveled off in the most recent time period, and gender differences in survival rates for patients with this tumor, which were present in the 1970s, have disappeared. Clinically significant improvements in survival rates were not apparent in patients aged 65 years and older.
Changes in diagnostic and treatment procedures since the mid-1970s have resulted in improved survival rates for patients diagnosed as having medulloblastoma, oligodendroglioma, and astrocytoma, controlling for age at diagnosis. Glioblastoma multiforme continues to be the most intractable brain tumor.
Konstantin V. Elisevich, Austin R. T. Colohan, Steven Brem, and Youssef Comair
✓ The authors describe a technique by which a properly demarcated regional cerebral exposure may be performed rapidly and safely. The method involves a linear scalp incision of varying length and orientation and a circumferential craniotomy of variable size and shape centered about a single burr hole. While providing for rapid exposure with reduced blood loss, the vascular integrity of the wound is also better preserved, allowing for rapid healing of the scalp. This technique provides satisfactory unilateral exposures of most cerebral sites not located in the vicinity of the frontal sinus or the sphenoid wing.
Hanoch Alpern-Elran, Nicholas Morog, Françoise Robert, Gayle Hoover, Norman Kalant, and Steven Brem
✓ Neovascularization is observed in complicated atherosclerotic plaques associated with cellular proliferation, plaque hemorrhage, and thrombosis. The angiogenic activity of 278 plaque fragments was tested; the fragments were taken from 12 patients with cerebral ischemia who underwent carotid endarterectomy. Angiogenesis, determined by the sustained ingrowth of new vessels in the rabbit cornea, was induced in 125 (45%) of these fragments. By contrast, angiogenesis was found in only two (2.4%) of 80 control tissues (p < 0.001): in none of 22 samples of boiled atherosclerotic plaque; in two of 26 samples of normal rabbit carotid artery; and in none of 32 samples of nonatherosclerotic human uterine artery. Histological evaluation revealed that the cellular zones (composed mainly of smooth-muscle cells) were highly angiogenic, with 97 (76%) of 127 samples showing angiogenesis compared with 23 (17%) of 132 acellular fragments that consisted of amorphic, necrotic, calcific, lipid-laden material (p < 0.001).
These results indicate that angiogenesis in vivo is a function of the cellular component of the advanced atherosclerotic plaque, and is not expressed in the normal, stable arterial wall. The fragile new vessels could promote the growth of the plaque or be a source of hemorrhages, microinfarcts, and plaque fissures that convert a stable, silent lesion to an expanding, ulcerated, thrombotic, symptomatic plaque.
Kaveh Barami, Allison Grow, Steven Brem, Elias Dagnew, and Andrew E. Sloan
✓During the past 25 years, radiosurgery has evolved as a primary treatment modality for certain meningiomas when resection would be associated with high patient morbidity. In addition, radiosurgery is now routinely used as an adjunctive therapy for residual or recurrent meningiomas after surgical removal. In this review the authors summarize the vascular complications that occur after radiosurgery for meningiomas as well as experimental study data that give insight into the pathogenesis of this complication. These data may be useful when discussing with patients the risk/benefit ratio of choosing among conservative management, radiosurgery, and surgery.
Clare W. Teng, Steve S. Cho, Yash Singh, Emma De Ravin, Keren Somers, Love Buch, Steven Brem, Sunil Singhal, Edward J. Delikatny, and John Y. K. Lee
Metastases are the most common intracranial malignancies and complete resection can provide relief of neurological symptoms and reduce recurrence. The authors’ prospective pilot study in 2017 demonstrated promising results for the application of high-dose, delayed imaging of indocyanine green (ICG), known as second window ICG (SWIG), in patients undergoing surgery for brain metastases. In this prospective cohort study, the authors evaluated intraoperative imaging and clinical outcomes of treatment using SWIG.
Patients were prospectively enrolled in an approved study of high-dose, delayed ICG (SWIG) and received 5 mg/kg (2014–2018) or 2.5 mg/kg (2018–2019) ICG 24 hours preoperatively. Intraoperatively, near-infrared (NIR) imaging was performed using a dedicated NIR exoscope. NIR images were analyzed and the signal-to-background ratio (SBR) was calculated to quantify fluorescence. Residual fluorescence on the postresection NIR view was compared and correlated to the residual gadolinium enhancement on postoperative MRI. Patient survival and predictive factors were analyzed.
In total, 51 intracranial metastases were surgically treated in 47 patients in this cohort. All 51 metastatic tumors demonstrated strong NIR fluorescence (mean SBR 4.9). In tumors ≤ 10 mm from the cortical surface, SWIG with 5 mg/kg ICG produced enhanced transdural tumor visibility (91.3%) compared to 2.5 mg/kg (52.9%; p = 0.0047). Neoplastic margin detection using NIR fluorescence compared to white light improved sensitivity, albeit lowered specificity; however, increasing the SBR cutoff for positive fluorescence significantly improved specificity without sacrificing sensitivity, increasing the overall accuracy from 57.5% to 72.5%. A lack of residual NIR fluorescence after resection was closely correlated with a lack of residual enhancement on postoperative MRI (p = 0.007). Among the 16 patients in whom tumor recurred at the site of surgery, postoperative MRI successfully predicted 8 cases, whereas the postresection NIR view predicted 12 cases. Progression-free survival rate at 12 months was greater for patients without residual NIR fluorescence (38%) than for those without residual enhancement on postoperative MRI (29%).
