Prognostic factors to predict postoperative survival in patients with recurrent glioblastoma

Background

There are no generally accepted criteria for selecting patients with recurrent glioblastoma for surgery. This retrospective study in a Danish population-based cohort aimed to identify prognostic factors affecting postoperative survival after repeated surgery for recurrent glioblastoma and to test if the preoperative New Scale for Recurrent Glioblastoma Surgery (NSGS) developed by Park CK et al could assist in the selection of patients for repeat glioblastoma surgery.

Methods

Clinical data from 66 patients with recurrent glioblastoma and repeated surgery were analyzed. Kaplan-Meier plots were produced to illustrate survival in each of the three NSGS prognostic groups, and Cox proportional hazard regression was used to identify prognostic variables. Multivariable analysis was used to identify differences in survival in the three prognostic groups.

Results

Six variables significantly affected postoperative survival: preoperative Karnofsky Performance Status (KPS) < 70 (p = 0.002), decreased KPS after second surgery (p = 0.012), ependymal involvement (p = 0.002), tumor volume ≧ 50 cm3 (p = 0.021), age (p = 0.033) and Ki-67 (p = 0.005). Retrospective application of the criteria previously published by Park CK et al showed that median postoperative survival for the three prognostic groups was 390 days (0 points), 279 days (1 point), and 80 days (2 points), respectively.

Conclusion

Several prognostic variables to predict postoperative survival in patients with recurrent glioblastoma were identified and should be considered when selecting patient for repeat surgery. The NSGS scoring system was useful as there were significant differences in postoperative survival between its three prognostic groups.

Gene expression analysis during progression of malignant meningioma compared to benign meningioma

OBJECTIVE

Meningioma is the most common primary intracranial neoplasm. Only 1%-3% of meningiomas are malignant according to the 2016 WHO criteria (WHO grade III). High-grade meningiomas present specific gene expression signatures indicating aggressive growth or recurrence. However, changes in gene expression and in neuroinflammatory gene expression signatures in WHO grade III meningiomas and during progression from WHO grade I or II to grade III are unknown.

METHODS

The authors used a NanoString targeted gene expression panel with focus on 787 genes relevant in meningioma pathology and neuroinflammatory pathways to investigate patients with grade III meningiomas treated at Rigshospitalet from 2000 to 2020 (n = 51). A temporal dimension was added to the investigation by including samples from patients' earlier grade I and II meningiomas and grade III recurrences (n = 139 meningiomas). The authors investigated changes in neuroinflammatory gene expression signatures in 1) grade I meningiomas that later transformed into grade III meningiomas, and 2) grade III meningiomas compared with nonrecurrent grade I meningiomas.

RESULTS

The authors' data indicate that FOXM1, TOP2A, BIRC5, and MYBL2 were enriched and the HOTAIR regulatory pathway was enriched in grade III meningiomas compared with nonrecurrent grade I meningiomas. They discovered a separation of malignant and benign meningiomas based only on genes involved in microglia regulation with enrichment of P2RY12 in grade I compared with grade III meningiomas. Interestingly, FOXM1 was upregulated in premalignant grade I meningioma years before the grade III transformation.

CONCLUSIONS

The authors found gene expression changes in low-grade meningiomas that predated histological transformation to grade III meningiomas. Neuroinflammation genes distinguished grade III from grade I meningiomas.

P12.08.A Uncovering the glioblastoma tumor-microenvironment by high-end multiplexing with imaging mass cytometry

Background

Glioblastoma is one of the most aggressive cancers, and hypoxia plays an essential role in its tumor- microenvironment. Tumor-associated microglia and macrophages (TAMs) have been reported to constitute up to 30 % of the cells, a fraction that is even higher in hypoxic areas. Single-cell mRNA sequencing of glioblastoma tumors has revealed vast heterogeneity, but the spatial aspects are not entirely defined yet. The aim of this study was to uncover differences between the hypoxic and normoxic tumor-microenvironment of human glioblastoma by high-end multiplexing with imaging mass cytometry.

Material and Methods

A tissue microarray (TMA) with normoxic and hypoxic areas from 4 IDH-wildtype glioblastomas was prepared based on the hypoxia marker hypoxia-inducing factor 1 alpha (HIF1 alpha). The TMA was stained with 18 metal-tagged antibodies covering TAMs, lymphocytes, immune checkpoints, vessels, tumor cells and proliferation. The Hyperion-CYTOF technology was used to ablate the samples and the images were analyzed by MCD viewer, Visiopharm software, and customized R scripts.

Results

Single-cell analysis of 160 fields covering around 45,000 cells in the glioblastoma microenvironment revealed multiple cellular phenotypes. It was revealed that proliferating TAMs (IBA1+, Ki67+) were more frequent in hypoxia, whereas proliferating vessels (CD34+, Ki67+) were more frequent in normoxia. Additionally, proliferating stem-like tumor cells (OLIG-2+, Ki67+) were more frequent in normoxia regions.

Conclusion

Our study revealed multiple cellular phenotypes in the glioblastoma microenvironment. The TAMs, endothelial and tumor cell phenotypes revealed may play a critical role in glioblastoma biology however this needs to be elucidated in future studies.

O-083 Tumors of the central nervous system among women treated with fertility drugs: a population-based cohort study

Study question

Is the use of fertility drugs among infertile women associated with tumors of the central nervous system (CNS)?

Summary answer

The use of most specific types of fertility drugs is not associated with an increased risk of CNS tumors overall.

What is known already

Few previous studies have investigated the association between fertility drugs and CNS tumors. Studies have reported inconsistent results regarding the risk of CNS tumors associated with assisted reproductive technologies such as in vitro fertilization (IVF). No studies have reported the risk associated with various specific fertility drugs.

Study design, size, duration

Retrospective population-based cohort study of all women included in the Danish Infertility Cohort. The study cohort consisted of 148 016 infertile women after exclusion of women who emigrated, died, were diagnosed with cancer before infertility diagnosis, and women for whom information on level of education was missing. The cohort was linked to various national health- and civil registers to study all 20- to 45-year old infertile women in Denmark during 1995-2017.

Participants/materials, setting, methods

The study cohort was linked to various national health and population registers to obtain information on fertility drugs (clomiphene citrate, gonadotropins, human chorionic gonadotropin, gonadotropin-releasing hormone receptor modulators and progesterone), CNS tumors, relevant covariates and vital and emigration status. Cox proportional hazard regression models were used to calculate hazard ratios and 95% confidence intervals for CNS tumors overall and for gliomas, meningiomas and diverse benign tumors of the brain and other parts of the CNS.

Main results and the role of chance

During a median 11.3 years of follow-up, 328 women were diagnosed with a CNS tumor. No marked associations were observed between use of most types of fertility drugs (clomiphene citrate, gonadotropins, gonadotropin releasing hormone receptor modulators and progesterone) and CNS tumors. However, ever use of human chorionic gonadotropin was associated with an increased rate of gliomas (HR 2.13 95% CI 0.90-5.01) but a decreased rate of meningiomas (HR 0.49 95% CI 0.28-0.87). No clear associations with CNS tumors were observed according to time since first use or cumulative dose for any specific fertility drugs. Additional studies with longer follow-up are necessary to support these findings.

Limitations, reasons for caution

The median age at end of follow-up (43.5 years) was lower than the median age for CNS tumors diagnosis (60 years). Information on estrogen use, treatment regimens and number of cycles is only partly available in the registers and these were not included in this study.

Wider implications of the findings

This study presents reassuring results regarding the risk of tumors of the CNS among women treated with fertility drugs. Our study is only generalizable to premenopausal women, and the risk for postmenopausal women remains to be assessed.

Trial registration number

not applicable

Granular clinical history and outcome in 51 patients with primary and secondary malignant meningioma

OBJECTIVE

WHO grade III meningiomas, also known as malignant meningiomas (MMs), are rare, and the heterogenous clinical course in patients with MM is not well described. To characterize the clinical course of patients with MM, granular clinical data were gathered from 51 patients treated at the Department of Neurosurgery and Radiation Oncology, Rigshospitalet, in Copenhagen, Denmark, between 2000 and 2020.

METHODS

The authors investigated outcome and timing in terms of 1) tumor progression and grade transformation in patients previously diagnosed with WHO grade I or II meningiomas (patients with a secondary MM [sMM]); 2) performance status and complications following surgery; and 3) transition to noncurative treatment and ultimately death. Complications, time between recurrences, and outcome (modified Rankin Scale [mRS] score) for every surgery were analyzed, both malignant and premalignant.

