Influence of acute jugular vein compression on the cerebral blood flow velocity, pial artery pulsation and width of subarachnoid space in humans

Unusual Case Report of Headache in 10-Year-Old Female Child

According to the literature, transverse sinus hypoplasia is not a normal variant and has a serious potential effect on cerebral blood flow. We are presenting a rare case of chronic headache due to severe hypoplasia of the left transverse and sigmoidal sinus. A 12-year-old female girl was admitted with a complaint of gradual progressive severe headache, throbbing in nature, confined to a bitemporal and frontal region in the last 4-5 months. Headache is not associated with fever, vomiting, photophobia, or vision problems. The child had no history of recurrent running nose, refractory vision, ear discharge, head trauma, exanthemata rash, or any drug history. On examination, the child was conscious and oriented. Vital signs are normal. The child was neurologically normal and had no focal signs. Other systemic examinations were normal. Based on History and examination, differential diagnosis was made, like Pseudo tumor cerebri, migraine, deep vein sinus thrombosis, and functional and Posterior fossa tumor. The child had normal routine investigations like complete blood count, electrolyte, and D-dimer. The fundoscopy was normal. In MRI, brain hypoplasia of the left transverse and sinusoidal sinus was suspected and confirmed by MRI venography. Thus, for any patient in an emergency with a chronic headache without focal signs and normal fundoscopy, one deferential should be considered for transverse and sigmoid sinus hypoplasia.

Effects of intubation technique on intracranial pressure: a cadaveric study

Patients are at risk of increased intracranial pressure (ICP) during manipulation for endotracheal intubation. The aim of this cadaveric study was to quantify this relationship. Five fresh frozen adult cadaveric heads were used. The internal carotid artery (ICA) and internal jugular vein (IJV) were dissected bilaterally. All vessels were occluded on the right side. To mimic central venous pressures, the left IJV was cannulated and filled with water to maintain a pressure of approximately 7 cm H2O. The ICA cannula was attached to an oscillating water pump. Next, an ICP monitor was placed. Normophysiological volumes of water were infused to maintain normal ICP. Baseline ICP and IJV pressures were recorded. The heads were then placed in the sniffing position and in neutral position for nasal intubation, and finally an oral endotracheal tube was placed using standard head/neck maneuvers. The ICP was recorded. Mean baseline ICP was 13 mmHg (range 4-18 mmHg) and mean IJV pressure was 6 cm H2O. In the sniffing position, ICP increased in all specimens by a mean of 5 mmHg. In the neutral position, after intubation, the ICP increased in all specimens by a mean of 3 mmHg. Nasal intubation resulted in an increase in four of the five specimens. The mean increase in ICP with this maneuver was 2 mmHg. We present a cadaveric model of ICP measurement during neck manipulation using intracranial fluid dynamics. The ICP increased consistently. Following clinical studies, physicians involved in intubating patients with concern for raised ICP should change the technique to avoid complications.

Approach considerations for the management of strangulation in the emergency department

Patients with a history of strangulation present to the emergency department with a variety of different circumstances and injury patterns. We review the terminology, pathophysiology, evaluation, management, and special considerations for strangulation injuries, including an overview of forensic considerations and legal framework for strangulation events.

Variations of human cerebral and ocular blood flow during exposure to multi-axial accelerations : A mathematical modeling study

Human hemodynamic responses during exposure to multi-axial acceleration was a relatively new topic in the fields of acceleration physiology. This study aimed to focus on these responses, especially variations of blood perfusion to brain and eyes, through mathematical modeling. A mathematical model was established using lumped parameter methods, containing compartments of four heart chambers, systemic arteries and veins, circulation of typical systemic organs, and some compartments for pulmonary circulation, together with autonomic regulation considered. This model was firstly validated by using experimental data from experiment of posture change and centrifuge tests of +Gz accelerations, and then applied to analyze human hemodynamic responses to typical multi-axial accelerations. Validation results demonstrated the mathematical model could generate reasonable responses of human cardiovascular system during posture change and exposure to +Gz accelerations. Simulation results of hemodynamic responses to multi-axial accelerations depicted Gy induced significant differences of blood flow to the left and right eyes. And some contour maps were generated based on these results, which provided a quick way to estimate blood flow variations in brain and eyes during exposure to different accelerations. Graphical Abstract This study aimed to focus on variations of blood perfusion to brain and eyes during exposure to typical multi-axial accelerations through mathematical modeling. This model was firstly validated by using experimental data from experiment of posture change and centrifuge tests of +Gz accelerations, and then applied to analyze human hemodynamic responses to typical multi-axial accelerations. Simulation results of hemodynamic responses to multi-axial accelerations depicted Gy induced significant differences of blood flow to the left and right eyes. And contour maps that generated based on these results provided a quick way to estimate blood flow variations in brain and eyes during exposure to different accelerations.

