https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(16)30668-7.pdf

Spontaneous subarachnoid haemorrhage

Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 × 1 × 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 × 2.5 × 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.

/pdf/continuous-wireless-pressure-monitoring-and-mapping-with-2ck30425dd.pdf

Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care

The glymphatic system is a glial-dependent waste clearance pathway in the brain, in place of lymphatic vessels, dedicated to drain away soluble waste proteins and metabolic products. Specifically, the glymphatic network serves as a "front end" for waste clearance, and is connected downstream to an authentic lymphatic network, associated with dura covering the brain as well as cranial nerves and large vessels at the skull exits. The anatomical and functional interconnections between these two networks are not completely understood. Several key physiological processes have been identified that control glymphatic transport function and waste clearance from brain. In this review, we aim to provide an overview and discussion of the concept behind the glymphatic system, current evidence, and controversies, while specifically focusing on the consequences of aging and evidence of its existence in human brain. Discovering novel strategies for optimizing and maintaining efficient brain waste clearance across the lifespan may in the future prove to be important for preventing cognitive decline and sustaining healthy aging.

/pdf/the-glymphatic-system-and-waste-clearance-with-brain-aging-a-ksqq5fetud.pdf

The Glymphatic System and Waste Clearance with Brain Aging: A Review

This work was supported by the National Institute for Health Research (RP-PG-0407-10314), Wellcome Trust (WT 086091/Z/08/Z), the Medical Research Council prognosis research strategy (PROGRESS) Partnership (G0902393/99558), and awards to establish the Farr Institute of Health Informatics Research at UCLPartners, from the Medical Research Council, Arthritis Research UK, British Heart Foundation, Cancer Research UK, Chief Scientist Office, Economic and Social Research Council, Engineering and Physical Sciences Research Council, National Institute for Health Research, National Institute for Social Care and Health Research, and Wellcome Trust (grant MR/K006584/1). SB and AB were supported by grants from the European Research Council (ERC-StG-2012- 309337_AlcoholLifecourse) and the Medical Research Council/Alcohol Research UK (MR/M006638/1). JG was funded by a NIHR doctoral fellowship (DRF-2009-02-50). ADS is supported by a clinical research training fellowship from the Wellcome Trust (0938/30/Z/10/Z). This article presents independent research funded in part by the NIHR. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health.

https://www.bmj.com/content/bmj/356/bmj.j909.full.pdf

Association between clinically recorded alcohol consumption and initial presentation of 12 cardiovascular diseases: population based cohort study using linked health records

In a recent systematic review and meta-analysis, the overall prevalence of unruptured intracranial aneurysms (IAs) is estimated as 3.2%.1 The prevalence of IAs is higher in patients with autosomal dominant polycystic kidney disease or a positive family history of IAs of subarachnoid hemorrhage (SAH).1 From the same review, the size of unruptured IAs is <5 mm in 66%, 5 to 9 mm in 27%, and ≥10 mm in 7%; the site of IAs is internal carotid artery, including posterior communicating artery in 42%, middle cerebral artery in 35%, and anterior cerebral artery and anterior communicating artery in 18%.

Most IAs are clinically silent until rupture, which is unpredictable and sometimes associated with SAH, intraparenchymal hematoma, and an intraventricular hemorrhage. The case fatality of IA rupture is high (from 27% to 44%), but has decreased during the past 3 decades because of the introduction of improved management strategies, including neurocritical care.2 The International Study of Unruptured Intracranial Aneurysms (ISUIA) showed an increased risk of IA rupture with aneurysm size and for posterior circulation aneurysms.3

Although treatment of a ruptured aneurysm is accepted as an emergency, indication for treatment of unruptured IAs is still being discussed. Decision for treatment is based on clinical and anatomic factors; among them, the most important being patient’s age, family history of IA(s), associated conditions (autosomal dominant polycystic kidney disease), symptomatic aneurysms, aneurysm size, and location. The randomized International Subarachnoid Aneurysm Trial (ISAT) study has clearly demonstrated the superiority of endovascular treatment (EVT) of ruptured aneurysms using coil technology over surgery.4 Since the publication of these results, EVT has rapidly evolved. Although for unruptured aneurysms a direct comparison between EVT and surgery is not available, EVT has been widely used in this subgroup as well.5

In fact the population presenting with …

Endovascular treatment of intracranial aneurysms: current status.

Monitoring of intracranial pressure (ICP) has been used for decades in the fields of neurosurgery and neurology. There are multiple techniques: invasive as well as noninvasive. This paper aims to provide an overview of the advantages and disadvantages of the most common and well-known methods as well as assess whether noninvasive techniques (transcranial Doppler, tympanic membrane displacement, optic nerve sheath diameter, CT scan/MRI and fundoscopy) can be used as reliable alternatives to the invasive techniques (ventriculostomy and microtransducers). Ventriculostomy is considered the gold standard in terms of accurate measurement of pressure, although microtransducers generally are just as accurate. Both invasive techniques are associated with a minor risk of complications such as hemorrhage and infection. Furthermore, zero drift is a problem with selected microtransducers. The non-invasive techniques are without the invasive methods' risk of complication, but fail to measure ICP accurately enough to be used as routine alternatives to invasive measurement. We conclude that invasive measurement is currently the only option for accurate measurement of ICP.

