Rapid glucocorticoid effects on excitatory amino acid levels in the hippocampus: a microdialysis study in freely moving rats

Glucocorticoids can rapidly affect neuronal function and behaviour in mammals. Several studies have suggested the possible existence of rapid, non-genomic effects of glucocorticoids in the hippocampus. To investigate whether glucocorticoids could affect neurotransmission in the hippocampus through rapid, non-genomic mechanisms, we studied the effects of acute glucocorticoid administration on extracellular amino acid levels in the CA1 area of the hippocampus. By means of microdialysis on freely moving rats, we observed that an intraperitoneal injection of corticosterone (2.5 mg/kg) induced a rapid (within 15 min) and transient (returning to basal levels by 35-45 min) increase in extracellular aspartate and glutamate levels ( approximately 155-160%), both in sham-operated and adrenalectomized rats. These effects occurred in parallel with a rise in corticosterone concentration, also detected by microdialysis, in this hippocampal area. Intrahippocampal perfusion of corticosterone by retrodialysis also produced the same fast and reversible effects on excitatory amino acid (EAA) levels. Extracellular concentrations of taurine and gamma-aminobutyric acid (GABA) were unchanged after intrahippocampal glucocorticoid administration. This corticosterone-mediated rise in EAA levels was not inhibited by the presence of specific antagonists for the two types of intracellular corticosteroid receptors, nor by a protein synthesis inhibitor, anisomycin. Perfusion of dexamethasone, a synthetic glucocorticoid, elicited a similar effect to that observed with corticosterone treatment in all studied cases. However, non-glucocorticoid steroids did not affect amino acid transmission in this hippocampal area. These results indicate that glucocorticoids induce a rapid and transient increase in hippocampal EAA levels in vivo that might be exerted through a novel non-genomic mechanism of action.

Effects of chronic stress on contextual fear conditioning and the hippocampal expression of the neural cell adhesion molecule, its polysialylation, and L1

Chronic stress has been shown to induce time-dependent neurodegeneration in the hippocampus, ranging from a reversible damage to a permanent neuronal loss. This damage has been proposed to impair cognitive function in hippocampus-dependent learning tasks. In this study, we have used a 21-day restraint stress procedure in rats, previously reported to induce reversible atrophy of apical dendrites of CA3 pyramidal cells, to assess whether it may influence subsequent performance in the contextual fear conditioning task under experimental conditions involving high stress levels (1 mA shock intensity as the unconditioned stimulus). In addition, we were interested in the study of the possible cellular and molecular mechanisms involved in the reversible phase of neural damage. Cell adhesion molecules of the immunoglobulin superfamily, such as the neural cell adhesion molecule and L1, are cell-surface macromolecules that, through their recognition and adhesion properties, regulate cell-cell interactions and have been reported to play a key role in cognitive functioning. A second aim of this study was to evaluate whether chronic stress would modulate the expression of the neural cell adhesion molecule, its polysialylation, and L1 in the hippocampus. The results showed that chronic stress facilitated subsequent contextual fear conditioning. They also showed that chronically stressed rats displayed reduced hippocampal neural cell adhesion molecule, but increased polysialylated expression as well as a trend towards exhibiting increased L1 expression. In summary, these results support the view that a 21-day chronic stress regimen predisposes individuals to develop enhanced contextual fear conditioning responses. They also indicate that cell adhesion molecules might play a role in the structural remodelling that occurs in the hippocampus as a consequence of chronic stress exposure.

Novelty-related rapid locomotor effects of corticosterone in rats

Glucocorticoids modulate brain function and behaviour through different mechanisms. Although classical effects are mediated through intracellular receptors that modulate gene transcription, recent evidence supports the existence of rapid, nongenomic steroid effects through the neuronal membrane. In this study, we explored possible rapid behavioural effects of corticosterone in the rat, which could provide a model to characterize further the mechanisms involved in rapid corticosteroid nongenomic actions. We found that a corticosterone injection, at doses (2.5 or 5 mg/kg) that mimic plasma concentrations produced by substantial stress, rapidly increases (within 7.5 min of its systemic administration) the locomotor response displayed by rats in a novel environment (activity cage). A lower dose of 1 mg/kg failed to induce this effect. In addition, corticosterone failed to increase locomotion when administered to rats that had been previously exposed to the activity cage. Corticosterone-induced increased locomotion in a novelty situation was not counteracted by either the intracerebroventricular administration of the protein synthesis inhibitor cycloheximide, or by the intracerebroventricular administration of specific antagonists for each type of intracellular corticosteroid receptor, i.e. RU28318, a mineralocorticoid receptor antagonist and RU38486, a glucocorticoid receptor antagonist. Further studies supported the viability of the receptor antagonists to display an anti-corticosteroid action interfering, as previously reported, with the behavioural &winning test. Therefore, the rapid actions of corticosterone in locomotor activity described here, which appear to be nongenomic, might provide a model for future research on the elucidation of the mechanisms involved in steroid-membrane interactions.

