Cerebral blood flow autoregulation in early experimental S. pneumoniae meningitis

Meningitis in Children: Still a Can't-Miss Diagnosis

Although vaccination and antimicrobial treatment have significantly impacted the frequency and outcomes of meningitis in children, meningitis remains a critical can't-miss diagnosis for children, where early recognition and appropriate treatment can improve survival and neurologic outcomes. Signs and symptoms may be nonspecific, particularly in infants, and require a high index of suspicion to recognize potential meningitis and obtain the cerebrospinal fluid studies necessary for diagnosis. Understanding the pathogens associated with each age group and specific risk factors informs optimal empirical antimicrobial therapy. Early treatment and developmental support can significantly improve the survival rates and lifelong neurodevelopment of children with central nervous system infections.

Inflammation and the role of infection: Complications and treatment options following neurotrauma

Traumatic brain injury can have devastating consequences for patients and extended hospital stays and recovery course. Recent data indicate that the initial insult causes profound changes to the immune system and leads to a pro-inflammatory state. This alteration in homeostasis predisposes patients to an increased risk of infection and underlying autoimmune conditions. Increased emphasis has been placed on understanding this process both in the clinical and preclinical literature. This review highlights the intrinsic inflammatory conditions that can occur within the initial hospital stay, discusses long-term immune consequences, highlights emerging treatment options, and delves into important pathways currently being investigated with preclinical models.

Cerebral Pressure Autoregulation in Brain Injury and Disorders-A Review on Monitoring, Management, and Future Directions

The role of cerebral pressure autoregulation (CPA) in brain injury and disorders has gained increased interest. The CPA is often disturbed as a consequence of acute brain injury, which contributes to further brain damage and worse outcome. Specifically, in severe traumatic brain injury, CPA disturbances predict worse clinical outcome and targeting an autoregulatory-oriented optimal cerebral perfusion pressure threshold may improve brain energy metabolism and clinical outcome. In aneurysmal subarachnoid hemorrhage, cerebral vasospasm in combination with distal autoregulatory disturbances precipitate delayed cerebral ischemia. The role of optimal cerebral perfusion pressure targets is less clear in aneurysmal subarachnoid hemorrhage, but high cerebral perfusion pressure targets are generally favorable in the vasospasm phase. In acute ischemia, autoregulatory disturbances may occur and autoregulatory-oriented blood pressure (optimal mean arterial pressure) management reduces the risk of hemorrhagic transformation, brain edema, and unfavorable outcome. In chronic occlusive disease such as moyamoya, the gradual reduction of the cerebral circulation leads to compensatory distal vasodilation and the residual CPA capacity predicts the risk for cerebral ischemia. In spontaneous intracerebral hemorrhage, the role of autoregulatory disturbances is less clear, but CPA disturbances correlate with worse clinical outcome. Also, in community-acquired bacterial meningitis, CPA dysfunction is frequent and correlates with worse clinical outcome, but autoregulatory management is yet to be evaluated. In this review, we discuss the role of CPA in different types of brain injury and disease, the strengths and limitations of the monitoring methods, the potentials of autoregulatory management, and future directions in the field.

Intracranial pressure dynamics and cerebral vasomotor reactivity in community-acquired bacterial meningitis during neurointensive care

OBJECTIVE

Community-acquired bacterial meningitis (CABM) is a severe condition associated with high mortality. In this study the first aim was to evaluate the incidence of intracranial pressure (ICP) insults and disturbances in cerebral vasomotor reactivity and the second aim was to evaluate the management and clinical outcome of CABM patients treated in the neurointensive care unit (NICU).

METHODS

CABM patients who were treated in the NICU of Uppsala University Hospital, Sweden, during 2008-2020 were included in the study. Data on demographics, admission variables, treatment, ICP dynamics, vasomotor reactivity, and short-term clinical outcome were evaluated in these patients.

