Corticosteroids, 11beta-hydroxysteroid dehydrogenase isozymes and the rabbit choroid plexus

Progress and recognition of idiopathic intracranial hypertension: A narrative review

BACKGROUND

Idiopathic intracranial hypertension (IIH) mainly affects obese young women, causing elevated intracranial pressure, headaches, and papilledema, risking vision loss and severe headaches. Despite weight loss as the primary treatment, the underlying mechanisms remain unclear. Recent research explores novel therapeutic targets.

AIMS

This review aimed to provide a comprehensive understanding of IIH's pathophysiology and clinical features to inform pathogenesis and improve treatment strategies.

METHODS

Recent publications on IIH were searched and summarized using PubMed, Web of Science, and MEDLINE.

RESULTS

The review highlights potential pathomechanisms and therapeutic advances in IIH.

CONCLUSION

IIH incidence is rising, with growing evidence linking it to metabolic and hormonal disturbances. Early diagnosis and treatment remain challenging.

Idiopathic intracranial hypertension: a step change in understanding the disease mechanisms

The understanding of idiopathic intracranial hypertension (IIH) has evolved over the past few years. Previously, IIH was considered a disease exclusively affecting the neuro-ophthalmic axis, characterized by raised intracranial pressure, headache and papilloedema, and resulting in the risk of severe and permanent visual loss and life-changing disabling headaches. Recent advances have begun to redefine IIH as a probable metabolic disease involving a range of systemic manifestations. More than 95% of individuals affected by the disease are women of reproductive age with obesity. The incidence is rapidly rising and parallels the escalating worldwide obesity rates. Contemporary insights identify associations with insulin resistance, type 2 diabetes and a twofold increased risk of cardiovascular disease in excess of that driven by obesity alone. Adipose distribution in people with IIH, like that in other metabolic diseases, is preferentially centripetal and is associated with changes in intracranial pressure. Evidence now demonstrates adipose tissue dysfunction in people with IIH, involving transcriptional and metabolic priming for lipogenesis and weight gain. Hormonal perturbations are also observed, including a unique phenotype of androgen excess that promotes cerebrospinal fluid secretion. Knowledge of these additional disease features is driving research into novel therapeutic targets and altering the approach to multidisciplinary care.

Experimental drugs for the treatment of idiopathic intracranial hypertension (IIH): shedding light on phase I and II trials

INTRODUCTION

Idiopathic intracranial hypertension is a neurological condition characterized by a raised intracranial pressure and papilledema that causes debilitating headaches. While the extent of the pathophysiology is being discovered, the condition is emerging as a systemic metabolic disease distinct to people living with obesity alone. Idiopathic intracranial hypertension is becoming more common and therefore establishing licensed therapeutics is a key priority.

AREA COVERED

The translation of preclinical work in idiopathic intracranial hypertension is evident by the two early phase trials evaluating 11-β-hydroxysteroid dehydrogenase inhibitor, AZD4017, and a glucagon like peptide-1 receptor agonist, Exenatide. This review summarizes these two early phase trials evaluating targeted medicines for the treatment of intracranial pressure. The modulation of these two distinct mechanisms have potential for therapeutic intervention in people living with idiopathic intracranial hypertension.

EXPERT OPINION

The clinical trial landscape in idiopathic intracranial hypertension is a challenge due to the rarity of the disease and the lack of agreed meaningful trial outcomes. Further preclinical work to fully understand the pathogenesis is required to enable personalized targeted drug treatment.

Cushing's Disease Associated With Partially Empty Sella Turcica Syndrome: A Case Report

The association between empty sella turcica (EST) syndrome and Cushing's disease has been rarely reported. It is plausible to hypothesize that EST syndrome in association with Cushing's disease can be attributed to intracranial hypertension. In this case report, we present a 47-year-old male patient who presented with weight loss, fatigue, easy bruising, acanthosis nigricans, and skin creases hyperpigmentation. Investigations revealed hypokalemia and confirmed the diagnosis of Cushing's disease. Magnetic resonance imaging (MRI) brain showed a partial EST syndrome and a new pituitary nodule as compared with previous brain imaging. Transsphenoidal surgery was pursued and was complicated by cerebrospinal fluid leakage. This case reflects the rare association of EST syndrome and Cushing's disease, suggesting the increased risk of postoperative complications in this setting and the diagnostic challenge that EST syndrome imposes. We review the literature for a possible mechanism of this association.

Glucocorticoids modify intracranial pressure in freely moving rats

BACKGROUND

Glucocorticoids (GCs) are widely prescribed for a variety of inflammatory diseases, but they are also used to treat raised intracranial pressure (ICP) caused by trauma or oedema. However, it is unclear if GCs independently modulate ICP and if GCs are involved in normal ICP regulation. In this study, we aimed to assess the ICP modulatory effects of GCs and their molecular consequences on choroid plexus (CP).