Modulation of adult hippocampal neurogenesis by thyroid hormones: implications in depressive-like behavior

Hormonal imbalances are involved in many of the age-related pathologies, as neurodegenerative and psychiatric diseases. Specifically, thyroid state alterations in the adult are related to psychological changes and mood disorders as depression. The dentate gyrus of the hippocampal formation undergoes neurogenesis in adult mammals including humans. Recent evidence suggests that depressive disorders and their treatment are tightly related to the number of newly born neurons in the dentate gyrus. We have studied the effect of thyroid hormones (TH) on hippocampal neurogenesis in adult rats in vivo. A short period of adult-onset hypothyroidism impaired normal neurogenesis in the subgranular zone of the dentate gyrus with a 30% reduction in the number of proliferating cells. Hypothyroidism also reduced the number of newborn neuroblasts and immature neurons (doublecortin (DCX) immunopositive cells) which had a severely hypoplastic dendritic arborization. To correlate these changes with hippocampal function, we subjected the rats to the forced swimming and novel object recognition tests. Hypothyroid rats showed normal memory in object recognition, but displayed abnormal behavior in the forced swimming test, indicating a depressive-like disorder. Chronic treatment of hypothyroid rats with TH not only normalized the abnormal behavior but also restored the number of proliferative and DCX-positive cells, and induced growth of their dendritic trees. Therefore, hypothyroidism induced a reversible depressive-like disorder, which correlated to changes in neurogenesis. Our results indicate that TH are essential for adult hippocampal neurogenesis and suggest that mood disorders related to adult-onset hypothyroidism in humans could be due, in part, to impaired neurogenesis.

Chronic stress induces opposite changes in the mRNA expression of the cell adhesion molecules NCAM and L1

The effects of 21-day exposure to restraint stress on mRNA levels of the cell adhesion molecules NCAM and L1 were evaluated in different hippocampal regions (CA1, CA3, and dentate gyrus) and other structures (thalamus, prefrontal and frontal cortices, and striatum) of the rat brain. A general decrease in gene expression of the neural cell adhesion molecule (NCAM) was found throughout the brain, particularly in all hippocampal subregions. On the contrary, transcripts for the adhesion molecule L1 were specifically increased at the level of the hippocampus, especially in the dorsal dentate gyrus and area CA3. mRNA for the NCAM180 isoform was detected unchanged in all brain areas examined after chronic stress. A second experiment explored whether there would be cognitive alterations associated with this stress procedure and molecular regulation. Thus, after exposure to the same restraint regimen, performance in the water maze was evaluated. Although stressed rats displayed the ability to learn the task throughout the training session, they showed a transient deficit in the initial phase of the acquisition. In conclusion, our findings indicate that chronic stress interferes with the mechanisms involved in the synthesis of cell adhesion molecules of the immunoglobulin superfamily. Furthermore, they suggest that these effects might be involved in the mechanisms by which stress induces structural and functional alterations in the central nervous system and, particularly, in the hippocampus.

Lack of thyroid hormone receptor alpha1 is associated with selective alterations in behavior and hippocampal circuits

Brain development and function are dependent on thyroid hormone (T3), which acts through nuclear hormone receptors. T3 receptors (TRs) are transcription factors that activate or suppress target gene expression in a hormone-dependent or -independent fashion. Two distinct genes, TRalpha and TRbeta, encode several receptor isoforms with specific functions defined in many tissues but not in the brain. Mutations in the TRbeta gene cause the syndrome of peripheral resistance to thyroid hormone; however, no alterations of the TRalpha gene have been described in humans. Here we demonstrate that mice lacking the TRalpha1 isoform display behavioral abnormalities of hippocampal origin, as shown by the open field and fear conditioning tests. In the open field test mutant mice revealed less exploratory behavior than wild-type mice. In the contextual fear conditioning test mutant mice showed a significantly higher freezing response than wild-type controls when tested 1 week after training. These findings correlated with fewer GABAergic terminals on the CA1 pyramidal neurons in the mutant mice. Our results indicate that TRalpha1 is involved in the regulation of hippocampal structure and function, and raise the possibility that deletions or mutations of this receptor isoform may lead to behavioral changes or even psychiatric syndromes in humans.

