Comparison of minimal detectable protoporphyrin IX concentrations with a loupe device and conventional 5-ALA fluorescence microscopy: an experimental study

Significance

The 5-aminolevulinic acid (5-ALA) fluorescence technique is now widely applied for intraoperative visualization of specific central nervous system (CNS) tumors. Previous technical implementations of this technique have relied on specifically modified surgical microscopes to visualize intratumoral fluorescent protoporphyrin (PpIX). While this approach evidently allows for reliable intraoperative tumor visualization, it requires the availability of specifically modified surgical microscopes and their use even in cases where the operating neurosurgeon would prefer to use surgical loupes. Recently, a novel loupe device was introduced that is also capable of visualizing 5-ALA fluorescence.

Aim

The aim of this study was therefore to compare the detected PpIX concentrations between the conventional fluorescence microscope and the novel loupe device.

Approach

We used fluorescence phantoms of different PpIX concentrations for comparison between a conventional fluorescence microscope and the novel loupe device. For this purpose, we created fluorescence images using the excitation light sources of the conventional fluorescence microscope and the loupe device with both available background illumination modes (low and high). Subsequently, the minimal detectable PpIX concentrations according to each technique were determined by five independent neurosurgeons.

Results

Using the conventional fluorescence microscope, the median minimal detectable PpIX concentration was 0.16    μ g / ml (range: 0.15 to 0.17    μ g / ml ). By the loupe device, the median minimal detectable PpIX concentration was 0.12    μ g / ml (range: 0.10 to 0.12    μ g / ml ) and 0.08    μ g / ml (range: 0.07 to 0.08    μ g / ml ) for the high- and low-modes, respectively. Altogether, the minimal detectable PpIX concentrations were significantly lower using the loupe device compared to the conventional fluorescence microscope (p = 0.007 ).

Conclusions

Our data indicate that the novel loupe device is able to visualize 5-ALA fluorescence with high sensitivity and thus might serve as a powerful tool for visualization of specific CNS tumors in the future.

CD34 microvascularity in low-grade glioma: correlation with 5-aminolevulinic acid fluorescence and patient prognosis in a multicenter study at three specialized centers

OBJECTIVE

Early markers are urgently needed in low-grade glioma (LGG) evaluation to rapidly estimate the individual patient's prognosis and to determine the optimal postoperative management. Generally, visible 5-aminolevulinic acid (5-ALA) fluorescence is present in only a few LGGs. Recently, the authors identified visible 5-ALA fluorescence as a powerful intraoperative marker for unfavorable outcome in LGG treatment. However, its precise histopathological correlate is unclear. Neoangiogenesis represents a crucial event in tumor evolution, and CD34 is an established marker for vascular endothelial progenitors potentially indicating tumor progression. The aim of this study was thus to correlate 5-ALA fluorescence and CD34 microvascularity as well as to investigate the prognostic value of CD34 in a large series of LGGs.

METHODS

In this retrospective study including 3 specialized centers, patients with histopathologically confirmed isocitrate dehydrogenase-mutated LGGs (WHO grade II) receiving 5-ALA prior to resection were included. During surgery, the presence of visible fluorescence was analyzed and one representative tumor sample from the area with the maximum fluorescence effect (tumor with focal fluorescence or nonfluorescing tumor) was selected for each LGG. All fluorescing or nonfluorescing tumor samples were stained for CD34 and semiquantitatively analyzed for microvascular proliferation patterns (physiological vessels, branching capillaries, or microvessel clusters) as well as automatically quantified for CD34 microvessel density (MVD) by standardized histomorphometry software. These semiquantitative/quantitative CD34 data were correlated to the fluorescence status and patient outcome including progression-free survival (PFS), malignant transformation-free survival (MTFS), and overall survival (OS).

RESULTS

In a total of 86 LGGs, visible fluorescence was found during surgery in 13 (15%) cases. First, the semiquantitative CD34 score significantly correlated with intraoperative fluorescence (p = 0.049). Accordingly, the quantitative CD34 MVD was significantly higher in tumors showing fluorescence (p = 0.03). Altogether, the semiquantitative CD34 score showed a strong correlation with quantitative CD34 MVD (p < 0.001). At a mean follow-up of 5.4 ± 2.6 years, microvessel clusters in semiquantitative analysis were a prognostic marker for poor PFS (p = 0.01) and MTFS (p = 0.006), but not OS (p = 0.28). Finally, quantitative CD34 MVD > 10 vessels/mm2 was a prognostic marker for poor PFS (p = 0.01), MTFS (p = 0.008), and OS (p = 0.049).

CONCLUSIONS

The data indicate that CD34 microvascularity is associated with intraoperative 5-ALA fluorescence and outcomes in patients with LGG. Thus, visible fluorescence in LGGs might indicate increased CD34 microvascularity, serving as an early prognostic marker for unfavorable patient outcome that is already available during surgery.

The impact of heme biosynthesis regulation on glioma aggressiveness: Correlations with diagnostic molecular markers

Background

The prognosis of diffusely infiltrating glioma patients is dismal but varies greatly between individuals. While characterization of gliomas primarily relied on histopathological features, molecular markers increasingly gained importance and play a key role in the recently published 5^th edition of the World Health Organization (WHO) classification. Heme biosynthesis represents a crucial pathway due to its paramount importance in oxygen transport, energy production and drug metabolism. Recently, we described a “heme biosynthesis mRNA expression signature” that correlates with histopathological glioma grade and survival. The aim of the current study was to correlate this heme biosynthesis mRNA expression signature with diagnostic molecular markers and investigate its continued prognostic relevance.

Materials and methods

In this study, patient data were derived from the “The Cancer Genome Atlas” (TCGA) lower-grade glioma and glioblastoma cohorts. We identified diffusely infiltrating gliomas correlating molecular tumor diagnosis according to the most recent WHO classification with heme biosynthesis mRNA expression. The following molecular markers were analyzed: EGFR amplification, TERT promoter mutation, CDKN2A/B homozygous loss, chromosome 7 + /10- aneuploidy, MGMT methylation, IDH mutation, ATRX loss, p53 mutation and 1p19q codeletion. Subsequently, we calculated the heme biosynthesis mRNA expression signature for correlation with distinct molecular glioma markers/molecular subgroups and performed survival analyses.

Results

A total of 649 patients with available data on up-to-date molecular markers and heme biosynthesis mRNA expression were included. According to analysis of individual molecular markers, we found a significantly higher heme biosynthesis mRNA expression signature in gliomas with IDH wildtype (p < 0.0005), without 1p19q codeletion (p < 0.0005), with homozygous CDKN2A/B loss (p < 0.0005) and with EGFR amplification (p = 0.001). Furthermore, we observed that the heme biosynthesis mRNA expression signature increased with molecular subgroup aggressiveness (p < 0.0005), being lowest in WHO grade 2 oligodendrogliomas and highest in WHO grade 4 glioblastomas. Finally, the heme biosynthesis mRNA expression signature was a statistically significant survival predictor after multivariate correction for all molecular markers (p < 0.0005).