METHODS

Adult female rats were implanted with telemetric ICP probes for physiological, continuous ICP recordings in a freely moving setup. Rats received prednisolone or vehicle via oral gavage in a randomized acute (24 h) ICP study. In a subsequent study rats received corticosterone or vehicle in drinking water for a 4-week chronic ICP study. CP were removed, and the expression of genes associated with cerebrospinal fluid secretion were assessed.

RESULTS

A single prednisolone dose reduced ICP by up to 48% (P < 0.0001), where ICP was reduced within 7 h and was maintained for at least 14 h. Prednisolone increases ICP spiking (P = 0.0075) while not altering ICP waveforms. Chronic corticosterone reduces ICP by up to 44%, where ICP was lower for the entirety of the 4-week ICP recording period (P = 0.0064). ICP daily periodicity was not altered by corticosterone. Corticosterone ICP reduction was not accompanied by ICP spike differences or alteration in ICP spike periodicity. Chronic corticosterone treatment had modest effects on CP gene expression, lowering the expression of Car2 at CP (P = 0.047).

CONCLUSIONS

GCs reduce ICP in both the acute and chronic setting to a similar degree. Moreover, GCs did not modify the diurnal rhythm of ICP, suggesting the diurnal variation of ICP periodicity is not under explicit control of GCs. ICP disturbances should be considered a consequence of GC therapy. Based on these experiments, GCs may have broader ICP therapeutic uses, but side effects must be taken into consideration.

Disease Course and Long-term Outcomes in Pregnant Women With Idiopathic Intracranial Hypertension: The IIH Prospective Maternal Health Study

BACKGROUND AND OBJECTIVES

Idiopathic intracranial hypertension (IIH) most typically occurs in women of childbearing age with increased weight as a key risk factor for development or exacerbation of the disease. Pregnancy is common in this group of patients. The longer-term effect of pregnancy on IIH has not been established and was the aim of this study.

METHODS

A prospective cohort study (IIH Life) recruited consecutive patients with IIH between 2012 and 2021 and evaluated outcomes including vision (logarithm of the minimum angle of resolution visual acuity, Humphrey visual field perimetric mean deviation, and optical coherence tomography [OCT] imaging) and headache. Four cohorts were evaluated: those with IIH diagnosed for the first time while pregnant, those with established IIH who became pregnant, those with a pregnancy prior to their diagnosis of IIH, and those with IIH who never became pregnant.

RESULTS

Three hundred seventy-seven people with IIH agreed to participate in the IIH Life maternal health study. Mean follow-up was 17.5 months (SD 20.5). IIH diagnosed in pregnancy was rare. Patients diagnosed with IIH while pregnant had greater papilledema (mean OCT total retinal thickness +11.59 µm/mo [95% CI 1.25-21.93]), although they had comparable visual field and acuity measures compared with those with established IIH who became pregnant during their disease course (-1.2 µm/mo [95% CI -2.6 to 0.21]). In those with established IIH, pregnancy did not adversely affect visual or headache outcomes over time, and the trajectory was akin to those with IIH who never had a pregnancy. Headache outcomes showed variability reflecting the IIH cohort as a whole.

DISCUSSION

A diagnosis of IIH while pregnant was rare but associated with more severe papilledema. Long-term visual outcomes in IIH were analogous irrespective of the timing of the pregnancy. These data are reassuring; however, close vigilance of IIH clinical features during pregnancy is recommended.

A viewpoint on aldosterone and BMI related brain morphology in relation to treatment outcome in patients with major depression

An abundance of knowledge has been collected describing the involvement of neuroendocrine parameters in major depression. The hypothalamic-pituitary-adrenocortical (HPA) axis regulating cortisol release has been extensively studied; however, attempts to target the HPA axis pharmacologically to treat major depression have failed. This review focuses on the importance of the adrenocortical stress hormone aldosterone, which is released by adrenocorticotropic hormone and angiotensin, and the mineralocorticoid receptor (MR) in depression. Depressed patients, in particular those with atypical depression, have signs of central hyperactivation of the aldosterone sensitive MR, potentially as a consequence of a reactive aldosterone release induced by low blood pressure and as a result of low sensitivity of peripheral MR. This is reflected in reduced heart rate variability, increased salt appetite and sleep changes in this group of patients. In addition, enlarged brain ventricles, compressed corpus callosum and changes of the choroid plexus are associated with increased aldosterone (in relation to cortisol). Furthermore, subjects with these features often show obesity. These characteristics are related to a worse antidepressant treatment outcome. Alterations in choroid plexus function as a consequence of increased aldosterone levels, autonomic dysregulation, metabolic changes and/or inflammation may be involved. The characterization of this regulatory system is in its early days but may identify new targets for therapeutic interventions.

