A Neuro-Ophthalmologist's Guide to Advances in Intracranial Pressure Measurements

Current Understanding of the Pathophysiology of Idiopathic Intracranial Hypertension

PURPOSE OF REVIEW

Development of safe targeted therapies for idiopathic intracranial hypertension requires a thorough understanding of recent evidence discovering the pathophysiology of the condition. The aim is to provide a review of studies that inform on the underpinning mechanisms that have been associated with idiopathic intracranial hypertension.

RECENT FINDINGS

People living with active idiopathic intracranial hypertension and obesity have been found to have with insulin resistance, hyperleptinaemia, and adverse cardiovascular outcomes. Clinically their adipose tissue is predominantly located in the truncal region and on detailed laboratory analysis the cells are primed for weight gain. There is evidence of androgen excess, altered glucocorticoid regulation and changes in pro-inflammatory cytokines. There are distinct alterations in metabolic pathways found in serum, urine and cerebrospinal fluid, that resolve following disease remission. These findings are associated with raised intracranial pressure and are likely secondary to cerebrospinal fluid hypersecretion. Idiopathic intracranial hypertension has a profile of systemic metabolic changes, endocrine dysfunction and cardiovascular risk profile distinct from that associated with obesity alone. These systemic metabolic changes are likely to contribute to dysregulation of cerebrospinal fluid dynamics, primarily hypersecretion but with a possible additional effect of reduced clearance resulting in the core feature of raised intracranial pressure.

Managing idiopathic intracranial hypertension in the eye clinic

Idiopathic intracranial hypertension (IIH) is a neuro-ophthalmological condition characterised by a raised intracranial pressure and papilloedema that causes disabling headaches. The main risk factors of female sex and living with obesity have been known for some time, however the knowledge of the underlying pathophysiology is evolving. Papilloedema can impact the visual function, and the majority of people are offered acetazolamide. Those with sight threatening disease need urgent management, though there is little high quality evidence to recommend any particular surgical intervention. Headache treatment is an unmet clinical need and simple medication overuse advice has the potential to reduce the chronification of migraine-like headaches. IIH is emerging as a systemic metabolic disease distinct from people living with obesity alone. While weight loss is the main stay of disease modifying therapy this is challenging to access and many healthcare professionals that manage the condition have no formal training or accessible pathways for weight management. The aim of this "how to do it" article is to present the latest advances in knowledge of IIH that we pragmatically included in routine clinical care for people living with the condition.

Detection and Management of Elevated Intracranial Pressure in the Treatment of Acute Community-Acquired Bacterial Meningitis: A Systematic Review

Acute bacterial meningitis (ABM) is associated with severe morbidity and mortality. The most prevalent pathogens in community-acquired ABM are Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Other pathogens may affect specific patient groups, such as newborns, older patients, or immunocompromised patients. It is well established that ABM is associated with elevated intracranial pressure (ICP). However, the role of ICP monitoring and management in the treatment of ABM has been poorly described.An electronic search was performed in four electronic databases: PubMed, Web of Science, Embase, and the Cochrane Library. The search strategy chosen for this review used the following terms: Intracranial Pressure AND (management OR monitoring) AND bacterial meningitis. The search yielded a total of 403 studies, of which 18 were selected for inclusion. Eighteen studies were finally included in this review. Only one study was a randomized controlled trial. All studies employed invasive ICP monitoring techniques, whereas some also relied on assessment of ICP-based on clinical and/or radiological observations. The most commonly used invasive tools were external ventricular drains, which were used both to monitor and treat elevated ICP. Results from the included studies revealed a clear association between elevated ICP and mortality, and possibly improved outcomes when invasive ICP monitoring and management were used. Finally, the review highlights the absence of clear standardized protocols for the monitoring and management of ICP in patients with ABM. This review provides an insight into the role of invasive ICP monitoring and ICP-based management in the treatment of ABM. Despite weak evidence certainty, the present literature points toward enhanced patient outcomes in ABM with the use of treatment strategies aiming to normalize ICP using continuous invasive monitoring and cerebrospinal fluid diversion techniques. Continued research is needed to define when and how to employ these strategies to best improve outcomes in ABM.

Does a Healthy Weight Body Mass Index at Onset of Idiopathic Intracranial Hypertension Change the Outcomes? A United Kingdom Prospective Cohort Study

Idiopathic intracranial hypertension (IIH) predominantly affects reproductive-aged females with obesity. However, the prevalence and impact of a healthy weight body mass index (BMI) at disease presentation is not known. This study aimed to evaluate the visual and headache outcomes stratified by the presenting BMI. This was a longitudinal prospective cohort study (IIH Life) based on a tertiary neuro-ophthalmology IIH service, University Hospitals Birmingham NHS Trust, United Kingdom, recruiting consecutive patients living with IIH between 2012 and 2021. Those with a presenting BMI were included. The outcome measures included visual outcomes of LogMAR visual acuity, Humphrey visual field perimetric mean deviation (PMD), optical coherence tomography (OCT) measurements, and headache outcomes of frequency, severity, and Headache Impact Test-6 score. Three hundred seventy-five people with IIH and a documented baseline BMI. About 3.7% of the entire cohort had a healthy weight BMI at IIH presentation and 15.5% BMI < 30 kg/m2. The baseline PMD was worse in patients without obesity; however, OCT papilloedema measures were similar. The presence of obesity was associated with a small but significant greater worsening in visual acuity but slower macular ganglion cell layer loss. There was no impact on PMD or papilloedema prognosis related to baseline obesity. The headache outcomes showed heterogeneity, with worse baseline headache frequency in patients with obesity. No BMI group was associated with worse headache outcomes. Patients with a healthy weight BMI or those without obesity at baseline make up a small proportion of IIH patients. BMI at presentation does not appear to influence long-term visual or headache outcomes.

The Pressure of Headache at the United Kingdom CSF Disorders Day 2023

Headache in intracranial disorders drives significant disability in our patients. Management principles for secondary headaches require a multidisciplinary approach with expertise from the neurological, neuro-ophthalmological, neuroradiological, and neurosurgical specialities. The Pressure of Headache was the theme of the annual United Kingdom CSF Disorders Day and saw speakers and panellists from Australia, Europe, and the United States. Among the topics presented were the newest concepts underpinning idiopathic intracranial hypertension management and spontaneous intracranial hypotension. Advances in our knowledge of cerebrospinal fluid secretion and the visual snow syndrome debate were particular highlights. This review provides a summary of the research on headache disorders that overlap the neuro-ophthalmological axis of care for patients.

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.