Elevated cerebral perfusion and preserved cognition in elite Brazilian Jiu-Jitsu athletes: Evidence for neuroprotection

Brazilian Jiu-Jitsu (BJJ) is a popular martial art that exposes participants to recurrent intermittent asphyxiation due to controlled application of neck chokes. To what extent the sport impacts the regulation of cerebral blood flow (CBF) and cognition has not been examined. This study compared eleven elite Brazilian Jiu-Jitsu athletes (aged 30 ± 8 y) who trained 12 ± 6 hours/week for 8 ± 4 years against eleven cardiorespiratory fitness (CRF)- and age-matched controls. Internal carotid (ICA) and vertebral artery (VA) blood flow were measured via duplex ultrasound to determine global cerebral blood flow (gCBF). Mild cognitive impairment and sub-domains of memory, attention/concentration/visual motor coordination, and executive function were determined by psychometric testing. There was no evidence of mild cognitive impairment in the athletes, and cognitive function was comparable between groups (all p > 0.05). In contrast, resting gCBF was selectively elevated in the athletes (741 ± 186 mL∙min^-1 vs. 573 ± 166 mL∙min^-1 , p = 0.037) due to combined differences in ICA (+65 mL∙min^-1 , p = 0.079) and VA (+19 mL∙min^-1 , p = 0.277) flow. In conclusion, the sustained elevation in resting cerebral perfusion provides preliminary evidence for adaptive neuroprotection that is independent of CRF and likely mediated by choke-induced cerebral preconditioning and/or lifelong exposure to BJJ-specific high-intensity interval training.

Subarachnomegaly-venous congestion of infancy

PURPOSE

Multiple names within the literature refer to a clinical picture affecting infants and consisting of a large or fast growing head circumference with enlarged cortical subarachnoid spaces (CSAS) while cranial sutures are open. This myriad of terms demonstrates the confusion about the entity, that may even group together different etiological processes. In this review, we aim to shed light on this matter in an effort to restate the defining features of the clinical picture and sum the evidence and current understanding of its pathophysiology and related imaging findings.

METHODS

Extensive and updated review of the literature with special focus on defining features, clinical history with long term evaluation and pathophysiological process.

RESULTS

Functional and molecular CSF studies as well as clinical evidence challenges the common pathophysiological theory based on non-functional arachnoid villi. Conversely, there is increasing evidence supporting cerebro-venous system abnormalities as the main pathophysiological factor. Additionally, long term cohorts studies show that it may have subtle but irreversible neurodevelopmental consequences.

CONCLUSION

Subarachnomegaly is an age-related condition of the infancy with radiological enlargement of CSAS and often self limiting course. However, considering the evidence on pathophysiology as outlined herein and long term outcome reports, further research effort is needed to assess the consequences of venous outflow impairment and enlarged CSAS and how this relates to imaging findings and neurodevelopment test results later in life.

[Intraoperative vascular air embolism : Evidence for risks, diagnostics and treatment]

The entry of gases into the vascular system is called vascular air embolism (VAE). The blocking of the pulmonary circulation by VAE can lead to fulminant right-sided heart failure and cardiocirculatory arrest. A VAE can occur at any time if there is an open connection between the environment and a venous vessel with subatmospheric pressure. This situation occurs during ear nose throat surgery, hip surgery, surgery of the lesser pelvis or breast surgery, if the surgical field is above the level of the heart; however, a VAE can also occur during routine tasks, such as insertion or removal of a central venous catheter or during endoscopic procedures with the insufflation of gas.Because during these procedures VAE is not the main focus of the anesthesia or surgery personnel, in such situations its sudden unexpected occurrence can have severe consequences. In contrast, in cardiac surgery or neurosurgery the risk of intraoperative VAE is much better known. In procedures with a higher risk of a clinically relevant VAE, a patent foramen ovale should be ruled out by preoperative transesophageal echocardiography (TEE). Intraoperatively TEE is the most sensitive procedure not only to detect a VAE but also to visualize the clinical expression, e.g. acute right heart overload.The avoidance of an initial and repeated air embolism is the primary measure to minimize the incidence and severity of VAE.Intraoperatively the following measures should be undertaken: excellent communication between anesthesia and surgery personnel with predetermined actions, maintenance of normal volume, patient positioning with minimal difference in height between heart and head, state of the art surgical technique with closure of potential air entry sites, sufficient detection of air by TEE, repeated jugular vein compression during neurosurgery, intraoperative Trendelenburg positioning of the patient during persisting or clinically evident VAE, differentiated adjustment of ventilatory settings and catecholamine treatment, aspiration of the blood-air mixture (air lock) at the junction of the superior vena cava and right atrium through a large bore central venous line and keeping check of the coagulation status.