RESULTS

Of 97 CABM patients, 81 (84%) received ICP monitoring, of whom 22% had ICP > 20 mm Hg during 5% or more of the monitoring time on day 1, which decreased to 9% on day 3. For those patients with ICP monitoring, 46% required CSF drainage, but last-tier ICP treatment, including thiopental (4%) and decompressive craniectomy (1%), was rare. Cerebral vasomotor reactivity was disturbed, with a mean pressure reactivity index (PRx) above 0.2 in 45% of the patients on day 1, and remained high for the first 3 days. In total, 81 (84%) patients had a favorable outcome (Glasgow Coma Scale motor score [GCS M] 6) at discharge, 9 (9%) patients had an unfavorable outcome (GCS M < 6) at discharge, and 7 (7%) patients died in the NICU. Those with favorable outcome had significantly better cerebral vasomotor reactivity (lower PRx) than the two other outcome groups (p < 0.01).

CONCLUSIONS

Intracranial hypertension was frequent following severe CABM and CSF drainage was often sufficient to control ICP. Cerebral vasomotor reactivity was commonly disturbed and associated with poor outcome. Clinical outcome was slightly better than in earlier studies.

Late Recovery from Severe Streptococcus pneumoniae Comatose Meningitis with Concomitant Diffuse Subcortical Cytotoxic Edema and Cortical Hypometabolism

A 75-year-old woman was admitted to ICU with coma following Streptococcus pneumoniae meningitis with bacteremia. Her Glasgow Coma Scale (GCS) score fluctuated around 4 to 6 over the next four weeks. There was no evidence of increased intracranial pressure (ICP). Electroencephalogram (EEG) showed only diffuse aspecific slowing. Impaired cerebral blood flow (CBF) autoregulation was suggested at transcranial Doppler (TCD). Repeated brain magnetic resonance imaging (MRI) examination failed to demonstrate venous thrombosis, arterial ischemic stroke, or brain abscesses but revealed diffuse but reversible cortical cytotoxic edema at diffusion-weighted (DW) sequences. The brain FDG-positron emission tomography (FDG-PET) showed diffuse cortical hypometabolism. The patient unexpectedly experienced a complete neuropsychological recovery the next few weeks. The suggested hypothesis to explain this unusual disease course could be a transient alteration of CBF autoregulation due to some degree of diffuse subcortical microangiopathy. A concomitant reduction of brain metabolism probably prevented the progression towards cortical irreversible ischemic damage.

The role of ICP monitoring in meningitis

Intracranial pressure (ICP) monitoring has been widely accepted in the management of traumatic brain injury. However, its use in other pathologies that affect ICP has not been advocated as strongly, especially in CNS infections. Despite the most aggressive and novel antimicrobial therapies for meningitis, the mortality rate associated with this disease is far from satisfactory. Although intracranial hypertension and subsequent death have long been known to complicate meningitis, no specific guidelines targeting ICP monitoring are available. A review of the literature was performed to understand the pathophysiology of elevated ICP in meningitis, diagnostic challenges, and clinical outcomes in the use of ICP monitoring.

Arterial spin-labeling perfusion imaging of childhood encephalitis: correlation with seizure and clinical outcome

PURPOSE

In childhood encephalitis, perfusion abnormalities have been infrequently reported to associate with clinical status. We investigated whether perfusion abnormalities correlated with seizure and clinical outcome in encephalitis.

METHODS

We retrospectively analyzed the MR studies of 77 pediatric patients with encephalitis. Pseudo-continuous arterial spin-labeling (ASL) imaging was performed on a 3-T scanner. The patients were divided into five groups according to ASL perfusion imaging pattern: normal perfusion (NP), focal hypoperfusion (Lf), extreme global hypoperfusion (LE), focal hyperperfusion (Hf), and extreme global hyperperfusion (HE). Clinical outcome at 3 weeks was dichotomized to unfavorable or favorable outcome according to the Glasgow outcome scale. Multivariate logistic regression was conducted to predict unfavorable outcome and presence of seizure separately, based on explanatory variables including age, sex, and ASL pattern.

RESULTS

Twenty-seven (35%) patients were designated as in group Hf, five (7%) in group Lf, 11 (14%) in group LE, none in group HE, and 34 (44%) in group NP. Multivariate logistic regression analysis showed that ASL pattern was significantly associated with unfavorable outcome (P = 0.005) and with presence of seizure (P = 0.005). For ASL pattern, group LE was 17.31 times as likely to have an unfavorable outcome as group NP (odds ratio confidence interval [CI] 3.084, 97.105; P = 0.001). Group Hf was 6.383 times as likely to have seizure as group NP (CI 1.765, 23.083; P = 0.005).