11βHSD1 Inhibition with AZD4017 Improves Lipid Profiles and Lean Muscle Mass in Idiopathic Intracranial Hypertension

BACKGROUND

The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) determines prereceptor metabolism and activation of glucocorticoids within peripheral tissues. Its dysregulation has been implicated in a wide array of metabolic diseases, leading to the development of selective 11β-HSD1 inhibitors. We examined the impact of the reversible competitive 11β-HSD1 inhibitor, AZD4017, on the metabolic profile in an overweight female cohort with idiopathic intracranial hypertension (IIH).

METHODS

We conducted a UK multicenter phase II randomized, double-blind, placebo-controlled trial of 12-week treatment with AZD4017. Serum markers of glucose homeostasis, lipid metabolism, renal and hepatic function, inflammation and androgen profiles were determined and examined in relation to changes in fat and lean mass by dual-energy X-ray absorptiometry.

RESULTS

Patients receiving AZD4017 showed significant improvements in lipid profiles (decreased cholesterol, increased high-density lipoprotein [HDL] and cholesterol/HDL ratio), markers of hepatic function (decreased alkaline phosphatase and gamma-glutamyl transferase), and increased lean muscle mass (1.8%, P < .001). No changes in body mass index, fat mass, and markers of glucose metabolism or inflammation were observed. Patients receiving AZD4017 demonstrated increased levels of circulating androgens, positively correlated with changes in total lean muscle mass.

CONCLUSIONS

These beneficial metabolic changes represent a reduction in risk factors associated with raised intracranial pressure and represent further beneficial therapeutic outcomes of 11β-HSD1 inhibition by AZD4017 in this overweight IIH cohort. In particular, beneficial changes in lean muscle mass associated with AZD4017 may reflect new applications for this nature of inhibitor in the management of conditions such as sarcopenia.

Emerging themes in idiopathic intracranial hypertension

PURPOSE

Idiopathic intracranial hypertension (IIH) is a rare disorder characterised by raised intracranial pressure. The underlying pathophysiology is mostly unknown and effective treatment is an unmet clinical need in this disease. This review evaluates key emerging themes regarding disease characteristics, mechanisms contributing to raised intracranial pressure and advances in potential therapeutic targets.

FINDINGS

IIH is becoming more common, with the incidence rising in parallel with the global obesity epidemic. Current medical management remains centred around weight management, which is challenging. Metabolic investigations of patients have identified specific androgen profiles in cerebrospinal fluid (CSF), which suggest an endocrine dysfunction impacting CSF secretion in IIH. Glucagon-like peptide-1 (GLP-1) and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) have been found to play a role in CSF dynamics in IIH and have formed the basis of the first clinical trials looking at new treatments.

CONCLUSIONS

Identification of novel molecular targets thought to underlie IIH pathology is now being translated to clinical trials.

Reviewing the Recent Developments in Idiopathic Intracranial Hypertension

There is increasing evidence and appreciation of idiopathic intracranial hypertension (IIH) in medicine. The pathological processes underlying raised intracranial pressure are being studied, with new insights found in both hormonal dysregulation and the metabolic neuroendocrine axis. These will potentially lead to novel therapeutic targets for IIH. The first consensus guidelines have been published on the investigation and management of adult IIH, and the International Headache Society criteria for headache attributable to IIH have been modified to reflect our evolving understanding of IIH. Randomized clinical trials have been published, and a number of studies in this disease area are ongoing.

Guide to preclinical models used to study the pathophysiology of idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is characterised by raised intracranial pressure (ICP) and papilloedema in the absence of an identifiable secondary cause typically occurring in young women with obesity. The impact is considerable with the potential for blindness, chronic disabling headaches, future risk of cardiovascular disease and marked healthcare utilisation. There have been marked advances in our understanding the pathophysiology of IIH including the role of androgen excess. Insight into pathophysiological underpinnings has arisen from astute clinical observations, studies, and an array of preclinical models. This article summarises the current literature pertaining to the pathophysiology of IIH. The current preclinical models relevant to gaining mechanistic insights into IIH are then discussed. In vitro and in vivo models which study CSF secretion and the effect of potentially pathogenic molecules have started to glean important mechanistic insights. These models are also useful to evaluate novel therapeutic targets to abrogate CSF secretion. Importantly, in vitro CSF secretion assays translate into relevant changes in ICP in vivo. Models of CSF absorption pertinent to IIH, are less well established but highly relevant and of future interest. There is no fully developed in vivo model of IIH but this remains an area of importance. Progress is being made to improve our understanding of the underlying aetiology in IIH including the characterisation of disease biomarkers and their mechanistic role in driving disease pathology. Preclinical models, used to evaluate IIH mechanisms are yielding important mechanistic insights. Further work to refine these techniques will provide translatable insights into disease aetiology.