RESULTS

Of the 51 patients, 24 (47%) had an sMM. The time to WHO grade III transformation in the sMM group varied widely (median 5.5 years, range 0.5-22 years), but after transformation to a WHO grade III tumor, patients with an sMM and those with a primary MM (pMM) did not differ significantly in overall survival and cumulative risk of progression. Median overall survival for all 51 patients was 4.2 years (95% CI 2.6-7.2 years). Time from the decision to shift from curative to noncurative treatment until death was 3.8 months and the 30-day mortality rate following surgery was 11.8%. From a cumulative number of 151 surgeries, 10 surgeries were followed by improvement on the mRS, mRS score was unchanged in 70, and it worsened in 71. The MM was the underlying cause of death in 30 of 31 patients who had died at the end of follow-up.

CONCLUSIONS

Together, these findings clearly show a significant morbidity and mortality from the disease itself and from the treatment. These findings warrant studies of prognostic factors for earlier support and adjuvant measures in MM and identify a need for better palliative strategies in this patient group.

Fluorescein-guided resection of cerebral metastases is associated with greater tumor resection

BACKGROUND

Sodium fluorescein (fluorescein) crosses a disrupted blood-brain barrier similarly to gadolinium contrast in contrast-enhancing cerebral tumors. When exposed to light with 560 nm wavelength during surgery, fluorescein emits a yellow-green fluorescent light that can be visualized through an operating microscope equipped with an appropriate emission filter. The distribution of the fluorescence correlates with the contrast on a gadolinium contrast-enhanced MRI.

OBJECTIVE

The objective of this single-center retrospective study was to investigate if the use of fluorescein would increase the extent of resection and to examine if fluorescein guided resection influences postoperative neurological status.

METHODS

During the study period from August 2014 to August 2018, 117 patients were operated for cerebral metastases. Of these, 56 operations were guided by fluorescein and 61 by traditional white light. All patients had an early postoperative MRI within 72 h after surgery.

RESULTS

The use of fluorescein increased the extent of resection in patients with cerebral metastases. The use of fluorescein was not associated with increased postoperative sequelae or neurological damage regardless of underlying primary cancer.

CONCLUSION

Fluorescein is a helpful supplement in the neurosurgical treatment of cerebral metastases.

Orthostatic hypotension after cervicomedullary junction surgery: illustrative case

BACKGROUND

Surgery at the cervicomedullary junction carries a risk of damaging vital brainstem functions. Because the nucleus of the solitary tract (NS) is involved in the baroreceptor reflex, damage to its integrity may lead to orthostatic hypotension.

OBSERVATIONS

A 56-year-old man with a medical history of hypertension, von Hippel-Lindau disease, and previous bilateral adrenalectomy due to pheochromocytoma was referred with symptoms of dysphagia and paralysis of the left vocal cord. Paralysis of the left vagus nerve was suspected. Magnetic resonance imaging revealed a contrast-enhancing cystic process in the cervicomedullary junction. Twenty-three years earlier, the patient had undergone surgical treatment for a hemangioblastoma in the same region. After repeated surgery, the patient temporarily developed orthostatic hypotension. At discharge, the patient no longer needed antihypertensive medication.

LESSONS

Surgery near the cervicomedullary junction can affect the NS, leading to disruption of the baroreceptor response that regulates blood pressure.

[Endoscopic evacuation of deep intracerebral spontaneous haematoma]

Deep-seated intracerebral spontaneous haematomas (ICHs) pose a neurosurgical challenge in decision-making process as summarised in this review. No studies have been able to demonstrate a significant effect on surgical removal. The challenge to surgical removal is the damage the surgery causes to the healthy brain in connection with the surgical procedure. The application of minimally invasive techniques in the form of endoscopic removal of deep-seated ICHs, results in significantly less "trauma" to the healthy brain and hopefully a better prognosis for patients with deep-seated spontaneous ICHs.

Study protocol for OptimalTTF-2: enhancing Tumor Treating Fields with skull remodeling surgery for first recurrence glioblastoma: a phase 2, multi-center, randomized, prospective, interventional trial

BACKGROUND

OptimalTTF-2 is a randomized, comparative, multi-center, investigator-initiated, interventional study aiming to test skull remodeling surgery in combination with Tumor Treating Fields therapy (TTFields) and best physicians choice medical oncological therapy for first recurrence in glioblastoma patients. OptimalTTF-2 is a phase 2 trial initiated in November 2020. Skull remodeling surgery consists of five burrholes, each 15 mm in diameter, directly over the tumor resection cavity. Preclinical research indicates that this procedure enhances the effect of Tumor Treating Fields considerably. We recently concluded a phase 1 safety/feasibility trial that indicated improved overall survival and no additional toxicity. This phase 2 trial aims to validate the efficacy of the proposed intervention.

METHODS

The trial is designed as a comparative, 1:1 randomized, minimax two-stage phase 2 with an expected 70 patients to a maximum sample size of 84 patients. After 12-months follow-up of the first 52 patients, an interim futility analysis will be performed. The two trial arms will consist of either a) TTFields therapy combined with best physicians choice oncological treatment (control arm) or b) skull remodeling surgery, TTFields therapy and best practice oncology (interventional arm). Major eligibility criteria include age ≥ 18 years, 1st recurrence of supratentorial glioblastoma, Karnofsky performance score ≥ 70, focal tumor, and lack of significant co-morbidity. Study design aims to detect a 20% increase in overall survival after 12 months (OS12), assuming OS12 = 40% in the control group and OS12 = 60% in the intervention group. Secondary endpoints include hazard rate ratio of overall survival and progression-free survival, objective tumor response rate, quality of life, KPS, steroid dose, and toxicity. Toxicity, objective tumor response rate, and QoL will be assessed every 3rd month. Endpoint data will be collected at the end of the trial, including the occurrence of suspected unexpected serious adverse reactions (SUSARs), unacceptable serious adverse events (SAEs), withdrawal of consent, or loss-to-follow-up.

DISCUSSION

New treatment modalities are highly needed for first recurrence glioblastoma. Our proposed treatment modality of skull remodeling surgery, Tumor Treating Fields, and best practice medical oncological therapy may increase overall survival significantly.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT0422399 , registered 13. January 2020.

P04.05 Targeted Gene-Expression analysis during malignant transformation in primary and secondary malignant meningioma

BACKGROUND

Malignant meningiomas comprise 2–5% of all meningiomas. The process of malignant transformation when benign meningiomas (WHO grade I-II) become malignant (WHO grade III) has not previously been investigated in sequential tumour surgeries. Upregulation of FOXM1 expression and DREAM-complex repression have shown phenotypical subgroups correlating with WHO grade and aggressiveness. We investigated the RNA expression of 30 genes central to meningioma biology and 770 genes involved in neuroinflammatory pathways in primary and secondary malignant meningioma patients who underwent one to several operations.

MATERIALS AND METHODS

We identified a cohort of consecutive malignant meningioma patients treated at Rigshospitalet, Copenhagen from 2000–2020 (n=51) and gathered their malignant tumours and previous WHO grade I/II tumours. The malignant cohort (MC) was counter matched with a benign cohort (BC) where patients had no recurrences during follow-up. RNA expression signatures from 140 samples from the MC and 51 samples from the BC were analysed with the Nanostring Neuroinflammation panel customized with 30 genes known to be relevant in meningioma phenotypes.

RESULTS

49% of MC patients had a previous grade I/II meningioma making them secondary malignant meningioma patients. Progression-free survival calculated from first malignant surgery to first recurrence or death showed no significant difference in the primary vs. secondary patients. Preliminary results of single-gene analysis of MC tumours showed FOXM1, MYBL2, TOP2A, BIRC5 expression was higher in WHO grade III samples. Gene-expression signatures in the individual patients and gene ontology enrichment analyses are in process.

CONCLUSIONS

FOXM1, MYBL2, TOP2A, BIRC5 RNA expression levels seem to rise during malignant progression across patients. Gene-expression analysis using the Nanostring technology is feasible and a potentially powerful tool to distinguish meningiomas prone to malignant transformation from truly benign meningiomas.

Validation of the newly conceived Surgical Swedish ICH grading scale for surgically treated patients with intracerebral hemorrhage: patient series

BACKGROUND

The authors sought to externally validate a newly developed clinical grading scale, the Surgical Swedish ICH (SwICH) score. Patients surgically treated for spontaneous supratentorial intracerebral hemorrhage (ICH) from 2009 to 2019 in a single center in Denmark were identified. Data were retrospectively collected from patient records and neuroimaging. Surgical SwICH and ICH scores were calculated for each patient, and the validity of the Surgical SwICH was assessed and compared.