Conclusion

Our data demonstrate a significant correlation between heme biosynthesis regulation and diagnostic molecular markers and a prognostic relevance independent of these established markers. Consequently, heme biosynthesis expression is a promising biomarker for glioma aggressiveness and might constitute a potential target for novel therapeutic approaches.

P11.44.A The impact of heme biosynthesis regulation on glioma aggressiveness: correlations with most recent diagnostic molecular markers

Background

The prognosis of patients with diffusely infiltrating gliomas is dismal but varies greatly between individuals. While characterization of gliomas was primarily relied on typical histopathological features, specific molecular markers increasingly gained importance and play a key role in the recently published 5th edition of the World Health Organization (WHO) classification. Heme biosynthesis represents a crucial pathway due to its key role in oxygen transport, energy production or drug metabolism. Recently, we described a “heme biosynthesis mRNA expression signature” that correlates with histopathological glioma grades and patient survival. The aim of the current study was to correlate the heme biosynthesis mRNA expression signature with the most recent diagnostic molecular markers for glioma stratification.

Material and Methods

In this study, patient data were derived from the “The Cancer Genome Atlas” (TCGA) lower-grade glioma and glioblastoma cohorts. We identified diffusely infiltrating gliomas correlating molecular tumor diagnosis according to the most recent WHO classification with heme biosynthesis mRNA expression. The following molecular markers were analyzed: EGFR amplification, TERT promoter mutation, CDKN2A/B homozygous loss, concurrent chromosome 7 gain/10 loss, MGMT methylation, IDH mutation, ATRX loss, p53 mutation and 1p19q co-deletion. Subsequently, we calculated the heme biosynthesis mRNA expression signature and correlated this signature with distinct molecular glioma markers as well as the resulting molecular subgroups.

Results

A total of 649 patients with available data on up-to-date molecular markers and heme biosynthesis mRNA expression were included. According to analysis of individual molecular markers, we found a significantly higher heme biosynthesis mRNA expression signature in gliomas with IDH wildtype (p&lt;0.0005), without 1p19q co-deletion (p&lt;0.0005), with homozygous CDKN2A/B loss (p&lt;0.0005) and with EGFR amplification (p=0.001). Furthermore, we observed that the heme biosynthesis mRNA expression signature increased with the aggressiveness of the molecular subgroups (p&lt;0.0005), being lowest in WHO grade 2 oligodendrogliomas and highest in WHO grade 4 glioblastomas.

Conclusion

Our data demonstrate a significant correlation between diagnostic molecular markers and heme biosynthesis regulation in diffusely infiltrating gliomas. Consequently, heme biosynthesis expression is a promising biomarker for glioma aggressiveness and might constitute a potential target for novel therapeutic approaches.

P07.07.A Fluorescence lifetime imaging for improved visualization of 5-ALA fluorescence during biopsies of suspected brain tumors

Background

Stereotactic brain tumor biopsies represent a standard neurosurgical technique enabling a precise histopathological tumor diagnosis which is of utmost importance for optimal further treatment allocation. However, non-diagnostic biopsies are not uncommon in routine clinical practice. To overcome this shortcoming, serial biopsies or intraoperative histopathology are typically performed prolonging the operating times and potentially increasing the risk of complications. Recently, the value of 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) fluorescence for visualization of diagnostic tumor tissue was demonstrated in navigation-guided brain tumor biopsies. However, a not negligible proportion of brain tumors lack visible fluorescence. In some of these tumors, a subvisual concentration of PpIX could be detected by spectroscopic analysis. Thus, detection of such subvisual PpIX accumulation in tumor samples in biopsies by the new “Fluorescence Lifetime Imaging” (FLIM) technique might lead to further improvement of this approach.

Material and Methods

Patients that underwent navigation-guided biopsy of a suspected brain tumor were eligible for inclusion in this study. After administration of 5-ALA, the tissue samples were checked for visible fluorescence during the navigation-guided stereotactic biopsy with a sterile microscope. In each sample the observed fluorescence signal was documented. Additionally, the tissue samples were investigated ex-vivo by FLIM for detection of PpIX accumulation. In each case, a histopathological diagnosis was established according to the WHO classification of CNS tumors.

Results

A total number of 20 tissue samples could be retrieved in 16 patients with suspected brain tumors. The biopsy with assistance of 5-ALA was feasible in all patients and no relevant side effects occurred. Visible PpIX fluorescence could be observed in 75% of cases. In contrast, 25% of samples did not show visible fluorescence. In one specimen, no fluorescence signal could be evaluated as the sample was covered by too much blood. However, significant accumulation of PpIX could be detected by FLIM in all samples in which evaluation was possible (n=19). A final histopathological diagnosis was feasible in all patients.

Conclusion

Fluorescence Lifetime Imaging is a promising new technique for improved detection of brain tumor tissue during navigation-guided biopsies. Thus, this new technique might lead in future to reduced operating times and complication rate by minimizing the cases that need serial biopsies or intraoperative histopathology.

Clinico-pathologic predictors of dismal course in atypical meningiomas: a retrospective single-centre analysis

BACKGROUND

Despite continuous refinement of the WHO classification for meningiomas, the biological behaviour of atypical meningiomas remains difficult to predict on the basis of this grading system alone. The aim of this study was to investigate the prognostic significance of clinical and radiological parameters in a series of atypical meningioma with long follow-up of minimum 5 years.

METHODS

Of 1675 meningiomas treated at the Medical University Vienna between 1993 and 2015, 179 were atypical meningioma. Of those, 93 patients were identified with follow-up of ≥5 years. Patients were grouped by recurrence and evaluated for overall and progression free survival as well as potential prognostic parameters such as age, gender, tumor size and location, edema, irregular surface, contrast enhancement, bone invasion and hyperostosis, necrosis, EOR and MIB-1.

RESULTS

From 42 (45%) patients in group recurrent and 51 (55%) patients in group nonrecurrent, seven independent factors were associated with decreased progression-free survival in univariate analysis: size ≥5 cm, age ≥60 years, male gender, subtotal resection, irregular surface, and necrosis on magnetic resonance imaging, and MIB-1 ≥6%. In multivariable analysis, only larger size, older age, necrosis and higher MIB-1 remained independent prognostic risk factors for recurrence of atypical meningioma.

CONCLUSIONS

We identified larger size, older age, presence of necrosis on magnetic resonance imaging, and higher MIB-1, as detrimental parameters for recurrence of atypical meningioma. Until molecular profiling of atypical meningioma becomes routinely available, these parameters may aid the clinician in decision making about surveillance intervals and adjuvant radiation treatment.

DNA Methylation Associates With Clinical Courses of Atypical Meningiomas: A Matched Case-Control Study

Background

Accounting for 15–20% of all meningiomas, WHO grade II meningiomas represent an intermediate group regarding risk of tumor recurrence. However, even within this subgroup varying clinical courses are observed with potential occurrence of multiple recurrences. Recently, DNA methylation profiles showed their value for distinguishing biological behaviors in meningiomas. Therefore, aim of this study was to investigate DNA methylation profiles in WHO grade II meningiomas.