Metabolic Concepts in Idiopathic Intracranial Hypertension and Their Potential for Therapeutic Intervention

BACKGROUND

Traditional risk factors associated with idiopathic intracranial hypertension (IIH) include obesity, weight gain, and female sex. The incidence of IIH is increasing and yet the underlying trigger and the fueling pathological mechanisms are still poorly understood.

EVIDENCE ACQUISITION

Review of ophthalmology, neurology, general surgery, obesity, endocrinology, nutrition, and neurosurgery literature was made.

RESULTS

The facts that implicate sex and obesity in IIH and headache are examined. The role of fat distribution in IIH is questioned, and the concept of adipose tissue functioning as an endocrine organ driving IIH is discussed. The impact of androgen metabolism in IIH is reviewed as is the emerging role of glucagon-like-peptide-1 analogues in modulating intracranial pressure. This introduces the concept of developing targeted disease-modifying therapeutic strategies for IIH.

CONCLUSIONS

This review will discuss the possible role of the adipose/gut/brain metabolism axis in IIH and speculate how this may impact the pathogenesis of IIH and therapeutic opportunities.

Eye Conditions in Women

Changes in vision can have significant impact on health and quality of life. Differences between women and men have been identified in the incidence of several eye conditions. Some of these differences are a result of the greater longevity of women. However, the eye, like other organs, is susceptible to the impacts of inflammation and sex steroids. Conditions, such as thyroid eye disease, optic neuritis, and dry eye disease are related to autoimmune or inflammatory conditions and are, thus, more common among women. Idiopathic intracranial hypertension occurs disproportionately in women of childbearing age; the etiology of this condition appears to be related to both inflammatory and sex hormone fluctuations.

11β-Hydroxysteroid dehydrogenase type 1 inhibition in idiopathic intracranial hypertension: a double-blind randomized controlled trial

Treatment options for idiopathic intracranial hypertension are limited. The enzyme 11β-hydroxysteroid dehydrogenase type 1 has been implicated in regulating cerebrospinal fluid secretion, and its activity is associated with alterations in intracranial pressure in idiopathic intracranial hypertension. We assessed therapeutic efficacy, safety and tolerability and investigated indicators of in vivo efficacy of the 11β-hydroxysteroid dehydrogenase type 1 inhibitor AZD4017 compared with placebo in idiopathic intracranial hypertension. A multicenter, UK, 16-week phase II randomized, double-blind, placebo-controlled trial of 12-week treatment with AZD4017 or placebo was conducted. Women aged 18–55 years with active idiopathic intracranial hypertension (>25 cmH₂O lumbar puncture opening pressure and active papilledema) were included. Participants received 400 mg of oral AZD4017 twice daily compared with matching placebo over 12 weeks. The outcome measures were initial efficacy, safety and tolerability. The primary clinical outcome was lumbar puncture opening pressure at 12 weeks analysed by intention-to-treat. Secondary clinical outcomes were symptoms, visual function, papilledema, headache and anthropometric measures. In vivo efficacy was evaluated in the central nervous system and systemically. A total of 31 subjects [mean age 31.2 (SD = 6.9) years and body mass index 39.2 (SD = 12.6) kg/m²] were randomized to AZD4017 (n = 17) or placebo (n = 14). At 12 weeks, lumbar puncture pressure was lower in the AZD4017 group (29.7 cmH₂O) compared with placebo (31.3 cmH₂O), but the difference between groups was not statistically significant (mean difference: −2.8, 95% confidence interval: −7.1 to 1.5; P = 0.2). An exploratory analysis assessing mean change in lumbar puncture pressure within each group found a significant decrease in the AZD4017 group [mean change: −4.3 cmH₂O (SD = 5.7); P = 0.009] but not in the placebo group [mean change: −0.3 cmH₂O (SD = 5.9); P = 0.8]. AZD4017 was safe, with no withdrawals related to adverse effects. Nine transient drug-related adverse events were reported. One serious adverse event occurred in the placebo group (deterioration requiring shunt surgery). In vivo biomarkers of 11β-hydroxysteroid dehydrogenase type 1 activity (urinary glucocorticoid metabolites, hepatic prednisolone generation, serum and cerebrospinal fluid cortisol:cortisone ratios) demonstrated significant enzyme inhibition with the reduction in serum cortisol:cortisone ratio correlating significantly with reduction in lumbar puncture pressure (P = 0.005, R = 0.70). This is the first phase II randomized controlled trial in idiopathic intracranial hypertension evaluating a novel therapeutic target. AZD4017 was safe and well tolerated and inhibited 11β-hydroxysteroid dehydrogenase type 1 activity in vivo. Reduction in serum cortisol:cortisone correlated with decreased intracranial pressure. Possible clinical benefits were noted in this small cohort. A longer, larger study would now be of interest.