Effect of a neck compression collar on cardiorespiratory and cerebrovascular function in postural orthostatic tachycardia syndrome (POTS)

Postural orthostatic tachycardia syndrome (POTS) is accompanied by reduced brain blood flow, autonomic dysfunction, and orthostatic intolerance. We hypothesized that wearing a neck compression collar would attenuate orthostatic symptoms, increase brain blood flow, and influence autonomic reflexes. Ten participants with POTS (9 women, age: 36 ± 10) underwent two trials of supine rest, paced deep breathing (6 breaths/min), Valsalva maneuver (40 mmHg for 15 s), and 70° upright tilt. For one trial, participants wore a neck compression device (Q30 Innovations). Blood pressure, heart rate (HR), brain blood flow velocity, stroke volume, respiratory rate, and end-tidal gases were continuously measured. The Vanderbilt Orthostatic Symptom Score was compiled at the end of tilt. The use of the collar reduced the orthostatic symptom score of participants with POTS during upright tilt (26.9 ± 12.5 to 18.7 ± 13.1, P = 0.04). Collar compression in the supine condition reduced the low-frequency domain of HR variability (60 ± 18 to 51 ± 23 normalized units, P = 0.04) and increased the change in HR (15 ± 5 to 17 ± 6 bpm, P = 0.02) and E:I ratio (1.2 ± 0.1 to 1.3 ± 0.1, P = 0.01) during paced deep breathing. Throughout tilt, wearing the collar reduced respiratory rate (baseline: 13 ± 3 to 12 ± 4 breath/min; tilt: 18 ± 5 to 15 ± 5 breath/min; main effect of collar P = 0.048), end-tidal oxygen (baseline: 115 ± 5 to 112 ± 5 mmHg; tilt: 122 ± 10 to 118 ± 11 mmHg; main effect of collar P = 0.026). In participants with POTS, wearing the Q-collar reduced orthostatic symptoms, increased the HR response to deep breathing, and decreased resting ventilation.NEW & NOTEWORTHY We found that using a neck compression collar alleviated orthostatic symptoms in upright posture in participants with postural orthostatic tachycardia syndrome (POTS). This could be due to compression of the baroreceptors and subsequent changes in autonomic function. Indeed, we observed increased heart rate responsiveness to paced deep breathing and reductions of respiratory rate and end-tidal O₂ (suggesting reduced ventilation). Further, wearing the collar reduced mean blood velocity in the brain during Valsalva perhaps due to higher brain blood volume.

All Tied Up: The Effect of Wearing a Necktie on Acoustic and Perceptual Measures of Male Solo Singing

The purpose of this study was to assess acoustically (long-term average spectra and multidimensional voice profile) and perceptually (participant perceived phonatory ease and expert listening panel) the effect of wearing a necktie on male singing in a solo setting. No study to date has assessed the potential effects of wearing neckties in a solo vocal setting. Among primary results: (a) statistically significant differences in spectral energy (0-10 kHz) between performances with and without a necktie, (b) increases in mean jitter and shimmer percentage measurements of singers with a necktie, (c) significant reduction in perceived phonatory ease when singing while wearing a necktie, and (d) listener preferences for singing without a necktie. Results were discussed in terms of limitations of the study, suggestions for future research, and implications for voice pedagogy.

Influence of a neck compression collar on cerebrovascular and autonomic function in men and women

OBJECTIVE

Neck compression collars have been proposed to reduce injury to the brain caused by head impacts. Our objective was to test if compression of the carotid artery affected the baroreflex and influenced blood pressure control.

METHODS

Cerebrovascular and autonomic responses of healthy young men and women (n = 8 each) to paced deep breathing, Valsalva, and 70o head-up tilt with or without use of a Q-collar were determined. Continuous measurements of heart rate, beat-to-beat blood pressure, transcranial Doppler, and end-tidal gases were obtained. Heart rate variability was measured during supine rest and head-up tilt. Carotid artery and jugular vein cross-sectional area were measured at end-inhalation and end-exhalation using cross-sectional ultrasound images at diastole.

RESULTS

Wearing the collar reduced carotid cross-sectional area (CSA; P = 0.022; η2 = 0.03) and increased jugular CSA (P = 0.001; η 2 = 0.30). In both men and women, wearing the collar increased systolic blood pressure during Valsalva (P<0.05; η 2 = 0.38). In only men, wearing the collar resulted in prolonged pressure recovery time during Valsalva (P = 0.02; η 2 = 0.05). In only women, wearing the collar increased baseline diastolic (P = 0.026; η 2 = 0.09) and mean (P = 0.041; η 2 = 0.06) middle cerebral artery (MCA) blood flow velocity, which attenuated the normal increase of diastolic (P = 0.01; η 2 = 0.03) and mean (P = 0.038; η 2 = 0.02) MCA blood flow velocity during Valsalva. There were no effects of sex or collar on the responses to deep breathing (P>0.05), and there were no effects of the collar on cerebrovascular function, hemodynamics, cardiovagal baroreceptor sensitivity, or heart rate variability (P>0.05) during upright tilt.

CONCLUSION

Use of the Q-collar compresses both the jugular vein and carotid artery influencing sympathetic nerve activity in both men and women while influencing brain blood flow in women.