OBSERVATIONS

The 126 patients included had an overall 30-day mortality rate of 23%. All patients with a Surgical SwICH score of 0 survived past one year. No patient scored the maximum Surgical SwICH score of 6. The 30-day mortality rates for Surgical SwICH scores 1, 2, 3, and 4 were 0%, 20%, 53%, and 25%, respectively (p <0.0001 for trend). Mortality rates for ICH scores 1, 2, 3, and 4 were 0%, 11%, 33%, and 76%, respectively (p <0.001 for trend). Receiver operator characteristics showed an area under curve of 0.78 for the Surgical SwICH score and 0.80 for the ICH score (p = 0.21 difference).

LESSONS

The Surgical SwICH score was a good predictor of 30-day mortality in patients surgically treated for spontaneous supratentorial ICH. However, the Surgical SwICH score did not outperform the previously established ICH score in predicting 30-day mortality.

Targeted next-generation sequencing of adult gliomas for retrospective prognostic evaluation and up-front diagnostics

AIMS

We aimed to reclassify a population-based cohort of 529 adult glioma patients to evaluate the prognostic impact of the 2016 World Health Organization (WHO) central nervous system tumour classification. Moreover, we evaluated the feasibility of gene panel next-generation sequencing (NGS) in daily diagnostics of 225 prospective glioma patients.

METHODS

The retrospective cohort was reclassified according to WHO 2016 criteria by immunohistochemistry for IDH-R132H, fluorescence in situ hybridization for 1p/19q-codeletion and gene panel NGS. All tumours of the prospective cohort were subjected to NGS analysis up-front.

RESULTS

The entire population-based cohort was successfully reclassified according to WHO 2016 criteria. NGS results were obtained for 98% of the prospective patients. Survival analyses in the population-based cohort confirmed three major prognostic subgroups, that is, isocitrate dehydrogenase (IDH)-mutant and 1p/19q-codeleted oligodendrogliomas, IDH-mutant astrocytomas and IDH-wildtype glioblastomas. The distinction between WHO grade II and III was prognostic in patients with IDH-mutant astrocytoma. The survival of patients with IDH-wildtype diffuse astrocytomas carrying TERT promoter mutation and/or EGFR amplification overlapped with the poor survival of IDH-wildtype glioblastoma patients.

CONCLUSIONS

Gene panel NGS proved feasible in daily diagnostics. In addition, our study confirms the prognostic role of glioma classification according to WHO 2016 in a large population-based cohort. Molecular features of glioblastoma in IDH-wildtype diffuse glioma were linked to poor survival corresponding to IDH-wildtype glioblastoma patients. The distinction between WHO grade II and III retained prognostic significance in patients with IDH-mutant diffuse astrocytic gliomas.

Desmoplastic myxoid tumor, SMARCB1-mutant: clinical, histopathological and molecular characterization of a pineal region tumor encountered in adolescents and adults

Atypical teratoid/rhabdoid tumor (ATRT) is a highly malignant brain tumor predominantly occurring in infants. Mutations of the SMARCB1 gene are the characteristic genetic lesion. SMARCB1-mutant tumors in adolescents and adults are rare and may show uncommon histopathological and clinical features. Here we report seven SMARCB1-deficient intracranial tumors sharing distinct clinical, histopathological and molecular features. Median age of the four females and three males was 40 years (range 15-61 years). All tumors were located in the pineal region. Histopathologically, these tumors displayed spindled and epithelioid cells embedded in a desmoplastic stroma alternating with a variable extent of a loose myxoid matrix. All cases showed loss of nuclear SMARCB1/INI1 protein expression, expression of EMA and CD34 was frequent and the Ki67/MIB1 proliferation index was low in the majority of cases (median 3%). Three cases displayed heterozygous SMARCB1 deletions and two cases a homozygous SMARCB1 deletion. On sequencing, one tumor showed a 2 bp deletion in exon 4 (c.369_370del) and one a short duplication in exon 3 (c.237_276dup) both resulting in frameshift mutations. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor Classifier (version v11b4). By unsupervised t-SNE analysis and hierarchical clustering analysis, however, all tumors grouped closely together and showed similarities with ATRT-MYC. After a median observation period of 48 months, three patients were alive with stable disease, whereas one patient experienced tumor progression and three patients had succumbed to disease. In conclusion, our series represents an entity with distinct clinical, histopathological and molecular features showing epigenetic similarities with ATRT-MYC. We propose the designation desmoplastic myxoid tumor (DMT), SMARCB1-mutant, for these tumors.

Antidepressant drug use and subdural hematoma risk

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) use may be associated with development of subdural hematoma (SDH).

OBJECTIVES

To estimate SDH risk associated with antidepressant use, including when combined with antithrombotics, or nonsteroidal anti-inflammatory drugs (NSAIDs).

PATIENTS/METHODS

We performed this case-control study based on Danish registries. We included 10 885 incident cases of SDH and 435 379 matched general population controls. We calculated odds ratios (95% confidence interval) adjusted for comorbidity, co-medication, education level, and income (aOR).

RESULTS

We found that current use of SSRIs (aOR1.32 [1.25-1.38]) and non-SSRIs (aOR 1.19 [1.13-1.26]) was associated with a higher SDH risk, compared with non-use of antidepressants. Risks were higher with short duration of current use (eg, <1 month of current use: aOR 2.55 [2.07-3.15] for SSRI, 1.88 [1.46-2.41] for non-SSRIs; >3 years of current use: 1.04 [0.93-1.17] for SSRI and 1.12 [0.98-1.28] for non-SSRIs). Combined use of antidepressants with either antithrombotics or NSAIDs yielded similar ORs to those observed for single use of antithrombotics or NSAIDs. Stronger associations were observed for antidepressants combined with both vitamin K antagonists (VKAs) and NSAIDs (SSRI, VKA, & NSAID: aOR 5.51 [2.70-11-22]; non-SSRI, VKA, & NSAID: 6.81 [2.37-19-60]).

CONCLUSIONS

Antidepressant use was associated with higher risk of SDH that seemed largely restricted to first year of treatment. In absolute terms this risk is judged to be small, given the low SDH incidence rate. With one possible exception (triple use of antidepressants, NSAIDs, and VKAs), risk estimates of SDH for combined regimens of antidepressants with antithrombotics or NSAIDs provided little evidence of interactions.

GENE-33. INTEGRATED GLIOMA DIAGNOSTICS USING TARGETED NEXT-GENERATION SEQUENCING

INTRODUCTION

Targeted next-generation sequencing (NGS) offers promising diagnostic perspectives by making it possible to detect genetic alterations with high accuracy in multiple genes as part of the daily diagnostic work-up. The importance of genetic alterations is reflected in the 2016 WHO classification of CNS tumors, where specific alterations are incorporated in the definition of certain entities. The aim of this study was to assess the diagnostic potential of a customized targeted glioma-tailored 20-gene panel to identify molecular entities of gliomas and explore their distinct mutational profiles. Moreover, the prognostic impact of molecular diagnostics was explored.

METHODS

We used a setup with NGS, immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) on a series of 756 glioma from both a retro- and prospective cohort. NGS data were obtained for 347 gliomas (225 analyzed prospectively, 122 analyzed retrospectively).

RESULTS

Three major clusters were identified by unsupervised hierarchial cluster analysis: 1) isocitrate dehydrogenase gene (IDH) 1 or 2 mutant astrocytomas with frequent mutations in TP53 (83%) and ATRX (69%), 2) IDH-mutant and 1p/19q-codeleted oligodendrogliomas with frequent mutations in TERT (65%) and CIC (52%), and 3) IDH-wildtype astrocytic gliomas/glioblastomas with frequent mutations in TERT (32%), PTEN (28%) and TP53 (22%). Among the IHC IDH1-R132H negative gliomas, NGS detected other IDH mutations in 16% of the cases. Moreover, rare but diagnostically important mutations such as BRAF V600E and H3F3A K27M were detected. Survival analysis of the reclassified gliomas showed a clear difference in survival between patients with WHO 2007 and 2016 diagnoses. Successful prospective NGS analyses were obtained for 98% of the gliomas in daily diagnostics.

CONCLUSION

Application of NGS panel sequencing improves diagnostic accuracy and is feasible in daily diagnostics. NGS is ready to become part of standard diagnostics in the field of gliomas.

Ultra-long-term subcutaneous home monitoring of epilepsy-490 days of EEG from nine patients

Objective

To explore the feasibility of home monitoring of epilepsy patients with a novel subcutaneous electroencephalography (EEG) device, including clinical implications, safety, and compliance via the first real‐life test.

Methods

We implanted a beta‐version of the 24/7 EEG SubQ (UNEEG Medical A/S, Denmark) subcutaneously in nine participants with temporal lobe epilepsy. Data on seizures, adverse events, compliance in using the device, and use of antiepileptic drugs (AEDs) were collected. EEG was recorded for up to 3 months, and all EEG data were reviewed visually to identify electrographic seizures. These were descriptively compared to seizure counts and AED changes reported in diaries from the same period.