Novel advances in monitoring and therapeutic approaches in idiopathic intracranial hypertension

PURPOSE OF REVIEW

The current article appraises the recent developments in idiopathic intracranial hypertension (IIH), with particular attention to novel therapeutic avenues and advanced clinical assessment and monitoring with optical coherence tomography and telemetric intracranial pressure devices.

RECENT FINDINGS

The incidence of IIH is increasing. The first consensus guidelines for IIH have been published detailing investigation and management algorithms for adult IIH. Improved understanding, clinical assessment and monitoring are emerging with the use of optical coherence tomography. Intracranial pressure telemetry is providing unique insights into the physiology of raised intracranial pressure in IIH. There are now an increasing number of ongoing clinical trials evaluating weight loss methods and novel targeted therapies, such as 11ß-HSD1 inhibition and Glucagon-like peptide 1 (GLP-1) receptor agonists.

SUMMARY

Several studies are evaluating new therapies for IIH. Monitoring techniques are advancing, aiding diagnosis and allowing the clinician to accurately evaluate changes in papilloedema and intracranial pressure.

European headache federation guideline on idiopathic intracranial hypertension

Background

Idiopathic Intracranial Hypertension (IIH) is characterized by an elevation of intracranial pressure (ICP no identifiable cause. The aetiology remains largely unknown, however observations made in a number of recent clinical studies are increasing the understanding of the disease and now provide the basis for evidence-based treatment strategies.

Methods

The Embase, CDSR, CENTRAL, DARE and MEDLINE databases were searched up to 1st June 2018. We analyzed randomized controlled trials and systematic reviews that investigate IIH.

Results

Diagnostic uncertainty, headache morbidity and visual loss are among the highest concerns of clinicians and patients in this disease area. Research in this field is infrequent due to the rarity of the disease and the lack of understanding of the underlying pathology.

Conclusions

This European Headache Federation consensus paper provides evidence-based recommendations and practical advice on the investigation and management of IIH.

Electronic supplementary material

The online version of this article (10.1186/s10194-018-0919-2) contains supplementary material, which is available to authorized users.

Idiopathic intracranial hypertension as a presenting sign of adrenal insufficiency

Idiopathic intracranial hypertension is a diagnosis of exclusion defined by elevated intracranial pressure without mass lesions or hydrocephalus. Causes of idiopathic intracranial hypertension include obesity, vitamin derangements, antibiotics, corticosteroids, and autoimmune disorders. Cushing’s disease and Addison’s disease have been associated with idiopathic intracranial hypertension. Secondary adrenal insufficiency following withdrawal of inhaled corticosteroids has been found to be a relatively common phenomenon. This case describes an 11-year-old boy who was previously on inhaled corticosteroids for severe asthma who presented with secondary adrenal insufficiency after withdrawal of steroids. The adrenal insufficiency presented as idiopathic intracranial hypertension. We described the hospital course and process of diagnosis for this child with secondary adrenal insufficiency following withdrawal of inhaled corticosteroids. The association between the discontinuation of this patient’s corticosteroids and his onset of headache suggests secondary adrenal insufficiency as the most likely cause of his idiopathic intracranial hypertension. The gradual improvement in his symptoms after steroid replacement further supports this. Due to the significant prevalence of children using inhaled corticosteroids, it is important for clinicians to be aware of the potential for the withdrawal of these drugs to induce hypothalamic–pituitary–adrenal axis suppression.

Impaired cerebrospinal fluid pressure

Abnormalities of cerebrospinal fluid (CSF) pressure are relatively common and may lead to a variety of symptoms, with headache usually being the most prominent one. The clinical presentation of alterations in CSF pressure may vary significantly and show a striking similitude to several primary headache syndromes. While an increase in CSF pressure may be of primary or secondary origin, a pathologic decrease of CSF pressure is usually the result of a meningeal rupture with a resulting leakage of CSF. The pathophysiologic mechanisms of idiopathic intracranial hypertension (IIH) remain largely unknown. However recent evidence indicates that an abnormality in CSF outflow and absorption is likely to play a significant role. Treatment usually consists of a combination of weight loss and a pharmacologic approach using carbonic anhydrase inhibitors. Recent results of the first randomized, double-blind, placebo-controlled trial (RCT) with acetazolamide proved its efficacy in reducing headache and visual disturbances. Clinical evidence suggests efficacy for topiramate and furosemide but no RCT has been conducted to date to confirm these results. In contrast to IIH, spontaneous intracranial hypotension frequently remits spontaneously without specific treatment. If necessary, treatment options range from conservative methods to epidural blood or fibrin sealant patches and surgical interventions.