Sleep-Disordered Breathing and Idiopathic Normal-Pressure Hydrocephalus: Recent Pathophysiological Advances

Purpose of Review

Idiopathic normal-pressure hydrocephalus (iNPH) is characterized clinically by ventriculomegaly, abnormal gait, falls, incontinence, and cognitive decline. This article reviews recent advances in the pathophysiology of iNPH concerning sleep-disordered breathing (SDB) and glymphatic circulation during deep sleep.

Recent Findings

The authors found iNPH frequently associated with obstructive sleep apnea (OSA). A critical factor in iNPH is intracranial venous hypertension delaying drainage of cerebrospinal fluid (CSF) into the cerebral venous sinuses. CSF-venous blood circulates in the jugular veins and finally drains into the heart. During SDB, repeated reflex attempts to breathe induce strong respiratory efforts against a closed glottis thereby increasing the negative intrathoracic pressure. This causes atrial distortion and decreases venous return to the heart resulting in retrograde intracranial venous hypertension. Additionally, repeated awakenings from OSA impede sleep-associated circulation of interstitial CSF into the glymphatic circulation contributing to hydrocephalus.

Summary

Sleep has become a critical element in the cognitive changes of aging including iNPH.

Predicting the Aqueductal Cerebrospinal Fluid Pulse: A Statistical Approach

The cerebrospinal fluid (CSF) pulse in the Aqueduct of Sylvius (aCSF pulse) is often used to evaluate structural changes in the brain. Here we present a novel application of the general linear model (GLM) to predict the motion of the aCSF pulse. MR venography was performed on 13 healthy adults (9 female and 4 males—mean age = 33.2 years). Flow data was acquired from the arterial, venous and CSF vessels in the neck (C2/C3 level) and from the AoS. Regression analysis was undertaken to predict the motion of the aCSF pulse using the cervical flow rates as predictor variables. The relative contribution of these variables to predicting aCSF flow rate was assessed using a relative weights method, coupled with an ANOVA. Analysis revealed that the aCSF pulse could be accurately predicted (mean (SD) adjusted r2 = 0.794 (0.184)) using the GLM (p < 0.01). Venous flow rate in the neck was the strongest predictor of aCSF pulse (p = 0.001). In healthy individuals, the motion of the aCSF pulse can be predicted using the GLM. This indicates that the intracranial fluidic system has broadly linear characteristics. Venous flow in the neck is the strongest predictor of the aCSF pulse.

No Established Link between Repeated Transient Chokes and Chronic Traumatic Encephalopathy Related Effects. Comment on Lim, L.J.H. et al. Dangers of Mixed Martial Arts in the Development of Chronic Traumatic Encephalopathy. Int. J. Environ. Res. Public Health 2019, 16, 254

This letter to the editor is in response to "Dangers of Mixed Martial Arts in the Development of Chronic Traumatic Encephalopathy" by authors Lim, Ho, and Ho, which was published in the International Journal of Environmental Research and Public Health (2019; 16: 254). This communication clarifies some potentially misleading word choices by the authors and addresses the insinuated, but not established, link between repeated transient choking episodes during martial arts training and a gradual decline in neuropsychiatric testing in the patient presented in the report.

Cerebro-venous hypertension: a frequent cause of so-called "external hydrocephalus" in infants

INTRODUCTION

External hydrocephalus (eHC) is commonly defined as a subtype of infant "hydrocephalus" consisting of macrocepahly associated with enlarged subarachnoid space and no or mild ventriculomegaly. This status is thought to be related to impaired CSF absorption because of arachnoid villi immaturity. However, other factors like the venous system might be involved in the development of the clinical picture.

METHODS

All patients diagnosed with eHC received prospectively contrast-enhanced 3D MR phlebography. Venous sis abnormalities were graded depending on the number of affected sinus segments and type. External CSF space volume was quantified planimetrically.

RESULTS

Seventeen patients with the typical clinical feature of eHC were included. In 15, venous sinus abnormalities were found. There was a significant correlation between the volume of the widened cortical subarachnoid space (CSAS) and the number of venous sinus segments affected. Conversely, ventricular volume was not correlated.

CONCLUSION

These results support the hypothesis that impaired venous outflow plays a major role in external hydrocephalus development. Raised venous pressure increases intracranial pressure accelerating head growth, resulting in an enlargement of the cortical subarachnoid space. Increased venous pressure increases the capillary bed pressure and brain turgor preventing ventricular space to enlarge forcing displacement of ventricular CSF to the subarachnoid space. As a result, ventriculomegaly is rarely found. The descriptive term "external hydrocephalus" implying a primary etiology within the CSF system is misleading and this work supports the notion that venous hypertension is the leading cause of the clinical picture.

Assessment of Hemodynamic Alterations in Cerebral Veins in Patients With Intracerebral Hemorrhage Using Duplex Color-Coded Sonography

OBJECTIVES

To investigate the contributions of hemodynamic alterations in cerebral veins to the prognosis of patients with primary intracerebral hemorrhage (ICH).