/pdf/intracranial-pressure-monitoring-invasive-versus-non-104jskb23h.pdf

Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review

Elevated intracranial pressure (ICP) is an important cause of secondary brain injury, and a measurement of ICP is often of crucial value in neurosurgical and neurological patients. The gold standard for ICP monitoring is through an intraventricular catheter, but this invasive technique is associated with certain risks. Intraparenchymal ICP monitoring methods are considered to be a safer alternative but can, in certain conditions, be imprecise due to zero drift and still require an invasive procedure. An accurate noninvasive method to measure elevated ICP would therefore be desirable. This article is a review of the current literature on noninvasive methods for measuring and evaluating elevated ICP. The main focus is on studies that compare noninvasively measured ICP with invasively measured ICP. The aim is to provide an overview of the current state of the most common noninvasive techniques available. Several methods for noninvasive measuring of elevated ICP have been proposed: radiologic methods including computed tomography and magnetic resonance imaging, transcranial Doppler, electroencephalography power spectrum analysis, and the audiological and ophthalmological techniques. The noninvasive methods have many advantages, but remain less accurate compared with the invasive techniques. None of the noninvasive techniques available today are suitable for continuous monitoring, and they cannot be used as a substitute for invasive monitoring. They can, however, provide a reliable measurement of the ICP and be useful as screening methods in select patients, especially when invasive monitoring is contraindicated or unavailable.

Measuring Elevated Intracranial Pressure through Noninvasive Methods: A Review of the Literature

We evaluated postural effects on intracranial pressure (ICP) and cerebral perfusion pressure [CPP: mean arterial pressure (MAP) − ICP] in neurosurgical patients undergoing 24-h ICP monitoring as pa...

https://www.physiology.org/doi/pdf/10.1152/ajpregu.00302.2015

Postural influence on intracranial and cerebral perfusion pressure in ambulatory neurosurgical patients

Reference values and physiological measurements of intracranial pressure (ICP) are primarily reported in the supine position, while reports of ICP in the vertical position are surprisingly rare considering that humans maintain the vertical position for the majority of the day. In order to distinguish normal human physiology from disease entities such as idiopathic intracranial hypertension and normal pressure hydrocephalus, we investigated ICP in different body postures in both normal and ill subjects. Thirty-one patients were included: four normal patients following complete removal of a solitary clearly demarcated small brain tumour and fitted with a telemetric ICP monitoring device for long-term ICP monitoring; 27 patients requiring invasive ICP monitoring as a part of their diagnostic work-up or monitoring of shunt treatment effect. ICP was recorded in the following body positions: upright standing, sitting in a chair, supine and right lateral lumbar puncture position. Linear regression of median ICP based on patient posture, group, and purpose of monitoring presented a significant model (p < 0.001), but could not distinguish between patient groups (p = 0.88). Regression of differences in median ICP between body postures and supine ICP as the baseline, presented a highly significant model (p < 0.001) and adjusted R
 2 = 0.86. Both body posture (p < 0.001) and patient group (p < 0.001) were highly significant factors. Differences in ICP between body postures enabled us to distinguish the normal group from patient groups. Normal patients appear able to more tightly regulate ICP when switching body postures.

Effect of postural changes on ICP in healthy and ill subjects

Aneurysmal subarachnoid hemorrhage (aSAH) is bleeding into the subarachnoid space from a cerebral aneurysm, defined as a thin-walled outpouching on one of the cerebral arteries.1 SAH represents 0.8% to 15% of strokes and has a low incidence of 0.03 to 0.2 per 1000 person-years with a female preponderance.2,3 However, SAH usually occurs at a relatively young age and has a high 1-month case fatality rate (32%), leading to a high loss of potential life years.2 Subsequently, primary prevention of aSAH by identifying and addressing modifiable risk factors has been a focus of research for decades.4

Although the main focus has been on identifying modifiable risk factors, less attention has been given to the underlying pathogenic mechanisms.

We, therefore, conducted a literature review to identify recognized modifiable risk factors for aneurysm development and aSAH and examined the pathogenesis by which these individual risk factors are suspected to contribute to aneurysm development and rupture.

We conducted MEDLINE searches using the PubMed database for relevant articles published between 1980 and 2012 in English. We used search words such as Cerebral Arteries [Majr], Subarachnoid Hemorrhage [Majr], or Intracranial Aneurysm [Majr] combined with Medical Subject Headings (MeSH) search words for different risk factors such as Alcohol drinking, Ethanol, Estrogens, Menopause, Hypertension, Smoking, Cholesterol, Diabetes Mellitus, and Cocaine. The first search was performed in June 2012 and the last in December 2012. Articles were screened by title and abstract, and if relevant the article was reviewed in its entirety. References lists in key publications were hand-searched to reveal additional relevant studies.

Initially, the focus was on epidemiological studies that helped establish the different modifiable risk factors for aSAH. Inclusion criteria comprised: (1) SAH analyzed as a separate stroke entity, although in some studies SAH was part of a hemorrhagic stroke …

Morten Andresen

Papers

Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review

Measuring Elevated Intracranial Pressure through Noninvasive Methods: A Review of the Literature

Postural influence on intracranial and cerebral perfusion pressure in ambulatory neurosurgical patients

Effect of postural changes on ICP in healthy and ill subjects

Modifiable Risk Factors for Aneurysmal Subarachnoid Hemorrhage