Pediatric Pseudotumor Cerebri Syndrome

Idiopathic intracranial hypertension, otherwise known as primary pseudotumor cerebri syndrome (PTCS), most frequently occurs in obese women of childbearing age. However, children may be affected as well. This review will address recent findings regarding demographics, diagnosis, and treatment of pediatric PTCS. Prepubertal children with primary PTCS have an equal sex distribution and less frequent obesity compared with adult patients. However, female gender and obesity are risk factors for primary PTCS in postpubertal children. Compared with adults, children with PTCS more frequently present with ocular motility deficits and more often have associated medical conditions that increase the risk of developing PTCS. Visual field testing may be unreliable, and the optimal modality to monitor visual function is unknown. MRI shows signs of elevated intracranial pressure (ICP) in children with PTCS similar to that of adults. It has now been established that elevated ICP in children ≤18 years old is greater than 25 cm H20 in nonobese, nonsedated children, and greater than 28 cm H2O in the remainder. Optical coherence tomography (OCT) may be used to distinguish pseudopapilledema from papilledema, monitor response to treatment in preverbal children, and identify patients with PTCS at risk for permanent visual loss. However, the precise role of OCT in the management of pediatric PTCS remains to be determined.

Pediatric Pseudotumor Cerebri Syndrome: Diagnosis, Classification, and Underlying Pathophysiology

Pseudotumor cerebri syndrome (PTCS) is defined by the presence of elevated intracranial pressure in the setting of normal brain parenchyma and cerebrospinal fluid. PTCS can occur in the pediatric and adult populations and, if untreated, may lead to permanent visual loss. In this review, discussion will focus on PTCS in the pediatric population and will outline its distinct epidemiology and key elements of diagnosis, evaluation and management. Finally, although the precise mechanisms are unclear, the underlying pathophysiology will be considered.

Amphetamine withdrawal differentially affects hippocampal and peripheral corticosterone levels in response to stress

Amphetamine withdrawal is associated with heightened anxiety-like behavior, which is directly driven by blunted stress-induced glucocorticoid receptor-dependent serotonin release in the ventral hippocampus. This suggests that glucocorticoid availability in the ventral hippocampus during stress may be reduced during amphetamine withdrawal. Therefore, we tested whether amphetamine withdrawal alters either peripheral or hippocampal corticosterone stress responses. Adult male rats received amphetamine (2.5mg/kg, ip) or saline for 14 days followed by 2 weeks of withdrawal. Contrary to our prediction, microdialysis samples from freely-moving rats revealed that restraint stress-induced corticosterone levels in the ventral hippocampus are enhanced by amphetamine withdrawal relative to controls. In separate groups of rats, plasma corticosterone levels increased immediately after 20min of restraint and decreased to below stress-naïve levels after 1h, indicating negative feedback regulation of corticosterone following stress. However, plasma corticosterone responses were similar in amphetamine-withdrawn and control rats. Neither amphetamine nor stress exposure significantly altered protein expression or enzyme activity of the steroidogenic enzymes 11β-hydroxysteroid dehydrogenase (11β-HSD1) or hexose-6-phosphate dehydrogenase (H6PD) in the ventral hippocampus. Our findings demonstrate for the first time that amphetamine withdrawal potentiates stress-induced corticosterone in the ventral hippocampus, which may contribute to increased behavioral stress sensitivity previously observed during amphetamine withdrawal. However, this is not mediated by either changes in plasma corticosterone or hippocampal steroidogenic enzymes. Establishing enhanced ventral hippocampal corticosterone as a direct cause of greater stress sensitivity may identify the glucocorticoid system as a novel target for treating behavioral symptoms of amphetamine withdrawal.

Idiopathic intracranial hypertension, hormones, and 11β-hydroxysteroid dehydrogenases

Idiopathic intracranial hypertension (IIH) results in raised intracranial pressure (ICP) leading to papilledema, visual dysfunction, and headaches. Obese females of reproductive age are predominantly affected, but the underlying pathological mechanisms behind IIH remain unknown. This review provides an overview of pathogenic factors that could result in IIH with particular focus on hormones and the impact of obesity, including its role in neuroendocrine signaling and driving inflammation. Despite occurring almost exclusively in obese women, there have been a few studies evaluating the mechanisms by which hormones and adipokines exert their effects on ICP regulation in IIH. Research involving 11β-hydroxysteroid dehydrogenase type 1, a modulator of glucocorticoids, suggests a potential role in IIH. Improved understanding of the complex interplay between adipose signaling factors such as adipokines, steroid hormones, and ICP regulation may be key to the understanding and future management of IIH.