METHODS

Duplex color-coded sonography was performed on 87 ICH patients between July 2016 and October 2017. The time-averaged peak velocity, the time-averaged mean velocity (TAMV), the blood flow volume (BFV) of bilateral internal jugular veins (IJVs) and vertebral veins (VVs), and the mean velocities of bilateral basal veins of Rosenthal, straight sinus, and bilateral transverse sinuses were calculated to understand the relationship of hemodynamic data with prognosis in patients with ICH.

RESULTS

The study revealed that the time-averaged peak velocities, TAMVs and BFVs of both right IJV and VV in ICH patients with good clinical outcomes were higher than those of the left IJV and VV, whereas statistically significant differences were not found in the mean velocity of bilateral veins of Rosenthal. The perihematomal edema volume, time-averaged peak velocities, TAMVs, and BFVs of the bilateral IJVs and right VV and the TAMV of the left VV were associated with the prognosis of ICH patients in the univariate analysis. However, the TAMV of the right IJV and BFV of the left IJV were the independent factors that predicted prognosis in multivariate analysis. Partial correlation showed that there was a linear dependence between the differences in TAMV and BFV between bilateral IJVs.

CONCLUSIONS

The presence of hemodynamic changes in cerebral veins in patients with ICH has an impact on prognosis.

Human subarachnoid space width oscillations in the resting state

Abnormal cerebrospinal fluid (CSF) pulsatility has been implicated in patients suffering from various diseases, including multiple sclerosis and hypertension. CSF pulsatility results in subarachnoid space (SAS) width changes, which can be measured with near-infrared transillumination backscattering sounding (NIR-T/BSS). The aim of this study was to combine NIR-T/BSS and wavelet analysis methods to characterise the dynamics of the SAS width within a wide range of frequencies from 0.005 to 2 Hz, with low frequencies studied in detail for the first time. From recordings in the resting state, we also demonstrate the relationships between SAS width in both hemispheres of the brain, and investigate how the SAS width dynamics is related to the blood pressure (BP). These investigations also revealed influences of age and SAS correlation on the dynamics of SAS width and its similarity with the BP. Combination of NIR-T/BSS and time-frequency analysis may open up new frontiers in the understanding and diagnosis of various neurodegenerative and ageing related diseases to improve diagnostic procedures and patient prognosis.

Oscillations of Subarachnoid Space Width as a Potential Marker of Cerebrospinal Fluid Pulsatility

In the cerebrospinal fluid (CSF) circulation, two components can be distinguished: bulk flow (circulation) and pulsatile flow (back and forth motion). CSF pulsatile flow is generated by both cardiac and respiratory cycles. Recent years have seen increased interest in cardiac- and respiratory-driven CSF pulsatility as an important component of cerebral homeostasis. CSF pulsatility is affected by cerebral arterial inflow and jugular outflow and potentially linked to white matter abnormalities in various diseases, such as multiple sclerosis or hypertension. In this review, we discuss the physiological mechanisms associated with CSF pulsation and its clinical significance. Finally, we explain the concept of using the oscillations of subarachnoid space width as a surrogate for CSF pulsatility.

Ultrasound diagnosis of transverse sinus hypoplasia using flow profiles of the internal jugular vein

Accurate diagnosis of subtypes of transverse sinus (TS) hypoplasia requires more expensive methods like magnetic resonance (MR) imaging. We hypothesized ultrasound findings of the internal jugular vein (IJV) can be surrogate indicators for diagnosis of TS hypoplasia. MR images were reviewed in 131 subjects to evaluate TS diameter and the location and degree of venous flow stenosis and obstruction. Ultrasound parameters including the cross-sectional lumen area (CSA), time-average-mean velocity (TAMV), and flow volume (FV) at each IJV segment were also evaluated. Sixty-nine subjects had TS hypoplasia based on MRV criteria, of which 39 TS hypoplasia were considered a subtype of TS hypoplasia, which is secondary to the downstream venous compression/stenosis or left brachiocephalic vein. In the ultrasound study, the CSA of the IJV ipsilateral to TS hypoplasia was significantly smaller. Further, a contralateral/ipsilateral IJV CSA ratio >1.55 provided good sensitivity, specificity, and positive predictive value for discriminating TS hypoplasia.

Increased inspiratory resistance affects the dynamic relationship between blood pressure changes and subarachnoid space width oscillations

BACKGROUND AND OBJECTIVE

Respiration is known to affect cerebrospinal fluid (CSF) movement. We hypothesised that increased inspiratory resistance would affect the dynamic relationship between blood pressure (BP) changes and subarachnoid space width (SAS) oscillations.

METHODS

Experiments were performed in a group of 20 healthy volunteers undergoing controlled intermittent Mueller Manoeuvres (the key characteristic of the procedure is that a studied person is subjected to a controlled, increased inspiratory resistance which results in marked potentiation of the intrathoracic negative pressure). BP and heart rate (HR) were measured using continuous finger-pulse photoplethysmography; oxyhaemoglobin saturation with an ear-clip sensor; end-tidal CO2 with a gas analyser; cerebral blood flow velocity (CBFV), pulsatility and resistive indices with Doppler ultrasound. Changes in SAS were recorded with a new method i.e. near-infrared transillumination/backscattering sounding. Wavelet transform analysis was used to assess the BP and SAS oscillations coupling.