Methods

All patients that underwent resection of WHO grade II meningiomas between 1993 and 2015 were screened for a dismal course clinical course with ≥2 recurrences. These were matched to control cases with benign clinical courses without tumor recurrence. DNA methylation was assessed using the Infinium Methylation EPIC BeadChip microarray. Unsupervised hierarchical clustering was performed for identification of DNA methylation profiles associated with such a dismal clinical course.

Results

Overall, 11 patients with WHO grade II meningiomas with ≥2 recurrences (Group dismal) and matched 11 patients without tumor recurrence (Group benign) were identified. DNA methylation profiles revealed 3 clusters—one comprising only patients of group dismal, a second cluster comprising mainly patients from group benign and a third cluster comprising one group dismal and one group benign patient. Based on differential methylation pattern associations with the Wnt and the related cadherin signaling pathway was observed.

Conclusion

DNA methylation clustering showed remarkable differences between two matched subgroups of WHO grade II meningiomas. Thus, DNA methylation profiles may have the potential to support prognostic considerations regarding meningioma recurrence and radiotherapeutic treatment allocation after surgical resection.

Multiplicity does not significantly affect outcomes in brain metastasis patients treated with surgery

Background

Brain metastasis quantity may be a negative prognostic factor for patients requiring resection of at least one lesion.

Methods

We retrospectively reviewed patients who underwent surgical resection of brain metastases from July 2018 to June 2019 at our institution, and examined outcomes including overall survival (OS), progression free survival (PFS) and rates of local failure (LF). Patients were grouped according to the number of metastases at the time of surgery (single vs multiple).

Results

We identified 130 patients who underwent surgical resection as the initial treatment modality. At the time of surgery, 87 patients had only one lesion (control) and 43 had multiple (&gt;1). Two-year OS for the entire cohort was 46%, with equal rates in both the multiple metastases group and the control group (p=0.335). 2-year PFS was 27%; 21% in the multiple metastases group and 31% in the control group (p=0.766). The rate of LF at 2-years was 32%, with equal rates in both the multiple lesion group and control group (p=0.889). On univariate analysis, multiplicity was not significantly correlated to OS (HR=0.80, 95% CI: 0.51-1.26, p=0.336), PFS (HR=1.06, 95% CI: 0.71-1.59, p=0.766) or LF (HR=1.06, 95% CI: 0.57-1.97, p=0.840). Multivariate analysis revealed preoperative tumor volume of the resected lesion to be the single correlate for OS (p=0.0032) and PFS (p=0.0081).

Conclusions

Having more than one metastasis does not negatively impact outcomes in patients treated with surgery. In carefully selected patients, especially those with large tumors, surgery should be considered regardless of the total number of lesions.

Efficacy, Outcome, and Safety of Elderly Patients with Glioblastoma in the 5-ALA Era: Single Center Experience of More Than 10 Years

Simple Summary

In the next decades, the incidence of patients with glioblastoma (GBM) will markedly increase due to the growth of the elderly population. Despite the increasing incidence of GBM, elderly patients are frequently excluded from clinical studies and thus, only few data are available specifically focusing on the elderly population. In the current study, we aimed to investigate the efficacy, outcome, and safety of surgically-treated GBM including resections and biopsies in the 5-ALA era in a large elderly cohort of altogether 272 patients. Our data of this large elderly cohort demonstrate for the first time the clinical utility and safety of 5-ALA fluorescence in GBM for improved tumor visualization in both resections as well as biopsies. Therefore, we recommend the use of 5-ALA not only in resections, but also in open/stereotactic biopsies to optimize the neurosurgical management of elderly GBM patients.

Abstract

Background: In the next decades, the incidence of patients with glioblastoma (GBM) will increase due to the growth of the elderly population. Fluorescence-guided resection using 5-aminolevulinic acid (5-ALA) is widely applied to achieve maximal safe resection of GBM and is identified as a novel intraoperative marker for diagnostic tissue during biopsies. However, detailed analyses of the use of 5-ALA in resections as well as biopsies in a large elderly cohort are still missing. The aim of this study was thus to investigate the efficacy, outcome, and safety of surgically- treated GBM in the 5-ALA era in a large elderly cohort. Methods: All GBM patients aged 65 years or older who underwent neurosurgical intervention between 2007 and 2019 were included. Data on 5-ALA application, intraoperative fluorescence status, and 5-ALA-related side effects were derived from our databank. In the case of resection, the tumor resectability and the extent of resection were determined. Potential prognostic parameters relevant for overall survival were analyzed. Results: 272 GBM patients with a median age of 71 years were included. Intraoperative 5-ALA fluorescence was applied in most neurosurgical procedures (n = 255/272, 88%) and visible fluorescence was detected in most cases (n = 252/255, 99%). In biopsies, 5-ALA was capable of visualizing tumor tissue by visible fluorescence in all but one case (n = 91/92, 99%). 5-ALA administration did not result in any severe side effects. Regarding patient outcome, smaller preoperative tumor volume (<22.75 cm³), gross total resection, single lesions, improved postoperative neurological status, and concomitant radio-chemotherapy showed a significantly longer overall survival. Conclusions: Our data of this large elderly cohort demonstrate the clinical utility and safety of 5-ALA fluorescence in GBM for improved tumor visualization in both resections as well as biopsies. Therefore, we recommend the use of 5-ALA not only in resections, but also in open/stereotactic biopsies to optimize the neurosurgical management of elderly GBM patients.

Reply to Stummer, W.; Thomas, C. Comment on "Hosmann et al. 5-ALA Fluorescence Is a Powerful Prognostic Marker during Surgery of Low-Grade Gliomas (WHO Grade II)-Experience at Two Specialized Centers. Cancers 2021, 13, 2540"

We greatly appreciate Dr. Stummer's and Dr. Thomas's interest in our study and their important comments [...].

Do standard surgical techniques lead to satisfying aesthetic results in nonsyndromic sagittal suture synostosis?

OBJECTIVE

Surgical correction of synostotic cranial sutures is typically performed early in an affected child's life. Depending on the severity of the cranial synostoses, different aspects of the surgical treatment may have varying degrees of importance. In this sense, the aesthetic appearance in children with normal neurological development in single-suture synostosis plays an important role in self-perception and social acceptance for both the patients themselves and their caregivers. Therefore, in this study, the authors aimed to evaluate the aesthetic outcome after surgical correction in a cohort of patients with nonsyndromic sagittal suture synostosis.

METHODS

Between December 2002 and December 2019, a total of 99 patients underwent surgical correction of a synostotic sagittal suture at the Medical University of Vienna. Depending on their age, patients underwent either an extended midline strip craniectomy (EMSC) (< 4 months) or a modified pi procedure (MPP) (≥ 4 months). After the surgical procedure, the outcome was evaluated by the treating neurosurgeon at 1- and 12-month follow-up visits, and after approximately 5 years, before the patient entered elementary school. In addition to that, the patients' caregivers were asked to evaluate the aesthetic outcome of the surgical procedure after 12 months. These results were then compared to evaluate potential differences in the perception of the surgical outcome.