Results

Four hundred ninety days of EEG and 338 electrographic seizures were collected. Eight participants completed at least 9 weeks of home monitoring, while one cancelled participation after 4 weeks due to postimplantation soreness. In total, 13 cases of device‐related adverse events were registered, none of them serious. Recordings obtained from the device covered 73% of the time, on average (range 45%‐91%). Descriptively, electrographic seizure counts were substantially different from diary seizure counts. We uncovered several cases of underreporting and revealed important information on AED response. Electrographic seizure counts revealed circadian distributions of seizures not visible from seizure diaries.

Significance

The study shows that home monitoring for up to 3 months with a subcutaneous EEG device is feasible and well tolerated. No serious adverse device‐related events were reported. An objective seizure count can be derived, which often differs substantially from self‐reported seizure counts. Larger clinical trials quantifying the benefits of objective seizure counting should be a priority for future research as well as development of algorithms for automated review of data.

Cerebral Metabolic Changes Related to Oxidative Metabolism in a Model of Bacterial Meningitis Induced by Lipopolysaccharide

BACKGROUND

Cerebral mitochondrial dysfunction is prominent in the pathophysiology of severe bacterial meningitis. In the present study, we hypothesize that the metabolic changes seen after intracisternal lipopolysaccharide (LPS) injection in a piglet model of meningitis is compatible with mitochondrial dysfunction and resembles the metabolic patterns seen in patients with bacterial meningitis.

METHODS

Eight pigs received LPS injection in cisterna magna, and four pigs received NaCl in cisterna magna as a control. Biochemical variables related to energy metabolism were monitored by intracerebral microdialysis technique and included interstitial glucose, lactate, pyruvate, glutamate, and glycerol. The intracranial pressure (ICP) and brain tissue oxygen tension (PbtO₂) were also monitored along with physiological variables including mean arterial pressure, blood glucose, lactate, and partial pressure of O₂ and CO₂. Pigs were monitored for 60 min at baseline and 240 min after LPS/NaCl injection.

RESULTS

After LPS injection, a significant increase in cerebral lactate/pyruvate ratio (LPR) compared to control group was registered (p = 0.01). This increase was due to a significant increased lactate with stable and normal values of pyruvate. No significant change in PbtO₂ or ICP was registered. No changes in physiological variables were observed.

CONCLUSIONS

The metabolic changes after intracisternal LPS injection is compatible with disturbance in the oxidative metabolism and partly due to mitochondrial dysfunction with increasing cerebral LPR due to increased lactate and normal pyruvate, PbtO₂, and ICP. The metabolic pattern resembles the one observed in patients with bacterial meningitis. Metabolic monitoring in these patients is feasible to monitor for cerebral metabolic derangements otherwise missed by conventional intensive care monitoring.

Comparison of 5-aminolevulinic acid and sodium fluorescein for intraoperative tumor visualization in patients with high-grade gliomas: a single-center retrospective study

OBJECTIVE

Maximal safe resection is an important surgical goal in the treatment for high-grade gliomas. Fluorescent dyes help the surgeon to distinguish malignant tissue from healthy. The aims of this study were 1) to compare the 2 fluorescent dyes 5-aminolevulinic acid (5-ALA) and sodium fluorescein (fluorescein) regarding extent of resection, progression-free survival, and overall survival; and 2) to assess the influence of other risk factors on clinical outcome and screen for potential disadvantages of the dyes.

METHODS

A total of 209 patients with high-grade gliomas were included in this retrospective study. Resections were performed in the period from 2012 to 2017 using 5-ALA or fluorescein. Extent of resection was assessed as the difference in tumor volume between early postoperative and preoperative MRI studies. Tumor progression-free survival and overall survival were analyzed using an adjusted Cox proportional hazards model.

RESULTS

One hundred fifty-eight patients were operated on with 5-ALA and 51 with fluorescein. The median duration of follow-up was 46.7 and 21.2 months, respectively. Covariables were evenly distributed. There was no statistically significant difference in volumetrically assessed median extent of resection (96.9% for 5-ALA vs 97.4% for fluorescein, p = 0.46) or the percentage of patients with residual tumor volume less than 0.175 cm3 (29.5% for 5-ALA vs 36.2% for fluorescein, p = 0.39). The median overall survival was 14.8 months for the 5-ALA group and 19.7 months for the fluorescein group (p = 0.06). The median adjusted progression-free survival was 8.7 months for the 5-ALA group and 9.2 months for the fluorescein group (p = 0.03).

CONCLUSIONS

Fluorescein can be used as a viable alternative to 5-ALA for intraoperative fluorescent guidance in brain tumor surgery. Comparative, prospective, and randomized studies are much needed.

The diagnostic value of continuous EEG for the detection of non-convulsive status epilepticus in neurosurgical patients - A prospective cohort study

•

The incidence of seizure activity was 10%.

•

Seizure activity was detected within the first 30 min in three of the five patients.

•

Markers for patient selection for cEEG in neurosurgical patients are needed.

Objective

To prospectively compare the diagnostic yields of standard EEG and continuous EEG (cEEG) monitoring for the diagnosis of non-convulsive status epilepticus (NCSE) in neurosurgical patients in the intensive care unit.

Methods

We included 50 consecutive patients with clinical suspicion of NCSE due to unexplained coma or subtle clinical phenomena such as discrete myoclonus. The initial 30-minute EEG recording and the following cEEG were analyzed separately for seizure activity. Data were collected on neurosurgical diagnosis, previous diagnosis of epilepsy, current medication, level of consciousness, and outcome at discharge from the neurosurgical department.

Results

Recurrent electrographic seizure activity was detected in five patients. This was within the first 30 mins for three patients and on the following cEEG for two patients. Antiepileptic treatment had been initiated in three of these patients. Most of the 50 patients had severe newly acquired neurological disability at discharge.

Conclusions

The prospective finding of a 10% seizure incidence was lower than reports from retrospective studies.

Significance

Use of cEEG led to detection of seizure activity in 2 of 50 patients (4%) and was thus a low-yield method in neurosurgical patients with suspicion of NCSE. Specific markers for patient selection for cEEG are needed.

Patterns of cerebral tissue oxygen tension and cytoplasmic redox state in bacterial meningitis

BACKGROUND

Compromised cerebral energy metabolism is common in patients with bacterial meningitis. In this study, simultaneous measurements of cerebral oxygen tension and lactate/pyruvate ratio were compared to explore whether disturbed energy metabolism was usually caused by insufficient tissue oxygenation or compromised oxidative metabolism of pyruvate indicating mitochondrial dysfunction.

SUBJECT AND METHODS

Ten consecutive patients with severe streptococcus meningitis were included in this prospective cohort study. Intracranial pressure, brain tissue oxygen tension (PbtO₂ ), and energy metabolism (intracerebral microdialysis) were continuously monitored in nine patients. A cerebral lactate/pyruvate (LP) ratio <30 was considered indicating normal oxidative metabolism, LP ratio >30 simultaneously with pyruvate below lower normal level (70 µmol/L) was interpreted as biochemical indication of ischemia, and LP ratio >30 simultaneously with a normal or increased level of pyruvate was interpreted as mitochondrial dysfunction. The biochemical variables were compared with PbtO₂ simultaneously monitored within the same cerebral region.

RESULTS

In two cases, the LP ratio was normal during the whole study period and the simultaneously monitored PbtO₂ was 18 ± 6 mm Hg. In six cases, interpreted as mitochondrial dysfunction, the simultaneously monitored PbtO₂ was 20 ± 6 mm Hg and without correlation with the LP ratio. In one patient, exhibiting a pattern interpreted as ischemia, PbtO₂ decreased below 10 mm Hg and a correlation between LP and PbtO₂ was observed.

CONCLUSION

This study demonstrated that compromised cerebral energy metabolism, evidenced by increased LP ratio, was common in patients with severe bacterial meningitis while not related to insufficient tissue oxygenation.

Abstract TP318: Ethyl Pyruvate Treatment Increases Post-ischemic Levels of Selected Metabolites Detected by Labelled Cerebral Microdialysis

Introduction: Metabolic perturbations associated with mitochondrial function are common after transient cerebral ischemia and are detectable using cerebral microdialysis (CMD). Several putative neuroprotective treatments including ethyl pyruvate (EP) target mitochondrial energy metabolism, but continuous real-time effects have not been described. Using 13 C-succinate labelled CMD with Liquid Chromatography - Mass Spectrometry (LC-MS) we hypothesized that effects of EP treatment on mitochondrial function after transient ischemia could be monitored in vivo.