Spatial learning impairment induced by chronic stress is related to individual differences in novelty reactivity: search for neurobiological correlates

Although chronic stress has been reported to induce deleterious effects on hippocampal structure and function, the possible existence of individual differences in the vulnerability to develop stress-induced cognitive alterations was hypothesized. This study was designed to evaluate (i) whether individual variability in behavioural reactivity to novelty could be related to a differential vulnerability to show spatial learning deficits after chronic stress in young adult rats, and (ii) to what extent, could individual differences in stress-induced cognitive alterations be related to alterations in specific neurobiological substrates. Four month-old Wistar male rats were classified according to their locomotor reactivity to a novel environment, as either low (LR) or highly (HR) reactive, and then either submitted to psychosocial stress for 21-days (consisting of the daily cohabitation of each young adult rat with a new middle-aged rat) or left undisturbed. The results showed that psychosocial stress induced a marked deficit in spatial learning in the water maze in HR, but not in LR, rats. Then, a second experiment investigated the possible differential expression of corticosteroid receptors (MR and GR) and cell adhesion molecules (NCAM and L1) in the hippocampus of HR and LR rats, both under basal conditions and after exposure to chronic social stress. Although chronic stress induced a reduction on the hippocampal expression of MRs and the NCAM-140 isoform, the levels of these molecules did not differ between stressed rats with and without spatial learning impairments; i.e., between HR- and LR-stressed rats, respectively. Nevertheless, it should be noted that the reduction of the hippocampal expression of NCAM-140 induced by psychosocial stress was particularly marked in HR stressed rats. However, the expression of GRs, NCAM-120 and NCAM-180 isoforms, and L1, was not affected by stress, regardless of the reactivity of the animals. Therefore, although we failed to find a neurobiological substrate that specifically correlated with the differential cognitive vulnerability to chronic stress shown by animals with a different novelty reactivity, this study confirms the hypothesis that rats differ in their susceptibility to display stress-induced impairments in hippocampus-dependent spatial learning tasks. In addition, it provides a model to further search for the neurobiological substrate(s) involved in the differential susceptibility to develop stress-induced cognitive impairments.

Decreased spontaneous motor activity and startle response in nitric oxide synthase inhibitor-treated rats

In the central nervous system, nitric oxide has been proposed to be a retrograde messenger mediating learning and synaptic plasticity. Since only pretraining injections of nitric oxide synthesis inhibitors were shown to impair learning, we examined the possibility that systemic administration of these inhibitors might influence some non-specific aspects related to the organism's general psychophysiological status. Intraperitoneal administration of NG-nitro-L-arginine methyl ester (30 or 100 mg/kg) 60 min pre-test to adult rats resulted in: (i) altered exploratory pattern and reduced locomotion in a novel environment; (ii) reduced startle response to either acoustic or electric stimuli; and (iii) cardiovascular alterations. In addition, intracerebroventricular administration of N-nitro-L-arginine (10 microliters of a 10 mM solution) diminished the acoustic startle response. Specificity of these effects through nitric oxide was supported by the ability of the nitric oxide precursor, L-arginine, to prevent the inhibitors actions. These findings indicate that nitric oxide inhibitors interfere with the general psychophysiological status of the organism.

Post-training administration of a synthetic peptide ligand of the neural cell adhesion molecule, C3d, attenuates long-term expression of contextual fear conditioning

