Optical Characterization of Neurosurgical Operating Microscopes: Quantitative Fluorescence and Assessment of PpIX Photobleaching.

Protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (5-ALA) is increasingly used as a fluorescent marker for fluorescence-guided resection of malignant gliomas. Understanding how the properties of the excitation light source and PpIX fluorescence interact with the surgical microscope is critical for effective use of the fluorescence-guided tumor resection technique. In this study, we performed a detailed assessment of the intensity of the emitted blue light and white light and the light beam profile of clinical grade operating microscopes used for PpIX visualization. These measurements revealed both recognized fluorescence photobleaching limitations and unrecognized limitations that may alter quantitative observations of PpIX fluorescence obtained with the operating microscope with potential impact on research and clinical uses. We also evaluated the optical properties of a photostable fluorescent standard with an excitation-emission profile similar to PpIX. In addition, we measured the time-dependent dynamics of 5-ALA-induced PpIX fluorescence in an animal glioma model. Finally, we developed a ratiometric method for quantification of the PpIX fluorescence that uses the photostable fluorescent standard to normalize PpIX fluorescence intensity. This method increases accuracy and allows reproducible and direct comparability of the measurements from multiple samples.

Confocal scanning microscopy provides rapid, detailed intraoperative histological assessment of brain neoplasms: Experience with 106 cases.

OBJECTIVES: Frozen section histological analysis is currently the mainstay for intraprocedural tissue diagnosis during the resection of intracranial neoplasms and for evaluating tumor margins. However, frozen sections are time-consuming and often do not reveal the histological features needed for final diagnosis when compared with permanent sections. Confocal scanning microscopy (CSM) with certain stains may be a valuable technology that can add rapid and detailed histological assessment advantage for the neurosurgical operating room. This study describes potential advantages of CSM imaging of fresh human brain tumor tissues labeled with acriflavine (AF), acridine orange (AO), cresyl violet (CV), methylene blue (MB), and indocyanine green (ICG) within the neurosurgical operating room facility. PATIENTS AND METHODS: Acute slices from orthotopic human intracranial neoplasms were incubated with AF/AO and CV solutions for 10 s and 1 min respectively. Staining was also attempted with MB and ICG. Samples were imaged using a bench-top CSM system. Histopathologic features of corresponding CSM and permanent hematoxylin and eosin images were reviewed for each case. RESULTS: Of 106 cases, 30 were meningiomas, 19 gliomas, 13 pituitary adenomas, 9 metastases, 6 schwannomas, 4 ependymomas, and 25 other pathologies. CSM using rapid fluorophores (AF, AO, CV) revealed striking microvascular, cellular and subcellular structures that correlated with conventional histology. By rapidly staining and optically sectioning freshly resected tissue, images were generated for intraoperative consultations in less than one minute. With this technique, an entire resected tissue sample was imaged and digitally stored for tele-pathology and archiving. CONCLUSION: CSM of fresh human brain tumor tissue provides clinically meaningful and rapid histopathological assessment much faster than frozen section. With appropriate stains, including specific cellular structure or antibody staining, CSM could improve the timeliness of intraoperative decision-making, and the neurosurgical-pathology workflow during resection of human brain tumors, ultimately improving patient care.

Less is more: Parahippocampal resection or endoscopic assistance in ambient cistern surgery? Qualitative and quantitative assessment of subtemporal approach.

The ambient cistern is an arachnoid complex that extends from the crural cistern to lateral border of cerebral colliculi. The subtemporal approach has been recognized as the best access to reach pathologies in the ambient cistern, however many disadvantages exist. The present work aims to analyze quantitatively the area of exposure provided by the subtemporal access. The objective is to evaluate if there are advantages of using the neuroendoscope in conventional subtemporal access when compared to the subtemporal access with resection of the parahippocampal gyrus. A subtemporal approach was performed in six brain hemispheres. Qualitative and quantitative analyses were made. The linear exposition of the vascular structures and the surgical exposure area were evaluated. The linear exposure to the posterior cerebral artery was 5.95 for subtemporal access (ST) and 13.6 for subtemporal access with resection of the parahippocampal gyrus (STh) (p = 0.019). The total exposure area was 104.8 mm2 for ST and 210.5 for STh (p = 0.0001). Regarding endoscope assistance the medial area, ST was 81.0 mm2, and STend was 176.2 mm2 (p = 0.038). For the total area of exposure, we obtained a value of 210.5 mm2 for ST and a value of 391.3 mm2 for STend (p = 0.041). In conventional subtemporal access, the use of the neuroendoscopes avoids the need for resection of the parahippocampal gyrus for better visualization of the ambient cistern structures.