Methods: Adult Sprague Dawley rats (n=11) were subjected to transient ischemia by stereotaxic microinjection of vasoconstricting endothelin-1 (ET-1) and monitored for 5 hours after reperfusion with trace amount labelled 13 C-succinate CMD during intravenous treatment with EP (40 mg/kg) or vehicle (Ringer’s solution). Using mixed effect linear regression, values of labelled and endogenous energy metabolites after reperfusion were compared to baseline.

Results: ET-1 induced vasoconstriction resulted in transient depression of glucose and elevation of lactate. After reperfusion labelled malate and endogenous xanthine displayed significantly higher concentrations in the EP-group compared to the placebo-group: (mean±SEM) 39.5±14.9%, p<0.01 and 93.9±28.3%, p<0.001 respectively. Endogenous glucose-6-phosphate, pyruvate, succinate, fumarate, malate and isocitrate showed larger variance and no significant difference. Neither did labelled pyruvate, lactate fumarate or isocitrate.

Conclusions: EP treatment potentiates mitochondrial de novo synthesis of malate after transient cerebral ischemia. Differences compared to other Krebs’ cycle intermediates may be explained by a pronounced labelling ratio difference influenced by proximity to labelling source in the metabolic pathway. Increased amounts of endogenous xanthine may be explained by ROS scavenging effects of EP maintaining a beneficial NAD + /NADH ratio required for efficient purine metabolism. Labelled CMD combined with LC-MS enables detailed temporal monitoring of energy metabolites aiding evaluation of putative neuroprotective treatments in vivo.

Abstract TP537: Jugular Bulb Microdialysis in Subarachnoid Hemorrhage

Introduction: Metabolic perturbations are common in patients with subarachnoid hemorrhage (SAH) and contribute to patient outcome. Cerebral microdialysis (CMD), used for monitoring of poor grade SAH patients, is intracranial invasive and highly regional, depending on proximity to lesions. Microdialysis of jugular bulb venous drainage has not been attempted in this patient group and it may give a measure of global cerebral metabolism detecting critical events potentially missed by regional monitoring.

Methods: Adult SAH patients were included at admission when local clinical guidelines prompted extended multimodal neuromonitoring (impaired consciousness and poor grade SAH). Patients were monitored using non-dominant frontal CMD combined with an intracranial pressure (ICP) and brain oxygen tension (PbtO 2 ) probe in a double lumen bolt (Raumedic®) as well as dominant jugular bulb microdialysis for a mean period of 5 days. Jugular bulb lactate/pyruvate ratio (LPR) and intracranial derived measurements were analysed for correlation. 6 month modified Rankin scale (mRs) was assessed.

Results: Twelve patients were included (mean age 62 years, mean mRs 3.7). There were no complications related to jugular bulb access. Of 1218 monitoring hours, 131 displayed elevated jugular bulb LPR (>20), 133 elevated ICP (>20 mmHg) and 287 reduced PbtO 2 (<20 mmHg). Periods of co-variation were seen in selected patients, but no significant correlations between jugular bulb LPR vs. cerebral LPR (r=-0.07, p=0.014), jugular bulb LPR vs. ICP (r=-0.03, p=0.72) or jugular bulb LPR vs. PbtO 2 (r=0.08, p=0.16) were found in Spearman analysis of critical periods. Concerning jugular LPR vs. mRs the study was underpowered (r=-0.36, p=0.27).

Conclusions: Intracranial regional monitoring events were not mirrored in jugular bulb LPR and periods of metabolic perturbations seen in jugular bulb LPR passed without consistent indication from regional modalities. Metabolic disturbances are potentially missed by regional monitoring in SAH.

Prevalence of hereditary hemorrhagic telangiectasia in patients operated for cerebral abscess: a retrospective cohort analysis

It is well described that patients with pulmonary arteriovenous malformations (PAVMs) and Hereditary Hemorrhagic Telangiectasia (HHT) have an increased risk of cerebral abscess (CA). However, as both CA and HHT are rare, the proportion of patients with CA who are diagnosed with HHT has not been previously described. A retrospective study was carried out of all patients treated surgically for CA between January 1995 and September 2014 at the Department of Neurosurgery, Odense University Hospital. The cases were then cross-referenced with the Danish HHT database. Eighty patients aged 5-79 years were included. The incidence of CA was 0.33/100,000/year. Two patients (2.5%) were registered as having HHT. Bacterial pathogens were identified in 70% of all cases, most frequently streptococci species (46.3%). The most common predisposing condition was odontogenic infection (20%), followed by post-operative infection (13.8%) and post-trauma (6.3%). Patients undergoing a full diagnostic program to determine predisposing conditions causing CA increased over the 20-year period from 11.8% to 65.2%. The 3-month and 1-year mortality rates were 7.5% and 11.25%, respectively. There is an overrepresentation of HHT patients in a cohort of patients with CA, and HHT should be investigated as the cause of the CA if no other apparent cause can be identified.

Use of intracranial pressure monitoring in bacterial meningitis: a 10-year follow up on outcome and intracranial pressure versus head CT scans

BACKGROUND

The aim of this study was to evaluate the clinical outcome of patients with severe bacterial meningitis where intracranial pressure (ICP) monitoring has been performed.

METHODS

A retrospective observational study including patients admitted 1st^. January 2005 to 31st^. December 2014. Thirty nine patients age 18-89 years were included. All the patients received intensive care with mechanical ventilation, ICP monitoring, sedation, antibiotics and corticosteroids according to current guidelines. Clinical outcome was defined as death during hospitalization or survival at hospital discharge.

RESULTS

The most common pathogen was Streptococcus pneumoniae (26; 67%). Thirteen patients died (33%) and neurologic impairment was noted in twenty two (84.6%) surviving patients. In S. pneumoniae cases patients with adverse outcome were significantly older (p = 0.0024) and immunosuppressed (p = 0.034). Lower mean-cerebral perfusion pressure (CPP) was found to correlate with adverse outcome (p = 0.005). Cerebrospinal fluid (CSF) was drained in fourteen patients. Increased ICP (>20 mmHg) was observed in twenty four patients. No significant correlation was found between measured ICP and head CT scans with signs of elevated ICP.

CONCLUSIONS

Patients with severe meningitis should be admitted to intensive care units and evaluated for ICP monitoring regardless of head CT findings.

Outcome of conservatively treated occipital condylar fractures - A retrospective study

Introduction:

Occipital condyle fracture (OCF) is rare. It may, however, pose a serious threat to the patient due to destabilization of the craniocervical junction. Correct diagnosis and effective treatment are essential to prevent long-term complications. The aim of this study was to retrospectively investigate our current treatment program with focus on the functional outcome. Diagnosis and classification systems were evaluated for their usefulness in the clinical practice.

Materials and Methods:

We retrospectively reviewed all patients treated conservatively for an occipital condylar fracture from 2010 to 2015 at our department. Fracture classifications were performed according to three established systems. The patients were followed up with clinical examination and plain radiographs at weeks 2, 6, and 12 with the addition of a dynamic flexion-extension X-ray at week 14.

Results:

Totally 24 patients met the inclusion criteria. One was lost to follow-up and two ended treatment before completing the full treatment program due to a clinical decision. Fracture displacement was neither detected nor was any neurological deficits observed. Most patients were pain free after 6 weeks. After 14 weeks’ treatment, two patients still had neck pain; the rest were pain free.

Conclusions:

Our data suggest that twelve weeks’ conservative treatment is not necessary for unilateral OCFs without atlanto-occipital dissociation (AOD). We recommend 6 weeks of conservative treatment, with clinical control and flexion-extension radiographs before ending treatment. Plain radiography is of limited value in the clinical control of this fracture type. Anderson and Montesano and Tuli et al. classification systems fulfill an academic role. We found the classification system by Mueller et al. to be more helpful in everyday clinical practice.

Trends in tumors in the central nervous system in elderly in Denmark, 2008-2012

BACKGROUND

Tumors in the central nervous system (CNS) comprise a heterogeneous group of tumors with different treatment strategies and prognoses. Current treatment regimens are based on studies on patients mainly younger than 70 years. The aim of the present study was to analyze and describe trends in incidence, mortality, prevalence, and relative survival in Denmark from 1980 to 2012 focusing on patients older than 70 years.

MATERIAL AND METHODS

Tumors in the CNS were defined as ICD-10 codes C70-72, D32-33 and D42-43. Data with comparable data on cancer incidence, mortality, prevalence and relative survival derived from the NORDCAN database were delivered from the Danish Cancer Registry and the Danish Cause of Death Registry with follow-up for death or emigration until the end of 2013.