CONCLUSIONS

In childhood encephalitis, patients with extreme global hypoperfusion had poor neurological outcome and those with focal hypoperfusion were more likely to have seizure.

Arterial spin-labeling perfusion imaging of childhood meningitis: a case series

INTRODUCTION

Conventional magnetic resonance imaging (MRI), which is mainly used to detect complications, is ineffective in determining the neurological status of patients with meningitis. Hemodynamic change in the brain may be more indicative of the neurological status but few imaging studies have verified this. Arterial spin-labeling (ASL) perfusion, a noninvasive MR method requiring no contrast agent injection, can be used to measure cerebral blood flow (CBF).

CASE REPORTS

We describe three pediatric patients with meningitis, who all showed regions of increased CBF on perfusion imaging. One patient, presenting with headache and conscious disturbance, had CBF changes in the frontal, temporal, and occipital regions. The other two patients, presenting with hallucinations, memory deficits, and seizures, had CBF changes in the frontal and temporal regions.

CONCLUSION

ASL perfusion imaging may be helpful in assessing patients with meningitis, demonstrating CBF changes more strongly correlating with the neurological status, and detecting active brain abnormalities.

Optic nerve sheath diameter as a marker for evaluation and prognostication of intracranial pressure in Indian patients: An observational study

BACKGROUND AND AIMS

The aim was to evaluate efficacy of optic nerve sheath diameter (ONSD) by ultrasound as a noninvasive method for detecting raised intracranial pressure (ICP) in intensive care unit, to compare with computed tomography/magnetic resonance imaging (MRI) findings of raised ICP and to prognosticate ONSD value with treatment.

MATERIALS AND METHODS

We conducted a prospective, observational study on 101 adults by including 41 healthy individuals in group A as control and 60 patients in group B admitted with fever, headache, vomiting, and altered sensorium. We examined them in supine position using 10 MHz linear array probe on closed eyelid. ONSD was measured 3 mm behind the globe in each eye. A mean binocular ONSD > 4.6 mm in female and 4.8 mm in male was considered abnormal. Midline shift, edema, effacement or ONSD > 5.0 mm on T2 MRI suggestive of elevated ICP was used to evaluate ONSD accuracy.

RESULTS

Group A mean ONSD was 4.6 mm in females and 4.8 mm in males. Group B mean ONSD for 17 females was 5.103 ± 0.6221 mm (P = 0.002) and for 43 males 5.081 ± 0.5799 mm (P = 0.032). Radiological sign of raised ICP was confirmed in 35 patients (females = 11 and males = 24) with high ONSD value. Sensitivity of detecting raised ICP by ONSD was 84.6% in females and 75% in males while specificity was 100% in both genders. Out of 25 patients without radiological signs of raised ICP 10 patients showed high ONSD (females = 4.735 mm and males = 4.907 mm). ONSD was well prognosticated with treatment modalities.

CONCLUSION

Bedside ocular ultrasonography for measuring ONSD can be used an early test for diagnosing raised ICP as it is a noninvasive, cost effective bedside test, which can be repeated for re-evaluation.

Mean perfusion pressure deficit during the initial management of shock--an observational cohort study

PURPOSE

It is unclear if blood pressure targets for patients with shock should be adjusted to pre-morbid levels. We aimed to investigate mean deficit between the achieved mean perfusion pressure (MPP) in vasopressor-treated patients and their estimated basal (resting) MPP, and assess whether MPP deficit has any association with subsequent acute kidney injury (AKI).

MATERIALS AND METHODS

Fifty-one consecutive, non-trauma patients, aged ≥40 years, with ≥2 organ dysfunction and requiring vasopressor≥4 hours were observed at an academic intensive care unit. Mean MPP deficit [=%(basal MPP-achieved MPP)/basal MPP] and % time spent with >20% MPP deficit were assessed during initial 72 vasopressor hours (T0-T72) for each patient.

RESULTS

Achieved MPP was unrelated to basal MPP (P=.99). Mean MPP deficit was 18% (95% CI 15-21). Patients spent 48% (95% CI 39-57) time with >20% MPP deficit. Despite similar risk scores at T0, subsequent AKI (≥2 RIFLE class increase from T0) occurred more frequently in patients with higher (>median) MPP deficit compared to patients with lower MPP deficit (56% vs 28%; P=.045). Incidence of subsequent AKI was also higher among patients who spent greater % time with >20% MPP deficit (P=.04).