Understanding idiopathic intracranial hypertension: mechanisms, management, and future directions

Idiopathic intracranial hypertension is a disorder characterised by raised intracranial pressure that predominantly affects young, obese women. Pathogenesis has not been fully elucidated, but several causal factors have been proposed. Symptoms can include headaches, visual loss, pulsatile tinnitus, and back and neck pain, but the clinical presentation is highly variable. Although few studies have been done to support evidence-based management, several recent advances have the potential to enhance understanding of the causes of the disease and to guide treatment decisions. Investigators of the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) reported beneficial effects of acetazolamide in patients with mild visual loss. Studies have also established weight loss as an effective disease-modifying treatment, and further clinical trials to investigate new treatments are underway. The incidence of idiopathic intracranial hypertension is expected to increase as rates of obesity increase; efforts to reduce diagnostic delays and identify new, effective approaches to treatment will be key to meeting the needs of a growing number of patients.

An integrated mechanism of pediatric pseudotumor cerebri syndrome: evidence of bioenergetic and hormonal regulation of cerebrospinal fluid dynamics

Pseudotumor cerebri syndrome (PTCS) is defined by the presence of elevated intracranial pressure (ICP) in the setting of normal brain parenchyma and cerebrospinal fluid (CSF). Headache, vision changes, and papilledema are common presenting features. Up to 10% of appropriately treated patients may experience permanent visual loss. The mechanism(s) underlying PTCS is unknown. PTCS occurs in association with a variety of conditions, including kidney disease, obesity, and adrenal insufficiency, suggesting endocrine and/or metabolic derangements may occur. Recent studies suggest that fluid and electrolyte balance in renal epithelia is regulated by a complex interaction of metabolic and hormonal factors; these cells share many of the same features as the choroid plexus cells in the central nervous system (CNS) responsible for regulation of CSF dynamics. Thus, we posit that similar factors may influence CSF dynamics in both types of fluid-sensitive tissues. Specifically, we hypothesize that, in patients with PTCS, mitochondrial metabolites (glutamate, succinate) and steroid hormones (cortisol, aldosterone) regulate CSF production and/or absorption. In this integrated mechanism review, we consider the clinical and molecular evidence for each metabolite and hormone in turn. We illustrate how related intracellular signaling cascades may converge in the choroid plexus, drawing on evidence from functionally similar tissues.

Pediatric idiopathic intracranial hypertension and the underlying endocrine-metabolic dysfunction: a pilot study

AIM

To unravel the potential idiopathic intracranial hypertension (IIH) endocrine-metabolic comorbidities by studying the natural (and targeted drug-modified) history of disease in children. IIH is a disorder of unclear pathophysiology, characterized by raised intracranial pressure without hydrocephalus or space-occupying lesion coupled with normal cerebrospinal fluid (CSF) composition.

METHODS

Retrospective study (years 2001-2010) of clinical records and images and prospective follow-up (years 2010-2013) in 15 children (11 girls, 4 boys; aged 5-16 years) diagnosed previously as "IIH", according to the criteria for pediatric IIH proposed by Rangwala, at four university pediatric centers in northern, central, and southern Italy.

RESULTS

We identified six potential endocrine-metabolic comorbidities including, weight gain and obesity (n=5), recombinant growth hormone therapy (n=3), obesity and metabolic syndrome (n=1), secondary hyperaldosteronism (n=1), hypervitaminosis A (n=1), and corticosteroid therapy (n=1). Response to etiologically targeted treatments (e.g., spironolactone, octreotide) was documented.

CONCLUSIONS

IIH is a protean syndrome caused by various potential (risk and) associative factors. Several conditions could influence the pressure regulation of CSF. An endocrine-metabolic altered homeostasis could be suggested in some IIH patients, and in this context, etiologically targeted therapies (spironolactone) should be considered.

Idiopathic intracranial hypertension; research progress and emerging themes

Idiopathic intracranial hypertension (IIH) is a condition characterised by increased intracranial pressure of unknown cause predominantly seen in obese women of childbearing age and associated with a history of recent weight gain. The aetiology is poorly understood and there are no evidence-based guidelines on the management of the disease. We aim to provide a review of the recent literature outlining the latest advances in this field over the past few years. Areas of emerging interest related to the pathophysiology of IIH will be discussed, such as the role of obesity, adipose tissue and 11β-hydroxysteroid dehydrogenase type 1. We consider the latest research on the role of venous sinus stenosis in IIH and ex vivo advances into cerebrospinal fluid drainage via the arachnoid granulation tissue. The latest techniques for optic nerve head evaluation and the role of optical coherence tomography will be summarised. Finally, we will discuss recent advances in the management of IIH, including weight loss, and medical and surgical treatment strategies.