RESULTS

During the period 1980-2012 the number of patients with CNS tumors increased from 603 to 1378 patients. The increase is seen mainly in the elderly patients, and especially in women aged 84-89 and 90 + at the time of diagnosis. During the same time period, the mortality rates increased within all age groups, most significantly in patients aged 70 years or older. This may reflect an increased focus on and identification of these patients. Noteworthy; the number of patients living with a CNS tumor increased from 2952 in 1980 to 12 147 patients in 2010.

CONCLUSION

This study suggests that the current treatment strategies in general may have improved survival in patients with CNS tumors, but in order to improve survival further in the increasing group of elderly patients more knowledge about treatment of these patients is needed.

Bedside evaluation of cerebral energy metabolism in severe community-acquired bacterial meningitis

BACKGROUND

Mortality and morbidity have remained high in bacterial meningitis. Impairment of cerebral energy metabolism probably contributes to unfavorable outcome. Intracerebral microdialysis is routinely used to monitor cerebral energy metabolism, and recent experimental studies indicate that this technique may separate ischemia and non-ischemic mitochondrial dysfunction. The present study is a retrospective interpretation of biochemical data obtained in a series of patients with severe community-acquired meningitis.

METHODS

Cerebral energy metabolism was monitored in 15 patients with severe community-acquired meningitis utilizing intracerebral microdialysis and bedside biochemical analysis. According to previous studies, cerebral ischemia was defined as lactate/pyruvate (LP) ratio > 30 with intracerebral pyruvate level < 70 µmol L(-1). Non-ischemic mitochondrial dysfunction was defined as LP-ratio > 30 at a normal or increased interstitial concentration of pyruvate (≥ 70 μmol L(-1)). Patients with LP-ratios < 30 were classified as no mitochondrial dysfunction.

RESULTS

The biochemical pattern was in 8 patients (10 microdialysis catheters) classified as no mitochondrial dysfunction, in 5 patients classified as non-ischemic mitochondrial dysfunction, and in 2 patients (3 catheters) classified as ischemia.

CONCLUSIONS

In patients with severe community-acquired meningitis, compromised cerebral energy metabolism occurs frequently and was diagnosed in 7 out of 15 cases. A biochemical pattern of non-ischemic mitochondrial dysfunction appears to be a more common underlying condition than cerebral ischemia.

A brain slice culture model for studies of endogenous and exogenous precursor cell migration in the rostral migratory stream

The rostral migratory stream (RMS) is the main pathway by which newly born subventricular zone (SVZ) cells reach the olfactory bulb (OB) in rodents. This migration has been well studied in vivo, but an organotypic in vitro model would facilitate more experimental investigations. Here we introduce a slice culture preparation of the rat forebrain including en suite the rostral part of the lateral ventricle, the RMS and the OB. The preparation was validated with regard to endogenous cell proliferation and migration by tracking bromodeoxyuridine (BrdU)-labelled cells in newly established and 3 and 6 week old cultures. For testing the migratory abilities of exogenous precursor cells, rat SVZ neurospheres and human neural (HNS1 cells) and mesenchymal (hMSC-TERT) stem cell lines were micrografted to the rostral SVZ of 1 and 7 day old cultures. Two weeks later graft derivatives were identified by immunohistochemical staining for human nuclei (HNS1/hMSC-TERT cells) and BrdU (HNS1 cells/neurospheres). Numerous HNS1 cells and BrdU-positive neurosphere cells were found in the RMS. Having reached the OB, subpopulations of the cells expressed the astroglial markers glial fibrillary acidic protein/hAM and the neuronal markers NeuN/tyrosine hydroxylase. Interestingly, the hMSC-TERT cells remained at the implantation site, demonstrating a diversity in migratory capability of different precursor cells. In conclusion, the RMS in rat forebrain slice cultures retains its ability to support migration of endogenous and exogenous neural precursors, making the cultures highly feasible for studies of conditions and factors regulating cell migration.

Modulator effects of interleukin-1beta and tumor necrosis factor-alpha on AMPA-induced excitotoxicity in mouse organotypic hippocampal slice cultures

The inflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha (TNF-alpha) have been identified as mediators of several forms of neurodegeneration in the brain. However, they can produce either deleterious or beneficial effects on neuronal function. We investigated the effects of these cytokines on neuronal death caused by exposure of mouse organotypic hippocampal slice cultures to toxic concentrations of AMPA. Either potentiation of excitotoxicity or neuroprotection was observed, depending on the concentration of the cytokines and the timing of exposure. A relatively high concentration of mouse recombinant TNF-alpha (10 ng/ml) enhanced excitotoxicity when the cultures were simultaneously exposed to AMPA and to this cytokine. Decreasing the concentration of TNF-alpha to 1 ng/ml resulted in neuroprotection against AMPA-induced neuronal death independently on the application protocol. By using TNF-alpha receptor (TNFR) knock-out mice, we demonstrated that the potentiation of AMPA-induced toxicity by TNF-alpha involves TNF receptor-1, whereas the neuroprotective effect is mediated by TNF receptor-2. AMPA exposure was associated with activation and proliferation of microglia as assessed by macrophage antigen-1 and bromodeoxyuridine immunohistochemistry, suggesting a functional recruitment of cytokine-producing cells at sites of neurodegeneration. Together, these findings are relevant for understanding the role of proinflammatory cytokines and microglia activation in acute and chronic excitotoxic conditions.

Differential expression of brain-derived neurotrophic factor transcripts after pilocarpine-induced seizure-like activity is related to mode of Ca2+ entry

Activity-dependent brain-derived neurotrophic factor (BDNF) expression is Ca2+-dependent, yet little is known about the Ca2+ channel contributions that might direct selective expression of the multiple BDNF transcripts. Here, effects of pilocarpine-induced seizure activity on total BDNF expression and on the individual sensitivity of BDNF transcripts to glutamate receptor and Ca2+ channel blockers were evaluated using hippocampal slice cultures and in situ hybridization of transcript-specific cRNA probes directed against mRNAs for the four 5' exons (I-IV) of the BDNF gene. mRNAs for nerve growth factor (NGF) and tyrosine kinase B (trkB) also were studied. Pilocarpine (5 mM) induced a dose- and time-dependent increase in total BDNF (exon V) mRNA expression in the dentate granule cells and CA3-CA1 pyramidal cells with maximal effects at 6 and 24 h, respectively. Increases were blocked by co-treatment with the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX: 25 microM) and the N-methyl-d-aspartic acid receptor antagonist 2-amino-5-phosphonovaleric acid (APV; 25 microM), whereas the L-type voltage sensitive Ca2+ channel blocker nifedipine (20 microM) was without detectable effect. Maximal NGF and trkB mRNA expression was induced by pilocarpine at 4 and 12 h, respectively. For the individual BDNF transcripts, APV blocked pilocarpine-induced increases in transcript II, whereas nifedipine blocked increases in transcripts I and III. Transcript IV levels were not altered by treatment. These results indicate that transcript II makes the greatest contribution to pilocarpine effects on total BDNF mRNA content in this model and provides evidence for regional and Ca2+ channel-specific differences in activity-dependent regulation of the different BDNF transcripts in hippocampus.

Perforant path lesioning induces sprouting of CA3-associated fibre systems in mouse hippocampal formation

In comparison to the rat, the anatomy of the mouse hippocampus, and in particular the response to entorhinal cortex lesioning, is less well characterised. Here we studied the axonal sprouting response after lesioning of the entorhinodentate perforant path projection in young adult SJL/J and C57BL/6 mice. We found that lesioning led to translaminar sprouting of Timm stained regio inferior hippocampus (CA3)-associated fibre systems into the denervated termination zones of the CA3 and dentate gyrus, from the adjacent non-denervated stratum radiatum of CA3. Differences were seen in the Timm staining pattern of the two strains of mice, while the response to lesioning appeared similar albeit less pronounced than that observed in the rat. We also observed an intensified acetylcholine esterase staining reflective of cholinergic sprouting in the denervated perforant path termination zones, which was particularly prominent in areas with sprouting of Timm stained CA3-associated fibres. Finally, we showed that some of the sprouting fibres within the CA3 were myelinated, due to an increased density of silver impregnated myelinated fibres in this region after lesioning. These results show that the basic characteristics of the response to perforant path lesioning in mice are similar to those in the rat, but suggest that the magnitude of the response in the two species is different.