RESULTS

After 12 months, the majority of the included patients were evaluated as having a good aesthetic outcome by the treating neurosurgeon (97%) and by their caregivers (89%). These differences did not show statistical significance (p = 0.11). Similarly, no differences in the aesthetic outcome depending on the surgical procedure performed could be found (p = 0.55). At the last follow-up visit, before entering elementary school, all available patients had an excellent or good surgical outcome. Moreover, the majority of caregivers (73%) reported that their child had a normal head shape appearance after surgical correction.

CONCLUSIONS

The results of this study have suggested that surgical correction of sagittal suture synostosis by simple operative techniques leads to a good aesthetic outcome and a normal head shape appearance in the majority of patients. An analysis of the evaluation of the surgical outcome by either the treating neurosurgeon or the patient caregivers showed comparable results and, thus, early intervention with simple surgical techniques can be recommended.

Clinical Outcome and Technical Nuances After Resection of Orbital Cavernous Venous Malformations-A Single-Center Experience

BACKGROUND

Cavernous venous malformations (CVMs) represent the most common benign intraorbital lesions. Enlarging or symptomatic CVMs (progressive proptosis or visual disturbances) are treated by surgical resection. For this, a variety of different surgical approaches have been described. The aim of this study was to present a contemporary series of orbital CVMs treated via open microsurgical approaches.

METHODS

In this study, patients who underwent resection of orbital CVMs between 2002 and 2019 were included. Presenting symptoms were noted and neuro-ophthalmologic examinations performed pre- and postoperatively. For surgical resection, the location of the orbital CVM and its relation to the orbital anatomy led to decision-making for appropriate approaches. A comparison between anatomical location and surgical outcome was performed.

RESULTS

Overall, 35 patients with orbital CVMs were included. Most common presenting symptoms were progressive proptosis (43%) and visual disturbances (34%). Most common location was the lateral quadrant (37%) followed by the superior quadrant (20%). A subfrontal craniotomy was performed in 40% of cases followed by a supraorbital craniotomy including the orbital rim in 34% of cases. For surgical excision, a cryo-probe was used in 30 patients, and complete resection was feasible in all cases. Location of a CVM within the superior quadrant was associated with improved postoperative recovery of visual acuity. No differences for clinical outcomes were observed depending on the surgical approach.

CONCLUSIONS

Resection of orbital CVMs is indicated in patients with visual disturbances or progressive proptosis. In these, microsurgical approaches can be used with minimal morbidity for complete removal of these well-circumscribed lesions.

Endoscopic extra-capsular resection of a giant pituitary adenoma: how I do it

BACKGROUND

Giant pituitary adenomas are characterized by their large size and potential to invade parasellar and suprasellar regions leading to visual decline and hypopituitarism. Thus, they remain a significant surgical challenge, and gross total removal is only achieved in the minority of cases.

METHOD

We aim to describe the key surgical steps for endoscopic extra-capsular resection of a giant pituitary adenoma with the aim of achieving complete tumor resection with description of the relevant surgical anatomy, indications and limitations.

CONCLUSION

Endoscopic extra-capsular resection of giant pituitary tumors when feasible allows for complete tumor resection, early identification of the gland and avoidance of manipulation of the optic apparatus.

5-ALA Fluorescence Is a Powerful Prognostic Marker during Surgery of Low-Grade Gliomas (WHO Grade II)-Experience at Two Specialized Centers

The prediction of the individual prognosis of low-grade glioma (LGG) patients is limited in routine clinical practice. Nowadays, 5-aminolevulinic acid (5-ALA) fluorescence is primarily applied for improved intraoperative visualization of high-grade gliomas. However, visible fluorescence is also observed in rare cases despite LGG histopathology and might be an indicator for aggressive tumor behavior. The aim of this study was thus to investigate the value of intraoperative 5-ALA fluorescence for prognosis in LGG patients. We performed a retrospective analysis of patients with newly diagnosed histopathologically confirmed LGG and preoperative 5-ALA administration at two independent specialized centers. In this cohort, we correlated the visible intraoperative fluorescence status with progression-free survival (PFS), malignant transformation-free survival (MTFS) and overall survival (OS). Altogether, visible fluorescence was detected in 7 (12%) of 59 included patients in focal intratumoral areas. At a mean follow-up time of 5.3 ± 2.9 years, patients with fluorescing LGG had significantly shorter PFS (2.3 ± 0.7 vs. 5.0 ± 0.4 years; p = 0.01), MTFS (3.9 ± 0.7 vs. 8.0 ± 0.6 years; p = 0.03), and OS (5.4 ± 1.0 vs. 10.3 ± 0.5 years; p = 0.01) than non-fluorescing tumors. Our data indicate that visible 5-ALA fluorescence during surgery of pure LGG might be an already intraoperatively available marker of unfavorable patient outcome and thus close imaging follow-up might be considered.

New-onset seizures after cranioplasty-a different view on a putatively frequently observed phenomenon

Background

New-onset seizures after cranioplasty (NOSAC) are reported to be a frequent complication of cranioplasty (CP) after decompressive hemicraniectomy (DHC). There are considerable differences in the incidence of NOSAC and contradictory data about presumed risk factors in the literature. We suggest NOSAC to be a consequence of patients’ initial condition which led to DHC, rather than a complication of subsequent CP. We conducted a retrospective analysis to verify our hypothesis.

Methods

The medical records of all patients ≥ 18 years who underwent CP between 2002 and 2017 at our institution were evaluated including incidence of seizures, time of seizure onset, and presumed risk factors. Indication for DHC, type of implant used, timing of CP, patient age, presence of a ventriculoperitoneal shunt (VP shunt), and postoperative complications were compared between patients with and without NOSAC.

Results

A total of 302 patients underwent CP between 2002 and 2017, 276 of whom were included in the outcome analysis and the incidence of NOSAC was 23.2%. Although time between DHC and CP differed significantly between DHC indication groups, time between DHC and seizure onset did not differ, suggesting the occurrence of seizures to be independent of the procedure of CP. Time of follow-up was the only factor associated with the occurrence of NOSAC.

Conclusion

New-onset seizures may be a consequence of the initial condition leading to DHC rather than of CP itself. Time of follow-up seems to play a major role in detection of new-onset seizures.

Cranioplasty following ventriculoperitoneal shunting: lessons learned

OBJECTIVE

Cranioplasty (CP) is considered as a straightforward and technically unchallenging operation; however, complication rates are high reaching up to 56%. Presence of a ventriculoperitoneal shunt (VPS) and timing of CP are reported risk factors for complications. Pressure gradients and scarring at the site of the cranial defect seem to be critical in this context. The authors present their experiences and lessons learned.

METHODS

A consecutive series of all patients who underwent CP at the authors' institution between 2002 and 2017 were included in this retrospective analysis. Complications were defined as all events that required reoperation. Logistic regression analysis and chi-squared test were conducted to evaluate the complication rates according to suspected risk factors.