CONCLUSIONS

Achieved blood pressure during vasopressor therapy had no relationship to the pre-morbid basal level. This resulted in significant and varying degree of relative hypotension (MPP deficit), which could be a modifiable risk factor for AKI in patients with shock.

[Non-invasive evaluation of intracranial pressure: how and for whom?]

The invasive monitoring of intracranial pressure is useful in circumstances associated with high-risk of raised intracranial pressure. However the placement of intracranial probe is not always possible and non-invasive assessment of intracranial pressure may be useful, particularly in case of emergencies. Transcranial Doppler measurements allow the estimation of perfusion pressure with the pulsatility index. Recently, new ultrasonographic methods of cerebral monitoring have been developed: the diameter of the optic nerve sheath diameter, a surrogate marker of raised intracranial pressure and the estimation of median shift line deviation.

[Degree of emergency for antibiotherapy in patients with presumed bacterial meningitis: experimental and clinical data]

No prospective randomized clinical studies are available to determine exactly how much time should be spent on investigation before initiating antibiotherapy in a patient with presumed bacterial meningitis. Experimental models show that antibiotics should be administered before the inflammatory response, but at this time the patient's symptoms are often unspecific. Models also demonstrate that a gain of time is beneficial at any time, in terms of inflammation, magnitude of bacteremia, or loss of hearing. Very few clinical studies address the acceptable delay between admission and administration of antibiotics and two of these show a correlation with outcome in adult meningitis. The available data supports the recommendation that hospital investigation of a patient with presumed bacterial meningitis should be conducted in such a way that efficient antimicrobial chemotherapy will be initiated within one hour after arrival.

Use of T2-weighted magnetic resonance imaging of the optic nerve sheath to detect raised intracranial pressure

Introduction

The dural sheath surrounding the optic nerve communicates with the subarachnoid space, and distends when intracranial pressure is elevated. Magnetic resonance imaging (MRI) is often performed in patients at risk for raised intracranial pressure (ICP) and can be used to measure precisely the diameter of optic nerve and its sheath. The objective of this study was to assess the relationship between optic nerve sheath diameter (ONSD), as measured using MRI, and ICP.

Methods

We conducted a retrospective blinded analysis of brain MRI images in a prospective cohort of 38 patients requiring ICP monitoring after severe traumatic brain injury (TBI), and in 36 healthy volunteers. ONSD was measured on T2-weighted turbo spin-echo fat-suppressed sequence obtained at 3 Tesla MRI. ICP was measured invasively during the MRI scan via a parenchymal sensor in the TBI patients.

Results

Measurement of ONSD was possible in 95% of cases. The ONSD was significantly greater in TBI patients with raised ICP (>20 mmHg; 6.31 ± 0.50 mm, 19 measures) than in those with ICP of 20 mmHg or less (5.29 ± 0.48 mm, 26 measures; P < 0.0001) or in healthy volunteers (5.08 ± 0.52 mm; P < 0.0001). There was a significant relationship between ONSD and ICP (r = 0.71, P < 0.0001). Enlarged ONSD was a robust predictor of raised ICP (area under the receiver operating characteristic curve = 0.94), with a best cut-off of 5.82 mm, corresponding to a negative predictive value of 92%, and to a value of 100% when ONSD was less than 5.30 mm.

Conclusions

When brain MRI is indicated, ONSD measurement on images obtained using routine sequences can provide a quantitative estimate of the likelihood of significant intracranial hypertension.