Vertebral artery transposition for revascularization of the posterior circulation: a critical assessment of temporary and permanent complications and outcomes.

OBJECT: Despite advances in medical management and endovascular therapies, including the introduction of statins, antiplatelet agents, and drug-eluting stents, some patients experience medically refractory vertebrobasilar insufficiency and may benefit from robust surgical revascularization. The aim of this study was to evaluate such patients after surgical revascularization, emphasizing long-term outcomes and rates of complications. METHODS: The authors retrospectively identified 22 patients (5 women and 17 men) whose mean age was 69.1 years (range 48-81 years) who underwent revascularization of the posterior circulation via a proximal vertebral artery-carotid artery transposition between 2005 and 2013. The patients' conditions before surgery were clinically summarized, and long-term outcomes and complication rates after surgery were evaluated. RESULTS: All the patients were symptomatic before surgery although they received the best medical therapy as defined by their primary care physician. Presenting symptoms consisted of stroke, transient ischemic attacks (TIAs), and/or findings attributable to posterior circulation hypoperfusion. There were no deaths associated with revascularization surgery. The postoperative complication rate was 45.5%, which included 3 cases of recurrent laryngeal nerve palsy, 1 case of thoracic duct injury, 2 cases of TIA, and 4 cases of Horner's syndrome. The thoracic duct injury was identified intraoperatively and ligated without sequelae, all the TIAs resolved within 24 hours of surgery, all 4 sympathetic plexus injuries resolved, and all but 1 of the recurrent laryngeal nerve palsies resolved, resulting in a 4.5% complication rate in a mean follow-up period of 8.8 months. All the patients had resolution of their presenting symptoms, and a single patient had symptomatic restenosis that required stenting and angioplasty, resulting in a restenosis rate of 4.5%. CONCLUSIONS: Despite the optimization of medical therapies and lifestyle modifications, a select subset of patients with posterior vascular circulation insufficiency remains. In the authors' experience, vertebral artery-carotid artery transposition provides a surgical option with relatively low long-term complication and restenosis rates that are comparable or lower than those reported with endovascular treatment.

Safety, efficacy, and cost of intraoperative indocyanine green angiography compared to intraoperative catheter angiography in cerebral aneurysm surgery.

Intraoperative angiography in cerebrovascular neurosurgery can drive the repositioning or addition of aneurysm clips. Our institution has switched from a strategy of intraoperative digital subtraction angiography (DSA) universally, to a strategy of indocyanine green (ICG) videoangiography with DSA on an as-needed basis. We retrospectively evaluated whether the rates of perioperative stroke, unexpected postoperative aneurysm residual, or parent vessel stenosis differed in 100 patients from each era (2002, "DSA era"; 2007, "ICG era"). The clip repositioning rate for neck residual or parent vessel stenosis did not differ significantly between the two eras. There were no differences in the rate of perioperative stroke or rate of false-negative studies. The per-patient cost of intraoperative imaging within the DSA era was significantly higher than in the ICG era. The replacement of routine intraoperative DSA with ICG videoangiography and selective intraoperative DSA in cerebrovascular aneurysm surgery is safe and effective.

Magnetic resonance imaging volumetric assessment of the extent of contrast enhancement and resection in oligodendroglial tumors.