RESULTS

A total of 302 patients underwent cranioplasty between 2002 and 2017. The overall complication rate was 17.5%. Complications included epi-/subdural fluid collection (7.3%) including hemorrhage (4.6%) and hygroma (2.6%), bone graft resorption (5.3%), bone graft infection (2.0%), and hydrocephalus (5.7%). Overall, 57 patients (18.9%) had undergone shunt implantation prior to CP. The incidence of epi-/subdural fluid collection was 19.3% in patients with VPS and 4.5% in patients without VPS, OR 5.1 (95% CI 2.1-12.4). Incidence of hygroma was higher in patients who underwent early CP. Patients with temporary shunt ligation for CP did not suffer from complications.

CONCLUSION

CP in patients with a VPS remains a high-risk procedure. Any effort to understand the pressure dynamics and to reduce factors that may trigger the formation of a large epidural space must be undertaken.

5-ALA fluorescence for intraoperative visualization of spinal ependymal tumors and identification of unexpected residual tumor tissue: experience in 31 patients

OBJECTIVE

Gross-total resection (GTR) is the treatment of choice in the majority of patients suffering from spinal ependymal tumors. In such tumors, the extent of resection (EOR) is considered the key factor for tumor recurrence and thus patient prognosis. However, incomplete resection is not uncommon and leads to increased risk of tumor recurrence. One important cause of incomplete resection is insufficient intraoperative visualization of tumor tissue as well as residual tumor tissue. Therefore, the authors investigated the value of 5-aminolevulinic acid (5-ALA)-induced fluorescence in a series of spinal ependymal tumors for improved tumor visualization.

METHODS

Adult patients who underwent preoperative 5-ALA administration and surgery for a spinal ependymal tumor were included in this study. For each tumor, a conventional white-light microsurgical resection was performed. Additionally, the fluorescence status (strong, vague, or no fluorescence) and fluorescence homogeneity (homogenous or inhomogeneous) of the spinal ependymal tumors were evaluated during surgery using a modified neurosurgical microscope. In intramedullary tumor cases with assumed GTR, the resection cavity was investigated for potential residual fluorescing foci under white-light microscopy. In cases with residual fluorescing foci, these areas were safely resected and the corresponding samples were histopathologically screened for the presence of tumor tissue.

RESULTS

In total, 31 spinal ependymal tumors, including 27 intramedullary tumors and 4 intradural extramedullary tumors, were included in this study. Visible fluorescence was observed in the majority of spinal ependymal tumors (n = 25, 81%). Of those, strong fluorescence was noted in 23 of these cases (92%), whereas vague fluorescence was present in 2 cases (8%). In contrast, no fluorescence was observed in the remaining 6 tumors (19%). Most ependymal tumors demonstrated an inhomogeneous fluorescence effect (17 of 25 cases, 68%). After assumed GTR in intramedullary tumors (n = 15), unexpected residual fluorescing foci within the resection cavity could be detected in 5 tumors (33%). These residual fluorescing foci histopathologically corresponded to residual tumor tissue in all cases.

CONCLUSIONS

This study indicates that 5-ALA fluorescence makes it possible to visualize the majority of spinal ependymal tumors during surgery. Unexpected residual tumor tissue could be detected with the assistance of 5-ALA fluorescence in approximately one-third of analyzed intramedullary tumors. Thus, 5-ALA fluorescence might be useful to increase the EOR, particularly in intramedullary ependymal tumors, in order to reduce the risk of tumor recurrence.

Is Intraoperative Pathology Needed if 5-Aminolevulinic-Acid-Induced Tissue Fluorescence Is Found in Stereotactic Brain Tumor Biopsy?

BACKGROUND

Intraoperative histopathology and acquisition of multiple tissue samples in stereotactic biopsies results in a prolonged length of surgery and potentially increased complication rate.

OBJECTIVE

To investigate the clinical benefits of a novel strategy for stereotactic brain tumor biopsies with the assistance of 5-aminolevulinic acid (5-ALA) induced fluorescence.

METHODS

Patients that received 5-ALA prior to stereotactic biopsy of a suspected brain tumor were included. According to our strategy, the procedure was terminated in the case of strong fluorescence of the biopsy samples. In contrast, intraoperative histology was demanded in the case of vague/no fluorescence. Length of surgery, number of biopsy samples, diagnostic rate, and periprocedural complications were compared between these 2 groups.

RESULTS

Altogether, 79 patients were included, and strong fluorescence was present in 62 cases (79%), vague fluorescence was in 4 cases (5%), and no fluorescence was in 13 cases (16%). The diagnostic rate was comparable in biopsies with strong fluorescence without intraoperative histopathology and cases with vague/no fluorescence with intraoperative histopathology (98% vs 100%; P = 1.000). A significantly shorter length of surgery (41 vs 77 min; P < .001) and reduced average number of biopsy samples (3.6 vs 4.9; P = .011) was found in patients with strong compared to vague/no fluorescence. However, no statically significant difference in periprocedural complications between cases with strong and vague/no fluorescence was found (7% vs 18%; P = .166).

CONCLUSION

Our data demonstrate the clinical benefits of a novel strategy for stereotactic brain tumor biopsies with assistance of 5-ALA. Thus, this biopsy strategy will increase the efficiency of this standard neurosurgical procedure in the future.

High Diagnostic Accuracy of Visible 5-ALA Fluorescence in Meningioma Surgery According to Histopathological Analysis of Tumor Bulk and Peritumoral Tissue

Background and Objectives

Complete neurosurgical resection of intracranial meningiomas is essential to avoid residual tumor tissue and thus minimize the risk of tumor recurrence. However, local recurrence of meningiomas is not uncommon mainly due to insufficient intraoperative detection of residual tumor tissue within the tumor bulk or peritumoral tissue such as bone and satellite lesions. Although 5‐aminolevulinic acid (5‐ALA) induced fluorescence was found to visualize the majority of meningiomas, no comprehensive histopathological assessment of fluorescing samples from the tumor bulk and peritumoral tissue is available. The aim of our study was thus to histopathologically analyze a large series of tissue samples derived from meningioma surgery to assess the positive predictive value (PPV) of visible 5‐ALA fluorescence.

Study Design/Materials and Methods

In this study, we retrospectively investigated a series of tissue samples with visible 5‐ALA fluorescence collected during surgery of intracranial meningiomas from the tumor bulk and peritumoral tissue including the bone flap, dura/dural tail, arachnoidea, adjacent cortex, and satellite lesions. The tumor diagnosis was established according to the World Health Organization (WHO) criteria and all collected fluorescing samples were screened for presence of tumor tissue to calculate the PPV.

Results

Altogether, 191 tissue samples with visible 5‐ALA fluorescence derived during surgery of 85 meningiomas (63 WHO grade I, 17 WHO grade II, and 5 WHO grade III) were included. In detail, 158 samples from the tumor bulk and 33 specimens from the peritumoral tissue were investigated. According to histopathological analysis, the PPV of 5‐ALA fluorescence was significantly higher in samples from the tumor bulk (100%) as compared with peritumoral tissue (73%; P < 0.001). With regard to peritumoral tissue, tumor tissue was present in most fluorescing samples from the satellite lesions (100%), the bone flap (92%), arachnoidea (83%), and dura/dural tail (75%). In contrast, tumor tissue was absent in the majority of samples from fluorescing cortex (six of seven samples; 86%). However, distinct reactive tissue alterations were found in all six tumor‐free fluorescing cortex samples and additional vascular proliferation in two cases.