Cerebral blood flow autoregulation in experimental liver failure

Patients with acute liver failure (ALF) display impairment of cerebral blood flow (CBF) autoregulation, which may contribute to the development of fatal intracranial hypertension, but the pathophysiological mechanism remains unclear. In this study, we examined whether loss of liver mass causes impairment of CBF autoregulation. Four rat models were chosen, each representing different aspects of ALF: galactosamine (GlN) intoxication represented liver necrosis, 90% hepatectomy (PHx90) represented reduction in liver mass, portacaval anastomosis (PCA) represented shunting of blood/toxins into the systemic circulation thus mimicking intrahepatic shunting in ALF, PCA+NH(3) provided information about the additional effects of hyperammonemia Rats were intubated and sedated with pentobarbital. We measured CBF with laser Doppler, intracranial pressure (ICP) was measured in the fossa posterior and registered with a pressure transducer, brain water was measured using the wet-to-dry method, and cerebral glutamine/glutamate was measured enzymatically. The CBF autoregulatory index in both the GlN and PHx90 groups differed significantly from the control group. Conversely, CBF autoregulation was intact in the PCA and PCA+NH(3) groups despite high arterial ammonia, high cerebral glutamine concentration, and increased CBF and ICP. Increased water content of the brainstem or cerebellum was not associated with defective CBF autoregulation. In conclusion, impairment of CBF autoregulation is not caused by brain edema/high ICP. Nor does portacaval shunting or hyperammonemia impair autoregulation. Rather, massive liver necrosis and reduced liver mass are associated with loss of CBF autoregulation.

In vivo study of experimental pneumococcal meningitis using magnetic resonance imaging

BACKGROUND

Magnetic Resonance Imaging (MRI) methods were evaluated as a tool for the study of experimental meningitis. The identification and characterisation of pathophysiological parameters that vary during the course of the disease could be used as markers for future studies of new treatment strategies.

METHODS

Rats infected intracisternally with S. pneumoniae (n = 29) or saline (n = 13) were randomized for imaging at 6, 12, 24, 30, 36, 42 or 48 hours after infection. T1W, T2W, quantitative diffusion, and post contrast T1W images were acquired at 4.7 T. Dynamic MRI (dMRI) was used to evaluate blood-brain-barrier (BBB) permeability and to obtain a measure of cerebral and muscle perfusion. Clinical- and motor scores, bacterial counts in CSF and blood, and WBC counts in CSF were measured.

RESULTS

MR images and dMRI revealed the development of a highly significant increase in BBB permeability (P < 0.002) and ventricle size (P < 0.0001) among infected rats. Clinical disease severity was closely related to ventricle expansion (P = 0.024). Changes in brain water distribution, assessed by ADC, and categorization of brain 'perfusion' by cortex DeltaSI(bolus) were subject to increased inter-rat variation as the disease progressed, but without overall differences compared to uninfected rats (P > 0.05). Areas of well-'perfused' muscle decreased with the progression of infection indicative of septicaemia (P = 0.05).

CONCLUSION

The evolution of bacterial meningitis was successfully followed in-vivo with MRI. Increasing BBB-breakdown and ventricle size was observed in rats with meningitis whereas changes in brain water distribution were heterogeneous. MRI will be a valuable technique for future studies aiming at evaluating or optimizing adjunctive treatments.

The effect of S. pneumoniae bacteremia on cerebral blood flow autoregulation in rats

In the present study, we studied the effect of bacteremia on cerebral blood flow (CBF) autoregulation in a rat model of pneumococcal bacteremia and meningitis. Anesthetized rats were divided into five groups (A to E) and inoculated with pneumococci intravenously and normal saline intracisternally (group A, N=10); saline intravenously and pneumococci intracisternally (group B, N=10); pneumococci intravenously and pneumococci intracisternally (group C, N=5); saline intravenously, antipneumococcal antibody intravenously (to prevent bacteremia), and pneumococci intracisternally (group D, N=10); or saline intravenously and saline intracisternally (group E, N=10), respectively. Positive cultures occurred in the blood for all rats in groups A, B, and C, and in the cerebrospinal fluid for all rats in groups D and E. Twenty-four hours after inoculation, CBF was measured with laser-Doppler ultrasound during incremental reductions in cerebral perfusion pressure (CPP) by controlled hemorrhage. Autoregulation was preserved in all rats without meningitis (groups A and E) and was lost in 24 of 25 meningitis rats (groups B, C, and D) (P<0.01). In group A, the lower limit was higher than that of group E (P<0.05). The slope of the CBF/CPP regression line differed between the meningitis groups (P<0.001), being steeper for group B than groups C and D, with no difference between these two groups. The results suggest that pneumococcal bacteremia in rats triggers cerebral vasodilation, which right shifts the lower limit of, but does not entirely abolish, CBF autoregulation in the absence of meningitis, and which may further aggravate the vasoparalysis induced by concomitant pneumococcal meningitis.