RESULTS

Initiating Mueller manoeuvres evoked cardiac SAS component decline (-17.8%, P<0.001), systolic BP, diastolic BP and HR increase (+6.3%, P<0.001; 6.7%, P<0.001 and +2.3%, P<0.05, respectively). By the end of Mueller manoeuvres, cardiac SAS component and HR did not change (+2.3% and 0.0%, respectively; both not statistically significant), but systolic and diastolic BP was elevated (+12.6% and +8.9%, respectively; both P<0.001). With reference to baseline values there was an evident decrease in wavelet coherence between BP and SAS oscillations at cardiac frequency in the first half of the Mueller manoeuvres (-32.3%, P<0.05 for left hemisphere and -46.0%, P<0.01 for right hemisphere) which was followed by subsequent normalization at end of the procedure (+3.1% for left hemisphere and +23.1% for right hemisphere; both not statistically significant).

CONCLUSIONS

Increased inspiratory resistance is associated with swings in the cardiac contribution to the dynamic relationship between BP and SAS oscillations. Impaired cardiac performance reported in Mueller manoeuvres may influence the pattern of cerebrospinal fluid pulsatility.

Effect of Internal Jugular Vein Compression on Intracranial Hemorrhage in a Porcine Controlled Cortical Impact Model

Internal jugular vein (IJV) compression has been shown to reduce axonal injury in pre-clinical traumatic brain injury (TBI) models and clinical concussion studies. However, this novel approach to prophylactically mitigating TBI through venous congestion raises concerns of increasing the propensity for hemorrhage and hemorrhagic propagation. This study aims to test the safety of IJV compression in a large animal controlled cortical impact (CCI) injury model and the resultant effects on hemorrhage. Twelve swine were randomized to placement of a bilateral IJV compression collar (CCI+collar) or control/no collar (CCI) prior to CCI injury. A histological grading of the extent of hemorrhage, both subarachnoid (SAH) and intraparenchymal (IPH), was conducted in a blinded manner by two neuropathologists. Other various measures of TBI histology were also analyzed including: β-amyloid precursor protein (β-APP) expression, presence of degenerating neurons, extent of cerebral edema, and inflammatory infiltrates. Euthanized 5 h after injury, the CCI+collar animals exhibited a significant reduction in total SAH (p = 0.024-0.026) and IPH scores (p = 0.03-0.05) compared with the CCI animals. There was no statistically significant difference in scoring for the other markers of TBI (β-APP, neuronal degeneration, cerebral edema, or inflammatory infiltration). In conclusion, IJV compression was shown to reduce hemorrhage (SAH and IPH) in the porcine CCI model when applied prior to injury. These results suggest the role of IJV compression for mitigation of not only axonal, but also hemorrhagic injury following TBI.

Diagnosis of Transverse Sinus Hypoplasia in Magnetic Resonance Venography: New Insights Based on Magnetic Resonance Imaging in Combined Dataset of Venous Outflow Impairment Case-Control Studies: Post Hoc Case-Control Study

In previous studies of transverse sinus (TS) hypoplasia, discrepancies between TS diameter measured by magnetic resonance venography (MRV) and contrast T1-weighted magnetic resonance (contrast T1) were observed. To investigate these discrepancies, and considering that TS hypoplasia is associated with neurological disorders, we performed a post hoc analysis of prospectively collected data from 3 case-control studies on transient global amnesia (TGA), transient monocular blindness (TMB), and panic disorders while retaining the original inclusion and exclusion criteria. Magnetic resonance (MR) imaging of 131 subjects was reviewed to evaluate TS diameter and the location and degree of venous flow stenosis and obstruction.MRV without contrast revealed that TS hypoplasia was observed in 69 subjects, whom we classified into 2 subgroups according to the concordance with contrast T1 observations: concordance indicated anatomically small TS (30 subjects), and discrepancy indicated that the MRV diagnosis is in fact flow-related and that TS is not anatomically small (39 subjects). The latter subgroup was associated with at least 1 site of venous compression/stenosis in the internal jugular vein (IJV) or the left brachiocephalic vein (BCV) (P < 0.001), which was significantly larger in patients than controls. Compensatory dilatation of contralateral TS diameter was only observed with MRV, not with contrast T1 imaging.The clinical implication of these results is that using MRV only, IJV/BCV compression/stenosis may be misdiagnosed as TS hypoplasia. And contralateral TS have no compensatory dilatation in its diameter in contrast T1 imaging, just compensatory increased flow volume.