Conclusion

In this largest series to date, visible 5‐ALA fluorescence is characterized by a high PPV detecting tumor bulk and peritumoral tissue in intracranial meningiomas. Thus, 5‐ALA fluorescence supports the neurosurgeon in identifying residual tumor tissue at relevant surgical sites to optimize meningioma surgery and minimize the risk of local recurrence. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC

Focal irregularities in 7-Tesla MRI of unruptured intracranial aneurysms as an indicator for areas of altered blood-flow parameters

OBJECTIVE

In the last several decades, various factors have been studied for a better evaluation of the risk of rupture in incidentally discovered intracranial aneurysms (IAs). With advanced MRI, attempts were made to delineate the wall of IAs to identify weak areas prone to rupture. However, the field strength of the MRI investigations was insufficient for reasonable image resolution in many of these studies. Therefore, the aim of this study was to analyze findings of IAs in ultra-high field MRI at 7 Tesla (7 T).

METHODS

Patients with incidentally found IAs of at least 5 mm in diameter were included in this study and underwent MRI investigations at 7 T. At this field strength a hyperintense intravascular signal can be observed on nonenhanced images with a brighter "rim effect" along the vessel wall. Properties of this rim effect were evaluated and compared with computational fluid dynamics (CFD) analyses.

RESULTS

Overall, 23 aneurysms showed sufficient image quality for further evaluation. In 22 aneurysms focal irregularities were identified within this rim effect. Areas of such irregularities showed significantly higher values in wall shear stress and vorticity compared to areas with a clearly visible rim effect (p = 0.043 in both).

CONCLUSIONS

A hyperintense rim effect along the vessel wall was observed in most cases. Focal irregularities within this rim effect showed higher values of the mean wall shear stress and vorticity when compared by CFD analyses. Therefore, these findings indicate alterations in blood flow in IAs within these areas.

Challenging the osseous component of sphenoorbital meningiomas

Background

Intraosseous growth is a unique feature of sphenoorbital meningiomas (SOM). Its close relation to neurovascular structures limits complete surgical resection and possibly contributes to the high recurrence rate.

Objective

To evaluate the growth behavior of intraosseous remnants and develop a protocol for precise intraoperative visualization of intraosseous SOM.

Methods

We included 31 patients operated for SOM from 2004 to 2017. The growth velocity of the intraosseous tumor component was volumetrically calculated in 20 cases. To improve accuracy of image guidance, we implemented a specialized bone surface-based registration algorithm. For intraoperative bone visualization, we included CT in multimodality continuous image guidance in 23 patients. The extent of resection (EOR) was compared with a standard MR-only navigation group (n = 8).

Results

In 11/20 cases (55%), a progressive regrowth of the intraosseous SOM remnant was noted during a mean follow-up of 52 months (range 20–132 months). We observed a mean increase of 6.2 cm³ (range 0.2–23.7 cm³) per patient and side during the follow-up period. Bone surface-based registration was significantly more accurate than skin surface-based registration (mean 0.7 ± 0.4 mm and 1.9 ± 0.7 mm, p < 0.001). The EOR of the intraosseous component was significantly higher using CT + MRI navigation compared with controls (96% vs. 81%, p = 0.044).

Conclusion

Quantitative assessment of the biological behavior of intraosseous remnants revealed a continuous slow growth rate independent of the soft tumor component of more than half of SOM. According to our data, application of a multimodal image guidance provided high accuracy and significantly increased the resection rate of the intraosseous component of SOM.

5-ALA–induced fluorescence as a marker for diagnostic tissue in stereotactic biopsies of intracranial lymphomas: experience in 41 patients

OBJECTIVE

Stereotactic needle biopsies are usually performed for histopathological confirmation of intracranial lymphomas to guide adequate treatment. During biopsy, intraoperative histopathology is an effective tool to avoid acquisition of nondiagnostic samples. In the last years, 5-aminolevulinic acid (5-ALA)–induced fluorescence has been increasingly used for visualization of diagnostic brain tumor tissue during stereotactic biopsies. Recently, visible fluorescence was reported in the first cases of intracranial lymphomas as well. The aim of this study is thus to investigate the technical and clinical utility of 5-ALA–induced fluorescence in a large series of stereotactic biopsies for intracranial lymphoma.

METHODS

This prospective study recruited adult patients who underwent frameless stereotactic needle biopsy for a radiologically suspected intracranial lymphoma after oral 5-ALA administration. During biopsy, samples from the tumor region were collected for histopathological analysis, and presence of fluorescence (strong, vague, or no fluorescence) was assessed with a modified neurosurgical microscope. In tumors with available biopsy samples from at least 2 different regions the intratumoral fluorescence homogeneity was additionally investigated. Furthermore, the influence of potential preoperative corticosteroid treatment or immunosuppression on fluorescence was analyzed. Histopathological tumor diagnosis was established and all collected biopsy samples were screened for diagnostic lymphoma tissue.

RESULTS

The final study cohort included 41 patients with intracranial lymphoma. Stereotactic biopsies with assistance of 5-ALA were technically feasible in all cases. Strong fluorescence was found as maximum level in 30 patients (75%), vague fluorescence in 2 patients (4%), and no visible fluorescence in 9 patients (21%). In 28 cases, samples were obtained from at least 2 different tumor regions; homogenous intratumoral fluorescence was found in 16 of those cases (57%) and inhomogeneous intratumoral fluorescence in 12 (43%). According to histopathological analysis, all samples with strong or vague fluorescence contained diagnostic lymphoma tissue, resulting in a positive predictive value of 100%. Analysis showed no influence of preoperative corticosteroids or immunosuppression on fluorescence.

CONCLUSIONS

The data obtained in this study demonstrate the technical and clinical utility of 5-ALA–induced fluorescence in stereotactic biopsies of intracranial lymphomas. Thus, 5-ALA can serve as a useful tool to select patients not requiring intraoperative histopathology, and its application should markedly reduce operation time and related costs in the future.

MGMT assessment in pituitary adenomas: comparison of different immunohistochemistry fixation chemicals

PURPOSE

Despite the established role of O6-methyl-guanine-DNA methyltransferase (MGMT) as a marker for temozolomide response, consensus of the most reliable method to assess MGMT expression in pituitary adenomas is still missing. Currently, immunohistochemistry (IHC) assessment of formaldehyde fixed tissue samples is most widely used in a semiquantitative description. As formaldehyde fails to completely preserve nucleic acids, RCL2, an alcohol-based formaldehyde-free fixative, has been proposed as a more reliable alternative in terms of cell stability. Furthermore, as the current method of IHC is semiquantitative and observer-dependent, pyrosequencing, an objective tool to evaluate the methylation status of the MGMT promoter, has emerged as a reliable and accurate alternative. The aim of this study was to validate the current IHC method for assessment of MGMT protein expression in pituitary adenomas.