The current study demonstrates the clinical benefits of the SWIG technique in surgery for patients with brain metastases. Specifically, this technique allows for dose-dependent, transdural localization of neoplasms and improved sensitivity in neoplastic margin detection. Postresection residual fluorescence can be a powerful tool to evaluate extent of resection in conjunction with MRI, and it may guide decisions on brain metastasis management.
Stephen B. Tatter, Edward G. Shaw, Mark L. Rosenblum, Kastytis C. Karvelis, Lawrence Kleinberg, Jon Weingart, Jeffrey J. Olson, Ian R. Crocker, Steven Brem, James L. Pearlman, Joy D. Fisher, Kathryn A. Carson, Stuart A. Grossman, and other members of The New Approaches to Brain Tumor Therapy Central Nervous System Consortium
Object. In this study the authors evaluated the safety and performance of the GliaSite Radiation Therapy System (RTS) in patients with recurrent malignant brain tumors who were undergoing tumor resection.
Methods. The GliaSite is an inflatable balloon catheter that is placed in the resection cavity at the time of tumor debulking. Low-dose-rate radiation is delivered with an aqueous solution of organically bound iodine-125 (Iotrex [sodium 3-(125I)-iodo-4-hydroxybenzenesulfonate]), which are temporarily introduced into the balloon portion of the device via a subcutaneous port. Adults with recurrent malignant glioma underwent resection and GliaSite implantation. One to 2 weeks later, the device was filled with Iotrex for 3 to 6 days, following which the device was explanted. Twenty-one patients with recurrent high-grade astrocytomas were enrolled in the study and received radiation therapy. There were two end points: 1) successful implantation and delivery of brachytherapy; and 2) safety of the device.
Implantation of the device, delivery of radiation, and the explantation procedure were well tolerated. At least 40 to 60 Gy was delivered to all tissues within the target volume. There were no serious adverse device-related events during brachytherapy. One patient had a pseudomeningocele, one patient had a wound infection, and three patients had meningitis (one bacterial, one chemical, and one aseptic). No symptomatic radiation necrosis was identified during 21.8 patient-years of follow up. The median survival of previously treated patients was 12.7 months (95% confidence interval 6.9–15.3 months).
Conclusions. The GliaSite RTS performs safely and efficiently. It delivers a readily quantifiable dose of radiation to tissue at the highest risk for tumor recurrence.
Ashwin G. Ramayya, H. Isaac Chen, Paul J. Marcotte, Steven Brem, Eric L. Zager, Benjamin Osiemo, Matthew Piazza, Nikhil Sharma, Scott D. McClintock, James M. Schuster, Zarina S. Ali, Patrick Connolly, Gregory G. Heuer, M. Sean Grady, David K. Kung, Ali K. Ozturk, Donald M. O’Rourke, and Neil R. Malhotra
Although it is known that intersurgeon variability in offering elective surgery can have major consequences for patient morbidity and healthcare spending, data addressing variability within neurosurgery are scarce. The authors performed a prospective peer review study of randomly selected neurosurgery cases in order to assess the extent of consensus regarding the decision to offer elective surgery among attending neurosurgeons across one large academic institution.
All consecutive patients who had undergone standard inpatient surgical interventions of 1 of 4 types (craniotomy for tumor [CFT], nonacute redo CFT, first-time spine surgery with/without instrumentation, and nonacute redo spine surgery with/without instrumentation) during the period 2015–2017 were retrospectively enrolled (n = 9156 patient surgeries, n = 80 randomly selected individual cases, n = 20 index cases of each type randomly selected for review). The selected cases were scored by attending neurosurgeons using a need for surgery (NFS) score based on clinical data (patient demographics, preoperative notes, radiology reports, and operative notes; n = 616 independent case reviews). Attending neurosurgeon reviewers were blinded as to performing provider and surgical outcome. Aggregate NFS scores across various categories were measured. The authors employed a repeated-measures mixed ANOVA model with autoregressive variance structure to compute omnibus statistical tests across the various surgery types. Interrater reliability (IRR) was measured using Cohen’s kappa based on binary NFS scores.
Overall, the authors found that most of the neurosurgical procedures studied were rated as “indicated” by blinded attending neurosurgeons (mean NFS = 88.3, all p values < 0.001) with greater agreement among neurosurgeon raters than expected by chance (IRR = 81.78%, p = 0.016). Redo surgery had lower NFS scores and IRR scores than first-time surgery, both for craniotomy and spine surgery (ANOVA, all p values < 0.01). Spine surgeries with fusion had lower NFS scores than spine surgeries without fusion procedures (p < 0.01).
There was general agreement among neurosurgeons in terms of indication for surgery; however, revision surgery of all types and spine surgery with fusion procedures had the lowest amount of decision consensus. These results should guide efforts aimed at reducing unnecessary variability in surgical practice with the goal of effective allocation of healthcare resources to advance the value paradigm in neurosurgery.