Effect of Maximal Apnoea Easy-Going and Struggle Phases on Subarachnoid Width and Pial Artery Pulsation in Elite Breath-Hold Divers

Purpose

The aim of the study was to assess changes in subarachnoid space width (sas-TQ), the marker of intracranial pressure (ICP), pial artery pulsation (cc-TQ) and cardiac contribution to blood pressure (BP), cerebral blood flow velocity (CBFV) and cc-TQ oscillations throughout the maximal breath hold in elite apnoea divers. Non-invasive assessment of sas-TQ and cc-TQ became possible due to recently developed method based on infrared radiation, called near-infrared transillumination/backscattering sounding (NIR-T/BSS).

Methods

The experimental group consisted of seven breath-hold divers (six men). During testing, each participant performed a single maximal end-inspiratory breath hold. Apnoea consisted of the easy-going and struggle phases (characterised by involuntary breathing movements (IBMs)). Heart rate (HR) was determined using a standard ECG. BP was assessed using the photoplethysmography method. SaO₂ was monitored continuously with pulse oximetry. A pneumatic chest belt was used to register thoracic and abdominal movements. Cerebral blood flow velocity (CBFV) was estimated by a 2-MHz transcranial Doppler ultrasonic probe. sas-TQ and cc-TQ were measured using NIR-T/BSS. Wavelet transform analysis was performed to assess cardiac contribution to BP, CBFV and cc-TQ oscillations.

Results

Mean BP and CBFV increased compared to baseline at the end of the easy phase and were further augmented by IBMs. cc-TQ increased compared to baseline at the end of the easy phase and remained stable during the IBMs. HR did not change significantly throughout the apnoea, although a trend toward a decrease during the easy phase and recovery during the IBMs was visible. Amplitudes of BP, CBFV and cc-TQ were augmented. sas-TQ and SaO₂ decreased at the easy phase of apnoea and further decreased during the IBMs.

Conclusions

Apnoea increases intracranial pressure and pial artery pulsation. Pial artery pulsation seems to be stabilised by the IBMs. Cardiac contribution to BP, CBFV and cc-TQ oscillations does not change throughout the apnoea.

Obstruction of Venous Drainage Linked to Transient Global Amnesia

Abnormal extracranial venous drainage modality has been considered an etiology of transient global amnesia (TGA). Evidence suggests that the transmission of the intrathoracic/intraabdominal pressure during a Valsalva maneuver (VM) is mainly through the vertebral venous system, and patency of internal jugular vein (IJV) is essential for venous drainage and pressure releasing. We hypothesize that obstruction of IJV venous drainage is a contributing factor in TGA pathogenesis. A magnetic resonance (MR) imaging protocol was used in 45 TGA patients and 45 age- and sex-matched controls to assess the morphologies of IJV, brachiocephalic vein (BCV) and asymmetry of transverse sinus (TS). The IJV was divided into the upper- and middle-IJV segments. Compared to the controls, TGA patients had significantly higher rates of moderate and severe compression/stenosis at the bilateral upper-IJV segment (left: 37.8% vs. 17.8%, P = 0.0393; right: 57.8% vs.15.6%, P<0.0012), in left BCV (60% vs. 8.9%, P<0.0004), and in TS hypoplasia (53.3%% vs. 31.1%, P = 0.0405). The prevalence of at least one site of venous compression/stenosis in IJV or BCV was significantly higher in patients than in controls (91.1% vs. 33.3%, P<0.0004). The diameter of the left TS in MRV, but not in T1 contrast imaging, was significantly smaller in TGA patients than in controls (0.31±0.21 vs. 0.41±0.19, P = 0.0290), which was compatible with downstream venous stenosis/obstruction. TGA patients have a higher prevalence of compression/stenosis of the bilateral IJV and the left BCV and TS hypoplasia, which is new evidence that supports the role of extracranial veins in TGA pathogenesis.

Intrajugular balloon catheter reduces air embolism in vitro and in vivo

Background

Neurosurgical procedures requiring a sitting position may put the patient at risk of a potentially life-threatening air embolism. Transient manual jugular venous compression limits further air entry in this situation. This study presents an alternative technique aimed at reducing the risk of air embolism.

Methods

In an in vitro model, an intrajugular balloon catheter was inserted to demonstrate that this device prevents air embolism. In an in vivo study, this device was bilaterally placed into jugular vessels in pigs. Using an ultrasound technique, blood flow was monitored and jugular venous pressure was recorded before and during cuff inflation. Air was applied proximally to the inflated cuffs to test the hypothesis that this novel device blocks air passage.

Results

In vitro, the intrajugular balloon catheter reliably prevented further air entry (n=10). Additionally, accumulated air could be aspirated from an orifice of the catheter (n=10). In vivo, inflation of the catheter balloon completely obstructed venous blood flow (n=8). Bilateral inflation of the cuff significantly increased the proximal jugular venous pressure from 9.8 (2.4) mm Hg to 14.5 (2.5) mm Hg (n=8, P<0.05). Under conditions mimicking an air embolism, air passage across the inflated cuffs was prevented and 78 (20%) (n=6) of the air dose could be aspirated by the proximal orifice of the catheter.