METHODS

The tissue samples of 8 macroadenomas with positive IHC MGMT expression (> 50%) were investigated: first, we compared the time dependent stability of MGMT protein expression after pituitary adenoma removal between formaldehyde vs. RCL2. Then, we compared positive IHC MGMT expression with methylated promoter status using pyrosequencing.

RESULTS

In the first 12 h after adenoma removal, tissue samples remained MGMT positive in significantly more samples when fixated with formaldehyde than with RCL2, respectively (96 vs. 81%, p = 0.025).

CONCLUSION

Our data confirm that the current method using formaldehyde tissue fixation and IHC reveals stable and reliable results of MGMT assessment in pituitary adenomas.

The Superior Thalamic Vein and its Variations: A Proposed Classification

BACKGROUND

The superior thalamic vein (STV) was first described comprehensively by Ferner in 1958 as the most prominent thalamic vein; it originates from the central superior portion of the thalamus, coursing medially to the third ventricular thalamic surface, where it turns posteriorly to parallel the internal cerebral vein (ICV) before ending into its posterior portion. Since historical anatomic and angiographic studies in the pre-computed tomography (CT)/magnetic resonance imaging era, the STV has not been investigated.

OBJECTIVE

To describe the anatomic course of the STV with its variations, and to propose a classification system based on its draining pattern.

METHODS

We retrospectively screened our imaging database for 50 patients who had a CT-angiography with predefined parameters. The images were independently reviewed by 3 neurosurgeons and 1 neuroradiologist to classify the STV into 4 types: type 1A-drainage into the anterior portion of the ICV, type 1B-drainage into the posterior portion of the ICV, type 2-drainage into the vein of Rosenthal, type 3-drainage into a medial (3A) or lateral (3B) atrial vein, and type 4-drainage into the vein of Galen.

RESULTS

In 50 patients, we could identify 96 STVs. In 2 hemispheres, the STV was doubled. The 92 single STVs were classified as type 1A in 25 hemispheres (27.2%), type 1B in 45 (48.9%), type 2 in 12 (13.0%), type 3A in 8 (8.7%), type 3B in 1 (1.1%), and type 4 in 1 (1.1%).

CONCLUSION

The draining pattern of the STV varies widely from the initial description.

Commentary: Giuseppe Campani (1635-1715, Rome, Italy): the First Use of a Microscope in Medicine and Surgery

Giuseppe Campani (1635-1715) was a polymath in Rome, Italy, during the Scientific Revolution in the XVIIth century. In particular, he forged the screw barrel microscope and was manufacturing his own lenses for microscopes and telescopes. He mastered the art of lens grinding. Those lenses have been analyzed with modern methods and turned out to be of extremely good quality, shining light on the fact that Giuseppe Campani mastered the theories of optics. Moreover, in a letter that Giuseppe Campani sent to Pope Innocent XI, he clearly described the use of a microscope for the examination of wounds of legs. This letter dates back to 15 August 1686 and is the first evidence of the use of microscopes to analyze wounds, sores, and anatomic specimens in medical and surgical settings. MG Yasargil previously showed the lithography accompanying this letter and was the first to recognize its great importance. We accessed this original letter in the Vatican Library, and for the first time we have translated it from Latin to English in order to unveil its significance in the context of the Scientific Revolution and the history of medicine and surgery.

Systematic histopathological analysis of different 5-aminolevulinic acid-induced fluorescence levels in newly diagnosed glioblastomas

OBJECTIVE Glioblastoma (GBM) is characterized by distinct intratumoral histopathological heterogeneity with regard to variable tumor morphology, cell proliferation, and microvascularity. Maximum resection of a GBM results in an improved prognosis and thus represents the aim of surgery in the majority of cases. Fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) is currently widely applied for improved intraoperative tumor visualization in patients with a GBM. Three intratumoral fluorescence levels (i.e., strong, vague, or no fluorescence) can usually be distinguished during surgery. So far, however, their exact histopathological correlates and their surgical relevance have not been clarified sufficiently. Thus, the aim of this study was to systematically analyze tissue samples from newly diagnosed GBMs with different fluorescence levels according to relevant histopathological parameters. METHODS This prospective study recruited patients who underwent 5-ALA fluorescence-guided resection of a newly diagnosed radiologically suspected GBM. Each patient received 5-ALA approximately 3 hours before surgery, and a modified neurosurgical microscope was applied for intraoperative visualization of 5-ALA-induced fluorescence. During surgery, tissue samples with strong, vague, or no fluorescence were collected. For each sample, the presence of tumor tissue, quality of tissue (compact, infiltrative, or no tumor), histopathological criteria of malignancy (cell density, nuclear pleomorphism, mitotic activity, and presence of microvascular proliferation/necrosis), proliferation rate (MIB-1 labeling index [LI]), and microvessel density (using CD34 staining) were investigated. RESULTS Altogether, 77 patients with a newly diagnosed, histopathologically confirmed GBM were included, and 131 samples with strong fluorescence, 69 samples with vague fluorescence, and 67 samples with no fluorescence were collected. Tumor tissue was detected in all 131 (100%) of the samples with strong fluorescence and in 65 (94%) of the 69 samples with vague fluorescence. However, mostly infiltrative tumor tissue was still found in 33 (49%) of 67 samples despite their lack of fluorescence. Strong fluorescence corresponded to compact tumors in 109 (83%) of 131 samples, whereas vague fluorescence was consistent with infiltrative tumors in 44 (64%) of 69 samples. In terms of the histopathological criteria of malignancy, a significant positive correlation of all analyzed parameters comprising cell density, nuclear pleomorphism, mitotic activity, microvascular proliferation, and necrosis with the 3 fluorescence levels was observed (p < 0.001). Furthermore, the proliferation rate significantly and positively correlated with strong (MIB-1 LI 28.3%), vague (MIB-1 LI 16.7%), and no (MIB-1 LI 8.8%) fluorescence (p < 0.001). Last, a significantly higher microvessel density was detected in samples with strong fluorescence (CD34 125.5 vessels/0.25 mm²) than in those with vague (CD34 82.8 vessels/0.25 mm²) or no (CD34 68.6 vessels/0.25 mm²) fluorescence (p < 0.001). CONCLUSIONS Strong and vague 5-ALA-induced fluorescence enables visualization of intratumoral areas with specific histopathological features and thus supports neurosurgeons in improving the extent of resection in patients with a newly diagnosed GBM. Despite the lack of fluorescence, tumor tissue was still observed in approximately half of the cases. To overcome this current limitation, the promising approach of complementary spectroscopic measurement of fluorescence should be investigated further.