Cerebrospinal Fluid Secretion by the Choroid Plexus

The choroid plexus epithelium is a cuboidal cell monolayer, which produces the majority of the cerebrospinal fluid. The concerted action of a variety of integral membrane proteins mediates the transepithelial movement of solutes and water across the epithelium. Secretion by the choroid plexus is characterized by an extremely high rate and by the unusual cellular polarization of well-known epithelial transport proteins. This review focuses on the specific ion and water transport by the choroid plexus cells, and then attempts to integrate the action of specific transport proteins to formulate a model of cerebrospinal fluid secretion. Significant emphasis is placed on the concept of isotonic fluid transport across epithelia, as there is still surprisingly little consensus on the basic biophysics of this phenomenon. The role of the choroid plexus in the regulation of fluid and electrolyte balance in the central nervous system is discussed, and choroid plexus dysfunctions are described in a very diverse set of clinical conditions such as aging, Alzheimer's disease, brain edema, neoplasms, and hydrocephalus. Although the choroid plexus may only have an indirect influence on the pathogenesis of these conditions, the ability to modify epithelial function may be an important component of future therapies.

Tissue-specific modulation of mineralocorticoid receptor function by 11β-hydroxysteroid dehydrogenases: an overview

In the last decade significant progress has been made in the understanding of mineralocorticoid receptor (MR) function and its implications for physiology and disease. The knowledge on the essential role of MR in the regulation of electrolyte concentrations and blood pressure has been significantly extended, and the relevance of excessive MR activation in promoting inflammation, fibrosis and heart disease as well as its role in modulating neuronal cell viability and brain function is now widely recognized. Despite considerable progress, the mechanisms of MR function in various cell-types are still poorly understood. Key modulators of MR function include the glucocorticoid receptor (GR), which may affect MR function by formation of heterodimers and by differential genomic and non-genomic responses on gene expression, and 11β-hydroxysteroid dehydrogenases (11β-HSDs), which determine the availability of intracellular concentrations of active glucocorticoids. In this review we attempted to provide an overview of the knowledge on MR expression with regard to the presence or absence of GR, 11β-HSD2 and 11β-HSD1/hexose-6-phosphate dehydrogenase (H6PDH) in various tissues and cell types. The consequences of cell-specific differences in the coexpression of MR with these proteins need to be further investigated in order to understand the role of this receptor in a given tissue as well as its systemic impact.

Cerebrospinal fluid corticosteroid levels and cortisol metabolism in patients with idiopathic intracranial hypertension: a link between 11beta-HSD1 and intracranial pressure regulation?

CONTEXT

The etiology of idiopathic intracranial hypertension (IIH) is unknown. We hypothesized that obesity and elevated intracranial pressure may be linked through increased 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity.

OBJECTIVE

The aim was to characterize 11β-HSD1 in human cerebrospinal fluid (CSF) secretory [choroid plexus (CP)] and drainage [arachnoid granulation tissue (AGT)] structures, and to evaluate 11β-HSD1 activity after therapeutic weight loss in IIH.

DESIGN AND SETTING

We conducted in vitro analysis of CP and AGT and a prospective in vivo cohort study set in two tertiary care centers.

PATIENTS OR OTHER PARTICIPANTS

Twenty-five obese adult female patients with active IIH were studied, and 22 completed the study.

INTERVENTION

Fasted serum, CSF, and 24-h urine samples were collected at baseline, after 3-month observation, and after a 3-month diet.

MAIN OUTCOME MEASURES

Changes in urine, serum, and CSF glucocorticoids (measured by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry) after weight loss were measured.

RESULTS

11β-HSD1 and key elements of the glucocorticoid signaling pathway were expressed in CP and AGT. After weight loss (14.2±7.8 kg; P<0.001), global 11β-HSD1 activity decreased (P=0.001) and correlated with reduction in intracranial pressure (r=0.504; P=0.028). CSF and serum glucocorticoids remained stable, although the change in CSF cortisone levels correlated with weight loss (r=-0.512; P=0.018).

CONCLUSIONS

Therapeutic weight loss in IIH is associated with a reduction in global 11β-HSD1 activity. Elevated 11β-HSD1 may represent a pathogenic mechanism in IIH, potentially via manipulation of CSF dynamics at the CP and AGT. Although further clarification of the functional role of 11β-HSD1 in IIH is needed, our results suggest that 11β-HSD1 inhibition may have therapeutic potential in IIH.