Conclusions

These findings may serve as a starting point for the development of intrajugular balloon catheters designed to reduce the risk of air embolism in patients undergoing neurosurgery in a sitting position.

Internal jugular vein blood flow in multiple sclerosis patients and matched controls

The aim of the study was to investigate the Internal Jugular Veins dynamics using contrast enhanced ultrasonography in Multiple Sclerosis patients, clinically isolated syndrome patients and healthy controls. Contrast enhanced ultrasonography imaging of the Internal Jugular Vein was performed in fifty-eight patients with Multiple Sclerosis, seven clinically isolated syndrome patients and in thirteen healthy controls. Time-intensity curves were quantified using a semi-automated method and compared with clinical disease outcomes. Wash-out parameters were calculated and six Time-intensity curves shapes were created. Significantly reduction of wash-out rate in Internal Jugular Veins was detected in Multiple Sclerosis patients compared to healthy controls [22.2% (2.7%–65.9%) vs. 33.4% (16.2%–76.8%); P<0.005]. Internal Jugular Vein enhancement was heterogeneous in patients with Multiple Sclerosis and consisted of slow wash-out Time-intensity curves shapes, compared with almost only one type of Time-intensity curves shape in control subjects that correspond to fast enhancement and fast wash-out. The vein wash-in parameters were similar in Multiple Sclerosis group compared with controls. A significant correlation was found between Internal Jugular Vein wash-out and level of disability (R = −0.402, p<0.05). Contrast enhanced ultrasonography of the Internal Jugular Vein with time intensity curve analysis revealed alterations of cerebral venous outflow in Multiple Sclerosis patients, however mechanisms that determine this condition remains unclear.

Venous hemodynamics in neurological disorders: an analytical review with hydrodynamic analysis

Venous abnormalities contribute to the pathophysiology of several neurological conditions. This paper reviews the literature regarding venous abnormalities in multiple sclerosis (MS), leukoaraiosis, and normal-pressure hydrocephalus (NPH). The review is supplemented with hydrodynamic analysis to assess the effects on cerebrospinal fluid (CSF) dynamics and cerebral blood flow (CBF) of venous hypertension in general, and chronic cerebrospinal venous insufficiency (CCSVI) in particular.CCSVI-like venous anomalies seem unlikely to account for reduced CBF in patients with MS, thus other mechanisms must be at work, which increase the hydraulic resistance of the cerebral vascular bed in MS. Similarly, hydrodynamic changes appear to be responsible for reduced CBF in leukoaraiosis. The hydrodynamic properties of the periventricular veins make these vessels particularly vulnerable to ischemia and plaque formation.Venous hypertension in the dural sinuses can alter intracranial compliance. Consequently, venous hypertension may change the CSF dynamics, affecting the intracranial windkessel mechanism. MS and NPH appear to share some similar characteristics, with both conditions exhibiting increased CSF pulsatility in the aqueduct of Sylvius.CCSVI appears to be a real phenomenon associated with MS, which causes venous hypertension in the dural sinuses. However, the role of CCSVI in the pathophysiology of MS remains unclear.

Near-infrared transillumination back scattering sounding--new method to assess brain microcirculation in patients with chronic carotid artery stenosis

Purpose

The purpose of the study was to assess the responses of pial artery pulsation (cc-TQ) and subarachnoid width (sas-TQ) to acetazolamide challenge in patients with chronic carotid artery stenosis and relate these responses to changes in peak systolic velocity (PSV), cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time to peak response (TTP).

Methods

Fifteen patients with carotid artery stenosis ≥90% on the ipsilateral side and <50% on the contralateral side were enrolled into the study. PSV was assessed using colour-coded duplex sonography, CBF, CBV, MTT and TTP with perfusion computed tomography, cc-TQ and sas-TQ with near-infrared transillumination/backscattering sounding (NIR-T/BSS).

Results

Based on the ipsilateral/contralateral cc-TQ ratio after acetazolamide challenge two groups of patients were distinguished: the first group with a ratio ≥1 and the second with a ratio <1. In the second group increases in CBF and CBV after the acetazolamide test were significantly higher in both hemispheres (ipsilateral: +33.0%±8.1% vs. +15.3%±4.4% and +26.3%±6.6% vs. +14.3%±5.1%; contralateral: +26.8%±7.0% vs. +17.6%±5.6% and +20.0%±7.3% vs. +10.0%±3.7%, respectively), cc-TQ was significantly higher only on the ipsilateral side (+37.3%±9.3% vs. +26.6%±8.6%) and the decrease in sas-TQ was less pronounced on the ipsilateral side (−0.7%±1.5% vs. −10.2%±1.5%), in comparison with the first group. The changes in sas-TQ following the acetazolamide test were consistent with the changes in TTP.

Conclusions

The ipsilateral/contralateral cc-TQ ratio following acetazolamide challenge may be used to distinguish patient groups characterized by different haemodynamic parameters. Further research on a larger group of patients is warranted.