OBJECT: Oligodendrogliomas that enhance on MR images are associated with poor prognosis. However, the importance of the volume of enhancing tumor tissue, and the extent of its resection, is uncertain. The authors examined the prognostic significance of preoperative and residual postoperative enhancing tissue volumes in a large single-center series of patients with oligodendroglioma. They also examined the relationship between enhancement and characteristic genetic signatures in oligodendroglial tumors, specifically deletion of 1p and 19q (del 1p/19q). METHODS: The authors retrospectively analyzed 100 consecutive cases of oligodendroglioma involving patients who had undergone T1-weighted gadolinium-enhanced MRI at diagnosis and immediately after initial surgical intervention. The presence of preoperative enhancement was determined by consensus. Preoperative and residual postoperative volumes were measured using a quantitative, semiautomated method by a single blinded observer. Intrarater reliability for preoperative volumes was confirmed by remeasurement in a subset of patients 3 months later. Intrarater and interrater reliability for residual postoperative volumes was confirmed by remeasurement of these volumes by both the original and a second blinded observer. Multivariate analysis was used to assess the influence of contrast enhancement at diagnosis and the volume of pre- and postoperative contrast-enhancing tumor tissue on time to relapse (TTR) and overall survival (OS), while controlling for confounding clinical, pathological, and genetic factors. RESULTS: Sixty-three of 100 patients had enhancing tumors at initial presentation. Presence of contrast enhancement at diagnosis was related to reduced TTR and OS on univariate analysis but was not significantly related on multivariate analysis. In enhancing tumors, however, greater initial volume of enhancing tissue correlated with shortened TTR (p = 0.00070). Reduced postoperative residual enhancing volume and a relatively greater resection of enhancing tissue correlated with longer OS (p = 0.0012 and 0.0041, respectively). Interestingly, patients in whom 100% of enhancing tumor was resected had significantly longer TTR (174 vs 64 weeks) and OS (392 vs 135 weeks) than those with any residual enhancing tumor postoperatively. This prognostic benefit was not consistently maintained with greater than 90% or even greater than 95% resection of enhancing tissue. There was no relationship between presence or volume of enhancement and del 1p/19q. CONCLUSIONS: In enhancing oligodendrogliomas, completely resecting enhancing tissue independently improves outcome, irrespective of histological grade or genetic status. This finding supports aggressive resection and may impact treatment planning for patients with these tumors.

The minipterional craniotomy: technical description and anatomic assessment.

OBJECTIVE: To describe a modification of the pterional approach (PT), the minipterional craniotomy (MPT), and compare the anatomic exposure provided by these two approaches. METHODS: The anatomic exposure offered by the MPT and PT were compared in eight sides of cadaver heads using a computerized tracking system, a robotic microscope, and an image-guidance system. The area of surgical exposure, angular exposure, and anatomic limits of each craniotomy were evaluated. Three recently operated clinical cases (EGF) are also reported. RESULTS: There were no statistical differences in the total area of surgical exposure between the two craniotomies (PT, 1524.7 +/- 305 mm; MPT, 1469.7 +/- 380.3 mm; P > 0.05) or among the ipsilateral, middle, and contralateral components of the area (P > 0.05). There were no differences in angular exposure along the longitudinal and transverse axis angles for the three selected targets, the bifurcations of internal carotid and middle cerebral arteries, and the anterior communicating artery (P > 0.05). Except for the distal portion of the operculoinsular compartment of the sylvian fissure, no significant differences in the limits of the surgical exposure through the PT and MPT were apparent on the image-guidance system. CONCLUSION: The MPT craniotomy provides comparable surgical exposure to that offered by the PT. The advantages of the MPT include reduction of tissue trauma and bony removal, a decrease in surgical time, and improved cosmetic outcomes.

Comparison of routine and selective use of intraoperative angiography during aneurysm surgery: a prospective assessment.

OBJECT: Whether routine intraoperative angiography is necessary for cerebral aneurysm surgery is currently under debate. In this study the authors prospectively assessed the cerebrovascular surgeon's accuracy in predicting the need for intraoperative angiography. METHODS: Between January 2002 and January 2003, 200 consecutive patients (141 female and 59 male patients, mean age 52.8 years) with 235 aneurysms underwent routine intraoperative angiography. Before the operation, the surgeons indicated whether they believed that intraoperative angiography was necessary. Their responses were recorded as "intraoperative angiography necessary" or "intraoperative angiography unnecessary." Regardless of the response, all patients underwent intraoperative angiography after the aneurysm had been clipped. Changes in treatment resulting from intraoperative angiography were compared with surgeons' preoperative predictions of the need for intraoperative angiography. Intraoperative angiography was predicted to be necessary in 41 cases (20%) and unnecessary in 159 cases (80%). Its use altered treatment in 14 patients. Seven of these patients were among the group in which intraoperative angiography was deemed necessary and seven were in the group in which it was considered unnecessary. In the latter group, two patients had residual aneurysms, three had parent vessel occlusion, and two had previously undiagnosed aneurysms. Only one patient (0.5%) sustained a major intraoperative complication attributed to angiography. CONCLUSIONS: Given the frequency of significant disease that remains undetected if intraoperative angiography is used on a selective basis and the low complication rate associated with the procedure, the use of intraoperative angiography should be considered in the majority of aneurysm cases.