Increased synthesis of heparin affin regulatory peptide in the perforant path lesioned mouse hippocampal formation

Heparin affin regulatory peptide (HARP), also known as pleiotrophin or heparin-binding growth-associated molecule, is a developmentally regulated extracellular matrix protein that induces cell proliferation and promotes neurite outgrowth in vitro as well as pre- and postsynaptic developmental differentiation in vivo. Here we have investigated the expression of HARP mRNA and protein in the perforant path lesioned C57B1/6 mouse hippocampal formation from 1 to 35 days after surgery. This type of lesion induces a dense anterograde and terminal axonal degeneration, activation of glial cells, and reactive axonal sprouting within the perforant path zones of the fascia dentata and hippocampus as well as axotomy-induced retrograde neuronal degeneration in the entorhinal cortex. Analysis of sham- and unoperated control mice showed that HARP mRNA is expressed in neurons and white and gray matter glial cells as well as vascular and pial cells throughout the normal, adult brain. Lesioning induced high levels of HARP mRNA in astroglial-like cells in the denervated zones of fascia dentata and hippocampus as soon as day 2 postlesion. This expression reached maximum at day 4, and declined toward normal at day 7-14. Combined HARP in situ hybridization and glial fibrillary acidic protein (GFAP) immunohistochemical staining and double immunofluorescent stainings for GFAP and HARP at day 4 postlesion showed colocalization of HARP mRNA and protein to hypertrophic GFAP-immunopositive astrocytes in the denervated areas. Finally, the axotomized entorhinal layer II neurons, which expressed high levels of HARP mRNA in the normal brain, exhibited a marked decline in hybridization signal after axotomy. The induction of high levels of HARP mRNA and protein in astrocytes in the denervated areas of fascia dentata and hippocampus is of particular interest as astrocytes and astrocyte-derived factors are known to be implicated in axonal growth and regeneration and in rescuing injured neurons.

Axonal sprouting regulates myelin basic protein gene expression in denervated mouse hippocampus

The regulation of oligodendrocyte gene expression and myelination in vivo in the normal and injured adult CNS is still poorly understood. We have analyzed the effects of axotomy-induced axonal sprouting and microglial activation, on oligodendrocyte myelin basic protein (MBP) gene expression from 2 to 35 days after transection of the entorhino-hippocampal perforant path axonal projection. In situ hybridization analysis showed that anterograde axonal and terminal degeneration lead to upregulated oligodendrocyte MBP mRNA expression starting between day 2 and day 4, in (1) the deep part of stratum radiatum of CA3 and the dentate hilus, which display axonal sprouting but no degenerative changes or microglial activation, and (2) the outer part of the molecular layer of the fascia dentata, and in stratum moleculare of CA3 and stratum lacunosum-moleculare of CA1, areas that display dense anterograde axonal and terminal degeneration, myelin degenerative changes, microglial activation and axotomi-induced axonal sprouting. Oligodendrocyte MBP mRNA expression reached maximum in both these areas at day 7. MBP gene transcription remained constant in stratum radiatum, stratum pyramidale and stratum oriens of CA1, areas that were unaffected by perforant path transection. These results provide strong evidence that oligodendrocyte MBP gene expression can be regulated by axonal sprouting independently of microglial activation in the injured adult CNS.

Microglial reactivity correlates to the density and the myelination of the anterogradely degenerating axons and terminals following perforant path denervation of the mouse fascia dentata

Transection of the entorhino-dentate perforant path is a well known model for lesion-induced axonal sprouting and glial reactions in the rat. In this study, we have characterized the microglial reaction in the dentate molecular layer of the SJL/J and C57Bl/6 mouse. The morphological transformation of the microglial cells and their densitometrically measured Mac-1 immunoreactivity were correlated with the density of silver-impregnated axonal and terminal degeneration and the myelination of the degenerating medial and lateral perforant pathways. Anterograde axonal and terminal degeneration leads to: (i) altered myelin basic protein immunoreactivity with the appearance of discrete myelin deposits preferentially in the denervated medial and significantly less so in the lateral perforant path zone from day 2 after lesioning; (ii) an increase in number and Mac-1 immunoreactivity of morphologically-changed microglial cells in the denervated perforant path zones with more pronounced morphological transformation of microglia in the medial than in the lateral perforant path zones at day 2 but not day 5 after lesioning; and (iii) a linear correlation between the density of microglial Mac-1 reactivity and axonal degeneration in the medial but not in the lateral perforant path zone at two days postlesion, and a linear correlation in both zones at five days postlesion. We propose that the differentiated microglial response is due to the different densities of axonal and terminal degeneration, as observed in the individual cases. The finding of a potentiated or accelerated microglial activation in the medial as compared to the lateral perforant path zone suggests different kinetics of microglial activation in areas with degenerating myelinated and unmyelinated fibers.

Dexamethasone selectively suppresses microglial trophic responses to hippocampal deafferentation

Hippocampal deafferentation increases the expression of insulin-like growth factor-1 by microglia, and of ciliary neurotrophic factor and basic fibroblast growth factor by astroglia in fields and periods of reactive axonal growth. Glucocorticoids attenuate lesion-induced hippocampal sprouting, possibly by reducing trophic signals that stimulate growth. With an interest in this hypothesis, the present studies evaluated the influence of systemic treatment with the synthetic glucocorticoid dexamethasone on entorhinal lesion-induced increases in neurotrophic factor expression in young adult rat hippocampus. Daily dexamethasone injections almost completely blocked increases in insulin-like growth factor-1 messenger RNA content, but did not perturb increases in ciliary neurotrophic factor or basic fibroblast growth factor messenger RNA content, in the deafferented dentate gyrus molecular layer. To determine if the suppression of insulin-like growth factor-1 expression was secondary to a general inhibition of microglial responses, and to identify the time period of glucocorticoid sensitivity, additional rats were prepared to evaluate the effects of semi-chronic (i.e. daily) and single dexamethasone injections on microglial proliferation, ED-1 immunoreactivity (a marker of microglial reactivity) and insulin-like growth factor-1 messenger RNA expression. Semi-chronic dexamethasone treatment attenuated all three measures of deafferentation-induced microglial reactivity. However, a single dexamethasone injection given two (but not one or three) days postlesion inhibited deafferentation-induced increases in insulin-like growth factor-1 messenger RNA content, without having significant effects on other measures. These results demonstrate that dexamethasone treatment preferentially suppresses microglial, as opposed to astroglial, trophic responses to deafferentation, and suggest that glucocorticoids attenuate reactive axonal sprouting by inhibiting the microglial production of insulin-like growth factor-1.

Transcript-specific effects of adrenalectomy on seizure-induced BDNF expression in rat hippocampus

Activity-induced brain-derived neurotrophic factor (BDNF) expression is negatively modulated by circulating adrenal steroids. The rat BDNF gene gives rise to four major transcript forms that each contain a unique 5' exon (I-IV) and a common 3' exon (V) that codes for BDNF protein. Exon-specific in situ hybridization was used to determine if adrenalectomy has differential effects on basal and activity-induced BDNF transcript expression in hippocampus. Adrenalectomy alone had only modest effects on BDNF mRNA levels with slight increases in exon III-containing mRNA with 7-10-day survival and in exon II-containing mRNA with 30-days survival. In the dentate gyrus granule cells, adrenalectomy markedly potentiated increases in exon I and II cRNA labeling, but not increases in exon III and IV cRNA labeling, elicited by one hippocampal afterdischarge. Similarly, for the granule cells and CA1 pyramidal cells, hilus lesion (HL)-induced recurrent limbic seizures elicited greater increases in exon I and II cRNA hybridization in adrenalectomized (ADX) as compared to adrenal-intact rats. In this paradigm, adrenalectomy modestly potentiated the increase in exon III-containing mRNA in CA1 but had no effect on exon IV-containing mRNA content. These results demonstrate that the negative effects of adrenal hormones on activity-induced BDNF expression are by far the greatest for transcripts containing exons I and II. Together with evidence for region-specific transcript expression, these results suggest that the effects of stress on adaptive changes in BDNF signalling will be greatest for neurons that predominantly express transcripts I and II.

Prevention of mouse-rat brain xenograft rejection by a combination therapy of cyclosporin A, prednisolone and azathioprine

Embryonic mouse hippocampal tissue was grafted as tissue blocks to the hippocampal region of adult rats and the effect of two different immunosuppressive treatments compared. Immunosuppression with cyclosporin A, prednisolone and azathioprine or with cyclosporin A alone was compared with placebo treatment. Eight weeks' postgrafting medication with cyclosporin A, prednisolone and azathioprine had resulted in survival of 14 out of 15 grafts (93%), compared with 11 out of 14 (79%) in the group treated with cyclosporin A alone. Only 2 out of 13 grafts (15%) survived in placebo-treated animals. Transplants in the trimedication group displayed distinct cell and neuropil layers and only minimal cellular infiltration by leukocyte common antigen-expressing cells, whereas grafts in cyclosporin A- and placebo-treated groups were densely infiltrated. The results are discussed in relation to the need for extended immunosuppressive and antiinflammatory therapies after intracerebral grafting of histoincompatible tissues.