The neural cell adhesion molecule (NCAM) plays a key role in synaptic plasticity and memory formation. We have recently developed a synthetic peptide, termed C3d, which, through the binding to the first, N-terminal immunoglobulin-like (Ig) module in the extracellular portion of NCAM, has been shown to promote neurite outgrowth and synapse formation in vitro, and to interfere with passive avoidance memory in rats in vivo. In this study, we investigated whether the i.c.v. administration of C3d, either 5.5 h after or 2 days before training, could be effective to modulate the strength at which emotional memory for aversive situations is established into a long-term memory. The effects of the peptide were evaluated in adult male Wistar rats trained in the contextual fear conditioning task. The results indicated that C3d significantly reduced the subsequent long-term retention of the conditioned fear response when administered 5.5 h post-training, as indicated by retention tests performed 2-3 and 7 days post-training. However, this treatment failed to influence conditioning for this task when injected 2 days pre-training. Additional experiments showed that C3d did not influence the emotional or locomotor behaviour of the animals, when tested in the open field task. Furthermore, hippocampal levels of microtubule-associated protein 2 (MAP2), Synaptophysin and NCAM were found unchanged when evaluated by enzyme-linked immunosorbent assay in crude synaptosomal preparations 2 days after peptide i.c.v. injection. Therefore, post-training injection of this synthetic peptide was efficient to attenuate the strength at which memory for contextual fear conditioning was enduringly stored, whilst it did not affect the acquisition of new memories. In addition to further support the view that NCAM is critically involved in memory consolidation, the current findings suggest that the NCAM IgI module is a potential target for the development of therapeutic drugs capable to reduce the cognitive impact induced by exposure to intensive stress experiences.

Nitric oxide synthesis inhibitors prevent rapid behavioral effects of corticosterone in rats

Corticosteroid actions at the brain can modulate neural function and behavioral processes. Classic corticosteroid effects are mediated through intracellular receptors which act primarily by regulation of DNA transcription. However, an alternative nongenomic mechanism mediating rapid corticosteroid actions by effecting the neuronal membrane has also been proposed. We have recently described a behavioral model of rapid corticosterone effects fulfilling criteria for considering nongenomic steroid actions, such as resistance to protein synthesis inhibition and to blockage of intracellular receptors through the use of specific receptor antagonists. The model consists of a rapid increase induced by a corticosterone injection (within 7.5 min of a systemic injection) on the locomotor response displayed by rats in a novel environment. In the present study, we aimed to study whether the gas molecule nitric oxide might be included among the effector systems involved in such rapid corticosterone effect. The administration of nitric oxide synthase inhibitors, given either systemically [NG-nitro-L-arginine methyl ester (L-NAME), 30 mg/kg body weight, i.p.] or centrally [N-nitro-L-arginine (N-Arg), 10 microliters of a 10-mM solution i.c.v.], prevented the increase in locomotion induced by corticosterone (Cort, 5 mg/kg body weight i.p.). Specificity of this effect was supported by the ability of the nitric oxide precursor L-arginine (L-Arg, 350 mg/kg body weight i.p.) to inhibit L-NAME action. This effect of nitric oxide synthase inhibition on steroid effects was shown to be task-specific, since L-NAME failed to influence another rapid behavioral effect of corticosterone, the suppression of the acoustic startle response. Under our experimental conditions, corticosterone failed to affect peripheral blood pressure, discarding that the antagonistic effect of nitric oxide synthase inhibition on the corticosterone-induced effect in locomotion were related to a peripheral action at the cardiovascular level. Therefore, these data suggest a role for nitric oxide on the neurochemical mechanisms elicited by corticosterone to rapidly enhance locomotion in a novel situation.

Differences in corticosterone level due to inter-food interval length: implications for schedule-induced polydipsia

The purpose of this study was to determine the effects of different food-reinforcement schedules on plasma corticosterone (CORT), and its possible involvement in the acquisition and maintenance of schedule-induced polydipsia (SIP). In Experiment 1, three groups of rats were submitted to two different fixed-interval (FI) schedules with inter-food intervals of 30 and 120 s, and to a massed-feeding presentation for 40 days until SIP was well stabilized. In Experiment 2, six groups of rats were exposed to the same schedules, FI 30s and FI 120s, and to the massed-feeding condition, but no water bottles were presented. CORT levels were determined on Days 3 and 40. Results of Experiment 1 indicated that FI 30s schedule, but not FI 120s or the massed-feeding condition, induces excessive drinking from Day 3. Results in Experiment 2 indicated that CORT levels were similar for all the groups on Day 3. However, only animals on the FI 30s schedule did increase their CORT levels on Day 40, with no variation in the hormone in the other two conditions, FI 120s and massed-feeding presentations. The data are discussed in terms of the implications of these results for hypotheses of SIP as anxiolitic behavior.