Analysis of the surgical benefits of 5-ALA-induced fluorescence in intracranial meningiomas: experience in 204 meningiomas

OBJECTIVE One of the most important causes for recurrence of intracranial meningiomas is residual tumor tissue that remains despite assumed complete resection. Recently, intraoperative visualization of meningioma tissue by 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence was reported. The aim of this study was to investigate the possible surgical benefits of PpIX fluorescence for detection of meningioma tissue. METHODS 5-ALA was administered preoperatively to 190 patients undergoing resection of 204 intracranial meningiomas. The meningiomas' PpIX fluorescence status, fluorescence quality (strong or vague), and intratumoral fluorescence homogeneity were investigated during surgery. Additionally, specific sites, including the dural tail, tumor-infiltrated bone flap, adjacent cortex, and potential satellite lesions, were analyzed for PpIX fluorescence in selected cases. RESULTS PpIX fluorescence was observed in 185 (91%) of 204 meningiomas. In the subgroup of sphenoorbital meningiomas (12 of 204 cases), the dural part showed visible PpIX fluorescence in 9 cases (75%), whereas the bony part did not show any PpIX fluorescence in 10 cases (83%). Of all fluorescing meningiomas, 168 (91%) showed strong PpIX fluorescence. Typically, most meningiomas demonstrated homogeneous fluorescence (75% of cases). No PpIX fluorescence was observed in any of the investigated 89 dural tails. In contrast, satellite lesions could be identified through PpIX fluorescence in 7 cases. Furthermore, tumor-infiltrated bone flaps could be visualized by PpIX fluorescence in all 13 cases. Notably, PpIX fluorescence was also present in the adjacent cortex in 20 (25%) of 80 analyzed cases. CONCLUSIONS The authors' data from this largest patient cohort to date indicate that PpIX fluorescence enables intraoperatively visualization of most intracranial meningiomas and allows identification of residual tumor tissue at specific sites. Thus, intraoperative detection of residual meningioma tissue by PpIX fluorescence might in future reduce the risk of recurrence.

Local image variance of 7 Tesla SWI is a new technique for preoperative characterization of diffusely infiltrating gliomas: correlation with tumour grade and IDH1 mutational status

OBJECTIVES

To investigate the value of local image variance (LIV) as a new technique for quantification of hypointense microvascular susceptibility-weighted imaging (SWI) structures at 7 Tesla for preoperative glioma characterization.

METHODS

Adult patients with neuroradiologically suspected diffusely infiltrating gliomas were prospectively recruited and 7 Tesla SWI was performed in addition to standard imaging. After tumour segmentation, quantification of intratumoural SWI hypointensities was conducted by the SWI-LIV technique. Following surgery, the histopathological tumour grade and isocitrate dehydrogenase 1 (IDH1)-R132H mutational status was determined and SWI-LIV values were compared between low-grade gliomas (LGG) and high-grade gliomas (HGG), IDH1-R132H negative and positive tumours, as well as gliomas with significant and non-significant contrast-enhancement (CE) on MRI.

RESULTS

In 30 patients, 9 LGG and 21 HGG were diagnosed. The calculation of SWI-LIV values was feasible in all tumours. Significantly higher mean SWI-LIV values were found in HGG compared to LGG (92.7 versus 30.8; p < 0.0001), IDH1-R132H negative compared to IDH1-R132H positive gliomas (109.9 versus 38.3; p < 0.0001) and tumours with significant CE compared to non-significant CE (120.1 versus 39.0; p < 0.0001).

CONCLUSIONS

Our data indicate that 7 Tesla SWI-LIV might improve preoperative characterization of diffusely infiltrating gliomas and thus optimize patient management by quantification of hypointense microvascular structures.

KEY POINTS

• 7 Tesla local image variance helps to quantify hypointense susceptibility-weighted imaging structures. • SWI-LIV is significantly increased in high-grade and IDH1-R132H negative gliomas. • SWI-LIV is a promising technique for improved preoperative glioma characterization. • Preoperative management of diffusely infiltrating gliomas will be optimized.

De Novo Aneurysm Formation at the Anastomosis Site Incidentally Detected 2 Years after Single-Barrel STA-MCA Bypass Surgery: Case Report and Review of the Literature

This case report describes the de novo aneurysm formation at the anastomosis site 2 years after single-barrel superficial temporal artery to middle cerebral artery bypass surgery. Correct bypass patency and morphology of the anastomosis site was documented intraoperatively and immediately postoperatively by indocyanine green videoangiography and digital subtraction angiography (DSA). Aneurysmatic dilatation at the anastomosis site was observed 2 years postoperatively upon computed tomography angiographic follow-up examination. After repeat DSA, the patient underwent microsurgical reexploration and clip ligation of the aneurysmatic portion of the donor artery. The possible underlying mechanisms are discussed and the current literature is reviewed.

Analysis of 5-aminolevulinic acid-induced fluorescence in 55 different spinal tumors

OBJECT

Subtotal resection (STR) of spinal tumors can result in tumor recurrence. Currently, no clinically reliable marker is available for intraoperative visualization of spinal tumor tissue. Protoporphyrin IX (PpIX) fluorescence induced by 5-aminolevulinic acid (5-ALA) is capable of visualizing malignant gliomas. Fluorescence-guided resections of malignant cerebral gliomas using 5-ALA have resulted in an increased rate of complete tumor removal. Recently, the application of 5-ALA has also been described in the first cases of spinal tumors. Therefore, the aim of this observational study was to systematically investigate 5-ALA-induced fluorescence characteristics in different spinal tumor entities.

METHODS

Three hours before the induction of anesthesia, 5-ALA was administered to patients with different intra- and extradural spinal tumors. In all patients a neurosurgical resection or biopsy of the spinal tumor was performed under conventional white-light microscopy. During each surgery, the presence of PpIX fluorescence was additionally assessed using a modified neurosurgical microscope. At the end of an assumed gross-total resection (GTR) under white-light microscopy, a final inspection of the surgical cavity of fluorescing intramedullary tumors was performed to look for any remaining fluorescing foci. Histopathological tumor diagnosis was established according to the current WHO classification.

RESULTS

Fifty-two patients with 55 spinal tumors were included in this study. Resection was performed in 50 of 55 cases, whereas 5 of 55 cases underwent biopsy. Gross-total resection was achieved in 37 cases, STR in 5, and partial resection in 8 cases. Protoporphyrin IX fluorescence was visible in 30 (55%) of 55 cases, but not in 25 (45%) of 55 cases. Positive PpIX fluorescence was mainly detected in ependymomas (12 of 12), meningiomas (12 of 12), hemangiopericytomas (3 of 3), and in drop metastases of primary CNS tumors (2 of 2). In contrast, none of the neurinomas (8 of 8), carcinoma metastases (5 of 5), and primary spinal gliomas (3 of 3; 1 pilocytic astrocytoma, 1 WHO Grade II astrocytoma, 1 WHO Grade III anaplastic oligoastrocytoma) revealed PpIX fluorescence. It is notable that residual fluorescing tumor foci were detected and subsequently resected in 4 of 8 intramedullary ependymomas despite assumed GTR under white-light microscopy.

CONCLUSIONS

In this study, 5-ALA-PpIX fluorescence was observed in spinal tumors, especially ependymomas, meningiomas, hemangiopericytomas, and drop metastases of primary CNS tumors. In cases of intramedullary tumors, 5-ALA-induced PpIX fluorescence is a useful tool for the detection of potential residual tumor foci.