Studies of the diffuse x-ray scattering from contracting frog skeletal muscles

Using x-rays from synchrotron radiation, we studied diffuse scattering, sometimes together with the myosin layer lines. With an area detector, sartorius muscles and a time resolution of 150 ms, earlier results from semitendinosus muscles contracting isometrically at 6 degrees C (Lowy, J., and F. R. Poulsen. 1987. J. Mol. Biol. 194:595-600) were confirmed and extended. Evidence from intensity changes both in the diffuse scattering and in the myosin layer lines showed that the majority of the heads become disordered at peak tetanic tension. With a linear detector and a time resolution of 5 ms, it was found that during tension rise the intensity increase of the diffuse scattering (which amounted maximally to 12% recorded near the meridian) runs approximately 20 ms ahead of the mechanical change, comparing half-completion times. This suggests that an appreciable number of heads change orientation before peak tension is reached. In quick release experiments the diffuse scattering intensity showed very little change. Recorded near the meridian during rapid shortening, however, it decreased progressively with a half-time of approximately 40 ms. This change amounted to approximately 35% of that observed during the initial tension rise. We interpret this to indicate that during rapid shortening a certain number of heads assume an orientation characteristic of the relaxed state. Viewed in the context of the behavior of the first myosin layer line and the (1, 1) equatorial reflection in similar experiments (Huxley, H. E., M. Kress, A. R. Faruqi, and R. M. Simmons. 1988. Molecular Mechanism of Muscle Contraction), the present results provide further support for the view that the diffuse scattering is mostly due to disordered myosin heads; whilst ordered heads produce the myosin layer lines (Poulsen, F. R., and J. Lowy.1983. Nature lLond.l. 303:146-152).

Diffuse X-ray scatter from myosin heads in oriented synthetic filaments

X-ray results are presented concerning the structural state of myosin heads of synthetic filaments in threads. These were made from purified rabbit skeletal muscle myosin and studied by x-ray diffraction and electron microscopy by Cooke et al. (Cooke, P. H., E. M. Bartels, G. F. Elliott, and R. A. Hughes, 1987, Biophys. J., 51:947-957). X-ray patterns show a meridional peak at a spacing of 14.4 nm. We concentrate here on the only other feature of the axial pattern: this is a central region of diffuse scatter, which we find to be similar to that obtained from myosin heads in solution (Mendelson, R. A., K. M. Kretzschmar, 1980, Biochemistry, 19:4103-4108). This means that the myosin heads have very large random displacements in all directions from their average positions, and that they are practically randomly oriented. The myosin heads do not contribute to the 14.4-nm peak, which must come entirely from the backbone. Comparison with x-ray data from the unstriated Taenia coli muscle of the guinea pig indicates that in this muscle at least 75% of the diffuse scatter comes from disordered myosin heads. The results confirm that the diffuse scatter in x-ray patterns from specimens that contain myosin filaments can yield information about the structural behavior of the myosin heads.

X-ray study of myosin heads in contracting frog skeletal muscle

Using synchrotron radiation, the behaviour of the diffuse X-ray scatter was investigated in the relaxed and active phases of auxotonic and isometric contractions. Muscles were stimulated tetanically for 0.75 of a second, leaving intervals of three minutes between successive contractions. In isometric contractions the scatter is very asymmetric, which means that the myosin heads have a strongly preferred orientation. During tension rise the scatter expands in the meridional direction and contracts in the equatorial direction, the maximal local intensity change being about 20%. The shape change indicates that on average the myosin heads become oriented more perpendicularly to the fibre axis. The distribution of orientations at peak tension is quite different from that we found previously in X-ray scattering data from rigor muscles. In auxotonic contractions where muscles shorten against an increasing tension the scatter is practically circularly symmetrical. This suggests that during shortening the myosin heads go evenly through a wide range of orientations. It is concluded that the results from both the auxotonic and isometric experiments provide strong support for the rotating myosin head model. In isometric contractions the transition between the relaxed phase and peak tension is accompanied by an overall increase in scattering intensity of about 10%: this corresponds to a relative increase in the fraction of disordered myosin heads by almost 30%.

Application of potential energy calculations to the determination of muscle structure from X-ray data with special reference to the configuration of myosin heads

A method that relates molecular structure to the forces that maintain it and to its X-ray diffraction pattern is described and applied to muscle. In a computer model, the potential energy of the movable components (here the myosin heads) is minimized by letting them move down the steepest gradient in three dimensions from a variety of starting positions. Initial values are assumed for the parameters that determine the forces, and for those that define the structure and arrangement of the fixed components. The X-ray pattern expected from the resulting structures can be calculated in a straightforward manner and compared with relevant observed data. Discrepancies can then be minimized by varying the values initially assumed for the parameters, as in the conventional "trial and error" method. This first application of the present method is concerned with the effects of the hexagonal lattice on the myosin head configuration in thick filaments of the type found in vertebrate skeletal muscle. For that purpose, a very simple model was used with the following main features: smooth cylinders for the thin filaments and for the thick filament backbones, two spherical heads attached by Hookean springs to each point of a 9/3 helix on the surface of the backbone, and repulsive forces of the electrostatic double-layer type acting between each head and all other surfaces. The myosin head configuration was calculated for an isolated thick filament and a study was made of the effects of packing such filaments into a hexagonal lattice of various side spacings in the presence or absence of thin filaments. For the isolated filament, it was found that the 9/3 helical symmetry is maintained in the myosin head configuration and that the two heads of each molecule are splayed azimuthally. When such filaments are packed into the hexagonal lattice with thin filaments present, the 9/3 helical symmetry of the myosin head configuration is lost. As the lattice side spacing is reduced, the myosin heads become increasingly displaced not only in the radial and azimuthal directions but also in the axial direction, although they interact primarily with smooth cylinders. The axial separation of the two heads in each molecule becomes different in one level from that in the other two in the 43 nm axial repeat, thus increasing the repeat in projection onto the axis from 14.3 to 43 nm. This effect may contribute to the "forbidden meridionals" described by Huxley & Brown (1967).(ABSTRACT TRUNCATED AT 400 WORDS)

Small-angle X-ray scattering from myosin heads in relaxed and rigor frog skeletal muscles

Low-angle X-ray diffraction patterns from relaxed and non-overlap rigor muscles show a central region of diffuse scattering (disk) which is circularly symmetrical, behaves as solution scattering and comes predominantly from myosin heads. In full-overlap rigor the disk is compressed in the diagonal direction, indicating that the myosin heads have a bent shape and a preferred orientation consistent with a 45 degree angle of attachment to actin.

Time-resolved X-ray diffraction studies of the structural behaviour of myosin heads in a living contracting unstriated muscle

The intensities of three regions of the low-angle X-ray diffraction pattern from a molluscan unstriated muscle have been followed during tension generation at a time resolution of 0.5-1 s using synchrotron radiation. The observed intensity changes can be reasonably interpreted in terms of myosin cross-bridge movements during the contractile cycle. A model that accounts for the intensity changes suggests that myosin heads move out from the thick filament during activation and attach to actin sites to produce tension with a small delay. During relaxation from both phasic and tonic contractions the heads remain attached to actin sites longer than it takes for tension to decay.

The structure of the myosin elements in vertebrate smooth muscles

Low-angle X -ray diffraction experiments with living relaxed and contracting guinea-pig taenia coli muscles have led to the discovery of a m eridional reflexion at about 14.3 nm whose presence establishes the existence of a regular assembly of myosin molecules in the form of filamentous elements (Lowy, Poulsen & V ibert 1970). From measurements of the shape of the 14.3 nm reflexion it is possible to deduce that in the axial direction the diffracting elements must be at least 500 nm long, while in a direction perpendicular to the fibre axis these elements must diffract coherently over a lateral distance of at least 60 nm. The latter feature can be straightforwardly interpreted in terms of the lateral register of the cross bridges across the faces of the ribbon-like myosin elements seen in the electron microscope by Lowy & Small (1970), Small, Lowy & Squire (1971) and Small & Squire (1972). The intensity of the 14.3 nm reflexion varies in patterns from muscles in various relaxed and contracted states. Nevertheless, we have detected no significant changes in the shape of this reflexion when the muscle passes from a resting to a contracted state, when it is loaded with weights from 1 to 10 g, or when it is incubated at different temperatures in Ringer solutions m ade hypertonic to various extents by the addition of sucrose. These observations suggest that the structure of the myosin elements responsible for the 14.3 nm reflexion persists unchanged regardless of the states of the muscle investigated. In our view this can be interpreted to indicate that the ribbons are present in relaxed muscles and interact with actin during contraction.