Effects of NMDA and AMPA receptor antagonists on corticosterone facilitation of long-term memory in the chick

Long-term memory formation for a weak passive avoidance task in day-old chicks is facilitated by corticosterone administration. Since (i) glutamatergic systems, through different receptor types, play a key role in learning and memory processes, and (ii) glucocorticoids increase glutamate concentrations in learning-related regions of the mammalian brain, we reasoned that glutamatergic activation might be a mechanism by which corticosterone facilitates the formation of an enduring memory. To assess this hypothesis, long-term retention was evaluated in chicks trained on a weak passive avoidance task and intracerebrally injected with NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists (MK-801 and 6-cyano-7-nitroquinoxaline-2,3-dione) with regard to training and corticosterone injection respectively. The results indicated that either of the antagonists prevented the facilitating effect of corticosterone when administered before the training trial, but failed to interfere with the steroid effect when injected before corticosterone administration in the post-training period, suggesting that their early effectiveness was not related to corticosterone-induced actions but to training-triggered mechanisms. In addition, administration of the AMPA antagonist, 5.5 h after training, was also effective in impairing the long-term memory-potentiating effect of corticosterone. These results support the view that corticosterone facilitates the formation of an enduring memory in this learning model, through the modulation of late events during the consolidation period, including the activation of the AMPA receptor type.

Regional and temporal modulation of brain glycoprotein synthesis by corticosterone

Corticosterone has a biphasic effect on memory formation, short-term effects being facilitating and long-term effects resulting in cognitive impairments. The effects of different patterns of temporal exposure to corticosterone-previously shown to biphasically modulate water maze performance-on glycoprotein synthesis were evaluated in four rat brain regions: hippocampus, striatum, frontal cortex and hypothalamus. Acute corticosterone administration resulted in decreased glycoprotein synthesis in hippocampus and striatum, which might be related to the memory facilitating effects of the steroid. However, sustained exposure to corticosterone in a subchronic (7 days) or chronic (21 days) regimen indicated the hypothalamus as the only region displaying reduced fucosylation after chronic treatment. These findings suggest that detrimental effects of chronic corticosterone treatment on hippocampal neurones and memory might be not related to an initial steroid action on fucosyl-glycoprotein expression.

Reduced oxygen consumption of brown adipocytes isolated from progesterone-treated rats

It has been previously shown that responsiveness to noradrenaline is reduced in brown adipocytes isolated from estradiol-treated rats. The possibility that high plasma levels of progesterone could also alter adrenergic response was checked. The oxygen consumption of brown adipocytes isolated from control and progesterone-treated rats was monitored in basal conditions and in the presence of increasing concentrations of noradrenaline. In both situations, cells isolated from treated animals showed a lower respiratory rate than those from control animals. These results suggest that not only estradiol but also progesterone could modulate the adrenergic response of brown adipocytes. The study of alpha 1- and beta-adrenergic responses indicates that the beta-response parallels the general reduction in oxygen consumption, although the alpha 1-response seems to be more deeply depressed. Estimation of cell number in brown fat depots indicates some hyperplasia induced by progesterone; this increase in cell number could counterbalance partially but not totally the decreased cellular oxygen consumption at the organ level.

Accuracy of verbal fluency tests in the discrimination of mild cognitive impairment and probable Alzheimer's disease in older Spanish monolingual individuals

The main objetive was to analyze the accuracy of different verbal fluency tests (VFTs) in discriminating cognitively healthy subjects from individuals with mild cognitive impairment (MCI) and probable Alzheimer's disease (AD) in a cohort of older Spanish speaking adults. As a result, we aimed to identify the VFT that best predicts conversion from MCI to probable AD. 287 subjects: 170 controls (HC), 90 stable MCI and 27 patients with MCI that evolved into probable AD (MCI-AD) were assessed with a neuropsychological battery test and five VFTs. The animal fluency test produced the best differentiation of HC from MCI (p < .001), of HC from MCI-AD (p < .001) and of MCI from MCI-AD converters (p < .001), with sensitivities 98.8%, 98.8% and 75.6%, respectively. Logistic regression showed that the animal fluency test (p < 0.001) appears to be the most useful and neuropsychological VFT to predict conversion to probable dementia.

A Medical Student's Guide to Online Resources in Neurosurgery

Early exposure to neurosurgery during medical school is critical to improving recruitment into the specialty. About 30% of medical schools in the U.S. lack a home program in neurosurgery, thereby, limiting their exposure to the field of neurosurgery. The transition to virtual education was largely facilitated through webinars during the coronavirus disease of 2019 pandemic. Advantages of these resources include their widespread global outreach, with a large number of attendees being international medical students. Although many such resources exist, they are primarily available through social media platforms. To our knowledge, there exists no clear outline of these resources. We identified 16 resources through a database search and through popular social media platforms. Nine out of 16 resources were video based, and 2 utilized the concept of spaced repetition through flashcards. Our review describes these educational resources and aims to serve as a guide for medical students interested in neurosurgery.

Systematic review and meta-analysis comparing Manta device and Perclose device for closure of large bore arterial access

Data comparing MANTA device with Perclose device for large bore arterial access closure is limited. We performed meta-analysis to compare safety and efficacy of the two devices in large (⩾14 Fr sheath) arteriotomy closure post-TAVR. Relevant studies were identified via PubMed, Cochrane, and EMBASE databases until June, 2022. Data was analyzed using random effect model to calculate relative odds of VARC-2 defined access-site complications and short-term (in-hospital or 30-day) mortality. A total of 12 studies (2 RCT and 10 observational studies) comprising 2339 patients were included. The odds of major vascular complications (OR 0.99, 95% CI 0.51-1.92; p = 0.98); life threatening and major bleeding (OR 0.77, 95% CI 0.45-1.33; p = 0.35); minor vascular complications (OR 1.37, 95% CI 0.63-2.99; p = 0.43); minor bleeding (OR 0.94, 95% CI 0.57-1.56; p = 0.82); device failure (OR 0.74, 95% CI 0.49-1.11; p = 0.14); hematoma formation (OR 0.76, 95% CI 0.33-1.75; p = 0.52); dissection, stenosis, occlusion, or pseudoaneurysm (OR 1.08, 95% CI 0.71-1.62; p = 0.73) and short-term mortality (OR 1.01, 95% CI 0.55-1.84; p = 0.98) between both devices were similar. MANTA device has a similar efficacy and safety profile compared to Perclose device.

Progesterone does not alter sympathetic activity in tissues involved in energy balance

Female rats acclimated to thermoneutrality to avoid cold influences received progesterone by means of subcutaneous implants. They increased their food intake and body weight above the values recorded in control animals. None the less, despite the enhanced food intake, no sign of activation of the sympathetic nervous system was observed, as judged by the unaltered noradrenaline content, half-life and turnover rate in brown adipose tissue, pancreas and heart. This indicates that progesterone increases food intake but prevents non-energy-conservation processes regulated by the sympathetic nervous system from taking place. Thus, it facilitates in two different ways the building up of energy stores. Because overfeeding induced by palatable diets increases the sympathetic tone to the organs studied, it is suggested that the central mechanisms regulating energy balance are probably influenced in a different manner by progesterone than by the sensory properties of palatable diets.

Utility of Sodium Fluorescein During Peripheral Nerve Tumor Surgery: A Scoping Review of Indications, Techniques, and Outcomes

OBJECTIVE

The primary treatment for peripheral nerve tumors involves maximal surgical resection while preserving nerve function. Sodium fluorescein shows potential for enhancing the safety and efficacy of nerve tumor surgery. This review evaluates the advantages and limitations of sodium fluorescein in this context.

METHODS

PubMed, EMBASE, Web-of-Science, and Scopus were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-scoping review guidelines to include studies reporting the use of sodium fluorescein in peripheral nerve tumors surgery. Intervention-related outcomes (i.e., extent of resection, clinical outcomes, complication rates, recurrence rates, and duration of surgery) were evaluated and summarized.

RESULTS

A total of 4 studies encompassing 166 patients with 168 tumors were included. Patients were mostly female (98; 53.6%), 101 (69.2%), had sporadic (nonsyndromic) tumors, and at histopathology, 114 (67.9%) tumors were WHO grade-1 schwannomas. Gross total resection was achieved in 146 (86.9%) tumors. Postoperative complications were reported in 16 cases (10.2%%), none related to side effects of the fluorescent dye. High tumor fluorescence was reported in 150 (94.3%) tumors, while absent and low parent nerve fluorescence was reported in 121 (79.6%) and 27 (17.8%), respectively. The median duration of surgery was 51.5 (range: 24-92) minutes.

CONCLUSIONS

Sodium fluorescein shows promise as assisting tool in nerve tumor surgery by facilitating differentiation among the tumor, parent nerve, and surrounding soft tissue. However, multicenter randomized controlled trials are necessary to determine its effect on extent of resection rates, clinical outcomes, postoperative complication rates, and surgical duration in comparison to current standard of care.